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Letters to the Editor

AIS’ Current Role in Anesthesiology RiskManagement Remains Uncertain

To the Editor:

I read with interest the article by Dr. Feldman (1). Despite the author’seffort to address an important topic, the approach to answering thiscomplex question has resulted in a potentially misleading conclusion.The article indicates that departments using AIS find that it does notinterfere with “risk management.” In addition, in the opinion of someof the surveyed departments, electronic records have been helpful indisposing of potential and actual malpractice actions more favorably.Unfortunately, there are substantial limitations in the study method-ology that preclude definite conclusions. This is due in part to manycurrently unresolved issues associated with the intermeshing of med-ical informatics and anesthesiology. A number of these issues are

enumerated below.First, there is still much to learn about managing biosignals

transduced to a real-time monitor, let alone a written record withstored data. For example, at this time all biosignals are analog innature. These signals must be electronically converted to digitalsignals to be recorded by a PC (or any computer) (2). In additionthere are real-time data sampling and data quantification prob-lems that can significantly alter read-out values (2). Conse-quently, data printed on a written record from stored computerdata is, by its intrinsic nature, data that has been manipulatedinto a form that may or may not be sufficiently accurate to reflectthe clinical situation in real time. This problem of computer datamanipulation is a limitation that is similar to the current handwritten record. It is not possible to know from the informationpresented whether the AIS surveyed are actually more accuratethan a written record.

Second, this paper does not define the term “risk management.”Risk management, as a field of study, incorporates specific methodsfor identifying and managing issues in an attempt to decrease notonly the risk of lawsuits but also for identifying and mitigatingmany other types of liability issues (3). In any JCAHO accreditedinstitution, risk management methods are regularly applied to prob-lems in the medical setting not related to provider negligence.Perhaps substituting the words “decrease in liability” or “decreas-ing liability” for “risk management,” in this article, would producea more understandable (but not more valid) interpretation of thesurvey data. Absent a specific definition of “risk management” inthe questionnaire, the respondents are left to apply their own inter-pretation to a term with several contextual definitions, which pro-foundly confounds our ability to interpret the survey results.

Third, the survey asks the questionnaire respondents to come toa legal conclusion about whether the increase in quality of docu-

mentation (which is presumed but not established by objectiveevidence) made a difference in legal actions such as voluntarilydismissing a suit or settling a suit by somehow decreasing liability.It seems exceedingly unlikely that the respondents to this surveycould definitively know the plaintiff’s actual reasoning for droppingor settling a suit and whether it was actually related to AIS, sincemost physicians do not understand the potential legal proof prob-lems associated with these electronic records. The AIS are propri-etary and they vary significantly because there is no establishedstandard for these systems. More importantly, using AIS is not thestandard of care currently. A well-qualified attorney could (andlikely would) raise substantial questions about the accuracy and thevalidity of any (AIS) system based on the aforementioned factors.Therefore, depending on the relationship between the anesthesiarecord and the particular liability issue in question, the use of AIScould influence the decision of opposing counsel in either direction:

to pursue or reject a claim, depending on the nature of the injurysustained and the ability to prove the relationship (in legal terms,the attachment of liability) between the presumed negligence andthe injury (proximate cause).

Fourth, this paper speculates incorrectly that any additional datanot printed on the anesthesia record may, in the future, be intro-duced into a legal proceeding in a manner that might be determined

by the institution or department in question. To suggest that a set of circumstances would arise where part of the record could be vol-untarily withheld is incorrect. Any additional data archived in anelectronic database of the AIS is now and will in the future be legallyavailable for analysis in any litigation. A patient’s record and alldata contained therein belong to the patient (4). The complete recordcannot be sequestered or remain undisclosed without creating asituation where the institution and/or the physician are in contemptof the court.

The methodology of this paper severely constrains our ability to

derive meaningful conclusions about AIS and its role in liabilityreduction and risk management. Additional investigation that ad-dresses the issues noted above will be required before we can makea valid determination of the utility of AIS for liability reduction andrisk management.

Philip Edward Lane, MD , JD , MPH, MBADepartment of AnesthesiologyRush University Medical CenterChicago, IL

[email protected]

References1. Feldman JM. Do anesthesia information systems (AIS) increase malpractice exposure?

Results of a survey. Anesth Analg 2004;99:840–3.2. Van Bemmel JH, Musen MA. Eds. Biosignal analysis in handbook of medical infor-

matics. New York: Springer, 1997:120–5.3. Vincent C. The development of clinical risk management. In: Clinical risk manage-

ment. London: BMJ Books, 2001:45–60.

4. Available at http://www.hhs.gov/ocr/hipaa/consumer_summary.pdf .

DOI: 10.1213/01.ANE.0000151477.28089.88

In Response:

In Dr. Lane’s letter on my article (1), he writes that the “paperseverely constrains our ability to derive meaningful conclusionsabout AIS and its role in liability reduction and risk management.”I agree that the question of the impact of AIS on malpracticeexposure remains open and that the information available from thearticle is not definitive. Any survey has major sampling limitationsand more importantly, the investigator cannot control the quality of the data collected. Dr. Lane does however seem to have misinter-preted some of the information presented in the article that I wouldlike to reiterate.

In the introduction to the article, I described opposing argumentssupporting the contentions that AIS increase and decrease malprac-

tice exposure. One of my primary goals in this study was to findevidence supporting either one of these arguments as they haveheretofore been based solely on opinion. Unfortunately, evidencefrom legal precedent could not be identified and the survey was theonly instrument for collecting any form of data. Of the departmentsresponding to the survey, there was not one report that the AISincreased malpractice exposure. As I stated in the article, “Theresults of the survey lend credibility to the argument that AIS helpto reduce malpractice exposure.” This conclusion was not intendedto be a definitive statement about the role of AIS in malpracticeexposure, only an assessment of the evidence collected by thesurvey.

Dr. Lane also seemed to misinterpret the discussion regardingdiscoverability of electronic data. This is a very important point thatis worthy of clarification. The article clearly states that a highresolution electronic version of the data collected during anesthesia

©2005 by the International Anesthesia Research Society Anesth Analg 2005;100:1537–49 1537


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is created by the AIS in addition to the printed version placed in thepatient’s medical record. Although I could not find evidence to datethat the electronic data has been part of the discovery process, thereis no question in my mind that it will be in the future. As AIS areadopted, risk managers will need to consider not only the impact of the printed record on malpractice exposure but also the impact of the high-resolution electronic archive.

Not only are AIS proliferating, there is momentum building onthe national level to make the entire patient record electronic. Wewill undoubtedly have to address not only the malpractice impli-cations, but also all of the complexities that will be introduced bythis technology. I certainly look forward to more definitive evidencefrom actual malpractice proceedings to document the role of AIS inthe malpractice process and to continued constructive dialogue onthis important question.

Jeffrey M. Feldman, MD, MSEDepartment of AnesthesiologyChildren’s Hospital of PhiladelphiaPhiladelphia, PA

[email protected]

Reference1. Feldman JM. Do anesthesia information systems (AIS) increase malpractice exposure?

Results of a survey. Anesth Analg 2004;99:840–3.

Effects of Hydroxyethyl Starch and Calciumon Platelet ActivationTo the Editor:

I read with great interest the article by Deusch et al. (1) whereincitrate anticoagulated blood diluted 20% with Hextend® (AbbottLaboratories, Chicago, IL) had greater platelet activation than otherhydroxyethyl starch solutions devoid of calcium. Furthermore,

blood samples diluted with a 600 kd-containing hydroxyethylstarch solution with addition of calcium equivalent to Hextend®

also had an increase in platelet activation. My concern with theseresults was that blood sample calcium concentrations could besufficiently increased by Hextend® to initiated thrombin generation.

To test this, pooled, citrated control plasma (Trinity Biotech, Ven-tura, CA) was either undiluted, diluted 20% with 6% hetastarch in0.9% NaCl (Abbott) or with Hextend® (n 3 per condition) at roomtemperature for 5 min prior to calcium determination with ananalyzer (model 1306, Instrumentation Laboratory, Lexington, MA).Calcium values were as follows (mM): undiluted 0.02 0.01,hetastarch 0.01 0.00, Hextend® 0.04 0.01. One-way analysisof variance demonstrated that the plasma diluted with Hextend®

had a significantly greater calcium concentration than the otherfluids. Nevertheless, this concentration is far below the thresholdrequired for thrombin generation. What other mechanism underlyingcalcium-mediated platelet activation would the authors suggest?

Another issue is the citation by Deusch and colleagues (1) of astudy wherein Hextend® administration resulted in enhanced he-mostasis assessed by thrombelastography (decreased R time) in arabbit model of hemorrhagic shock (2). Deusch et al. (1) in their

discussion imply that our findings were explained by calcium con-tained in Hextend®—a conclusion that is not true, as Hextend®

decreased endogenous heparinoid release and did not affect bloodcalcium concentration (2). In fact, there has never been a significantchange in blood calcium concentration documented in any of our invivo rabbit studies involving hemodilution (3,4). However, while40% dilution with Hextend® did not change R values (3), 75%dilution did significantly decrease R values in rabbits (4).

Vance G. Nielsen, MDDepartment of AnesthesiologyThe University of Alabama at BirminghamBirmingham, [email protected]

References1. Deusch E, Thaler U, Kozek-Langenecker SA. The effects of high molecular weight

hydroxyethyl starch solutions on platelets. Anesth Analg 2004;99:665–8.2. Nielsen VG. Resuscitation with Hextend® decreases endogenous circulating heparin

activity and accelerates clot initiation after hemorrhage in the rabbit. Anesth Analg2001;93:1106–10.

