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Critical illness is defined as “any patient who is physiologically unstable, requiring constant and minute-to-minute titration of therapy according to the evolution of the disease process.”1 It is a continuum often culminating in rapid decline, shock, organ failure, and, frequently, patient demise. Traditionally, shock is defined as a clinical diagnosis identified through physical manifestations observed by medical staff.2 Complementing clinical acumen is the recognition of accumulating oxygen debt due to perturbations of microvascular circulation. Early phases of evolving shock may manifest through biochemical markers with minimal physical alterations.3–5 Although typically considered an intensive care unit (ICU) ailment, shock develops well before ICU admission with patients often initially presenting to the emergency department (ED). Effective, timely shock treatment requires a continuum of care beginning with prehospital providers, continuing within the ED, and concluding within the ICU.6,7 Thus, shock treatments should be defined by level of care rather than location of care.8
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With the ever-increasing incidence of the critically ill and injured initially presenting through the ED, active emergency medicine participation in the continuum of care is essential. The number one reason for ED overcrowding is reported as a severe lack of accessible ICU beds.9 Lambe et al noted a 59% increase of ED critical care volume with an 8% decrease in nonurgent patients10 (Figure 46-1). This is mirrored nationally with 23% of ED patients triaged as requiring immediate or emergent (within 15 minutes) care. One of every 10 patients hospitalized from the ED is directly admitted to the ICU.11 Underscored is the clinical reality that emergency medicine physicians are seeing a higher volume of patients, with more patients severely ill than in the past.
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ED epidemiology of shock remains speculative as it is typically veiled within other diagnoses. However, shock is a significant contributor to ED critical care volume; an estimated 1.1 million patients present to the ED with potential shock each year.12 From 1999 to 2002, the prevalence of patients requiring emergent resuscitation increased from 17% to 22%.11,13 Mortality is high, ranging from 23% to 80%, depending on the type of shock, patient age, and comorbidities.14–17 As Americans age, the incidence of shock is expected to increase with estimates of one half of patients initially presenting to the ED.15
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Traditionally, the diagnosis of shock is made based on clinical signs and symptoms such as hypotension, tachycardia, weak pulse, and cold, clammy skin. Unfortunately, due to diverse circumstances, many of these signs and symptoms—or their absence—prove to be unreliable gauges of the presence and/or degree of shock. Furthermore, different etiologies of shock often result in differing ...