*Assistant Professor

tVisiting Assistant Professor

Address reprint requests to Dr. Pennant at the Department of Anesthesiology and Pain Management, University of Texas South- western Medical School, 5323 Harry Hines Blvd., Dallas, TX 75235-9068, USA.

Received for publication October 26. 1992; revised manuscript accepted for publication January 21, 1993.

01993 Butterworth-Heinemann

Je Glin. Anesth. 522~230, 1993.

Department of Anesthesioiogy and Pain Management, University of Texas South- western Medical School, Dallas, TX.

Study Objective: TO deter-mine zuhelher the luryngeui mask airwuy has a ~usejiul rote in the airway) management of patients whose cervical spines are immobilized in a rigid cervical collar. D)es@: A randomized study comparing the d$fficulty, rapidity, and success rate oj ventilating patients with immobilized cervical spines using a laryngeal mask airwall and an endotracheal tube. Setting: Medical center surgical unit. Patients: Twenty-eight ASA thy sical status I and II women scheduled to undergo elective gynecologic surgery requirirzg general anesthesia. Interventions: Tracheas of all anesthetized patients were sequentially in&rated with an endotracheal tube and had a laryngeal mask inserted in random order. Measurements and Main Results: iMouth opening was measured, and a Mallampati classification iuas made in each subject both -with and without a rigid ~h~~adeLph~a collar in situ. The view at laryngoscopy was recorded. The time taken to insert both devices to allow for satisfactory ventilation and the degree of difficulty encountered were determined. With a cervical collar in situ, mouth opening was reduced u$ to 60%.

The Mallampati assessment and laryngoscopic uiew were shifted to one suggestive of a more difficuit intubation. The time taken to ventilate these patients and the daffiiculties encountered were significantly less when using the laryngeal mask (p = 0.0001). A successful outcome was more likely following insertion of the laryngeal mask than, when attempting intubation with an endotracheal tube. Conclusions: The laryngeal mask airway compared favorably with an endot~a~kea~ tube in success rate, difficulty of insertion, and time to position correctly in this patient population. Although the laryngeal mask does not reliably protect against aspiration, we believe it may plain a useful role if more conventional methods of airways management fail. Further studies in the trauma scenario are indicated.

s: Equipment and supplies-larynx; laryngeal mask airway; imtubation, tracheal; spinal cord anjuries; trauma.

Multiply injured trauma patients frequently present for emergency surgery before radiologic studies of their cervical spines can be completed. To mini- mize the risk of secondary neurologic injury devel g during: Wanspo~: from the Scene of the accident to the operating ro ) or during tracheal intubation, such patients are immobilized in a rig according to proto-

226 2. Clin. Anesth., vol. 5, MaylJune 1993

hyngeal mask and immobile crruicni $xne: Pennant et al,

cols established by the Advanced Trauma Life Support (ATLS) ~~bcornrn~t~e~ of the American College of Sur- geons.! This device impairs adoption of the classic “sniff- ing” Position for laryngoscopy and frequently makes tracheal intubation more difficult. Excessive force may be applied to the tissues during this maneuver, further jeopardizing the integrity of the cervical spine.

The laryngeal mask airway (LMA) has achieved wide- spread popularity for routine general anesthesia and for managing the difficult airway. However, its role in the emergency scenario has yet to be defined. It may not reliably protect the airway from contamination with gas- tric contents We attempted to evaluate its usefulness in airway management using fasted patients immobilized in a semirigid cervical collar and compared these findings with the more conventional technique of tracheal intuba- tion.

s

oval from the Institutional Review oard of the IJni sity of Texas Southwestern Medical enter at Dallas, we obtained written informed consent

from 28 ASA physical status I and II females aged 18 to 5 1 years (mean 29 years), weighing 44 to 130 kg (mean 69 kg), and presenting for minor elective gynecologic surgery requiring tracheal intubation. Patients at risk for

iration of gastric contents were excluded, as were patients with uncontrolled hypertension, disorders of blood coagulation, or known disease of the cervical spine.

All patients were fasted overnight and premeditated with metoclo~ram~de 10 mg and ranitidine 150 mg orally I hour preoperatively. Sodium citrate 30 ml orally was given on arrival in the OR.

urements of the mouth opening between the up nd lower incisor teeth were made, and a Mallam- Pati classification* was assigned to each supine patient before and after the application of an appropriate-size, semirigid, two-piece Philadelphia collar.

With the cervical collar in place and using routine monitoring equipment, including pulse oximeter, Sara- cap capnograph (IPPG, Lenexa, KS), we induced general anesthesia intravenously with thiopental sodium 5 mgi kg and fentanyl.3 kg/kg. Anesthesia was maintained with 1% isoflurane in oxygen. Neuromuscular blockade was obtained using vecnronium 0.1 mgikg.