3. McCammon AT, Wright JP, Figueroa M, Nielsen VG. Hemodilution with albumin, butnot Hextend®, results in hypercoagulability as assessed by thrombelastography inrabbits: role of heparin-dependent serpins and factor VIII complex. Anesth Analg2002;95:844–50.

4. Nielsen VG, Baird MS. Extreme hemodilution in rabbits: an in vitro and in vivothrombelastographic analysis. Anesth Analg 2000;90:541–5.

DOI: 10.1213/01.ANE.0000149041.17161.FF

In Response:

Thank you for the opportunity to respond to the comments of Dr.Nielsen to our article (1).

Enhanced hemostasis may result from an increase in procoagulantssuch as activated platelets or increased levels of ionized calcium, adecrease in anticoagulants such as heparin-dependent serpins, or acombination of both. The novel hetastarch diluted in a balanced elec-trolyte formulation containing calcium, lactate buffer, and a physio-logic level of glucose (Hextend®) has been reported to enhance hemo-stasis: lower thromboelastographic R values were found in patientsreceiving Hextend® compared with hetastarch in saline (2). Similarly,lower R times were observed by Nielsen et al. after 75% in vitro dilutionof blood with Hextend® (3) and after about 40% isovolemic hemodi-lution in rabbits (4) when compared with albumin. The underlyingmechanisms for enhanced dynamic clot formation after Hextend® still

remain unclear. Among other factors, ionized calcium levels affect Rtime. In vitro 75% hemodilution using albumin significantly deceasedcalcium concentrations and prolonged R time, which was reversible bycalcium supplementation (3). In contrast to albumin, isovolemic he-modilution using Hextend® containing calcium in the commerciallyavailable solution resulted in no decrease in calcium levels (3–5). Sim-ilarly, Hextend-treated patients required less intraoperative calciumand were less likely to receive calcium supplementation than patientstreated with hetastarch in saline (2). In his letter, Dr. Nielsen stated thatwe misinterpreted his studies in our discussion section (1). However,the discussion on the importance of calciumin facilitating hemostasis wasclearly related to our study results performed in citrated whole blood.

R time is also dependent on platelet procoagulant activity. Our invitro experiments demonstrated an increase in platelet activationafter incubation of citrated whole blood with Hextend® and indicatethat this effect is, at least in part, due to the solvent of Hextend®

containing calcium (1). Maintenance of calcium concentrationwithin physiological ranges and acid-base balance may attenuatefluid-specific pharmacodynamic effects of Hextend® on platelets.Nielsen questions in his letter this potential mechanism by demon-strating some data on low calcium levels achieved after in vitroHextend® dilution that were below the threshold for plasma clottingkinetics. To the best of our knowledge a calcium level threshold forcalcium-mediated platelet activation has not been determined. Cal-cium is the key second messenger in platelets and although notdetermined in detail so far, a high sensitivity of platelets to theextracellular electrolyte milieu can be anticipated.

R time is further dependent on anticoagulants. Since in vitroexperiments exclude many compensatory changes such as antico-agulant production, secretion, and removal, as well as modifyingmechanisms of the endothelium, our findings are not likely to berelated to anticoagulant activities. In vivo, however, the decrease in

heparin-dependent serpin activities in the presence of Hextend

®

asreported by Nielsen et al. (4,5) has to be considered as a cause of enhanced hemostasis.

E. Deusch, MDS. Kozek-Langenecker, MD

Medical University of ViennaVienna, [email protected]

References1. Deusch E, Thaler U, Kozek-Langenecker S. The effects of high molecular weight

hydroxyethyl starch solutions on platelets. Anesth Analg 2004;99:665–8.2. Gan TJ, Bennett-Guerrero E, Phillips-Bute B, et al. Hextend, a physiologically balanced

plasma expander for large volume use in major surgery: a randomized phase IIIclinical trial. Anesth Analg 1999;88:992–8.

3. Nielsen VG, Baird MS. Extreme hemodilution in rabbits: an in vitro and in vivothrombelastographic analysis. Anesth Analg 2000;90:541–5.

4. Nielsen VG. Resuscitation with Hextend® decreases endogenous circulating heparinactivity and accelerates clot initiation after hemorrhage in the rabbit. Anesth Analg

2001;93:1106–10.

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5. McCammon AT, Wright JP, Figueroa M, Nielsen VG. Hemodilution with albumin, but notHextend®, results in hypercoagulability as assessed by thrombelastography in rabbits: roleof heparin-dependent serpins and factor VIII complex. Anesth Analg 2002:95:844–50.

Skin Sensitivity to Rocuronium and

Vecuronium: Prick-Tests Are NotIntradermal TestTo the Editor:

We read with interest the study by Dhonneur et al. (1). The authorsreport a 50% and 40% incidence of positive skin reaction to undilutedrocuronium and vecuronium, respectively. They state that these resultsare in contradiction with the recent guidelines published by the SociétéFrançaise d’Anesthésie et de Réanimation (SFAR) (2). Unfortunately,these authors did not follow the recommendations for positivity crite-ria established by SFAR. In these guidelines, the criterion of a positiveprick test is theappearance ofan edematous whealwitha diameterat least3 mm greater than that induced by the negative control solution. Incontrast, for Dhonneur et al., the association of a wheal and a flare definesa positive skin reaction irrespective of their size. Moreover, by injecting 50L, the authors confuse prick-testing which corresponds to an injection of a volume of 20 nL, and intradermal testing which requires an injection of 20 to 50 L. Use of completely different criteria and administration of atleast 1000-fold more allergen than recommended by SFAR may explainthe unexpected high proportion of positive reactions observed.

The authors state that their observations are supported by arecent Scandinavian report (3). Unfortunately, in the latter no pos-itive prick test to undiluted rocuronium or cisatracurium was re-ported. Similarly, other large studies from the literature publishedin different countries are in contradiction with Dhonneur et al.’sresults (4,5). The authors also claim that their results are in line withthose reported by Levy et al. (6). Unfortunately, no prick-test wasperformed in this study.

Finally, Dhonneur et al. suggest that their findings may explainthe intriguingly high incidence of allergic reactions in France andcall into doubt whether NMBDs are the main cause of anaphylaxisduring anesthesia (7,8). However, anaphylactic reactions to anes-

thetic drugs have been reported in Australia, New Zealand, theUnited Kingdom, Norway, Belgium, and Spain with a similar esti-mated incidence, and in all these studies, NMBDs are the mostcommon cause of anaphylaxis during anesthesia.

In conclusion, the results reported by Dhonneur et al. are, in ouropinion, in contradiction with the literature, and we do not believethat they support the conclusion drawn by these authors regardingthe reality of the risk of anaphylaxis during anesthesia.

P. M. Mertes, MD, PhDM. C. Laxenaire,Department of Anesthesia and Intensive CareUniversity Hospital of Nancy, France

[email protected]

J. M. Malinovsky, MD , PhDDepartment of Anesthesia and Intensive CareUniversity Hospital of Reims, France

E. Florvaag, MDLaboratory of Clinical Biochemistry

Haukeland University HospitalBergen, Norway

D. A. Moneret-Vautrin, MDDepartment of AllergologyUniversity Hospital of Nancy, France

References1. Dhonneur G, Combes X, Chassard D, Merle JC. Skin sensitivity to rocuronium and

vecuronium: a randomized controlled prick-testing study in healthy volunteers.Anesth Analg 2004;98:986–9.

2. Reducing the risk of anaphylaxis during anaesthesia [abbreviated text]. Ann Fr AnesthReanim 2002;21(Suppl 1):7s–23s.

3. Berg CM, Heier T, Wilhelmsen V, Florvaag E. Rocuronium and cisatracurium-positiveskin tests in non-allergic volunteers: determination of drug concentration thresholdsusing a dilution titration technique. Acta Anaesthesiol Scand 2003;47:576–82.

4. Leynadier F, Sansarricq M, Didier JM, Dry J. Prick tests in the diagnosis of anaphylaxis

to general anaesthetics. Br J Anaesth 1987;59:683–9.

5. Fisher MM, Bowey CJ. Intradermal compared with prick testing in the diagnosis of anaesthetic allergy. Br J Anaesth 1997;79:59– 63.

6. Levy JH, Gottge M, Szlam F, et al. Weal and flare responses to intradermal rocuroniumand cisatracurium in humans. Br J Anaesth 2000;85:844–9.

7. Laxenaire M, Mertes PM, Groupe d’Etudes des Reactions Anaphylactoides Peranes-thesiques. Anaphylaxis during anaesthesia: results of a 2 year survey in France. Br JAnaesth 2001;87:549–58.

8. Mertes PM, Alla F, Laxenaire MC, Anaphylactic and anaphylactoid reactions occurringduring anesthesia in France in 1999 –2000. Anesthesiology 2003;99:536–45

DOI: 10.1213/01.ANE.0000149043.37250.61

In Response:

I want to thank Mertes et al. for offering such an important tribuneto argue comments and remarks about the results, methodology anddiscussion of our study (1). Before giving a point-by-point responseto Mertes et al., I would like to specify that I am not an expert inimmunology and I do not make a living in the neuromuscular

blocking drugs nor the allergy industry.Regarding the Methods section, Mertes et al. suggests that we

“confused prick testing and intradermal testing.” This remark is notacceptable and I believe that the title of this letter is inappropriate.We did not perform any injection of any sort but just applied GoodClinical Practice (GCP) recommendations for prick testing. GCPsare GCPs! A single investigator working in the cosmetic departmentof one of the most important French CRO performed all prick tests.A calibrated 50-L drop of a solution is placed on the skin on theforearm that is pricked with a commercially available device: 1-mmtip at 1 mm deep 20 nL of active substance delivered. Under theseconditions, the amount of active substance, rather than “allergen,” isstrictly linked to the concentration of the contact solution.

