Fentanyl co-administration decreases the induction dose requirement of propofol in patients with supratentorial tumors and not in patients with spinal lesions.

BACKGROUND: The requirement of anesthetic drugs in a patient with an intracranial space-occupying lesion is of relevance to the neuroanesthetist. The requirement is often presumed to have reduced or at least altered. However, not much research has focused on this issue. Hence, we conducted this study to examine whether intracranial tumors reduce the induction dose of propofol in patients undergoing craniotomy based on plasma and effect site concentrations (Ce) of propofol and the effect of additional fentanyl.

METHODS: A total of 80 patients were recruited into the study. The study group included patients with supratentorial tumors undergoing craniotomy, and the control group consisted of patients undergoing spinal surgeries. Patients in each group were randomized further to receive propofol alone or propofol preceded by fentanyl for induction of anesthesia. They were divided into the following groups: patients with supratentorial tumor receiving only propofol (group T1), or fentanyl and propofol (group T2); patients who were undergoing spinal surgery and receiving only propofol (group S1) or fentanyl and propofol (group S2). Anesthesia was induced with infusion of propofol through a Target Controlled Infusion pump. At the point of loss of verbal contact, plasma concentration (Cp) and Ce of propofol, time taken for loss of consciousness, and the total dose of propofol required were noted. Hemodynamic variables were recorded before and after induction of anesthesia.

RESULTS: There were 19, 21, 19, and 21 patients in groups TI, T2, S1, and S2, respectively. In group T2 the Cp, Ce, time to loss of verbal contact, and dose required for induction were all significantly lower compared with the other groups. There were no significant differences in the study parameters between T1 and S1, whereas the differences were significant between T2 and S2 (Cp: 3.9±1.1 vs. 4.9±1.2 μg/mL; Ce: 2.6±1.0 vs. 3.7±1.2 μg/mL; P<0.05).

CONCLUSIONS: Propofol dose for induction of anesthesia was significantly reduced when administered after fentanyl in patients with supratentorial tumors. Tumors per se without fentanyl coadministration do not decrease the propofol requirement for induction of anesthesia.