When complete muscle paralysis was demonstrated with a peripheral nerve stimulator, insertion of either a tracheal tube (TT) or LMA was attempted. Following

rtion and a further period of ventilation, A was removed and the Procedure re-

peated using the other device. Each patient was randomly instrumented with both devices. We all had several years’ anesthesia training and extensive experience with the LMA. A #3 LMA was used in patients weighing less than 65 kg, and a #4 LMA was used in larger patients. The LMA was inserted blindly, as described in the instruction manual.3 The TT was inserted orally using a laryngo- scope with a Macintosh #3 or #4 blade in all cases. The

T&lie B. View of Pharyngeal Structures (as described by Mallampati)* in Supine Patients with amd without a Rigid Cervicai Coliar

I 8 (33) 3 (12.5) ?I ?O (42) 5 (21) 111 6 (25) 13 (54) IV 0 (0) 3 (12.5)

*Mallampati SR, Ga:t SP, Gngino LD, et al: A clinical sign to predict difficult tracheal intubation: a prospective study. Can J Anaesth :985;32:429-34.

Note: Data are number (percentage).

view obtained at laryngoscopy was graded according to Cormack and Lehane’s classification.”

The time taken to insert the LMA or TTwas measured from the moment the face mas was removed until gentle hand ventilation with the reservoir bag produced an end- tidal carbon dioxide greater than 25 mmHg on the cap- nograph. Any problems encountered were recorded, and he difficulty of insertion was assessed using a 10 cm visual analog scale (VAS).

If a decision was made to abandon intubation, the timing was stopped and then resumed at the commence- ment of the next attempt after a Period of face mask ventilation. Once the recordings were complete, the col- !ar was removed and the remainder of the operation continued as planned. All patients were visited postoper- atively to determine whether there were any complica- rions.

The time and difficulty of insertion were statistically compared for both the TT and LMA using a Wilcoxon matched-Pairs signed-rank test.

The range of mouth opening was 3.0 t0 6.0 cm (mean, 4.1 cm) without the collar in place and 1.5 to 5.0 cm (mean, 3.1 cm) when the collar was applied. Similarly, the view of pharyngeal structures visible on maximal mouth opening, as described by Mallampati et a1.2 and modified by Samsoon and Ysung,” demonstrated a shift to classes III and IV when the collar w I). The laryngoscopic view, as described Lehane,” assessed 4I% of patients as g as grade IV.

Three patients could not be incubated with a TT in three attempts despite the experience ofthe anesthesiolo- gist, the use of a stylet, and attempts by an assistant to manipulate the larynx into a more favorable Position. In 2 of se subjects, the view of the larynx was a grade IV, a “blind” attempts to intubate trachea initially resul in esophageal intubation. T 3 patients were easily intubated when the cervical collar was removed and full mobility of the cervical spine restored. The LMA was easily inserted in all 3 patients in 23 to 7’5 seconds

Orzginal Contrzbutions

Be 2. Time for Insertron of Tracheal Tube (TT) and Laryngeal Mask Airway (LMA) and Degree of Difficulty Encountered

Number of patients enrolled lnsertioniintubation failures Number of patients analyzed Insertioniintubation time (SK)*

Minimum Maximum Mean SD

Insertioniintubation difficulty (VAS)? Minimum Maximum Mean SD

28

24

22 26 87 117 32 47 16.6 26.0

0.30 6.70 1.60 1.60

28 3

24

0.50 9.30 4.13 2.97

*p = 0.0001. lip = 0.0001. VAS = visual analog scale.

(mean, 43 seconds). One patient could not be ventilated with the LMA, but her trachea was intubated in 28 sec- onds using a TT. These 4 patients were excluded from statistical analysis of the remaining 24 subjects.

Management of subjects who could be intubated was not always straightforward. Nine patients (37%) required an intubating stylet or manipulation of the cricoid carti- lage to allow intubation with the TT. In one case, it was difficult to negotiate the posterior pharyngeal curve with the LMA, and a laryngoscope was needed to guide the cuff tip around the back of the tongue.

LMA insertion was accomplished in 22 to 87 seconds (mean, 32 seconds) and was successful on the first attempt in 22 patients (91%). Tracheal intubation took 26 to 117 seconds (mean, 46 seconds) and was successfm on the first attempt in 19 patients (79%) (Table 2). These times are significantly different ($I = O.OOOi). At no time did arterial oxygen saturation fall below 90%.