The present letter also states that we did not follow the recom-mendations for “positivity” criteria established by SFAR. Of course,we did not. We challenged the skin of selected healthy volunteers,and we defined arbitrarily in the Methods section our criteria of positive skin reaction. Indeed, the association of a wheal and flarecharacterized in our study a positive reaction irrespective of theirsize. As written in the introduction section, “this study was per-formed to determine the concentration-response curves for pricktests with rocuronium and vecuronium in healthy volunteers” butnot to diagnose allergy. We did investigate the relationship betweendose of relaxants and skin responses looking at a nonspecific effect

of aminosteroid drugs that we characterized for the flare responses.Our results are not disputable because of the study design.Regarding the Discussion section, we never affirmed that our

results were “in contradiction with the recent guidelines published by the SFAR but rather that ”our observations contrast“ with theFrench group’s estimation of normally nonreactive concentration of rocuronium and vecuronium. Guidelines are guidelines and ourresults cannot be in contradiction with guidelines. On the otherhand, our results question the pertinence of recommendations forclinical diagnosis of allergy. Discussion and interpretation of ourresults is based on these recommendations.

To putour results in perspective,we strictly applied the onecriterionfor positive prick test proposed by the French group recalled by Merteset al. in this letter: an edematous wheal with a diameter at least 3 mmgreater than that induced by the negative control solution. Calculationof the area of a wheal reaction is linked to its diameter. Since none of

our volunteers reacted to the negative control solution, all prick-testswere considered positive if the surface of the wheal was greater than7 mm2 [ * (3.0/2) (2)]. To assess the quality of our results, weapplied other criteria for positive prick tests (some are proposed in Eu-rope, other in the United States) such as comparing individual weal orflare surface ratios between that of the positive control and active dilutedsolutions of relaxants. Interestingly, this quality control procedure dem-onstrated that wherever the cursor is placed, there are at least 15% of thevolunteers being significantly responsive to undiluted rocuronium andvecuronium, respectively. Although allergy is of rare occurrence in anes-thesia, I am convincedthat a rate offalse positive10%is unacceptable fora diagnostic test. Even under this new insight our conclusion remainspertinent, prick tests to undiluted stock solutions of aminosteroids musclerelaxants should not be used to diagnose or confirm allergy.

Although, the formulation is awkward, our results confirm theobservations of both Berg et al. (2) and Levy et al. (3) that demon-

strated frequent false positive rate associated with “skin testing”

ANESTH ANALG LETTERS TO THE EDITOR 15392005;100:1537–49


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and pleaded in their respective papers for a clinically applicablediscriminant test technique able to separate true positive tests fromfalse positive tests. Moreover, I cannot understand how our resultscan be in contradiction with other large studies published in differ-ent countries such as that of Fisher et al. (4) and Leynadier et al. (5),since these studies were performed in patients suspected or knownto be allergic but not in healthy volunteers.

As all clinicians, I am still waiting for an important study includ-ing a large cohort of healthy volunteers from several countries andof different skin colors tested to determine real skin sensitivity toNMBAs, unless this study has already been performed in France butnot published. Unfortunately, in the absence of such major study for

better application of skin testing and validation of other diagnosticapproach of allergy to anesthetic drugs, it is not certain that we aremaking the correct diagnostic of allergy to rocuronium and vecu-ronium using prick responses to undiluted stock solutions.

We are aware that the French group has performed an immense taskin the area of allergy and largely “sensitized” all anesthesiologists (notonly French professionals) to this risk. We are better prepared for suchrisk, and special operating diagnostic and therapeutic procedures arenow systematically applied in case of suspicion of an allergic accident.The French group did a great job for patients’ security. We accept thefact that neuromuscular blocking drugs are probably the most com-

mon cause of anaphylaxis during anesthesia. However, real incidenceof allergy is difficult to establish and do vary among countries. Report-ing problems pollute the numerator, and the denominator is highlyvariable. Dr. Levy (6) suggested in an editorial that the only way toexplain this widely divergent perspective is to understand how thediagnosis is made and to define threshold skin tests concentrations.This was our main goal.

We believe that there is now probably enough material that callsinto question the past practice of skin testing in anesthesia for ourFrench eminent specialists, the leaders in this area, to manageindisputable international studies and propose worldwide-agreedguidelines for the diagnostic of allergy in anesthesia.

We also believe that stigmatizing neuromuscular blocking drugsor dealing with fear of allergy is an attitude that promotes “epider-mic reactions” and blocks off the potential allergic risk of otherdrugs used in the clinical practice of anesthesia.

Gilles Dhonneur, MDDepartment of Anesthesia and Critical Care Medicine Henri Mondor University Hospital of CréteilUniversity of Paris XII Val-de-MarneSchool of Medicine of CréteilCrétei l, France

[email protected]

References1. Dhonneur G, Combes X, Chassard D, Merle JC. Skin sensitivity to rocuronium and

vecuronium: a randomized controlled prick-testing study in healthy volunteers.Anesth Analg 2004;98:986–9.

2. Berg CM, Heier T, Wilhelmsen V, Florvaag E. Rocuronium and cisatracurium-positiveskin tests in non-allergic volunteers: determination of drug concentration thresholdsusing a dilution titration technique. Acta Anaesthesiol Scand 2003;47:576–82.

3. Levy JH, Gottge M, Szlam F, et al. Weal and flare responses to intradermal rocuroniumand cisatracurium in humans. Br J Anaesth 2000;85:844–9.

4. Fisher MM, Bowey CJ. Intradermal compared with prick testing in the diagnosis of anaesthetic allergy. Br J Anaesth 1997;79:59– 63.

5. Leynadier F, Sansarricq M, Didier JM, Dry J. Prick tests in the diagnosis of anaphylaxis

to general anaesthetics. Br J Anaesth 1987;59:683–9.6. JH Levy. Anaphylactic reactions to neuromuscular blocking drugs: are we making thecorrect diagnosis. Anesth Analg 2005;98:881–2.

Local Anesthetics for Breakthrough Pain inPatients Receiving Intrathecal Treatment forCancer Pain ManagementTo the Editor:

Neuraxial administration of drugs is often used to optimize the treat-ment in patients no longer responsive to systemic analgesics (1). De-spite optimal analgesia, patients may suffer from fluctuations in painintensity (breakthrough pain) (2). This condition is challenging forphysician, as no specific indications have been provided for patients

receiving a continuous spinal drug combination. We report three casesof patients selected for intrathecal therapy, implanted with a port-system and an external pump, and presenting breakthrough episodestreated by the use of local anesthetics as needed. The first patient, a57-year-old male, with colon cancer was admitted for abdominal paindue to extensive visceral involvement. The second patient was a 40-year-old female, admitted for unbearable pain due to pelvic relapse of

colon cancer, presenting multiple metastases (spleen, pancreas, leftcolon, presacral area, left ischiorectal fossa, bladder, left ala ilii, abdom-inal wall, ureter, lung, and liver). She complained of abdominal-pelvicpain with irradiation to the left leg, with a mixed component, visceral,neuropathic, and somatic. The third patient, a 76-year-old male withlung cancer, was admitted for vertebral, chest wall, and shoulder pain,irradiated to the left arm, which increased in intensity on movementdue to chest wall involvement. An intrathecal catheter was introducedat the level of corresponding segmental area and connected with asubcutaneous port placed in the anterior thoracic wall, after tunnelingthe catheter subcutaneously. The proper position of the catheter tipwas checked by contrast medium injection. These patients received anintrathecal mixture containing morphine and levobupivacaine, indoses of 25–80 mg and 6–40 mg, respectively, with a mean infusionrate of levobupivacaine of 37 mg/day (about 1.5 mg/h), allowing anacceptable basal pain relief (4 on a numerical scale of 0–10). Episodes

of breakthrough pain, unresponsive to large doses of systemic opioids,were relieved by intrathecal boluses of about 1.25 mg (0.5 mL of levobupivacaine), by a three-way stopcock placed in the external sys-tem, close to the port. This means that the dose required to treat

breakthrough events was approximately the hourly dose. No infectionsigns or important hemodynamic changes were observed, despite therepeated boluses. Of interest, the treatment was subsequently main-tained at home by properly instructed relatives, without reportingcomplications for a survival time of 10, 45, 32 days, respectively. Thisis the first report on the use of local anesthetics as an intrathecal bolusfor treating breakthrough pain in cancer patients receiving a spinalanalgesic treatment. This treatment should be reserved to very selectedpopulation, providing the best methods to prevent the risk of infectiondue to the high rate of manipulations.

Sebastiano Mercadante, MDPatrizia Ferrera, MD

Patrizia Villari, MD Anesthesia and Intensive Care UnitPain Relief and Palliative Care UnitLa Maddalena Cancer CenterPalermo, [email protected]

Edoardo Arcuri, MDIntensive Care and Pain Therapy UnitNational Cancer Institute Regina ElenaRome, Italy

References1. Mercadante S. Problems of long-term spinal opioid treatment in advanced cancer

patients. Pain 1999;79:1–13.2. Portenoy RK, Hagen NA. Breakthrough pain: definition, prevalence, and characteris-

tics. Pain 1990;41:273–81.

DOI: 10.1213/01.ANE.0000149045.24425.68

An Uncommon Complication of ThoracicEpidural Anesthesia: Pleural PunctureTo the Editor:

Thoracic epidural analgesia is commonly used to provide perioper-ative analgesia in patients undergoing thoracic surgery, and pleuralpuncture by the needle or the catheter is an uncommon and alife-threatening complication (1–4).

