Shock series 2 of 6 Neurogenic

In part Two we look at Neurogenic Shock
One of the three in the distributive shock family.

Recapping: Shock is a syndrome characterised by poor cellular perfusion. It can be preceded by

• blood volume loss (Hypovolaemia)
• obstruction of blood flow into the heart (obstructive)
• failure to pump (cardiogenic), or
• available blood being maldistributed (distributive)

This trauma pearl edition continues to explore distributive shock; specifically neurogenic shock.
Neurogenic means : originated in the nerves. It is a form of volume maldistribution caused through loss of venous return , where the sympathetic nervous controller of vessel diameter has been injured.
Lets go back a bit. The autonomic nervous system regulates many functions including heart rate, blood pressure, blood vessel and bronchial diameter.
Two branches: sympathetic = vasoconstriction, increase heart, increase BP.
Parasympathetic does the opposite! It slows the heart, drops BP, and dilates blood vessels.
I spinal injured patients, an injury to the spinal cord at or above the T6 vertebrae, can disrupt or sever the sympathetic influence on the heart.
Loss of sympathetic control, means the the parasympathetic influence over whelms.
Like a red army fighting a blue army on a battlefield: remove one side, and the other charges forward. This is seen in the neurogenic shock patient as bradycardia (slow heart rate) a widespread vasodilation, causing a maldistribution of volume, and results in ineffective circulation (loss of Blood pressure). Another feature of neurogenic shock is poikilothermia - which is an inability to sweat, shiver or regulate temperature. Poikilothermia patients get cold fast as the start to assume the temperature of the room. In neurogenic shock patients, hypothermia is a silent killer and one of the deadly triad. The clinician needs to aggressively keep these patients warm.
So neurogenic shock is not caused by the parasympathetic nervous system misbehaving, it is just that there is limited sympathetic tone to offer resistance. Loss of sympathetic tone therefore is the route cause of neurogenic shock. Venous pooling is treated using positioning, judicious fluid resuscitation (remember they have all their blood just maldistributed), and vasopressor drugs. Pharmacological agents like norepinephrine (noradrenaline), Aramine, and Epinephrine can offer assistance in countering vasodilation.
Neurogenic shock is not the same as spinal shock. Whilst the cause of both is a spinal cord injury, spinal shock is a symptom set that includes flaccidity of muscle tone below the level of injury, loss of reflexes, sensation and movement.
Spinal shock is not really a form of shock at all. Yet it can coexist with neurogenic shock in the same patient.
In Summary: neurogenic shock is a life threatening loss of sympathetic nerve tone caused through a spinal injury above the level of T6. It is a true shock in that it causes poor cellular perfusion secondary to maldistribution of circulating blood.
Keep the patient warm, flat and well oxygenated.