Shock is acute circulatory failure threatening multiple organ systems and demands prompt diagnosis and urgent resuscitation.
The main types of shock are hypovolemic, cardiogenic, and distributive shock.
Shock must be managed rapidly by identifying and treating acute, reversible causes; restoring intravascular volume; infusing vasoactive drugs; using mechanical adjuncts, when applicable; and supporting vital functions until recovery.
Bedside goal-directed echocardiography should be performed to clarify or confirm the etiology of shock; identify readily treatable contributors (such as tension pneumothorax or cardiac tamponade); and seek clues to fluid responsiveness.
A comprehensive assessment of the adequacy of perfusion is useful to guide resuscitation, rather than merely aiming for an arbitrary mean arterial pressure.
Shock is acute circulatory failure threatening multiple organ systems and producing a grave threat to survival. Most patients will be hypotensive (mean arterial blood pressure [MAP] < 60 mm Hg) and are often tachycardic, tachypneic, and exhibit overt end-organ dysfunction, such as oliguria, encephalopathy, or lactic acidosis (Table 21–1). The basis for shock may be readily evident from the presentation, such as following trauma, or when symptoms or signs of hemorrhage, fluid loss, or sepsis are evident. A subset of shock patients will have normal blood pressure (even hypertension is possible); many will also lack tachycardia. In such patients, the diagnosis may be challenging, especially since there is such interindividual variance in normal values for blood pressure. Subtle or atypical presentations of shock may require a high index of clinical suspicion. Initially, shock is reversible, but rapidly progresses to cellular injury, cell death, failure of critical organ systems, and an irreversible state that terminates in death. Timely resuscitation blunts inflammation and mitochondrial damage, potentially reducing the burden of early and late morbidity. Because delays in resuscitation may be lethal, shock demands prompt diagnosis and urgent resuscitation.
Table 21–1Recognizing shock. |Favorite Table|Download (.pdf) Table 21–1 Recognizing shock.
Tachypnea, respiratory failure, or respiratory alkalosis
Encephalopathy, anxiety, or agitation
Oliguria or AKI
Skin mottling, cool extremities, cyanosis, livedo reticularis
Low mixed venous or central venous oxyhemoglobin saturation values
DIFFERENTIAL DIAGNOSIS OF SHOCK
Shock is divided into three types: hypovolemic, cardiogenic, or distributive. In a patient with new-onset shock, it is usually possible to categorize the type of shock within minutes based on a concise history and targeted examination. In a patient with shock, a wide pulse pressure accompanied by warm extremities and brisk capillary refill is evidence of high cardiac output (CO; distributive shock). Alternatively, a narrow pulse pressure, cool extremities, and delayed capillary refill suggest low CO. Low CO shock is comprised of hypovolemia and pump failure. In the subset of low output shock, an assessment of intravascular volume can further differentiate hypovolemia from cardiogenic causes of shock. Bedside goal-directed echocardiography1 (GDE) should be performed to clarify or confirm the etiology of shock (Table 21–2); identify readily treatable contributors (such as tension pneumothorax or cardiac tamponade); and ...