A 67-year-old female patient, body mass index 36 kg/m2 (weight,105 kg; height, 170 cm) was scheduled for lobectomy. The awakepatient was placed in the left lateral decubitus position. An 18-gauge Tuohy needle was inserted at the T6–7 interspace with amidline approach. Technical difficulties were encountered becauseof poor body landmarks and decreased resistance of the deeper



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tissue levels. On the fourth attempt, a loss of resistance to saline wasdetected, and the epidural catheter was threaded easily. No chestsymptoms were observed. Ten milliliters of 0.25% bupivacaine and100 g fentanyl were injected from the catheter. Unfortunately,there was not enough time to assess the level of sensory block beforethe induction. When the chest cavity was entered, the epiduralcatheter was found penetrating the parietal pleura in close proxim-ity to both the spine and the thoracic aorta (Fig. 1). There was noobvious bleeding or injury to the lung. The catheter was withdrawnand the postoperative course was uncomplicated.

Only few cases about the misplacement of the thoracic catheter

into the pleural cavity have been reported in the literature (1–4). Inmost of these case reports, the paramedian approach was usedduring needle insertion (1–4). Our case report is the only one inwhich the midline approach was used. The paramedian approach tothe thoracic epidural space is thought to have fewer potential tech-nical problems but a higher complication rate; therefore, it is be-lieved that the use of the midline approach may minimize the risk(2). However our case report showed that the midline approach isnot free from complications. Sprung et al. (5) investigated the factorsthat may predict the difficulty of performing neuraxial blocks andconcluded that the quality of body landmarks was the most signif-icant independent predictor of difficulty and the obese patients hadthe highest incidence of having poor landmarks.

In conclusion, in obese patients with poor body landmarks, the sensorylevel of analgesia should be assessed preoperatively or the correct place-ment of the catheter should be verified by radiography to decrease the

incidence of technique-related complications during epidural analgesia.Zeynep Eti, MD*Tunç Laçin, MD†Bedrettin Yıldızeli, MD†Varlık Dogan, MD*F. Yılmaz Gögüs, MD*Mustafa Yüksel, MD†*Departments of Anesthesiology and †Thoracic Surgery

Medical Faculty of Marmara UniversityIstanbul, [email protected]

References1. Furuya A, Takashi M, Ozaki M, Kumazawa T. Interpleural misplacement of an

epidural catheter. J Clin Anesth 1998;10:425–6.2. Patt RB, Reddy S, Wu CL, Catania JA. Pneumothorax as a consequence of thoracic

subarachnoid block. Anesth Analg 1994;78:160–2.3. Grieve PP, Whitta RKS. Pleural puncture: an unusual complication of a thoracic

epidural. Anesth Intensive Care 2004;32:113–6.

4. Koch J, Nielsen JU. Rare misplacements of epidural catheters. Anesthesiology 1986;65:556–7.5. Sprung J, Bourke DL, Grass J, et al. Predicting the difficult neuraxial block: a prospec-

tive study. Anesth Analg 1999;89:384–9.

DOI: 10.1213/01.ANE.0000149046.59469.48

Measurement of Isoflurane and DesfluraneDegradationTo the Editor:

Laster et al. (1) suggest that only small amounts of isoflurane and desflu-rane are degraded in their studies of anesthetic absorbent fires. The mon-itoring device used for anesthetic concentrations was a monochromaticinfrared monitor (RGM 5250, Ohmeda, Louisville, CO), which is prone tointerference becausethe infraredabsorbance is measured at a single wave-length. The reported anesthetic concentration is based on a user-enteredcalibration factor for each anesthetic. Because trifluoromethane (CHF3) isproduced during the breakdown of isoflurane and desflurane (2), andinterferes with anesthetic drug monitoring (3), CHF3 may cause falselyelevated reported concentrations of the selected anesthetic. Calcula-tions (not shown) based on our study (3) demonstrate that the RGM5250 monitor reports approximately 0.9% isoflurane or 1.2% desfluranefor each 1% CHF3. The breakdown of 1 mole isoflurane or desfluraneproduces 0.23 and 0.84 moles of CHF3, respectively. Therefore, thereported concentration of isoflurane is falsely elevated by about 21%and desflurane by about 98% of the degraded amount due to theinterference of CHF3. Thus, little if any change in reported desfluraneconcentration can result. Although the ratio of the amount of CHF3produced for each mole of anesthetic degraded depends somewhat onreaction temperature (4), it is probable that little, if any, decrease in theconcentration of desflurane can be detected by the RGM 5250 monitor

because of the interference of CHF3. Figure 5 in Laster et al.’s article (1)may indicate little to no desflurane degradation as a result, and thediscrepancy at the initial measurement may be due to temperaturedependence, since the absorbent is under 25°C at that time.

Marshall B. Dunning III, PhD , MSDivision of Pulmonary/Critical Care [email protected]

Harvey J. Woehlck, MDDepartment of Anesthesiology

Medical College of Wisconsin

Milwaukee, WI

Figure 1. Thoracic epidural catheter lying in the chest cavity.



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References1. Laster M, Roth P, Eger EI II. Fires from the interaction of anesthetics with desiccated

absorbent. Anesth Analg 2004;99:769–74.2. Eger EI II, Strum D. The absorption and degradation of isoflurane and I-653 by dry

soda lime at various temperatures. Anesth Analg 1987;66:1312–5.3. Woehlck HJ, Dunning MB III, et al. The response of anesthetic agent monitors to

trifluoromethane warns of the presence of carbon monoxide from anesthetic break-down. J Clin Monit 1997;13:149–55.

4. Woehlck HJ, Dunning M III, Nithipatikom K, et al. Mass spectrometry provides

warning of carbon monoxide exposure via trifluoromethane. Anesthesiology 1996;84:1489–93.

DOI: 10.1213/01.ANE.0000149047.06813.41

In Response:

Dunning and Woehlck have correctly taken us to task for neglectingthe effect of desflurane degradation products on the RGM 5250 de-termination of desflurane (and isoflurane) concentration. Using gaschromatography, we confirmed the correctness of their criticism bymeasuring the concentrations of desflurane in the presence of des-iccated Baralyme®. Duplicate measurements (two runs) suppliedthe data for desflurane presented in Figure 1. As in the previousstudy (1), peak temperatures of 100°C were reached 20–30 min afterinitiating delivery of 9% desflurane. Temperatures declined there-after, despite appreciable continuing desflurane degradation for upto an hour of desflurane delivery.

Although the data presented in Figure 1 quantitatively differ greatlyfrom the data presented in a similar figure in ouroriginal report (Fig. 5)(1), the qualitative implications are unchanged. Degradation of desflu-rane, and to a lesser extent isoflurane, is not sustained. In contrast,degradation of sevoflurane continues at appreciable levels for theduration of sevoflurane administration (note that data for the full2 hours are not presented because fire occurred in one run, andinclusion of those data would skew the results). The data fordesfluraneand isoflurane are consistent with an action of potassium hydroxide

(KOH) on these anesthetics. The limited presence of KOH (5% of base),and its consequent rapid depletion, restricts the degradation of desflu-rane and isoflurane. Degradation of desflurane decreases faster thandegradation of isoflurane because the concentration of desflurane isthree times greater, thus exhausting the stores of KOH sooner. Thecontinuing degradation of sevoflurane suggests that barium hydroxideand/or calcium hydroxide, as well as KOH, degrade sevoflurane.

The important message of our previous report (1) remains un-changed by the present correction. Sevoflurane degradation by desic-cated Baralyme® can lead to temperatures exceeding 150°C and to firein the anesthetic circuit. In contrast, degradation of desflurane andisoflurane by desiccated Baralyme® leads to lower temperatures (peaksof 100°C), and these lower temperaturesdo not lead to fire. As an aside,we note that a concern that fires from sevoflurane degradation may bemore likely with Baralyme® than soda lime has resulted in the with-drawal of desiccated Baralyme® from commercial use. Whether thisproblem extends to soda lime remains to be determined.

[Dr. Eger is a paid consultant to Baxter Healthcare, the manufac-turer of desflurane.]

Michael J. Laster, DVMPatricia Roth, MDEdmond I Eger II, MDDepartment of Anaesthesia

University of California, San FranciscoSan Francisco, [email protected]

Reference1. Laster M, Roth P, Eger EI II. Fires from the interaction of anesthetics with desiccated

absorbent. Anesth Analg 2004;99:769–74.

Cervical Plexus Block ProvidesPostoperative Analgesia After ClavicleSurgeryTo the Editor:

We report a case of successful postoperative analgesia after clavic-

ular open reduction and internal fixation (ORIF) using a cervicalplexus block (CPB). While an interscalene block could provideanalgesia, at the price of motor and sensory blockade of the upperextremity, using a CPB, to our knowledge, has not been described

before.A healthy 49-year-old woman undergoing right clavicular ORIF

was given preoperatively a deep (C2–C4) and superficial CPB ac-cording to the classic approach (1) using 0.5% bupivacaine. Thesurgical procedure was performed under general anesthesia. Fol-lowing awakening from general anesthesia, the patient was pain-free until 14 hours postoperatively. She then took one dose of oralanalgesics before discharge.

The innervation of the clavicle and the overlying skin variesdepending on the source in the literature between C3 and C6. Figure1 summarizes the dermatome distributions published by severalauthors. The clavicle itself has been reported to be innervated either

by C4, or by C5 and C6 (subclavian nerve).This case demonstrates that a cervical plexus block can provideanalgesia after clavicle ORIF. It remains to be determined whether aCPB could be used as a sole anesthetic for clavicle ORIF in selectedpatients.

Daniel S. Choi, MD , MBAArthur Atchabahian, MDAnthony R. Brown, MDDepartment of AnesthesiologyColumbia University College of Physicians and SurgeonsNew York, NY [email protected]

References1. Adriani J. Blocking of spinal nerves. In: Adriani J, ed. Labat’s Regional anesthesia:

techniques and clinical applications. St. Louis: Warren H. Green, 1985:236–54.2. Foerster O. The dermatomes in man. Brain 1933;56:1–39.3. Head H, Campbell AW. The pathology of herpes zoster and its bearing on sensory

localization. Brain 1900;23:353–523.

