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    DOI 10.1378/chest.07-02912007;132;1678-1687Chest

    Steven M. Hollenberg

    *Vasopressor Support in Septic Shock

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    services can be found online on the World Wide Web at:The online version of this article, along with updated information and

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    written permission of the copyright holder.

    this article or PDF may be reproduced or distributed without the priorDundee Road, Northbrook, IL 60062. All rights reserved. No part ofCopyright2007by the American College of Chest Physicians, 3300Physicians. It has been published monthly since 1935.

    is the official journal of the American College of ChestChest

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    Vasopressor Support in Septic Shock*

    Steven M. Hollenberg, MD, FCCP

    When fluid administration fails to restore an adequate arterial pressure and organ perfusion inpatients with septic shock, therapy with vasopressor agents should be initiated. The ultimate goalsof such therapy in patients with shock are to restore effective tissue perfusion and to normalizecellular metabolism. Although arterial pressure is the end point of vasopressor therapy, and therestoration of adequate pressure is the criterion of effectiveness, BP does not always equate toblood flow; so, the precise BP goal to target is not necessarily the same in all patients. There hasbeen longstanding debate about whether one catecholamine vasopressor agent is superior toanother, but different agents have different effects on pressure and flow. The argument about

    which catecholamine is best in a given situation is best transformed into a discussion about which

    agent is best suited to implement the therapeutic strategy chosen. Despite the complexpathophysiology of sepsis, an underlying approach to its hemodynamic support can be formulatedthat takes both pressure and perfusion into account when choosing therapeutic interventions.The efficacy of hemodynamic therapy in sepsis should be assessed by monitoring a combinationof clinical and hemodynamic parameters. How to optimize regional blood and microcirculatoryblood flow remains uncertain. Thus, specific end points for therapy are debatable and are likelyto evolve. Nonetheless, the idea that clinicians should define specific goals and end points, titratetherapies to those end points, and evaluate the results of their interventions on an ongoing basisremains a fundamental principle. (CHEST 2007; 132:16781687)

    Key words: dopamine; epinephrine; norepinephrine; phenylephrine; sepsis; septic shock; vasopressin; vasopressor

    Abbreviations: ACCCM American College of Critical Care Medicine; pHi intracellular pH

    Septic shock results when infectious agents orinfection-induced mediators in the bloodstream

    produce hemodynamic decompensation. Its patho-genesis involves a complex interaction among patho-logic vasodilation, relative and absolute hypovolemia,myocardial dysfunction, and altered blood flow dis-tribution due to the inflammatory response to infec-tion; even after the restoration of intravascular vol-

    ume, microcirculatory abnormalities may persist andlead to the maldistribution of cardiac output.1,2

    About half of the patients who succumb to septicshock die of multiple organ system failure, and mostother nonsurvivors have progressive hypotensionwith low systemic vascular resistance that is refrac-tory to therapy with vasopressor agents.1 Althoughmyocardial dysfunction is not uncommon, deathfrom myocardial failure is rare.3

    The initial priority in managing septic shock is tomaintain a reasonable mean arterial pressure andcardiac output to keep the patient alive while thesource of infection is identified and addressed. An-other therapeutic goal is to interrupt the pathogenicsequence leading to septic shock. While these lattergoals are being pursued, adequate organ systemperfusion and function must be maintained, guidedby cardiovascular monitoring.

    This review will focus on vasopressor support forpatients with septic shock. Hemodynamic therapyfor sepsis can be conceptualized in three broad

    *From the Robert Wood Johnson Medical School/University ofMedicine and Dentistry of New Jersey, Camden, NJ.The author has reported to the ACCP that no significant conflictsof interest exist with any companies/organizations whose productsor services may be discussed in this article.Manuscript received January 31, 2007; revision accepted April16, 2007.Reproduction of this article is prohibited without written permissionfrom the American College of Chest Physicians (www.chestjournal.org/misc/reprints.shtml).Correspondence to: Steven M. Hollenberg, MD, FCCP, Divisionsof Cardiovascular Disease and Critical Care Medicine, CooperUniversity Hospital, One Cooper Plaza, 366 Dorrance, Camden,

    NJ 08103; e-mail: [email protected]: 10.1378/chest.07-0291

    CHEST Postgraduate Education CornerCONTEMPORARYREVIEWS IN CRITICALCARE MEDICINE

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    categories: fluid resuscitation, vasopressor therapy,and inotropic therapy. Although many vasoactiveagents have both vasopressor and inotropic actions,the distinction is made on the basis of the intendedgoals of therapy; vasopressor actions raise BP, whileinotropic actions raise cardiac output. This is not tominimize the importance of assessing the effects of vasoactive agents on perfusion, as should be made

    clear from the discussion below.

