Neurogenic and spinal shock 

Following a spinal cord injury (SCI), a person may experience either neurogenic shock or spinal shock. While both conditions can share similar symptoms, they are distinct and have different underlying causes and treatments.

Neurogenic shock

Neurogenic shock typically occurs after spinal cord injury at or above the level of T6. It results from disruption to the sympathetic nervous system, which affects the body’s ability to regulate blood pressure, heart rate, and other autonomic functions. Symptoms typically last 48–72 hours but may persist for several weeks or even months in some cases. Symptoms include:

• Loss of vascular tone: Blood vessels lose their ability to constrict, leading to peripheral pooling in the arms and legs. Hypotension, defined as a systolic blood pressure <90 mmHg can occur.

• Cardiac dysfunction: Interruption of the sympathetic nerves that control the heart (T1–T4) results in unopposed vagal activity. This slows heart rate (bradycardia) and decreases the ability of the heart muscle to contract and pump blood effectively (myocardial contractility).
• Unopposed vagal activity: The vagus nerve, part of the parasympathetic nervous system, typically acts to slow heart rate and lower blood pressure. When the sympathetic nervous system is disrupted, vagal activity dominates.

Other clinical considerations

• Fluid overload and pulmonary oedema: Extra fluid in the body may lead to fluid buildup in the lungs.
• Slower motility of the gastrointestinal tract: Decreased gastric peristalsis increases the risk of paralytic ileus and bowel obstruction.
• Decreased urine output: Reduced kidney function leading to less urine being produced.
• Fluid retention and swelling: This can cause oedema in the arms, legs, and other areas of the body.
• Skin breakdown: Increased risk of pressure injuries.
• Temperature regulation issues: Difficulty maintaining thermoregulation.
• Increased risk of blood clots: Higher likelihood of thromboembolism (blood clots).
• Electrolyte imbalances: Low potassium (hypokalaemia) and low sodium (hyponatraemia) can occur.

Management

Neurogenic shock requires intensive monitoring and management, ideally in an Intensive Care Unit (ICU).

• Initial fluid resuscitation is essential to maintain tissue perfusion but should be balanced to avoid overload.
• Vasopressors and inotropes may be needed as second-line treatment, to maintain a target mean arterial pressure (MAP) of 85–90 mmHg in the acute phase.

Spinal shock 

Spinal shock is a temporary condition that occurs immediately after a spinal cord injury, typically lasting 4 to 6 weeks. It results in:

• a complete loss of sensation, muscle activity, tone and reflexes below the level of injury.
• impaired autonomic nervous system function of all associated body organs—impacting heart rate regulation, airway resistance, vascular tone, blood pressure, sputum production, bladder, and bowel activity.

A positive bulbocavernosus reflex (observed during an anorectal exam) indicates the end of spinal shock and the return of reflex activity. It’s important to note that reflexes return gradually, and not all reflexes return at once.

Comparison of neurogenic and spinal shock

	Neurogenic shock	Spinal shock
Onset	Within minutes to hours after SCI	Immediately after SCI
Duration	Typically 48–72 hours	Typically  4–6 weeks
Patient	Typically people with spinal cord injury at or above the level of T6	Can occur with any level of spinal cord injury
Cause	Disruption of the sympathetic nervous system	Universal response to spinal cord trauma due to an abrupt loss of descending excitatory input from the brain
Key features	Low blood pressure (hypotension): Systolic BP <90 mmHg Slow heart rate (bradycardia) Loss of autonomic function (i.e. blood pressure regulation, temperature control, and bladder or bowel activity)	Areflexia Loss of autonomic reflex activity
Autonomic effects	Severe disruption in autonomic control of heart rate, blood pressure, and vessels	Disruption in autonomic reflex activity.
Reflex activity	Reflexes generally intact	Absent reflexes below the level of injury
Resolution indicator	Stabilisation of blood pressure and heart rate	Return of reflexes i.e. bulbocavernosus, deep tendon and bladder voiding reflexes
Treatment	ICU care Fluid resuscitation Vasopressors/inotropes to maintain Mean Arterial Pressure (MAP) 85–90 mmHg	Supportive care Monitoring for reflex return
Overlap	Can occur alongside spinal shock	Can occur with or without neurogenic shock

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