Effects of mannitol and steroid therapy on intracranial volume-pressure relationships in patients

The intracranial volume-pressure response was measured in 61 patients undergoing continous monitoring of intraventicular pressure. This test, which determlnes the increase in intracranial pressure induced by an addition of 1 ml in ventricular CSF volume in 1 sencond, yields information concerning spatial compensation in patients with intracranial space-occupying processes. On the basis of variability tests, a change in volume-pressure response of 2 mm Hg/ml was accepted as significant. Pronounced enlargement of the ventricles interferes with the test. In patients with intracranial hypertension, intravenous mannitol (0.5gm/kg) and intramuscular betamethasone (26 mg) both reduce the volume-pressure response significantly more than they reduce intracranial pressure. This suggests that these agents favorably alter the configuration of the volume-pressure curve.