    General Approach

    Septic shock requires early, vigorous resuscitation.An integrated approach directed at rapidly restoringsystemic oxygen delivery and improving tissue oxy-genation has been demonstrated4 to improve survivalsignificantly in patients with septic shock. While thespecific approach that is utilized may vary, there arecritical elements that should be incorporated into

    any resuscitative effort. Therapy should be guided byparameters that reflect the adequacy of tissue andorgan perfusion. Fluid infusion should be vigorousand titrated to clinical end points of volume reple-tion. Systemic oxygen delivery should be supportedby ensuring arterial oxygen saturation, maintainingadequate levels of hemoglobin, and using vasoactiveagents that are directed to physiologic and clinicalend points.

    In shock states, the estimation of BP using a cuff maybe inaccurate, and the use of an arterial cannulaprovides a more appropriate and reproducible mea-

    surement of arterial pressure.5,6

    These catheters alsoallow beat-to-beat analysis so that decisions regardingtherapy can be based on immediate and reproducibleBP information, facilitating the administration of largequantities of fluids and potent vasopressor and inotro-pic agents to critically ill patients.1

    Although patients with shock and mild hypovole-mia may be treated successfully with rapid fluidreplacement alone, hemodynamic monitoring maybe useful in providing a diagnostic hemodynamicassessment in patients with moderate or severeshock. In addition, because hemodynamics can

    change rapidly in patients with sepsis, and becausenoninvasive evaluation is frequently incorrect inestimating filling pressures and cardiac output, he-modynamic monitoring is often useful for monitor-ing the response to therapy.

    Goals and Monitoring of Vasopressor Therapy

    When fluid administration fails to restore an ade-quate arterial pressure and organ perfusion, therapy with vasopressor agents should be initiated.6 Theultimate goals of hemodynamic therapy in patientswith shock are to restore effective tissue perfusion

    and to normalize cellular metabolism. In patients with septic shock, tissue hypoperfusion results notonly from decreased perfusion pressure attributableto hypotension but also from abnormal shunting of anormal or increased cardiac output.1 Cellular alter-ations may also occur. Hemodynamic support ofsepsis thus requires the consideration of both globaland regional perfusion.

    Arterial pressure is the end point of vasopressortherapy, and the restoration of adequate pressure isthe criterion of effectiveness. BP, however, does notalways equate to blood flow, and the precise level ofmean arterial BP to aim for is not necessarily thesame in all patients. Animal studies7,8 have suggestedthat below a mean arterial BP of 60 mm Hg,autoregulation in the coronary, renal, and CNSvascular beds is compromised, and flow may becomelinearly dependent on BP. Loss of autoregulation canoccur at different levels in different organs, however,

    and the degree to which septic patients retain intactautoregulation is uncertain. Some patients (espe-cially those with preexisting hypertension) may re-quire higher BPs to maintain adequate perfusion.

    The precise BP goal to target in patients withseptic shock remains uncertain. Most experts agree,largely on the basis of the animal studies cited aboveand on physiologic reasoning, that in septic patients with evidence of hypoperfusion, the mean arterialpressure should be maintained at 60 mm Hg6 or65 mm Hg.9 There are no data from randomizedclinical trials demonstrating that failure to maintain

    BP at this level worsens outcome, but it seemsunlikely that such a clinical trial will be conductedsoon. It should be recognized that individual patientsmay have BPs that are somewhat lower than thesethresholds without hypoperfusion; it is the scenarioof hypotension with shock that merits vasopressorsupport.