Examination of the WAS (in which the operator as- sessed degree of insertion difficulty from 0 = the easiest insertion possible to 10 = the most difficult) showed a mean score of 1.6 (range, 0.3 to 6.7) for LMA insertion and a mean score of 4.1 (range, 0.5 to 9.3) for intubation. These findings also are significantly different (p = 0.0001).

The multiple-trauma victim poses several airway man- agement dilemmas for the anesthesiologist. As many as 3% of these patients have cervical spine injuries;* be-

“Bryson BE, Mulkey 41, Mumford B, Schwedhelm M, Warren K: Cervical spine injury: incidence and diagnosis [Abstract].j Trauma 1’386:26:669.

tween 25% and ‘75% of these (injuries) are unstable. .?re-. hospital care protocols usually involve the application of a rigid cervical collar. The technique used for securing he airway may have a profound effect on eventual neu- rologic outcome. Selection of the method is best left LIP

to the individual practitioner and will depend on his or her personal preference and experience. Awake tracheal intubation does not appear to increase the frequency of secondary neurologic defects6a7 although carefully per- formed orotracheal intubation using in-line stabilization is equally safe.s

The occurrence of secondary neurologic injury is 7.5 times more common in patients in whom cervical spine damage was not suspected or diagnosed.g Unfortunately, two-thirds of trauma patients have multiple injuries that preclude adequate assessment of the cervical spine, since surgery or other therapeutic maneuvers may need to be performed urgently. The anesthesiologist is often pre- sented with a multiply injured patient who may be hypo- volemic or combative secondary to head injury, hypoxemia, or intoxication. Clearly, awake intubation in such a scenario is inadvisable. Rapid-sequence mduction of generai anesthesia must be performed with the rigid cervical collar in place.

The Philadelphia collar reduces flexion and extension of the cervical spine to about 30% of normall and impairs alignment of the laryngeal axis with the mouth at iaryn- goscopy, making incubation more difficult. Removal of the anterior component of the collar, as practiced by Hastings and Marks,“’ permits greater mouth opening and easier intubation but allows more cervical spine ex- tension, particularly at the atlanto-axial joint.ln This could increase the risk of neurologic injury, aitbough no data exist to support or refute this issue. The ATLS course manual does not offer any guidelines on whether the anterior component of the collar should be removed in these situations,’ We noted that the restriction of mouth opening in our patients was due to the chin abut- ting the anterior component of the collar. Our wore the complete collar for this study, and our measure- ments of mouth opening confirm that it is reduced up to 60% when the collar is applied.

Similarly, the Mallampati assessment also indicated a shift toward classes suggestive of a more difficult intuba- Con (Tabte I), although it was performed with the patient supine. There were more grade 111 and IV ?aryngoscopic views than expected, again implying a difficult or impos- sible intubation.4,5 Normally, fewer than 1% of patients would fall into these categories.4-5

In summary, intubation is safest if the complete collar is worn. Yet paradoxically, immobilization of the neck makes the procedure more difficult. Measures to assist in managing the difficult airway, such as jaw t&rust, chin

lift, and cricoid manipulation, may be impossible to per- form with the collar in place,r3 and ali maneuvers may impart flexion-extension forces to the cervical spine, ne- gating the very principle of the device.

The purpose of our investigation was to evaluate the usefulness of the LMA in managing ventilation of tbe patient with an immobilized cervical spine. Apart from

228 J. Clin. Anesth., vol. 5, May/June 1993

two case rcnorts of its use in elective surgerv.*4.15 to our knowledge’no previous studies exist in vthis’area. Our finding of successful LMA insertion on the first attempt in 91 “/o of the cases is of the same order as in anoth- er study in which a normal intubating position was

suggesting that spinal immobilization does not rect placement. We reasoned that in those

situations where intubation might be impossible because of immobility the LMA could be a useful adjunct to airway management before cricothyroidotomy or trans- tracheal ventilation are attempted. Indeed, the LMA may be a superior method, since cricothyroidotomy is invasive and time-consuming, requires the release ofcricoid pres- sure, may cause spinal movement, and may be difficult to perform with a collar in place. Similarly, transtracheal ventilation may not be easily performed if the head can- not be extended. In addition, it does not protect the airway from aspiration and may not enable hyperventila- tion of bead-injured cases with elevated intracranial pres- sure.ll A recent airway management algorithm suggests using the LMA in the “can’t intubate, can’t ventilate” scenario prior to attempting transtracheal ventilation.17

Our results demonstrate that the LMA is an effective method of ventilation when the cervical spine is immobi- lized. Insertion was both easier and quicker, was success- ful on the first attempt, and was eventually successful in a higher proportion of patients compared with the TT. Intubation with the TT required a stylet or laryngeal manipulation in 37% of the cases, whereas assistance with a laryngoscope was necessary in only one LMA insertion.