Figure 1. Degradation of 1.5 MAC (2.8%) sevoflurane exceeds deg-radation of 1.5 MAC isoflurane (1.8%), which, in turn, exceedsdegradation of 1.5 MAC desflurane (9%). Percent degradation wascalculated as 100 times (the difference between the delivered andend-tidal concentrations) divided by the delivered concentration.Concentrations in the case of desflurane were measured by gaschromatography, whereas concentrations of sevoflurane and isoflu-rane were measured by the Ohmeda RGM 5250 (Louisville, CO). Forthe reasons offered by Dunning and Woehlck, the values for isoflu-

rane probably are underestimated.



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4. Bonica JJ. Applied anatomy relevant to pain. In: Bonica JJ, ed. Management of pain. 2nded. Malvern: Lea & Febiger, 1990:133–58.

5. Keegan JJ, Garrett FD. The segmental distribution of the cutaneous nerves in the limbsof man. Anat Rec 1948;102:409–37.

DOI: 10.1213/01.ANE.0000149049.08815.00

Dangerous Design Flaw in the Ohmeda

Aespire Anesthesia SystemTo the Editor:

We believe there is a dangerous design flaw in the Ohmeda AespireAnesthesia system (Datex-Ohmeda, Helsinki, Finland.). Althoughthis narrative is being prepared as part of a larger article on anes-thesia machine design and safety, we feel that this matter is urgentenough to warrant expedited notification of the readership.

Recently during a routine anesthetic, one of our most experiencedCRNA’s called for engineering assistance when the Model 7100ventilator on a new Aespire anesthesia machine began to intermit-tently fail. During normal controlled ventilation of an adult patient,the ventilator would periodically shut down and a sustained pres-sure alarm would flash. After switching to bag ventilation, theventilator would reset and then function for several minutes until itagain repeated the failure cycle. The machine was removed from

service and evaluated by biomedical engineering. They found that

the machine would indeed abruptly shut off the ventilator and flasha sustained pressure alarm while maintaining a pressure of approx-imately 9 cm H2O in the circuit. The system would reset after severalminutes of hand ventilation by bag. On further examination it wasfound that the waste gas scavenging system’s flow regulator had

been turned nearly to off. On the Aespire system this is located,along with the scavenger bag, in a difficult to access location behindthe left rear leg of the machine. It was determined that the lowsuction flow allowed waste gas to accumulate in the bag and when

the pressure reached 9 cm H2O in the bag, the ventilator was shutoff and the pressure was maintained throughout the patient circuit.We initially assumed this was simply a manufacturing defect, butwere very confused by the fact that, even if a defective pressurerelease valve was not venting waste gas to the atmosphere, why wasthe waste gas scavenging system linked to the ventilator? Afterextensive discussion with Ohmeda’s technical services office, wewere informed that this was, in fact, purposely designed to functionin the manner we encountered! Apparently, the rationale for thisdesign is that, in the event of low suction flow and a buildup of gasin the waste system, it is preferable to shut off ventilation and holdthe patient at 9 cm of CPAP, rather than vent the gas to the roomand contaminate the atmosphere. Ohmeda states that the thresholdfor ventilator shutoff is 7.5 cm H2O, but may vary with fresh gasflow. When we advised Ohmeda that this was unacceptable, theyoffered a choice of replacement valves that would either convert the

system to a full passive unsuctioned or full unregulated active

Figure 1. Dermatome distributions determined by different methods: A, Foerster’s map, constructedusing stimulation of nerve stumps and observing forvasodilatation (2). B, Head’s diagram, from observation of patients with herpes zoster lesions (3). C, Bonica’s map, developed “on the basis of personalobservation and data published by others” (4). D, Keegan’s chart, established on the pattern of hypoalgesia following loss of a single nerve root (5).



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suctioned mode. (Strangely, the full active system still had a flowregulator on the suction hose near the line connector.)

We have subsequently filed an FDA Form 3500 expressing ourconcern about this design feature. Representatives from Ohmeda ad-vise us that this is supplied as standard because some surgical facilitiesare unable to generate the suction flow required for proper evacuationof the system and do not want the full active system. Until recently,

anesthesia machine design and appearance has largely reflected safetyinnovations as a result of lessons learned through clinical misadven-ture. Newer systems, however, are sleeker and more esthetically pleas-ing, while hiding crucial components, such as flow sensors, unidirec-tional valves, and waste gas scavenging systems. This is, in essence, atriumph of style over safety. Furthermore, the desire to accommodatehypothetical fears of trace anesthesia gas in the OR atmosphere hastrumped the very real hazard to individual patients of interruptedventilation and sustained airway pressure. Users of the Aespire anes-thesia system should be aware of this design issue and take care to besure waste gas is evacuated appropriately. On their newest model, theADU, this full suction system is the only available waste gas scaveng-ing system.

George Mychaskiw II, DOProfessor of Anesthesiology

Steve Morris

Director, Perioperative Biomedical EngineeringDepartment of AnesthesiologyUniversity of Mississippi School of Medicine

Jackson, MS [email protected]

DOI: 10.1213/01.ANE.0000149050.32419.20

How Likely Is Awareness DuringAnesthesia?To the Editor:

The report by Sebel et al. (1) provides data on an issue of greatconcern to anesthetists. In a prospective study using a structured

interview, the investigators identified 25 cases of awareness duringanesthesia in 19,575 patients for an incidence of 0.13%. In support of their finding, this incidence parallels the incidence found in severalother similar studies cited by the authors. They added that theirestimate of the incidence was relatively conservative and suggestedthe possibility that the true incidence might be closer to 0.36%. Wesuggest that a contrary interpretation is possible.

1. The investigators appear to define awareness by both objectiveand subjective criteria: the “recalled event was confirmed by attend-ing personnel (objective criteria), or the investigators were con-vinced that the memory was real, but no confirmation could beobtained (subjective criteria).” Awareness during anesthesia is dif-ficult to certify objectively. In our view it requires remembrance of an event by the patient that uniquely connects that remembrance toan event unequivocally occurring during anesthesia/surgery. Thereport by Saucier et al. supplies such an example (2). In the study bySebel et al., the patient who “heard the doctor ask for a stent whichwas identified by a number” meets this criterion, assuming that thesurgeon corroborated the remembrance. However, the patient whosaid she had an out of body experience provides subjective evi-dence. It would be helpful to know how many of the experiences inTable 4 in their article were corroborated by the surgeons/operatingroom staff and which relied solely on convincing the investigators.

2. Awareness during anesthesia (especially during surgery) may bedifficult to distinguish from awareness (remembrance) during awak-ening or in the Post Anesthesia Care Unit (PACU). Could the surgeonsindicate the timing of the remembrance of the voice that said that “thedoctor forgot to connect the catheter of the bag; the floor was full of urine. Other jumbled conversations, someone was angry and yellingabout it.” (“Yelling”? In a hospital in North America?) Without objec-tive confirmation of the time of this conversation, we can only conjec-ture whether this represents recall of an event during surgery, emer-gence from anesthesia, or in the PACU.

3. In the same vein, the authors observed that “we interviewedpatients in the PACU and again after seven days because it has previ-ously been demonstrated that approximately 35% of cases are detectedonly at a delayed postoperative interview (3). Approximately one half of the cases in our study were detected only at the second interview.”Is it possible that repeated interviews of patients who knew they wereparticipating in a study of awareness falsely (albeit unconsciously)

increased the incidence of patients’ self-reports?4. We do not know the number of patients in the present study

only given anesthesia with an IV anesthetic and thus cannot assignan incidence of awareness during one form of anesthesia (IV) versusanother (potent inhaled anesthetic) or, indeed, to one as opposed toanother inhaled anesthetic. This would be useful to know. Is recallmore likely during IV versus inhaled anesthesia? If so, is the studypopulation representative of the surgical population as a whole, inits proportion of patients receiving IV versus inhaled anesthesia?Five of the 25 cases were found in patients who did not receive apotent inhaled anesthetic. In an additional 5 or 6 patients, remem-

brance appears to have taken place during induction of anesthesia,again in the probable absence of a potent inhaled anesthetic. Be-cause anesthesia solely with IV anesthetics is less usual in NorthAmerica, and assuming the study population reflects this practice, itappears that awareness is more likely in patients given general

anesthesia with an IV anesthetic.5. The authors note that others have found an incidence of aware-ness 64% greater (0.18% versus 0.11%) in the presence of neuromus-cular blockade (3). Approximately 80% of the patients with aware-ness in the present study had neuromuscular blocking drugs, andhalf these patients had a sense of paralysis as part of their remem-

brance of awareness. Paralysis is not anesthesia, and 20 of thepatients in the present study may not have been adequately anes-thetized. Of the 5 patients who were not given neuromuscular

blocking drugs, and thus were presumably adequately anesthe-tized, one had an out of body experience (see above), one felt a tubein her throat and did not know if surgery was ongoing (was thisawakening during intubation?), one was concerned about spilturine (see above), one heard the doctor ask for a stent (see above),and one having a procedure for cervical stenosis had a “sensation of two flat surfaces moving on each other leaving sharp, intense pain;felt sensation in the neck, sensation of choking and felt bone beingcut away from the neck” (but despite the report of noxious sensa-tions there is no mention of movement in this unparalyzed patient).Apart from the patient whose surgeon asked for a stent, it is notclear to us that the remaining unparalyzed patients rememberedevents during anesthesia.

6. The authors explored several risk factors for awareness. Wewould have benefited from an evaluation of two that were nottested: 1. Did the choice of anesthetic affect the incidence of aware-ness (IV versus inhaled)? 2. Did the use of neuromuscular blockingdrugs increase the risk of awareness? These may be factors of particular importance because, unlike demographic factors, they areunder the control of the anesthetist.