    Some investigators, however, have argued thathigher BP targets are warranted. The renal circulationmay be especially sensitive to perfusion pressure, andvasopressor therapy to augment renal perfusion pres-sure has been shown to increase urine output and/or

    creatinine clearance in a number of open-label clinicalseries1017; the targeted mean BP varied, but was ashigh as 75 mm Hg. Improvements in renal functionwith increased perfusion pressure, however, have notbeen demonstrated in prospective, randomized studies.Randomized trials18,19 comparing norepinephrine ti-trated to either 65 or 85 mm Hg in patients with septicshock have found no significant differences in meta-bolic variables or renal function.

    It is important to supplement end points such asBP with an assessment of regional and global perfu-sion. Bedside clinical assessment provides a good

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    indication of global perfusion. Indications of de-creased perfusion include oliguria, clouded senso-rium, delayed capillary refill, and cool skin. Somecaution is necessary in interpreting these signs inseptic patients, however, since organ dysfunction canoccur in the absence of global hypoperfusion.

    Clinical assessments can be supplemented byother measures, such as serum lactate levels and

    mixed venous oxygen saturation. Elevated lactatelevels in patients with sepsis may result from globalhypoperfusion or from cellular metabolic alterations,which may or may not represent tissue hypoxia,20 butits prognostic value, particularly of the trend inlactate concentrations, has been well established inseptic shock patients.2123 Mixed venous oxyhemo-globin saturation reflects the balance between oxy-gen delivery and consumption, and can be elevatedin septic patients due to the maldistribution of bloodflow, so values must be interpreted in the context ofthe wider hemodynamic picture. Low values, how-

    ever, suggest increased oxygen extraction and there-fore potentially incomplete resuscitation. A 2001study4 showed that the monitoring of central venousoxygen saturation can be a valuable guide to earlyresuscitation. The correlation between central ve-nous oxygen saturation and mixed venous oxyhemo-globin saturation is reasonable,24 but may not alwaysbe reliable.25

    The adequacy of regional perfusion is usually as-sessed clinically.1 Methods for measuring regional per-fusion more directly have been under investigation, with a focus on the splanchnic circulation, which is

    especially susceptible to ischemia and may drive organfailure.26 Measurements of oxygen saturation in thehepatic vein have revealed oxygen desaturation in asubset of septic patients, suggesting that the hepato-splanchnic oxygen supply may be inadequate in somepatients, even when more global parameters appear tobe adequate.27 Direct visualization of the sublingualcirculation28 or sublingual capnometry29 may be usefulto monitor the restoration of microvascular perfusion inpatients with sepsis.

    Adrenergic Agents

    There has been longstanding debate about whether one catecholamine vasopressor agent issuperior to another. While these discussions areenlightening in that they tend to highlight differ-ences in pharmacology among the agents, sometimesthe arguments tend to focus on the agents them-selves when actually it is the therapeutic strategy thatdiffers. Different catecholamine agents have differ-ent effects on -adrenergic and -adrenergic recep-tors, as shown in Figure 1. The hemodynamic actions

    of these receptors are well known, with -adrenergicreceptors promoting vasoconstriction, 1-adrenergicreceptors increasing heart rate and myocardial con-tractility, and 2-adrenergic receptors causing pe-ripheral vasodilation.

    The result of these differential effects on adren-ergic receptors is that the different agents havedifferent effects on pressure and flow, as shown inFigure 2. Conceived in these terms, the argumentabout which catecholamine is best to use in a givensituation is transformed into a discussion aboutwhich agent is best suited to implement the thera-peutic strategy chosen. This may or may not makethe choice easier, but it does emphasize the need todefine the goals and end points of therapy, and toidentify how those end points will be monitored.

    Individual Vasopressor Agents

    Dopamine

    Dopamine, the natural precursor of norepineph-rine and epinephrine, has distinct dose-dependentpharmacologic effects. At doses of 5 g/kg/min,dopaminergic receptors are activated, leading tovasodilation in the renal and mesenteric beds.30 Atdoses of 5 to 10 g/kg/min, 1-adrenergic effectspredominate, increasing cardiac contractility andheart rate. At doses of 10 g/kg/min, 1-adrener-gic effects predominate, leading to arterial vasocon-striction and an increase in BP. There is a great dealof overlap in these effects, particularly in critically illpatients.

    Figure 1. -adrenergic and -adrenergic effects of vasoactivecatecholamines.

