92 - Approach to the Patient with Shock

Abstract

Shock, which is acute circulatory dysfunction that results in inadequate tissue perfusion, is a medical emergency requiring prompt diagnosis and intervention to prevent circulatory collapse, multisystem organ failure, and death. The four major, not mutually exclusive, categories of shock are cardiogenic, distributive, hypovolemic, and obstructive. Cardiogenic, hypovolemic, and obstructive shock are a result of reduced cardiac output, whereas distributive shock is caused by loss of vasomotor tone. Septic shock, which is predominantly distributive, accounts for over half of the 500,000 or so cases of shock per year in the United States. A presumptive diagnosis is based on hypotension, signs of hypoperfusion, and lactic acidosis. A rapid history, clinical examination, and bedside ultrasound help establish the probable type of shock, which can guide therapy as well as help identify the inciting cause and any concomitant problems. Respiratory support is provided with supplemental oxygen and mechanical ventilation. Obstructive shock requires specific procedures to relieve obstruction, such as needle thoracostomy for tension pneumothorax. Rapid intravenous fluid resuscitation with crystalloids, accompanied by vasopressors as necessary, is key for all forms of shock except cardiogenic shock. In cardiogenic shock, a small fluid bolus may still be necessary, but inotropic support is the primary strategy. The adequacy of resuscitation is determined by ensuring adequate cardiac preload via dynamic measures, such as straight leg raises, and monitoring blood pressure, lactate clearance, and clinical signs of hypoperfusion. Even when the initial resuscitation is successful, patients often will develop multisystem organ dysfunction that requires admission to intensive care for ongoing management.