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CHAPTER 33: Shock 249

• Hatib F, Jansen JRC, Pinsky MR. Peripheral vascular decoupling CHAPTER Shock
in porcine endotoxic shock. J Appl Physiol. 2011;111(3):853-860.
doi: 10.1152/japplphysiol.00066.2011. [physiological study dem- 33 Keith R. Walley
onstrating why changes in peripheral vasomotor may markedly
impair existing cardiac output algorithms ability to estimate
cardiac output because peripheral vascular compliance changes
can be great]
• LeDoux D, Astiz ME, Carpati CM, Rackow EC. Effects of perfu- KEY POINTS
sion pressure on tissue perfusion in septic shock. Crit Care Med. • Shock is present when there is evidence of multisystem organ
2000;28:2729-2732. [rationale for targeting a mean arterial pressure hypoperfusion; it often presents as decreased mean blood pressure.
of >60 mm Hg] • Initial resuscitation aims to establish adequate airway, breathing,
• Lopes MR, Oliveira MA, Pereira VO, Lemos IP, Auler JO Jr, and circulation. Rapid initial resuscitation (usefully driven by pro-
Michard F. Goal-directed fluid management based on pulse pres- tocol) is fundamental for improved outcome, since “time is tissue.”
sure variation monitoring during high-risk surgery: a pilot ran-
domized controlled trial. Crit Care. 2007;11:R100. [clinical trial • A working diagnosis or clinical hypothesis of the cause of shock
using pulse pressure variation minimization to improve outcome in should always be made immediately, while treatment is initiated,
high-risk surgical patients] based on clinical presentation, physical examination, and by
observing the response to therapy.
• Marik PE, Levitov A, Young A, Andrews L. The use of bioreac-
tance and carotid Doppler to determine volume responsiveness • Drug and/or definitive therapy for specific causes of shock must be
and blood flow redistribution following passive leg raising in considered and implemented early (eg, hemostasis for hemorrhage,
hemodynamically unstable patients. Chest. 2013;143(2):364-370. revascularization for myocardial infarction, appropriate antibiotics, etc).
• Michard F, Teboul JL. Predicting fluid responsiveness in ICU • The most common causes of shock are high cardiac output hypoten-
patients. Chest. 2002;121:2000-2008. [meta-analysis demonstrat- sion, or septic shock; reduced venous return despite normal pump
ing the uselessness of traditional static hemodynamic measures to function, or hypovolemic shock; reduced pump function of the heart,
predict volume responsiveness] or cardiogenic shock; and obstruction of the circulation, or obstruc-
tive shock. Overlapping etiologies can confuse the diagnosis, as can a
• Moller JT, Pedersen T, Rasmussen LS, et al. Randomized evaluation short list of other less common etiologies, which are often separated
of pulse oximetry in 20,802 patients: I- design, demography, pulse by echocardiography and pulmonary artery catheterization.
oximetry failure rate and overall complication rate. Anesthesiology.
1993;78:436-444. [largest study to examine pulse oximetry showing • Shock has a hemodynamic component, which is the focus of the
absolutely no clinical outcome benefit] initial resuscitation, but shock has also a systemic inflammatory
component (ameliorated by rapid initial resuscitation) that leads to
• Pearse R, Dawson D, Fawcett J, Rhodes A, Grounds RM, Bennett adverse sequelae including subsequent organ system dysfunction.
ED. Early goal-directed therapy after major surgery reduces com-
plications and duration of hospital stay. A randomised, controlled
trial [ISRCTN38797445]. Crit Care. 2005;9:R687-R693. [functional
application of hemodynamic monitoring to guide resuscitation therapy This chapter discusses shock with respect to the bedside approach: first
in postoperative critically ill patients] with an early working diagnosis, then an approach to urgent resuscita-
• Pinsky MR. Hemodynamic evaluation and monitoring in the ICU. tion that confirms or changes the working diagnosis, followed by a pause
Chest. 2007;132:2020-2029. [overview of the rationale for hemody- to ponder the broader differential diagnosis of the types of shock and the
namic monitoring] pathophysiology of shock leading to potential adverse sequelae. Effective
• Reinhart K, Kuhn HJ, Hartog C, Bredle DL. Continuous central initial diagnosis and treatment at a rapid pace depend in large part on
venous and pulmonary artery oxygen saturation monitoring in understanding cardiovascular pathophysiology.
the critically ill. Intensive Care Med. 2004;30:1572-1578. [one of the
ESTABLISHING A WORKING DIAGNOSIS
larger original studies showing the similarities and differences in Sv O 2
in humans]
and Scv O 2 OF THE CAUSE OF SHOCK
• Rhodes A, Cecconi M, Hamilton M, et al. Goal-directed therapy ■
in high-risk surgical patients: a 15-year follow-up study. Intensive DEFINITION OF SHOCK
Care Med. 2010:36:1327-1332. [long-term follow-up documenting Shock is present if evidence of multisystem organ hypoperfusion is appar-
improved patient-centered outcomes for goal-directed therapy] ent. Evidence of hypoperfusion includes tachycardia, tachypnea, low
• Shah MR, Hasselblad V, Stevenson LW, et al. Impact of the pul- mean blood pressure, diaphoresis, poorly perfused skin and extremities,
monary artery catheter in critically ill patients: meta-analysis of altered mental status, and decreased urine output. Hypotension has spe-
randomized clinical trials. JAMA. 2005;294:1664-1670. [systematic cial importance because it commonly occurs during shock, because blood
review of many of the clinical studies showing no effect of pulmonary pressure is easily measured, and because extreme hypotension always
artery catheterization on outcome from critical illness] results in shock. Important caveats are (1) relatively low blood pressure is
• Vincent JL, Rhodes A, Perel A, et al. Update on hemodynamic normal in some healthy individuals and (2) systolic blood pressure may
monitoring: a consensus of 16. Crit Care. 2011;15:229 [position be preserved in some patients in shock by excessive sympathetic tone. In
statement on all the devices discussed in this chapter from a diverse the latter case, it is important to anticipate that sedation will unmask
group of extremely well-published investigators] hypotension. Further, cuff blood pressure measurements may mark-
edly underestimate central blood pressure in low flow states. The focus
1
of initial resuscitation is reversing the hemodynamic component of
shock, which leads to tissue hypoxia and lactic acidosis. However, all
REFERENCES types of shock are also associated with a systemic inflammatory compo-
nent that is a key contributor to subsequent multisystem organ failure
Complete references available online at www.mhprofessional.com/hall and death. The development of the systemic inflammatory component

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