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    Dopamine increases mean arterial pressure andcardiac output, primarily due to an increase in strokevolume, and to a lesser extent to an increase in heartrate.3141 In open-label trials,3141 dopamine (me-dian dose, 15 g/kg/min) increased mean arterialpressure by 24% in septic patients who remainedhypotensive after receiving optimal fluid resuscita-

    tion. Dopamine has been shown to increase oxygendelivery, but its effects on calculated or measuredoxygen consumption have been mixed, suggestingthat tissue oxygenation may not always be improved,perhaps due to a failure to improve microcirculatoryflow.32,33,42,43 The effect of dopamine on splanchnicperfusion has also been mixed. Increases in splanch-nic blood flow have been reported,31,32,34,4446 buthave not always been associated with increases insplanchnic oxygen consumption, beneficial effects ongastric intramucosal pH, or improvement in hepato-splanchnic energy balance.

    Low doses of dopamine increase renal blood flowand glomerular filtration rate in laboratory animalsand healthy volunteers, supporting the idea thatdopamine can reduce the risk of renal failure incritically ill patients by increasing renal blood flow.This notion has now been put to rest by a definitiveclinical trial47 that randomized 328 critically ill pa-tients with early renal dysfunction to low-dose (re-nal) dopamine (2 g/kg/min) or placebo. No differ-ence was found in either the primary outcome (peakserum creatinine level), other renal outcomes (in-crease in creatinine level, need for renal replace-

    ment, and urine output), or secondary outcomes(survival to either ICU or hospital discharge, ICU orhospital stay, or arrhythmias).47

    Dopamine use was associated with increased mor-tality in patients with shock in an observationalcohort study48 of 198 European ICUs and remaineda significant predictor after multivariate analysis.Given the limitations of observational studies, thisfinding will need to be confirmed by prospectivestudies. A large prospective randomized clinical trialcomparing dopamine to norepinephrine in patientswith septic shock is ongoing.

    Dopamine effectively increases mean arterialpressure in patients who remain hypotensive afteroptimal volume expansion, largely as a result ofincreasing cardiac index, so it may be chosen inpatients with compromised cardiac function or car-diac reserve. Its major side effects are tachycardiaand arrhythmogenesis, both of which are moreprominent than with other vasopressor agents. Thereis also concern about the potential for decreasedprolactin release, lymphocyte apoptosis, and conse-quent immunosuppression.49,50

    Norepinephrine

    Norepinephrine is a potent -adrenergic agonist with less pronounced -adrenergic agonist effects.Norepinephrine increases mean arterial pressure byvasoconstriction, with a small increase (10 to 15%) incardiac output and stroke volume.1012,16,51,52 Fillingpressures are either unchanged1012,16,53 or modestly

    increased (1 to 3 mm Hg).15,17,32,34,36Norepinephrine is more potent than dopamine

    and may be more effective at reversing hypo-tension in septic shock patients. In open-labeltrials,11,12,16,17,34,5255 norepinephrine administrationat doses ranging from 0.01 to 3.3 g/kg/min has beenshown to increase mean arterial pressure in patientswho remained hypotensive after fluid resuscitationand dopamine. The large doses of the drug requiredin some patients may be due to -receptor down-regulation in sepsis.56

    In the only randomized trial36 comparing vaso-

    pressor agents, 32 volume-resuscitated septic pa-tients were given either dopamine or norepinephrineto achieve and maintain normal hemodynamic andoxygen transport parameters for at least 6 h. Dopa-mine administration was successful in only 31% ofpatients, whereas norepinephrine administration(mean [ SD] dose, 1.5 1.2 g/kg/min) was suc-cessful in 93% (p 0.001). Of the 11 patients whodid not respond to dopamine, 10 responded whennorepinephrine was added to therapy. Serum lactatelevels were decreased as well, suggesting that nor-epinephrine therapy improved tissue oxygenation.36

    Figure 2. Effects of vasoactive catecholamines on pressure and

    blood flow. PE phenylephrine; NE norepinephrine;Dopa dopamine; Epi epinephrine; Dobut dobutamine;Dopex dopexamine; Iso isoproterenol.

