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Neurogenic Shock: Causes, Symptoms, and Treatment

signs of neurogenic shock after spinal cord injury

After a spinal cord injury, neurogenic shock can occur and significantly affect cardiovascular functions. Fortunately, with immediate medical attention, blood pressure, heart rate, and vascular tone can be stabilized.

To help you better understand what neurogenic shock is, this article will discuss its causes, symptoms, and treatment.

Causes of Neurogenic Shock

neurogenic shock t6 spinal cord injury and higher

Neurogenic shock can occur when a disruption to the central nervous system (like a spinal cord injury at or above the T6 level of injury) causes loss of sympathetic stimulation.

The sympathetic nervous system is responsible for activating your “fight or flight” response. When activated, the blood vessels tighten (constrict), and blood pressure and heart rate increase.

The sympathetic nervous system is opposed by the parasympathetic nervous system, which is responsible for your “rest and digest” functions. When activated, the blood vessels expand (dilate), blood pressure and heart rate decrease, and digestion is stimulated.

Loss of sympathetic stimulation following a spinal cord injury results in unopposed parasympathetic stimulation. As a result, individuals with neurogenic shock experience decreased blood pressure and heart rate. It mostly affects your cardiovascular system, but if left untreated, neurogenic shock can lead to permanent tissue damage and be fatal.

In the following section, we’ll discuss common symptoms of neurogenic shock.

Symptoms of Neurogenic Shock

why neurogenic shock occurs after SCI

Neurogenic shock generally lasts anywhere between 1-6 weeks after injury.  Therefore, it’s essential to be aware of its symptoms and seek immediate medical treatment.

Loss of sympathetic tone causes the blood vessels to expand and loosen in a process called vasodilation. Because there’s limited pressure pushing blood throughout the body, your cells are not properly fueled with the oxygen and nutrients necessary for the body to function optimally.

Loss of sympathetic tone may also cause blood to pool in your veins. Instead of going back to the heart, the blood collects in your arms and legs. It’s a harmful cycle where less and less blood circulates throughout the body.

Common symptoms of neurogenic shock include:

  • Hypotension: Low blood pressure (lower than 90 mm Hg systolic or 60 mm Hg diastolic).
  • Bradycardia: Slower than normal heart rate (below 60 beats a minute).
  • Body Temperature Dysregulation: Initially, vasodilation and the pooling of blood in the extremities (arms and legs) may cause warm, dry skin. Over time, however, hypothermia may develop due to heat loss.

Individuals with cervical spinal cord injuries are more likely to experience neurogenic shock than those with thoracic SCIs.  Generally, the higher and more complete the SCI, the more severe the shock.

In order to avoid permanent tissue damage due to insufficient circulation, symptoms of neurogenic shock should be addressed immediately. In the following section, we’ll discuss treatments.

Neurogenic Shock Treatment

iv fluid treatment for neurogenic shock

The goals of neurogenic shock treatment are to restore heart rate and blood pressure to normal levels.

Below, we’ll discuss 3 common treatments for neurogenic shock.

  • IV Fluids. IV fluids are the primary treatment for low blood pressure. They replenish fluid levels in the veins to help stabilize blood pressure.
  • Vasopressors. If IV fluids prove ineffective, vasopressors can help tighten blood vessels and increase blood pressure. Commonly used vasopressors include norepinephrine, phenylephrine, dopamine, and epinephrine.
  • Atropine. If your heart rate is low, your doctor may prescribe atropine.  It helps normalize heart rate by inhibiting parasympathetic activity.

It’s also recommended by the American Association of Neurological Surgeons and the Congress of Neurological Surgeons’ Guidelines for the Management of Acute Cervical Spine and Spinal Cord Injuries that mean arterial blood pressure (MAP) is maintained at 85–90 mmHg for the first 7 days following acute SCI.

Up next, we’ll compare and contrast the differences between two types of shock that can occur following a spinal cord injury.

Neurogenic Shock vs. Spinal Shock

Neurogenic shock and spinal shock are two separate conditions that are often confused for one another because they can both occur after a spinal cord injury. They can also share symptoms including hypotension and bradycardia.

Unlike neurogenic shock (which occurs at the T6 level of injury or higher), spinal shock can occur for injury to any region of the spinal cord.

Neurogenic shock is a disruption of the sympathetic nervous system that affects tone in your blood vessels. Without sympathetic tone, blood cannot efficiently circulate throughout the body, which results in a decreased heart rate, low blood pressure, and temperature dysregulation.

In contrast, spinal shock results in the temporary loss of all motor, sensory, and reflex functions below your level of injury. Once the inflammation and swelling of the spinal cord are reduced, individuals may gradually recover some reflexes, sensation, and motor control. This will primarily depend on the severity of the spinal cord injury.  

Neurogenic Shock: Key Points

Neurogenic shock following a spinal cord injury causes loss of sympathetic (“fight or flight”) stimulation. As a result, the body’s parasympathetic (“rest and digest”) functions are unopposed, leading to vasodilation, decreased heart rate, and low blood pressure.

We hope this article helped you understand what neurogenic shock is and why immediate medical attention is necessary to stabilize cardiovascular functions. Good luck!

Featured image: iStock/metamorworks

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