EFFECTS OF ALFENTANIL ON CEREBRAL HEMODYNAMICS IN AN EXPERIMENTAL-MODEL OF TRAUMATIC BRAIN INJURY

Alfentanil is reported to increase intracranial pressure (ICP) after n eurotrauma. A direct cerebral vasodilator effect has been postulated. We studied 17 Sprague-Dawley rats allocated to one of three groups. An imals were anaesthetized and their lungs ventilated, and arterial pres sure, ICP and/or regional cerebral blood flow (CBF) measurements were undertaken. Group 1 (n=6) received a severe closed head injury while g roup 2 (n=5) received no injury. ICP and mean arterial pressure (MAP) were measured before, during and after rapid infusion of alfentanil 25 0, 500 and 750 mu g kg(-1). CBF was measured by hydrogen clearance bef ore rapid infusions and at 30-min intervals after starting a subsequen t slow infusion of alfentanil 500 mu g kg(-1) h(-1). Group 3 (n=6) und erwent CBF measurement only, for comparison with those of groups 1 and 2. They received an injury but no alfentanil. ICP or MAP values did n ot differ significantly between groups 1 and 2. Rapid i.v. doses of al fentanil produced increases in ICP and reductions in MAP. ICP changes were consistent with a drug effect (P<0.001) but were small. Reduction s in MAP were significant (P<0.05) and preceded changes in ICP. CBF va lues were similar and unaffected by slow alfentanil infusion in groups 1 and 2, and did not differ significantly between groups 1 and 3. We conclude that alfentanil did not appear to exert a direct effect on th e cerebral circulation. Changes in ICP after rapid infusion were secon dary to reductions in SAP. Slow infusion did not cause such changes.