What are the effects of neurogenic shock?

From the Guidelines

Neurogenic shock causes a cascade of cardiovascular and physiological effects resulting from the disruption of sympathetic nervous system control, leading to hypotension, bradycardia, and peripheral vasodilation. The primary effects of neurogenic shock include:

• Hypotension (low blood pressure)
• Bradycardia (slow heart rate)
• Peripheral vasodilation leading to warm, dry skin below the level of injury Patients typically present with systolic blood pressure below 90 mmHg and heart rate under 60 beats per minute. Other manifestations include:
• Temperature dysregulation (particularly hypothermia)
• Respiratory compromise
• Urinary retention
• Gastrointestinal ileus Treatment focuses on maintaining adequate blood pressure with IV fluids (typically crystalloids like normal saline or lactated Ringer's at 1-2 L bolus initially) and vasopressors if needed (norepinephrine 0.1-0.5 mcg/kg/min or phenylephrine 10-200 mcg/min) 1. Atropine (0.5-1 mg IV) may be used for severe bradycardia. These effects occur because spinal cord injury disrupts descending sympathetic pathways, causing loss of vasomotor tone and unopposed parasympathetic activity through the vagus nerve. This autonomic imbalance leads to widespread vasodilation and decreased cardiac output, distinguishing neurogenic shock from other shock types where compensatory tachycardia would typically occur. In terms of vasoactive agents, norepinephrine is recommended as the initial vasoactive drug after appropriate fluid resuscitation 1. The use of other vasoactive agents, such as vasopressin, dobutamine, and levosimendan, may be considered in specific situations, but their effects on microcirculation are still uncertain 1. Overall, the management of neurogenic shock requires a tailored approach to individual patient needs, with a focus on maintaining adequate blood pressure and perfusion to vital organs.

From the Research

Effects of Neurogenic Shock

The effects of neurogenic shock are multifaceted and can have significant consequences on the patient's health. Some of the key effects include:

• Hypotension: Neurogenic shock is characterized by severe arterial hypotension, which can lead to inadequate blood flow to vital organs 2, 3.
• Bradycardia: Bradycardia, or a slow heart rate, is another common effect of neurogenic shock, which can further exacerbate the hypotension 2, 3.
• Vascular dysfunction: Spinal cord injury can disrupt the autonomic nervous system, leading to vascular dysfunction and orthostatic hypotension 3.
• Cardiac dysfunctions: Neurogenic shock can also lead to cardiac dysfunctions, including cardiac dysrhythmias, cardiac arrest, and hypotension 4.
• Impaired autonomic nervous control: The loss of supraspinal control over the sympathetic nervous system can result in reduced overall sympathetic activity below the level of injury and unopposed parasympathetic outflow through the intact vagal nerve 3, 4.

Clinical Management

The clinical management of neurogenic shock is crucial to prevent further complications and improve patient outcomes. Some of the key aspects of clinical management include:

• Vasopressor support: Vasopressors, such as dopamine and phenylephrine, may be used to maintain blood pressure and perfusion to vital organs 5.
• Fluid management: Fluid management is critical in the treatment of neurogenic shock, and a net fluid intake of zero or less may be recommended 6.
• Early decompression: Early decompression may be recommended for incomplete deficits seen in the first 6 hours after injury 2.
• Cardiac rehabilitation: Cardiac rehabilitation and prophylaxis, including non-pharmacologic and pharmacological strategies, may be necessary to prevent cardiac complications 4.

Incidence and Progression

The incidence and progression of neurogenic shock can vary depending on the clinical definition used and the level of spinal cord injury. Some of the key findings include:

• Incidence: The reported incidence of neurogenic shock varies greatly depending on the clinical definition used, but a novel combination of hemodynamic and laboratory criteria may provide a more accurate estimate 6.
• Progression: Neurogenic shock can progress over time, with a characteristic decline in blood pressure after the first week post-injury 6.