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    The vasoconstrictive effects of norepinephrine canhave detrimental effects on renal hemodynamics inpatients with hypotension and hypovolemia, with apotential for renal ischemia.5759 The situation maydiffer in adequately resuscitated patients with hyper-dynamic septic shock.15 Norepinephrine has agreater effect on efferent than afferent renal arterio-lar resistance and increases the filtration fraction.Several studies10,13,15,17,32,36,37,53,60 have shown in-creases in urine output and renal function in patientswith septic shock treated with norepinephrine aloneor with norepinephrine added to dobutamine.

    The results of studies of the effects of norepineph-rine on splanchnic blood flow in patients with septicshock have been mixed. The effects of norepinephrineon both splanchnic blood flow and oxygen consumptionhave been unpredictable both among patients andwithin groups.31,34 Comparisons between norepineph-rine and other vasoactive agents have also been vari-able. One pilot study32 found that gastric mucosalintracellular pH (pHi) was significantly increased dur-ing 3 h of treatment with norepinephrine but signifi-cantly decreased during treatment with dopamine. Amore recent study61 compared the effects of norepi-nephrine, epinephrine, and dopamine in 20 patients with septic shock. In the 10 patients with moderateshock, no differences in splanchnic blood flow orgastric-arterial Pco2 difference were observed. In the10 patients with severe shock, the effects of norepi-nephrine and dopamine were similar. Epinephrineincreased cardiac index more than norepinephrine, butsplanchnic blood flow was lower despite this highercardiac index.61

    Norepinephrine can increase BP in patients withseptic shock without causing a deterioration in cardiacindex and organ function. Although the effect of thedrug on oxygen transport variables and splanchnicparameters has varied in different studies, other clinicalparameters of peripheral perfusion, such as urine flowand lactate concentration, are significantly improved inmost studies. In a multivariate analysis62 including 97septic shock patients, mortality was favorably influ-enced by the use of norepinephrine; the use of high-dose dopamine, epinephrine, or dobutamine had nosignificant effect. Controlled data comparing norepi-nephrine to other catecholaminergic agents are sparse, with only one randomized study.36 Whether usingnorepinephrine in septic shock patients affects mortal-ity compared to dopamine or epinephrine will hope-fully be clarified by the ongoing prospective clinicaltrials.

    Phenylephrine

    Phenylephrine, a selective 1-adrenergic agonist,increases BP by vasoconstriction. Its rapid onset,

    short duration, and primary vascular effects make itan attractive agent in the management of hypoten-sion associated with sepsis, but there are concernsabout its potential to reduce cardiac output in thesepatients.

    Few studies have evaluated the use of phenyleph-rine in patients with hyperdynamic sepsis. As such,guidelines on its clinical use are limited. Phenyleph-rine has been shown to increase BP when adminis-tered to normotensive hyperdynamic septic patientsat doses of 0.5 to 8 g/kg/min, with little change incardiac output or stroke volume.63,64

    Only one small study65 of 13 patients has evaluatedthe effects of phenylephrine on treating patients withhypotension associated with sepsis. Phenylephrineadded to either low-dose dopamine or dobutamineincreased mean arterial pressure and cardiac indexwithout a change in heart rate. A significant increasein urine output without a change in serum creatininelevel was observed during phenylephrine therapy.65

    The limited information available on phenyleph-rine therapy suggests that this drug can increase BPmodestly in fluid-resuscitated septic shock patientswithout impairing cardiac or renal function. Phenyl-ephrine is a second-line agent but may be a goodtherapeutic option when tachyarrhythmias limittherapy with other vasopressors.6

    Epinephrine

    Epinephrine is a potent -adrenergic and -ad-renergic agent that increases mean arterial pressure

    by increasing both cardiac index and peripheral vascular tone.14,6668 Epinephrine increases oxygendelivery, but oxygen consumption may be increasedas well.6670 Lactate levels can be increased after theuse of epinephrine in sepsis patients, althoughwhether this results from excess vasoconstriction andcompromised perfusion or increased lactate produc-tion remains uncertain.54,66,70

