H emodynamic shock (HS) is a clinical syndrome that is commonly observed in hospitalized patients. Prompt recognition and intervention are the cornerstones of mitigating the dire consequences of HS. Untreated HS usually leads to death. Unlike other types of clinical syndromes (e.g., chest pain), for which a clinical diagnosis is made before treatment is initiated in earnest, the treatment of shock often occurs concurrently or ahead of the diagnostic process. The maintenance of end-organ perfusion is critical to prevent irreversible organ injury and failure, and this frequently requires the use of fluid resuscitation and vasopressors. A complete review of all of the signs and symptoms, diagnosis, and treatment of HS has been reviewed in detail elsewhere (1). This article provides a concise summary of how to approach the patient in HS, diagnostic and therapeutic decision making, and the use of vasopressors. In addition, the effects of vasopressors on end organs with particular focus on renal hemodynamics is reviewed.
Clinical Manifestations and Recognition of Hemodynamic ShockHS is classically described as "an acute clinical syndrome initiated by ineffective perfusion, resulting in severe dysfunction of organs vital to survival" (1). As clinicians, we take great pains to teach our trainees that shock is not just hypotension, but that shock represents hypoperfusion of end organs. This rationale leads to the common refrain: "Normotensive patients can often suffer from shock." The clinical manifestations of HS are related directly to the end organs that are not receiving adequate perfusion and can be categorized on the basis of the organ affected. Besides hypotension, the classic signs and symptoms of HS are tachycardia, relative hypotension (a decrease in baseline BP of 40 mmHg), tachypnea, cool and clammy extremities, oliguria, dysglycemia, and delirium (1). Patients who are hypotensive (systolic BP Ͻ90 mmHg in patients whose baseline BP is usually low) but show no signs or symptoms of shock should have their BP rechecked. An indwelling arterial catheter or Doppler may be necessary to resolve a false low BP reading (1). In the absence of hypotension, the diagnosis of HS can be more challenging and will require the clinician to increase his or her scrutiny of the patient and either rule in or rule out HS with further clinical investigations. For patients who are normotensive, the measurement of serum lactate will often reveal the presence of HS in a patient whose clinical evaluation is equivocal. This entity of a normotensive patient with some clinical signs of HS with an elevated lactate is often referred to as "cryptic shock." In this condition, the patient is not yet in critical condition but cannot meet their body's oxygen demand, resulting in evidence of significant anaerobic metabolism. Previous trials showed that presence of HS and a serum lactate concentration of Ͼ4.0 mmol/L are associated with a mortality of 30 to 45% (2).Once HS is recognized, interventions to restore tissue perfusion are mandatory. Three ...