Amelioration of hypoxemia by neuromuscular blockade following brain injury

Brain injury has been commonly associated with respiratory failure and uncontrolled skeletal muscle activity. In the present study, neuromuscular (NM) blockade induced by injection of succinylcholine hydrochloride was used to block uncontrolled muscle contractions in dogs with brain injury caused by rapid elevation of intracranial pressure (ICP). Decerebrate posturing, a decrease in value (mean +/- SEM) of arterial oxygen tension (Pa02) of 26 +/- 1 torr, and an increase in arterial carbon dioxide tension (PaCO2) of 11 +/- 1 torr occurred in the dogs, which were supported by mechanical ventilation. The arterial hypoxemia developed independently of the decerebration; however, dogs that demonstrated decerebrate posturing exhibited significantly larger decreases in Pa02 than dogs that did not (P less than 0.01). NM blockade ameliorated the effects of elevated ICP on the arterial blood gases; i.e., the amount of hypoxemia in decerebrate dogs was significantly less in dogs subjected to NM blockade than in dogs not subjected to NM blockade. It is concluded that uncontrolled skeletal muscle activity that exacerbates arterial hypoxemia associated with brain injury is ameliorated by use of NM blockade as a therapeutic adjunct to mechanical ventilation.