    The chief concern with the use of epinephrine inpatients with sepsis is the potential to decreaseregional blood flow, particularly in the splanchniccirculation.54,7173 In a study61 of patients with severe

    septic shock, epinephrine administration increasedglobal oxygen delivery and consumption, but causedlower absolute and fractional splanchnic blood flowand lower indocyanine green clearance, thus validat-ing the adverse effects of therapy with epinephrinealone on the splanchnic circulation. Another grouphas reported74 improved gastric mucosal perfusion with epinephrine compared to a norepinephrine/dobutamine combination, but subsequently the samegroup reported superiority of a therapy with a nor-epinephrine/dopexamine combination over therapywith epinephrine.75 A fairly large (n 330) random-

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    ized clinical trial76 comparing therapy with epineph-rine to that with norepinephrine with or withoutdobutamine has been completed, and preliminaryresults were reported at the European Society ofIntensive Care Medicine meeting; no significantdifference was found in the rates of 28-day mortality,ICU mortality, or hospital mortality.

    Epinephrine administration can increase BP inpatients who are unresponsive to traditional agents.It increases heart rate, and has the potential toinduce tachyarrhythmias, ischemia, and hypoglyce-mia. Because of its effects on gastric blood flow andits propensity to increase lactate concentrations,epinephrine has been considered a second-lineagent, the use of which should be considered inpatients failing to respond to traditional therapies.6

    Vasopressin

    Vasopressin is a peptide hormone that is synthe-

    sized in the hypothalamus and is then transported toand stored in the pituitary gland. Released in re-sponse to decreases in blood volume, decreasedintravascular volume, and increased plasma osmola-lity, vasopressin constricts vascular smooth muscledirectly via V1 receptors and also increases respon-siveness of the vasculature to catecholamines.77,78

    Vasopressin may also increase BP by the inhibition ofvascular smooth muscle nitric oxide production79 andK-ATP channels.78,80

    Normal levels of vasopressin have little effect onBP in physiologic conditions,77 but vasopressin helps

    to maintain BP during hypovolemia,81 and seems torestore impaired hemodynamic mechanisms and alsoto inhibit pathologic vascular responses in patients with shock.78 Increased levels of vasopressin havebeen documented in patients with hemorrhagicshock,82 but a growing body of evidence indicatesthat this response is abnormal or blunted in those with septic shock. One study83 found markedly in-creased levels of circulating vasopressin in 12 pa-tients with cardiogenic shock, but much lower levelsin 19 patients with septic shock, which were hypoth-esized to be inappropriately low. One potential

    mechanism for this relative vasopressin deficiencywould be the depletion of pituitary stores, possibly inconjunction with impaired synthesis. The depletionof vasopressin stores in the neurohypophysis evalu-ated by MRI has in fact been described in a smallgroup of septic shock patients.84 A 2003 prospectivecohort study85 of patients with septic shock foundthat vasopressin levels were almost always elevatedin the initial hours of septic shock and decreasedafterward; relative vasopressin deficiency, as definedby the investigators, developed in one third ofpatients.

    Given this theoretical rationale, observationalstudies8688 have demonstrated that the addition of alow dose of vasopressin (0.01 to 0.04 U/min) to acourse of catecholamines can raise BP in patientswith pressor-refractory septic shock. Two small ran-domized studies89,90 comparing vasopressin to nor-epinephrine have demonstrated that the initiation of vasopressin decreases catecholamine requirements,

    and one of these89 showed improved renal function.Similar data are available for terlipressin, a syntheticvasopressin analog.91 There is concern, however, that vasopressin infusion in septic patients may eitherdecrease splanchnic perfusion or redistribute bloodflow away from the splanchnic mucosa.92,93 Vaso-pressin should be thought of as replacement therapyfor relative deficiency rather than as a vasopressoragent to be titrated to effect.