e most interesting patients were those in whom we could not secure the airway. Three subjects could not be intubated with the TT despite several at- tempts by an experienced anesthesiologist, use of a stylet, and manipulation of the larynx. In each case, only the tip of the epiglottis was visualized (Cormack and Lehane’s grade IV).+z5 In two cases, an attempt to blindly pass the TT behind the epiglottis resulted in intubation of the esophagus. The LMA was successfully placed in all three failed intubations in a mean time of 43 seconds. All were

tubated with the TT following removal of the suggesting that immobilization per

eexisting abnormality of the airway sible for the difficulty encountered.

The reason for difficulty in inserting the LMA into the patient who could not be ventilated with this device is unclear. Xv0 attempt was made to introduce a laryngo- scope gently to ascertain or remedy the problem, but it is most likely that the tip had snagged on the posterior pharyngeal wall, causing the cuff to fold back on itself, as has been reported elsewhere.18

To our knowledge, the VAS has not been previously used as a measure of intubating difficulty. Unfortunately, our VAS was subject to investigator bias. We believe that the estimated degree of difficulty in using a laryngoscope was directly related to the extension force applied to the cervical spine. It is our subjective belief that considerably greater stress was imparted to structures in the neck when a laryngoscope was used in an attempt to bring the larynx into view compared with the relatively atraumatic

tqngeal mask and immobile cervical spine: Pennant et al.

insertion of the LMA. These impressions codd not be quantified or subjected to statistical analysis but clearly become important considerations if there is s bility. A modified laryngoscope capable of measuring intubation forces has recently been described,19 and fur- ther studies of this phenomenon will be useful.

Both the #3 and #4 LMA have a 12 mm internal diameter silicone shaft that is more rigid than a TT. When in position, the L A may act as an internal strut and provide stability to the upper cervical spine, although no data exist to support or refute this view.

For patients presenting for emergency surgery with uncleared cervical spines, it may be necessary to perform

induction of general anesthesia using Gentie laryngoscopy should be per-

d orotracheal tube inserted with the neck immobilized in a rigid cervical collar. Removal of the anterior component of the collar and in-line stabiliza- tion of the cervical spine may allow successfuP tracheal intubation. Should this maneuver prove difficult, the LMA may be an effective temporizing measure to obtain an airway while cricothyroidotomy or transtracheal venti- lation is attempted. As stated earlier, the ATLS protocol is unclear regarding the undoing of t must remember that spinal stability is r collar is removed. Nevertheless, it is reasonable to at- tempt a gentle intubation wit&i the collar undone before either a LMA is inserted or a surgicaii airway is obtained. Once the LMA is in place, it may be used as an aid to tracheal intubation.20a21

The risk of aspiration with the LMA remains unre- solved but appears to be small in elective case+ and may outweigh the disastrous consequences of hypoxemia in the trauma victim whose trachea cannot be intubated.23 Furthermore, ventilation with a face mask leaves the air- -way completely unprotected, Insertion of the LMA in the field in a semiconscious patient with possible spinal injuries is not likely to be successful, but then neither Is tracheal intubation. If pulmonary aspiration has oc- curred, if pulmonary compliance is po& (e.g.> hemotho- rax or pulmonary contusion is present), or if upper airway pathology exists (e.g., hematoma or tissue disrup- tion has occurred), use of the LMA is contraindicated. The leak around the cuff (which occurs at an airway pressure of 15 to 20 cmH@) may prohibit effective venti- lation.

Since our study investigated airway management by experienced anesthesiologists in healthy9 fasted females with intact cervical spines, extrapolati.on of our findings to the multiply injured trauma patient are only specula- tive. The LMA also may be useful in managing the elec- live patient with known cervical spine instability. Further studies are indicated to evaluate the role of the LMA in these situations.

:. .4dvanced Trauma Lfe &@ort Course Mand.. Chicago: Ameri- can College of Surgeons, Chicago, 3991:153.

2. Mallampad SR, Gatt SP, Gugino LD, et ai: A clinical sign to

J. Clin. Anesth., voi. 5, y/June 1993 229

Origznal Contribwtions

3.

4.

5

6.

7.

8.

9.

10.

! 1.

12.

13.

predict difficult sracheai intubation: a prospective study. can ] Anaesth 1985;32:429-34.

management and spiinnng techniques. Ann !?in~l-g :Wrd !984;13:584-7.

Brain AIJ: The Intavent Laryngeal Mask. Instruction Manual. 2cE ed. Henley-on-Thames, LJK:Intavent, 1991.