We suggest that the report by Sebel et al. (1) may overestimate theincidence of awareness during anesthesia. We suggest that patientsadequately anesthetized with a potent inhaled anesthetic (i.e., des-flurane, isoflurane, or sevoflurane at 0.5 MAC or greater) have an

incidence of awareness that is vanishingly small.Dr. Eger is a paid consultant to Baxter Healthcare Corp, the

manufacturer of desflurane.

Edmond I Eger II, MD James M. Sonner, MDDepartment of Anesthesia and Perioperative CareUniversity of California, San FranciscoSan Francisco, [email protected]

References1. Sebel PS, Bowdle TA, Ghoneim MM, et al. The incidence of awareness during anes-

thesia: a multicenter United States study. Anesth Analg 2004;99:833–9.2. Saucier N, Walts LF, Moreland JR. Patient awareness during nitrous oxide, oxygen,

and halothane anesthesia. Anesth Analg 1983;62:239– 40.3. Sandin RH, Enlund G, Samuelsson P, Lennmarken C. Awareness during anaesthesia:

a prospective case study. Lancet 2000;355:707–11.

DOI: 10.1213/01.ANE.0000151467.79077.08



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In Response:

Drs. Eger and Sonner have raised interesting and worthwhile ques-tions about our study that also pertain to most studies of intraop-erative awareness.

Their first point is that the patient’s remembrance of intraop-erative awareness should be unequivocally linked to an intraop-erative event that can be corroborated. We agree that this is themost convincing kind of evidence to have in a case of intraoper-ative awareness. However, if we were to adhere to this very highstandard of evidence, we would almost certainly underestimatethe incidence of intraoperative awareness. Since the patient’sinternal experience is subjective, it is impossible to know the“true” incidence of intraoperative awareness. The most inclusivestandard of evidence forintraoperativeawareness would be simply thepatient’s belief that he or she was awake during surgery. If the patient

believes t hat he or she was awake during surgery, and there is noevidence to the contrary, how can we know that he or she wasnot?

Because of the difficulty in judging the likelihood of intraopera-tive awareness based on patients’ descriptions, we divided thereports in our study into 2 categories, likely awareness and possibleawareness, based on the investigators’ assessments of the reports.Realizing the subjective nature of this data analysis, we deliberately

published the descriptions of the likely awareness cases for thereaders to judge on their own. We believe that the incidence of awareness that we have reported is a reasonable estimate and isunlikely to either greatly overestimate or underestimate the trueincidence.

Eger and Sonner ask whether interviewing the patients in thePACU and then at a later time might cause patients to falsely reportintraoperative awareness. This seems unlikely to us. There wascertainly no benefit of any kind to be gained for the patients indoing so. The questions, which were repeated in the second inter-view, may “jog” the patients’ memories by their repetition but theydo not contain leading information that might cause “false” mem-ories. The second interview was included specifically because of previous studies showing that patients may not report an episode of intraoperative awareness immediately following surgery (1,2).

Eger and Sonner ask whether recall is more likely during IV

versus inhaled anesthesia. Unfortunately, because this study wasnot designed to examine the effects of different anesthetic drugs, thedrug data collected by the study are incomplete and we are not ableto answer this interesting question.

Eger and Sonner state that the “5 patients [with putative intraoper-ative awareness] who were not given neuromuscular blocking drug-s. . .were presumably adequately anesthetized”. We presume theymean because the patients had not received neuromuscular blockingdrugs,and were apparently not movingduring anesthesia, the patientsmust have been adequately anesthetized. We do not agree with thisconcept. Reports of intraoperative awareness occur in the absence of obvious clues to awareness, including the absence of movement, tachy-cardia or hypertension, so the absence of movement does not guaran-tee that the patient is adequately anesthetized or will not have intra-operative awareness. In fact, in the very case report cited by Drs. Egerand Sonner, a patient not receiving neuromuscular blocking drugs had

a well-corroborated episode of intraoperative awareness without anyapparent movement noticed by the anesthesiologist (3).Finally, Drs. Eger and Sonner state that patients receiving potent

inhaled anesthetics at 0.5 MAC or greater have a “vanishingly small”incidence of awareness. We are not sure what “vanishingly small”means, but we believe that an incidence of intraoperative awareness of 0.1%, or 1 in a 1,000 should be improved upon, and there is little doubtthat patients would agree with us. We are not aware of the evidencethat 0.5 MAC end tidal agent results in a “vanishingly small” incidenceof awareness during surgery. While isoflurane at 0.45 MAC preventedrecall in volunteers given verbal stimuli, the authors noted that“whether the arousing effect of surgery may increase the anestheticconcentrations required to prevent conscious and unconscious mem-ory is not known” (4). Since there are many cases of intraoperativeawareness that have been reported in the presence of what appeared tothe anesthesiologist to be adequate doses of potent volatile agent, and

because there is such enormous biological variation in response to

anesthetic agents, we would advise caution in relying on any particular“recipe” of drug or dose for avoiding intraoperative awareness.

T. Andrew Bowdle, MD , PhDUniversity of Washington Medical CenterSeattle, WA

Peter S. Sebel, MB BS, PhD, MBAEmory University School of Medicine

Atlanta, GA [email protected]

Mohamed M. Ghoneim, MDUniversity of IowaIowa City, IA

Ira J. Rampil, MDSUNY Stony Brook, NY

Roger E. Padilla, MD Memorial Sloan-Kettering Cancer CenterNew York, NY

Tong Joo Gan, MB BS, FRCA, FFARCSDuke UniversityDurham, NC

Karen B. Domino, MD , MPH Harborview Medical CenterSeattle, WA

References1. Sandin RH, Enlund G, Samuelsson P, Lennmarken C. Awareness during anaesthesia:

a prospective case study. Lancet 2000;355:707–11.2. Nordstrom O, Englstrom AM, Persson S, Sandin R. Incidence of awareness in total iv

anaesthesia based on propofol, alfentanil and neuromuscular blockade. Acta Anaes-thesiol Scand 1997;41:978– 84.

3. Saucier N, Walts LF, Moreland JR. Patient awareness during nitrous oxide, oxygen andhalothane anesthesia. Anesth Analg 1983;62:239– 40.

4. Dwyer R, Bennett HL, Eger EI, Heilbron D. Effects of isoflurane and nitrous oxide insubanesthetic concentrations on memory and responsiveness in volunteers. Anesthe-siology 1992;77:888–92.

Concern About the Safety of IntrocanSafety® Intravenous Catheters

To the Editor:Leading health care and health care worker safety authorities, includ-ing the Association for Professionals in Infection Control and Epide-miology, Occupational Safety and Health Administration, and Centersfor Disease Control and Prevention have advocated the adoption of passive sharps safety devices (1). The passive Introcan Safety® IVCatheter (B. Braun Medical Inc., Bethlehem, PA) was purchased at ourinstitution to minimize accidental needle sticks without requiring user

Figure 1. Introcan® Safety IV Catheter (22 gauge, 1 inch) withseveral protuberances on the external surface.



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activation and to increase safety for both health care workers andpatients. With the use of the FEP (hexafluoropropylene and polytetra-fluoroethylene) catheters, we frequently noticed that there are protu-

berances on the external surface of these IV catheters (Fig. 1). Althoughno immediate adverse effect would be noticed, this observation wouldremain a concern. FEP is associated with more local tissuereaction thanpercutaneous venous (2), silicone (3), and vialon (4–6) catheters. More

worrisome is that these particles observed on the external surface of theFEP Introcan Safety® IV catheters can be detached upon rubbing theexternal surface of the catheter and have the potential to flow into the

bloodstream, in which case the consequences although not docu-mented, may be at the least undesirable.

Claude Abdallah, MD , MScDivision of AnesthesiologyChildren’s National Medical CenterWashington, [email protected]

References1. Needle points: An AFSCME guide to sharps safety. Washington, DC: American

Federation of State, County and Municipal Employees, 2002:1.2. Reynolds J. Comparison of percutaneous venous catheters and Teflon catheters for

intravenous therapy in neonates. Neonatal Netw 1993;12:33–9.3. Reynolds JV, Walsh K, Ruigrok J, Hyland JM. Randomised comparison of silicone

versus Teflon cannulas for peripheral intravenous nutrition. Ann R Coll Surg Engl

1995;77:447–9.4. Jacquot C, Fauvage B, Bru JP. Peripheral venous catheterization: influence of catheter

composition on the occurrence of thrombophlebitis. Ann Fr Anesth Reanim 1989;8:620– 4.5. Gaukroger PB, Roberts JG, Manners TA. Infusion thrombophlebitis: a prospective

comparison of 645 Vialon and Teflon cannulae in anaesthetic and postoperative use.Anaesth Intensive Care 1988;16:265–71.

6. McKee JM, Shell JA, Warren TA, Campbell VP. Complications of intravenous therapy:a randomized prospective study—Vialon vs. Teflon. J Intraven Nurs 1989;12:288–95.

DOI: 10.1213/01.ANE.0000151469.79550.12

Can Capnography Substitute forAuscultation in Sedation Cases?To the Editor:

Soto et al. (1) found that the frequent apneas that occurred during IV

sedation were readily detected by capnography but “none weredetected by the anesthesia providers.” This is not surprising, sincethe anesthesia providers were not using continuous auscultation,and thus were constrained to recognize apnea visually. Had theyused a simple precordial stethoscope placed in the suprasternalnotch, I suspect that not only would all cases have been detected,

but also before the 20-second lapse required for a CO2-based apneaalarm. Conceivably, an obstructive apnea lasting more than 20seconds could evolve to negative pressure pulmonary edema.

