Effect of elevated intracranial pressure on gastric acid secretion, mucosal blood flow and mucosal injury.

Head injury is frequently accompanied by an increase in intracranial pressure and gastric lesion formation. We used a model of controlled intracranial pressure to investigate the effect of elevated intracranial pressure on gastric acid secretion and mucosal blood flow and on the susceptibility of the gastric mucosa to lesion formation. With increasing intracranial pressure, there was a corresponding increase in gastric acid output but no significant change in gastric mucosal blood flow. This imbalance between acid secretion and blood flow could be a factor in the pathogenesis of the gastric lesions seen with head injury. Susceptibility to gastric mucosal injury then was studied in a model that is independent of the acid secretory state--exogenous intragastric HCl plus ethanol. Elevated intracranial pressure did render the gastric mucosa more susceptible to injury in this model, but there was no impairment of the increased gastric mucosal blood flow response to the increased acid back-diffusion. In this situation, factors other than altered overall blood flow appear to be responsible for the increased lesion formation.