Cormack RS, LehaneJ: Difficult tracheal intubation in obstet- rics. Anaesthesia 1984;39: 1105-l 1.

Samsoon CL, Young JR: Difficult tracheal intubation: a retro- spective study. Anaesthesia 1987;42:487-90.

Crosby ET: Tracheal intubation in the cervical spine-injured patient. CanJ Anaesth 1992;39: 105-9.

Meschino A, Devitt JH, Koch JP, Szalai JP, Schwartz ML: The safety of awake tracheal intubation in cervical spine injury. Can / Anaesth 1992;39: 114-7.

Suderman VS, Crosby ET, Lui A: Elective oral tracheal intuba- tion in cervical spine-injured adults. Can J Anaesth 1991; 38:785-9.

Reid DC, Henderson R, Saboe L, Miller JD: Etiology and clini- cal course of missed spine fractures.: Trauma 1987;27:980-6.

Johnson RM, Hart DL, Simmons EF, Ramsby GR, Southwick WO: Cervical orthoses. A study comparing their effectiveness in restricting cervical motion in normal subjects. J Bone Joint surg 1977;59:332-9.

14.

15.

16.

17.

ia.

19.

20.

21.

22.

23.

Thomson KD, Ordman AJ, Parkhouse N, Morgan RG: Use oii the Brain laryngeal mask airway in anticipation of difficult tracheal intubation. BrJ Plast Surg 1989;42:478-80. Logan AS: Use of the laryngeal mask in a patient with an unstable fracture of the cervical spine [Letter]. Anaesthesia 1991;46:987. Brodrick PM, Webster NR, Dunn JF: The laryngeal mask air- way. A study of 100 patients during spontaneous breathing. Anaesthesia 1989:44:238-41. Benumof JL: Management of the difficult adult airway. With special emphasis on awake tracheal intubation. Anesthesiology 1991;75:1087-110. Nandi PR, Nunn JF, Charlesworth CH, Taylor SJ: Radioiogical study of the laryngeal mask. Eur J Ancestheszol 1991; Sllppl4:33-9. Bucx MJ, Scheck PA, Van Gee! RT, Den Ouden AH, ?jiesing R: Measurement of forces during laryngoscopy. Anaesthesia 1992;47:348-5 1. Heath ML, AllagainJ: Intubation through the laryngeal mask. A technique for unexpected difficult intubation. Anaesthesia 1991;46:545-8.

Hastings RH, Marks JD: Airway management for trauma pa- tients with potential cervical spine injuries. Anesth Analg !991;73:471-82.

Benumof JL: Use of the laryngeal mask airway to facilitate fiberscope-aided tracheal intubation [Letter]. Anesth Analg 1992;74:313-5.

Horton WA, Fahy L, Charters P: Disposition of cervical verte- brae, atlanto-axial joint, hyoid and mandible during x-ray lar- yngoscopy. Br J Anaesth 1989;63:435-8.

Vergese Cc, Smith TGC, Young E: A prospective survey on the use of the laryngeal mask airway in 2359 patients. Anaesthesia (In press).

Aprahamian C, Thompson BM, Finger WA, Darin JC: Experi- mental cervical spine injury model: evaluation of airway

Greene MK, Roden R, Hinchley 6: The!aryngeal mask airway. Two cases of prehospital trauma care. Anaesthesia 1992; 47:688-g.

Tracheal In

Ottawa General Hospital, TJniversity of Ottawa, Ottawa, Cana

eiay in the diagnosis of clinica;ly important fractures still occurs in 10% of the spine-injured patients. The most common factors cited in delayed diagnosis are failure to x-ray and misinterpretation of the x-ray. The incidence of secondary neurological injury in these patients is comparable with outcomes generated 20 years ago. . . . There is little doubt of the value in maintaining a high index of suspicion for neck injury in trauma victims, of maintaining neck immobilization until a assess-

f stability is completed, and aggressively pursuing such assessments in at-risk s in reducing the incidence of secondary injury and preserving neurological

t1on. . . . There are abundant data that confirm that induction of general anaesthesia followed by tracheal intubation is widely performed in neck-injured patients and that the resulting good neurological outcomes compare favorably with similar patient populations undergoing awake tracheal intubation. . Finally, there is good evidence that in-line immobilization appropriately performed during airway manoeuvres results in a reduction in the amount of spinal movement and that, overall, immobilization reduces the likelihood of secondary injury.

eprinted with permission from the CanadianJourrml ofAna&hesia 1992;39: 105-I 09.

J. Clin. Anesth., vol. 5, May/June I993