Auscultation is effective in detecting partial airway obstruction,which often precedes complete obstruction, and hypoventilationpreceding central apnea. Diminished and absent breath sounds areimportant findings! Of course, auscultation is not subject to lapseswhile the machine recalibrates.

Although modern electronic monitors have brought basic physi-ology into clinical management, they still do not substitute for the

basic vigilance principle to “always stay in contact with the patient.”Possibilities include visual inspection, auscultation, hand on a

breathing bag, or voice contact during light sedation. The authorsdismissed auscultation by noting that its use has been declining inrecent years. Their conclusion urging research into methods todiagnose antecedents of adverse outcomes might include teachingeffective “hands-on” vigilance skills. Continuous auscultation witha well-fitted earpiece is unencumbering and best of all, providesabundant, free information about the patient not as easily obtainedotherwise.

Quentin A. Fisher, MD, FAAPProfessor of Anesthesia and PediatricsDirector, Pediatric Anesthesia

Medstar-Georgetown University HospitalWashington, DC

[email protected]

Dr. Soto does not wish to respond.

Reference1. Soto RG, Fu ES, Vila H Jr, Miguel RV. Capnography accurately detects apnea during

monitored anesthesia care. Anesth Analg 2004;99:379– 82

DOI: 10.1213/01.ANE.0000151470.50760.4A

Accidental Epidural Injection of PancuroniumTo the Editor:

A 41-year-old man, 51 kg, ASA status I, was scheduled for antero-posterior resection due to cancer of the rectum. Combined epidural-general anesthesia was planned. The epidural catheter was success-fully placed at L2–3 interspace through the 18-gauge Tuohy needleafter the “ loss of resistance to air technique.”

Before induction of general anesthesia, pancuronium (4 mg) wasaccidentally injected through epidural catheter instead of fentanyl100 g.

After induction of general anesthesia with thiopental 5 mg/kg,

the syringe of pancuronium that was prepared for intubation wasfound to be empty. The trachea was then intubated after IVpancuronium 0.1 mg/kg and anesthesia was maintained withN2O, O2, halothane. Neuromuscular blockade was monitored byacceleromyography using train-of-four (TOF-watch®, Organon(Ireland) Ltd, Swords, Dublin, Ireland) mode. The operation wasuneventful and lasted for 3 h. No added neuromuscular blockadefor the entire procedure after the first dose. The patient started to

breath spontaneously during suturing the skin. Neuromuscular blockade was reversed with IV neosti gmine 0.04 mg/kg andatropine 0.02 mg/kg at the end of the operation. TOF ratios were0.4 after 10 min and 0.86 after 25 min, respectively. The tracheawas extubated 30 min later.

He was discharged from the PACU at the 7th postoperative hourwithout any adverse effects and from the hospital on the 14thpostoperative day. He had been followed up for 2 months and there

were no clinical signs of neurotoxicity.Local anesthetics, opioids, and steroids are commonly injectedinto the epidural space in medical practice. In the history of regionalanesthesia, various substances have been accidentally injected intoepidural space, with consequences ranging from no clinical effect toirreversible paralysis (1–4). To our knowledge, no data about acci-dental injection of pancuronium through an epidural catheter inhuman were documented in the literature. In this report, we admin-istered pancuronium both IV and epidurally. We found that thetime from injection of pancuronium epidurally to recovery at TOFratio of 0.86 was 230 min while the action of pancuronium injectedIV was normally lasted for 60–90 min (5). No data on the rate of absorption of pancuronium from the epidural space was found inthe literature. Neuromuscular blocking drugs cause excitement andseizures when introduced into the central nervous system (6–8).Acute intrathecal administration of these drugs leads to dose-

dependent central nervous system effects in the rat (6). Because noclinical or experimental data exist about interaction between pan-curonium and other drugs injected epidurally, no other drugsshould be given at this site.

Although we injected saline into the epidural space to acceleratesystemic absorption of pancuronium (“volume effect”), there is nosufficient evidence in the literature that this maneuver is effective (9).

In conclusion, the anesthesiologist must be careful during admin-istration of the anesthesia, as human error can be catastrophic to thecare of patients.

Janjira Krataijan, MDNawal Laeni, MDDepartment of AnesthesiologyFaculty of MedicinePrince of Songkla University

Hadyai, [email protected]



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References1. Shanker KB, Palkar NV, Nishkala R. Paraplegia following epidural potassium chloride.

Anaesthesia 1985;40:45–7.2. Dahl JB, Jacobsen JB. Accidental epidural narcotic overdose. Anesth Analg 1990;70:

321–2.3. Dror A, Henriksen E. Accidental epidural magnesium sulfate injection. Anesth Analg

1987;66:1020–1.4. Whiteley MH, Laurito CE. Neurologic symptoms after accidental administration of

epidural glucose. Anesth Analg 1997;84:216–7.

5. Savarese JJ, Caldwell JE, Lien CA, Miller RD. Neuromuscular blockade. In: Miller RD,ed. Anesthesia. 5th ed. Philadelphia: Churchill Livingstone, 2000:412–90.

6. Szenhradszky J, Trevor AJ, Bickler P. Central nervous system effects of intrathecalmuscle relaxants in rats. Anesth Analg 1993;76:1304–9.

7. Cardone C, Szenohradszky J, Yost S, Bickler PE. Activation of brain acetylcholinereceptors by neuromuscular blocking drugs: a possible mechanism of neurotoxicity.Anesthesiology 1994;80:1155–61.

8. Scheepestra GL, Vree TB, Crul JF. Convulsive effects and pharmacokinetics of lau-danosine in the rats. Eur J Anaesthesiol 1986;3:371–83.

9. Kostopanagiotou G, Mylona M, Massoura L, Siafaka I. Accidental epidural injection of vecuronium. Anesth Analg 2000;91:1550–1

DOI: 10.1213/01.ANE.0000151471.73967.52

Peripheral Nerve Blocks for PostoperativePain Relief After Total Knee Replacement:

More Questions Than AnswersTo the Editor:

Singelyn et al. (1) reported that a continuous three-in-one femoralnerve block (CFNB) would facilitate rehabilitation after total kneereplacement (TKR). While some authors argue that it would be essen-tial to add an obturator nerve block to the CFNB, others have reportedthat over 80% of the patients had better postoperative analgesia whena continuous sciatic nerve block is added to a CFNB (2,3).

We have compared continuous posterior lumbar (psoas com-partment) blocks (CPCB) and CFNB with a simple morphine IVPCA in a randomized prospective study that included 60 patientsundergoing TKR (4). The obturator nerve was blocked in a sig-nificantly higher percentage of patients with the CPCB technique(90 vs 47%), but during the first 48 h, morphine consumption wasthe same for the two types of continuous nerve blocks (36.1

25.8 vs 37.3 34.7 mg, mean sd). Verbal analogical pain scoresmeasured at rest (6, 24, and 48 h) and during physiotherapy werealso comparable for these two groups (4). Although our studywas not designed to compare the effects of these two regionalanesthesia techniques on rehabilitation, from the data that can beretrospectively retrieved from the charts of these patients one cansee that the difference in the amplitude of the knee flexion

between the CFNB group and the PCA group was small and didnot last beyond the first few days and that there was absolutelyno trend toward a faster rehabilitation in the CPCB group com-pared with the CFNB group (Fig. 1). Furthermore, the number of patients who achieved a 90-degree flexion at 7 days (PCA: 58.3%,CFNB: 66.7%, and CPCB: 60%) and the length of hospitalization(PCA: 7 days [5–30 days], CFNB: 7 days [5–13 days], and CPCB:7 days [5–15 days], median [range]) was not improved by any of the two regional anesthesia techniques.

Since there is an inherent risk of complication with any techniqueand because the addition of any of them would, at least theoreti-cally, increase the number of related complications, it would appearessential to evaluate the real benefits of these proposed combina-tions of peripheral nerve blocks (single shot or continuous) not onlyin term of reduced need for opioids administration, but also in theirreal ability to facilitate rehabilitation.

Joanne Guay, MD, FRCPClinical Associate Professor, AnesthesiaUniversity of Montreal

Montreal, Quebec, Canada [email protected]

Drs. Singelyn and Bouziz do not wish to respond.

References1. Singelyn FJ, Deyaert M, Joris D, et al. Effects of intravenous patient-controlled anal-

gesia with morphine, continuous epidural analgesia, and continuous three-in-one block on postoperative pain and knee rehabilitation after unilateral total knee arthro-plasty Anesth Analg 1998;87:88–92.

2. Macalou D, Trueck S, Meuret P, et al. Postoperative analgesia after total knee replace-ment: the effect of an obturator nerve block added to the femoral 3-in-1 nerve blockAnesth Analg 2004;99:251–4.

3. Ben-David B, Schmalenberger K, Chelly JE. Analgesia after total knee arthroplasty: iscontinuous sciatic blockade needed in addition to continuous femoral blockade?Anesth Analg 2004;98:747–9.

4. Kaloul I, Guay J, Côt é C, Fallaha M. The posterior lumbar ple xus (psoas compartment)and the three-in-one femoral nerve block provide similar postoperative analgesia aftertotal knee replacement. Can J Anaesth 2004;51:45–51.

DOI: 10.1213/01.ANE.0000151472.37849.81

In Response:

Dr. Guay’s recent paper on analgesia following total knee re-placement (1) demonstrated (a) approximately a 50% reduction inopiate consumption with both CFNB and CPCP, (b) a small but

statistically insignificant further reduction in opiate consumptionwith CPCB versus CFNB, (c) a significant reduction in VAS scoreat rest with both techniques, (d) a small but statistically insignificantfurther reduction in VAS with CPCB versus CFNB, and(e) no reduction in VAS with physical therapy. We accept these data asvalid and feel they support our own experience and published work(2). That is, we agree with and accept the conclusion that beyond theanalgesia of femoral blockade, obturator blockademakes only a limitedcontribution to analgesia following TKR.

