Cardiogenic shock is defined by persistent hypotension (systolic BP <90 mmHg) with severely reduced cardiac output, reflected in cool extremities, low urine output and changes in the mental state. Often there is pulmonary oedema.

• Cardiogenic shock may be due to a range of cardiac disorders (Table 49.1). In 75% of cases, the cause is acute myocardial infarction with left ventricular failure, or, less commonly, ventricular septal rupture, papillary muscle rupture, free wall rupture or right ventricular infarction.
• The mortality of cardiogenic shock is high. In patients at particularly high risk of death because of advanced age (>80 years) or severe comorbidities, aggressive management may not be appropriate.

See Chapter 2 for the initial assessment and management of the patient with hypotension and shock. Focused clinical assessment and investigation in suspected cardiogenic shock are summarized in Tables 49.2 and 49.3. Seek urgent advice from a cardiologist.

• Correct major arrhythmias (Chapters 39, 40, 41, 42, 43, 44).
• If there is ECG evidence of ST-segment-elevation acute coronary syndrome, consider primary angioplasty if feasible (Chapter 45).
• If there is no clinical evidence of pulmonary oedema, give a fluid challenge (500 mL crystalloid over 15 min), repeated once if systolic BP remains <90 mmHg without evidence of pulmonary oedema.
• Arrange urgent echocardiography to assess left and right ventricular function and to exclude ventricular septal rupture, cardiac tamponade (Chapter 54) and acute aortic or mitral regurgitation (Chapters 51 and 52) (Table 49.4).
• Increase the inspired oxygen, aiming for an oxygen saturation of >90%/arterial PO₂ >8kPa. If these targets are not met despite an inspired oxygen concentration of 60%, use a continuous positive airway pressure system (Chapter 113). Intubation and mechanical ventilation may be appropriate in some patients: discuss this with an intensivist and cardiologist.

• Start inotropic/vasopressor therapy (Tables 2.6 and 2.7) if systolic BP remains <90 mmHg despite correction of major arrhythmias, and fluid challenge if indicated.

  Diuretics are relatively ineffective in patients with cardiogenic shock, but can be used in case of fluid overload once the cardiac output has increased (as shown by improvement in the patient's mental state and skin perfusion): if renal function is normal, give furosemide 40 mg IV.

• Providing the systolic BP has increased to at least 100 mmHg, start a nitrate infusion, initially at low dose (e.g. isosorbide dinitrate 2 mg/h).
• If the patient is not improving, consider haemodynamic monitoring using pulse contour or thermodilution techniques to allow more accurate titration of therapy. Adjust the doses of inotropic/vasopressor and nitrate therapy, aiming for normalization of tissue perfusion parameters (serum lactate, urine output, skin perfusion).