Shock is a condition of severe impairment of tissue perfusion leading to cellular injury and dysfunction. Rapid recognition and treatment are essential to prevent irreversible organ damage and death. Common causes are listed in Table 12-1 Categories of Shock.
- Hypotension (mean arterial bp <60 mmHg), tachycardia, tachypnea, pallor, restlessness, and altered sensorium.
- Signs of intense peripheral vasoconstriction, with weak pulses and cold clammy extremities. In distributive (e.g., septic) shock, vasodilation predominates and extremities are warm.
- Oliguria (<20 mL/h) and metabolic acidosis common.
- Acute lung injury and acute respiratory distress syndrome (ARDS; see Chap. 16 Acute Respiratory Distress Syndrome) with noncardiogenic pulmonary edema, hypoxemia, and diffuse pulmonary infiltrates.
| APPROACH TO THE PATIENT | ||
ShockObtain history for underlying causes, including cardiac disease (coronary disease, heart failure, pericardial disease), recent fever or infection leading to sepsis, drug effects (e.g., excess diuretics or antihypertensives), conditions leading to pulmonary embolism (Chap. 135 Pulmonary Thromboembolism and Deep-Vein Thrombosis), and potential sources of bleeding. |
Jugular veins are flat in oligemic or distributive (septic) shock; jugular venous distention (JVD) is typical in cardiogenic shock; JVD in presence of paradoxical pulse (Chap. 112 Physical Examination of the Heart) suggests cardiac tamponade (Chap. 118 Pericardial Disease). Check for asymmetry of pulses (aortic dissection-Chap. 127 Diseases of the Aorta). Assess for evidence of heart failure (Chap. 126 Heart Failure and Cor Pulmonale), murmurs of aortic stenosis, acute mitral or aortic regurgitation, and ventricular septal defect. Tenderness or rebound in abdomen may indicate peritonitis or pancreatitis; high-pitched bowel sounds suggest intestinal obstruction. Assess stool for GI bleeding.
Fever and chills typically accompany septic shock. Sepsis may not cause fever in elderly, uremic, or alcoholic pts. Skin lesions may suggest specific pathogens in septic shock (see Chap. 14 Sepsis and Septic Shock).
Obtain lactate, CBC, renal and liver function tests, PT, PTT, and cardiac troponin if myocardial ischemia, myocarditis, or pulmonary embolism is suspected. Arterial blood gas usually shows metabolic acidosis (in septic shock, respiratory alkalosis precedes metabolic acidosis). If sepsis is suspected, draw blood cultures, perform urinalysis, and obtain cultures of sputum, urine, and other suspected sites.
Obtain ECG (myocardial ischemia/infarction or acute arrhythmia) and chest x-ray (heart failure, tension pneumothorax, pneumonia). Echocardiography is often diagnostic of underlying cause (e.g., cardiac tamponade, left/right ventricular dysfunction, aortic dissection, right ventricular strain due to pulmonary embolism).
CVP or pulmonary capillary wedge (PCW) pressure measurements may be necessary to distinguish between different categories of shock (Table 12-2 Characteristics of Forms of Shock): Mean PCW <6 mmHg suggests hypovolemic or distributive shock; PCW >20 mmHg suggests left ventricular failure/cardiogenic shock. Cardiac output is decreased in cardiogenic, hypovolemic, and obstructive shock, and increased in distributive shock.