However, Dr. Guay would have been wise to limit her conclu-sions to the question posed by their study—as to the relative anal-gesic contribution of obturator blockade. We believe that their pa-tients’ opiate needs would have been much further reduced and theanalgesia during PT far more effective had they added continuoussciatic blockade to their protocol. Furthermore, neural blockadedoes not alter the inflammatory response and sensitization (central

or peripheral) and will be far more effective if combined with COX-2

Figure 1. Effects of postoperative analgesic technique on the recoveryof knee flexion after total knee replacement. Retrospective data re-trieved from patients’ charts. PCA: IV morphine patient controlledanalgesia (PCA) alone; CFNB: IV morphine PCA plus continuousthree-in-one femoral nerve block; CPCB: IV morphine PCA plus continu-

ous posterior lumbar plexus (psoas compartment) block. Mean sd

.



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inhibition (3). Where Dr. Guay sees a failed technique (neural block-ade) we see a failure to use the technique properly. One may not beable to travel far in a car with one wheel, but that does not leavewalking as the only option. One might try attaching the other wheels.

More disturbing than extrapolating beyond the limits of her workis Dr. Guay’s use of dubious retrospective “outcome data.” This isworse than meaningless. It is misleading. For example, how do we

know that the physical therapists didn’t actually measure but sim-ply approximated flexion? Would that not lead to fairly routinizedcharting, thus making any comparative data worthless? The ex-tremely long hospitalizations of 7 days suggests that hospital staywas dictated by standard practice rather than by a set of dischargecriteria, thus debasing any conclusion as to the influence of analge-sia technique on hospital length of stay. As she herself noted, theirstudy was not designed to assess rehabilitation. That was correct.She should have heeded her own caution.

On the basis of false extrapolation, meaningless data, and suppo-sition (as to complications), Dr. Guay would admonish us to recon-sider the use of neural blockade as a postoperative analgesic tech-nique. We would admonish her to be more careful with such

baseless, sweeping, and hubristic commentary.

Bruce Ben-David, MD Jacques E. Chelly, MD, PhD , MBA

Department of AnesthesiologyUniversity of Pittsburgh Medical CentersPittsburgh, [email protected]

References1. Kaloul I, Guay J, Côt é C, Fallaha M. The posterior lumbar ple xus (psoas compartment)

and the three-in-one femoral nerve block provide similar postoperative analgesia aftertotal knee replacement. Can J Anaesth 2004;51:45–51.

2. Ben-David B, Schmalenberger K, Chelly JE. Analgesia after total knee arthroplasty: iscontinuous sciatic blockade needed in addition to continuous femoral blockade:Anesth Analg 2004;98:747–9.

3. Buvanendran A, Kroin JS, Tuman KJ, et al. Effects of perioperative administration of aselective cyclooxygenase 2 inhibitor on pain management and recovery of functionafter knee replacement: a randomized controlled trial. JAMA 2003;290:2411–8.

Does Paralysis Contribute to AwarenessUnder Anesthesia?To the Editor:

Sebel et al. (1). deserve commendation for their prospective study of awareness during general anesthesia. The study validated someclinical suspicions (sicker patients undergoing emergent operationsare at high risk) but not others (females are not at higher risk; theeffect of BIS monitoring is undetectable).

One clinical suspicion was not directly addressed. Many clini-cians believe an unparalyzed patient is the best protection againstrecall: presumably an inadequately anesthetized patient will move,provoking more anesthetic before recall occurs. However, this ismerely intuition. Table 4 in their article lists the 25 patients withfrank recall. Four patients did not receive muscle relaxants while 19(80%) did (one patient lacked documentation). If the authors candetermine what percentage of all participating patients receivedmuscle relaxants, they may provide a long-awaited answer to sup-plant a clinical practice based on faith alone.

Samuel Metz, MDOregon Anesthesiology GroupPortland, [email protected]

Reference1. Sebel PS, Bowdle TA, Ghoneim MM, et al. The incidence of awareness during anes-

thesia: multicenter United States study. Anesth Analg 2004;99:833–9

DOI: 10.1213/01.ANE.0000151474.73594.80

In Response:

We thank Dr. Metz for his interest in our study and question concern-ing the relationship of awareness under general anesthesia and neu-romuscular blockade. As Dr. Metz points out, 5 patients in our study

had intraoperative awareness despite the lack of neuromuscular block-ing agents. Although our study was not designed to evaluate therelationship of awareness with anesthetic agents, our limited data forapproximately half of the study patients suggests that neuromuscular

blockade was used in 65% percent of the study patients.The fact that awareness can occur in a patient who is fully capable

of movement is well described in a study of nearly 12,000 Swedish

patients by Sandin et al. (1). The incidence of awareness was 0.10%in the absence of neuromuscular blocking drugs (4 patients), com-pared with 0.18% in the presence of neuromuscular blockade (14patients). In addition, other studies have observed awareness andrecall in the absence of neuromuscular blockade (2). While nonpara-lyzed patients may recall intraoperative events, they may less likelyto describe severe pain or anxiety than patients who are incapable of movement. Sandin et al. (1) found that none of the 4 nonparalyzedpatients had anxiety during the period of recall or postoperativenightmares and anxiety. However, the long-term outcome of pa-tients with intraoperative awareness is unclear, as these investiga-tors found a surprising number of psychological sequelae afterintraoperative awareness in a 2-year postoperative follow-up of their patients (3). In fact, two of the patients who had been awareduring nonrelaxant anesthesia and had denied nightmares in theimmediate postoperative period, developed moderate symptoms of

posttraumatic stress disorder.Thus, awareness with recall during general anesthesia can occurin the absence of neuromuscular blockade. While these episodesmay be associated with less pain or anxiety than in the paralyzedpatient, the ultimate psychological outcome is unclear.

Peter S. Sebel, MB BS, PhD, MBAEmory University School of Medicine

Atlanta, GA [email protected]

T. Andrew Bowdle, MD , PhDUniversity of Washington Medical CenterSeattle, WA

Mohamed M. Ghoneim, MDUniversity of IowaIowa City, IA

Ira J. Rampil, MD

State University of New York Stony Brook, NY

Roger E. Padilla, MD Memorial Sloan-Kettering Cancer CenterNew York, NY

Tong Joo Gan, MB BS, FRCA, FFARCSIDuke UniversityDurham, NC

Karen B. Domino, MD , MPH Harborview Medical CenterSeattle, WA

References1. Sandin RH, Enlund G, Samuelsson P, Lennmarken C. Awareness during anaesthesia:

a prospective case study. Lancet 2000;355:707–11.2. Wennervirta J, Ranta SOV, Hynynen M. Awareness and recall in outpatient anesthesia.

Anesth Analg 2002;95:72–7.3. Lennmarken C, Bildfors K, Enlund G, et al. Victims of awareness. Acta Anaesthesiol

Scand 2002;46:229–31.

Dexamethasone Dose Attenuates Pain onInjection Following DiazepamHydrochlorideTo the Editor:

To test the hypothesis of whether a prior injection of dexamethasoneattenuated or abolished pain following diazepam injection, we con-ducted a randomized, prospective, double-blind, placebo-controlledclinical trial to compare dexamethasone, metoclopramide, and nor-mal saline in 120 ASA class I and II men aged 20–45 years. Thesubjects were randomly allocated into one of the three groups:



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Group 1: 2 mL IV normal saline in one hand and 2 mL dexa-methasone in the other, simultaneously.

Group 2: 2 mL IV normal saline into one hand and 2 mL meto-clopramide in the other, simultaneously.

Group 3: 2 mL IV metoclopramide in one hand and 2 mL dexa-methasone in the other, simultaneously.

After 30 seconds, diazepam hydrochloride was injected simulta-neously into each of patients’ hand veins, and maximal VerbalAnalog Scale (VAS) was assessed for discomfort. In Group 1, themean of VAS for pain was significantly less in dexamethasone thansaline pretreatment (P 0.001), whereas in Group 2, metoclopra-mide pretreatment had significantly more effect than saline in re-ducing pain (P 0.001). In Group 3, the pain observed on abovescale was significantly less in dexamethasone than metoclopramide.In conclusion, although both dexamethasone and metoclopramideproved effective in reducing the severity of pain following diazepam,the former proved to be more efficacious. Efficacy of metoclopramidein reducing pain on injection following diazepam is clear (1).

Ali Movafegh, MDFarid Abolhasan Gharehdaghi, MDZahid Hussain Khan, MDGita Shoeibi, MD

Department of Anesthesiology and Critical CareDr. Ali Shariati HospitalTehran University of Medical SciencesTehran, Iran

[email protected]@movafegh.com

Reference1. Majedi H, Rabiee M, Hussain Khan Z, Hassannasab B. A comparison of metoclopra-

mide and lidocaine for preventing pain on injection on diazepam. Anesth Analg2002;95:1297–9.

DOI: 10.1213/01.ANE.0000151567.76745.A6

Airway Obstruction Due to a Damage tothe Laryngeal MaskTo the Editor:

Drs. von Urgern-Sternberg and Erb reported a case of airwayobstruction during the use of a size 2 laryngeal mask airway due

to an unnoticed detachment of the cuff weld near the device tip(1). There have already been several reports of the same problem(2–4).

The authors were surprised to hear that the manufacturer claimedthe incident was “user’s fault,” because such a deformity may occurduring sterilization if air or moisture is in the cuff (1). If 1–2 mL of air is remaining in the cuff, air may expand by 20 times (up to

40 mL) during sterilization (5). This volume should be no problemfor a size 3 or larger (6), but could in theory decrease the integrity of the cuff of a size 2 or smaller. Water in the cuff evaporates

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