Neurogenic shock is a type of shock caused by the sudden loss of the autonomic nervous system signals to the smooth muscle in vessel walls.
This results in loss of background sympathetic stimulation, which is responsible for maintenence of tone of blood vessels. As a result of loss of vascular tone, the vessels suddenly relax resulting in a sudden decrease in peripheral vascular resistance and decreased blood pressure.
Failure of the autonomic nervous system can arise from
- Regional anesthetics
- Injuries to the spinal cord (cervical spine and upper thoracic spine)
- Administration of autonomic blocking agents.
The cardiac output decreases because the venule and small veins lose tone. Blood pools in the periphery and blood pressure falls. In the normal situation, a reflex increase in heart rate will occur to compensate for the peripheral pooling of blood. However, in neurogenic shock, the sympathetic pathways to the heart are blocked or damaged by trauma, resulting in a bradycardia.
Symptoms and Signs
The surroundings leading to shock are very important in making the diagnosis.
Diagnosis of neurogenic shock rests on knowledge of the history surrounding the onset of shock. The features suggesting neurogenic shock are
- Warm, dry extremities
- Peripheral vasodilation and venous pooling
- Poikilothermia ( Cold Body)
- Decreased cardiac output (with cervical or high thoracic injury)
- Fluid challenge
- Beta-blockers can be implemented.
- Phenylephrine or norepinephrine can be used