    A large randomized clinical trial (Vasopressin vsNorepinephrine in Septic Shock Study)94 has nowbeen completed comparing vasopressin to norepi-

    nephrine therapy in 776 patients with pressor-de-pendent septic shock, and the preliminary resultswere presented at the European Society of IntensiveCare Medicine meeting. Patients were randomizedto receive vasopressin (0.03 U/min) or 15 g/minnorepinephrine in addition to their original vasopres-sor infusion; the primary end point was 28-daymortality rate; a prespecified subgroup analysis wasperformed in patients with less severe septic shock(norepinephrine, 5 to 14 g/min) and more severeseptic shock (norepinephrine, 15 g/min). For thegroup as a whole, there was no difference in mortal-

    ity, but vasopressin appeared to be better in the lesssevere subgroup.94

    Vasopressin (0.03 U/min) added to norepineph-rine appears to be as safe and effective as norepi-nephrine in fluid-resuscitated patients with septicshock. Vasopressin may be more effective in patientsreceiving lower doses of norepinephrine than whenstarted as rescue therapy, although the answer to thequestion of what therapy to administer in patients with high vasopressor requirements despite vaso-pressin infusion remains uncertain.

    Complications of Vasopressor Therapy

    All of the catecholamine vasopressor agents cancause significant tachycardia, especially in patientswho have received inadequate volume resuscitation.Tachyarrhythmias can occur as well. In patients withsignificant coronary atherosclerosis, vasopressor-induced coronary artery constriction may precipitatemyocardial ischemia and infarction; this is of partic-ular concern in patients treated with vasopressin. Inthe presence of myocardial dysfunction, excessive

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    vasoconstriction can decrease stroke volume, cardiacoutput, and oxygen delivery. Should this occur, thedose of the vasopressor should be lowered or theaddition of an inotropic agent such as dobutamineshould be considered.52 Excessive doses of vasopres-sors can also cause limb ischemia and necrosis.

    The administration of vasopressors may potentiallyimpair blood flow to the splanchnic system, and this

    can be manifested by stress ulceration, ileus, malab-sorption, and even bowel infarction.54,70 Gut mucosalintegrity occupies a key position in the pathogenesisof multiple organ failure, and countercurrent flow insplanchnic microcirculation gives the gut a highercritical threshold for oxygen delivery than otherorgans. Thus, it makes sense to avoid episodes ofintramucosal acidosis, which might be detected ei-ther by a fall in gastric mucosal pHi or an increase ingastric mucosal Pco2, if possible. Whether to moni-tor these parameters routinely is less certain, as pHior gastric Pco2-directed care has not been shown to

    reduce mortality in patients with septic shock inprospective randomized controlled trials.

    Consensus Recommendations

    Consensus recommendations regarding vasopres-sor support in patients with septic shock have beenput forth by the American College of Critical CareMedicine (ACCCM)6,95 and the Surviving Sepsiscampaign9; these recommendations differ more in wording than in substance, and are compiled in

    Table 1. The Surviving Sepsis campaign will likelyamend the vasopressin section to take the Vasopres-sin vs Norepinephrine in Septic Shock Study trialresults under consideration.

    Conclusion

    The ultimate goals of hemodynamic therapy inshock are to restore effective tissue perfusion and tonormalize cellular metabolism. In patients with sep-sis, both global and regional perfusion must be

    considered. In addition, mediators of sepsis canperturb cellular metabolism, leading to the inade-quate utilization of oxygen and other nutrients de-spite adequate perfusion; one would not expectorgan dysfunction mediated by such abnormalities tobe corrected by hemodynamic therapy.

    Despite the complex pathophysiology of sepsis, anunderlying approach to its hemodynamic supportcan be formulated that is particularly pertinent withrespect to vasoactive agents. Both arterial pressureand tissue perfusion must be taken into account when choosing therapeutic interventions, and the

    efficacy of hemodynamic therapy should be assessedby monitoring a combination of clinical and hemo-dynamic parameters. It is relatively easy to raise BP,but somewhat harder to raise cardiac output in septicpatients. How to optimize regional blood and micro-circulatory blood flow remains uncertain. Thus, spe-cific end points for therapy are debatable and arelikely to evolve. Nonetheless, the idea that clinicians

    should define specific goals and end points, titratetherapies to those end points, and evaluate theresults of their interventions on an ongoing basisremains a fundamental principle. The ACCCM prac-tice parameters6,95 were intended to emphasize theimportance of such an approach so as to provide afoundation for the rational choice of vasoactiveagents in the context of evolving monitoring tech-niques and therapeutic approaches.

    References

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    DOI 10.1378/chest.07-02912007;132; 1678-1687Chest

    Steven M. Hollenberg

    *Vasopressor Support in Septic Shock

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