Neurogenic shock

Associate Editor-In-Chief: Ayan Sen, M.D, Henry Ford Hospital, Detroit MI, USA

Overview
Neurogenic shock is shock caused by the sudden loss of the sympathetic nervous system signals to the smooth muscle in vessel walls. This can result from severe central nervous system (brain and spinal cord) damage. With the sudden loss of background sympathetic stimulation, the vessels suddenly relax resulting in a sudden decrease in peripheral vascular resistance and decreased blood pressure.

Differential diagnosis of underlying causes of neurogenic shock

 * 1) Spinal cord injury / Ischemia
 * 2) Regional Anesthesia
 * 3) Drugs
 * 4) Neurological Disorders

Signs and symptoms
The classic presentation of a patient in neurogenic shock is almost the opposite to that found in other shock states. In hypovolaemic shock the patient presents with cold, clammy, and pale or cyanotic peripheries. In neurogenic shock, the extremities may remain pink, warm and well perfused. Due to the loss of sympathetic function, he is unable to initiate the vasoconstriction required to divert blood to the central vital organs; and thus it pools in the peripheral vascular compartments.

Similarly, a hypovolaemic patient typically presents with tachycardia and hypotension; the increased heart rate represents an early and sustained attempt to support the failing circulation, and maintain central perfusion. In neurogenic shock, the cardiovascular system cannot stimulate compensatory changes in the same way; and thus the patient may present with a normal heart rate. As vital signs and physical assessment do not indicate shock, this factor may also mask other underlying causes of the shock state, such as hypovolemia.

Symptoms of neurogenic shock may include:


 * Hypotension
 * Bradycardia
 * Warm, dry extremities
 * Peripheral vasodilation
 * Venous pooling
 * Poikilothermia
 * Priapism Due to PNS stimulation
 * Decreased cardiac output (with cervical or high thoracic injury)

Treatment of Neurogenic shock

 * Large volumes of fluid may be needed to restore normal hemodynamics
 * Vasopressors (Norepinephrine)
 * Atropine (this vagolytic reduces vagal tone, increases heart rate and increases cardiac output)