CATECHOLAMINE RESPONSE TO A GRADUAL INCREASE OF INTRACRANIAL-PRESSURE

To determine the catecholamine response to progressive intracranial hy pertension, intracranial pressure (ICP) was raised gradually by contin uous expansion of an epidural balloon in seven dogs. Hemodynamic param eters, ICP, and cerebral perfusion pressure (CPP) were monitored conti nuously and serum catecholamine levels began to rise when CPP was in t he low-positive range (20 to 30 mm Hg), reaching a peak just after bra in death (CPP less-than-or-equal-to 0 mm Hg). There was no correlation between ICP and the catecholamine peak. Compared to control values, t he mean increase was 286-fold for epinephrine and 78-fold for norepine phrine. Temporally, the catecholamine peak corresponded well with the observed hemodynamic changes. These results suggest that ischemia in c ertain parts of the brain stem is responsible for the hemodynamic chan ges observed in intracranial hypertension (such as the Cushing respons e), and they show that catecholamines play an important role in these hemodynamic changes.