Neurogenic Shock and Spinal Injury

Anesthesia Implications

Anesthesia Implications

This condition should NOT be confused with spinal shock. Neurogenic shock is a true form of shock and described as a hemodynamic disruption (reduced heart rate and blood pressure) as a result of a spinal injury. Since spinal injuries result in this condition, the anesthetic implications will cover both neurogenic shock and spinal injury in general.

Hemodynamic instability – Liberal crystalloid and blood administration should be used to correct hemodynamic drops – especially in cervical and/or thoracic injuries where sympathectomy causes widespread vasodilation. Standard drugs such as phenylephrine and ephedrine are also acceptable if not otherwise contraindicated.

Spinal clearance – always get a spinal clearance. Even if the patient is cleared, take precautions to limit the possibilities of injury while moving the patient or manipulating the airway.

Fiberoptic intubation – if there’s any question of cervical instability, maintain the head and neck in a neutral position at all times and utilize fiberoptic intubation to secure the airway.

Cervical collars/braces – these do not always provide optimal stabilization. DO NOT assume the patients C-spine is stable.

Tracheobronchial suctioning – associated with bradycardia and cardiac arrest! This should only be done after optimal oxygenation.

Avoid nitrous oxide – In the event that there is diffuse trauma along with the spinal injury, air entrainment in closed spaces could expand/migrate with the use of nitrous.

Monitor and supplement O2 EARLY – muscle weakness, sympathectomy, etc. all contribute to arterial hypoxemia, which is very common after spinal cord injury. Cervical injury (especially C3-C5) – associated with hypoxemia due to disruption of diaphragm innervation. Hypoxemia is an early sign of cervical injury.

Rocurronium/Vecuronium – these are the nondepolarizing neuromuscular blockers (NDNMB) of choice. As a general rule, RSI with Rocurronium is the most common approach to avoid the potential for hyperkalemia associated with Succinylcholine. Succinylcholine may be used for the first 24 hours after the injury, but should be avoided thereafter.

Prolonged ventilation – These patients may require prolonged mechanical ventilation depending on the spinal levels affected and severity of the injury.

C-spine precautions – During transport, always use the C-collar or brace.

Smooth transitions – Ensure the patient is deep enough before intubation. If not contraindicated, deep extubation is sometimes preferred to prevent bucking/coughing. Coughing and/or bucking in these transitions may cause disruption of the surgical site and/or damage to the spine.

Poikilothermia – This is the inability to regulate one’s body temperature and is common in spinal cord injuries. Be ready to monitor and maintain normothermia.

Pathophysiology

Neurogenic shock describes is a hemodynamic disruption characterized by a reduction in blood pressure and/or heart rate severe enough to impair organ function.

Neurogenic shock may last hours to weeks. The average is 1-3 weeks.

Sympathectomy, bradycardia, and increased SVR are all associated with cervical fractures. Sympathectomy causes widespread vasodilation and shock.

Cervical injury is the primary cause for hemodynamic changes. Thoracic injuries are also associated with hemodynamic changes, but to a lesser extent when compared to cervical injury.

T1-T4 injury is more especially related to bradycardia because these nerves supply sympathetic innervation to the heart.

The major cause of morbidity/mortality in these patients is a combination of alveolar hypoventilation and inability to clear secretions. Be cognizant of atelectasis and perform recruitment maneuvers where possible.

The patient should be able to generate a tidal volume > 10-15 cc/kg and/or a negative inspiratory force of 20 mmHg.

Additional Notes:

Cervical Collar Considerations:
DO NOT remove the collar or brace if the patient arrives with one.
Soft collars have little effect on limiting mobility – so take extra precaution to stabalize the spinal cord during movement of any kind
Hard collars only limit flexion and extension by 25%.
Halo-thoracic braces are the most effective in preventing cervical spine movement.

Classification of this condition uses the International Standards for Neurologic Classification of Spinal Cord Injury (ISNCSCI). This tests 28 dermatomes:
Complete injury (classification A) would be total sensory and motor function loss below the level of injury.
Incomplete injury (classification B-D) would be some sensory or motor function maintained below the level of injury.
Normal function (classification E) is injury without the loss of motor or sensory function below the level of injury.

References

Hines. Stoelting’s anesthesia and co-existing disease. 7th edition. 2018.
Nagelhout. Nurse anesthesia. 5th edition. 2014.
Farag. Airway management for cervical spine surgery. Best Practice & Research: Clinical Anesthesiology. 2016.