Effects of butorphanol and fentanyl on cerebral pressures and cardiovascular hemodynamics during tunneling phase for ventriculoperitoneal shunt insertion.

PURPOSE Subcutaneous tunneling for ventriculoperitoneal shunt insertion is the most painful step of this surgery. It is associated with intense hemodynamic response, may influence the intracranial pressure, and thus may worsen the existing intracranial pathology. The purpose of this report is to evaluate the commonly used opioid fentanyl, along with butorphanol, an agonist-antagonist compound. METHODS Twenty adult patients undergoing ventriculoperitoneal shunt surgery were induced with fentanyl 2-mcg.kg(-1) and thiopentone 4-5 mg.kg(-1). Intubation followed the administration of rocuronium 1 mg.kg(-1). All patients were put on mechanical ventilation to maintain end-tidal carbon dioxide levels of 32 +/- 2 mmHg. Anesthesia was maintained with isoflurane in N2O and O2 (MAC 1.0 +/- 0.2). Routine monitoring, arterial blood pressure and intracranial pressures were measured. Three minutes prior to the tunneling phase, patients received either fentanyl 1 mcg.kg(-1) or butorphanol 1 mg in a randomized manner. Thereafter hemodynamic and intracranial pressure changes were noted during tunneling and each minute in the post-tunneling period for 5 minutes. The duration of the tunneling phase was also noted. Data were presented as number (proportion) or mean +/- SD/median (range) as appropriate. Statistical analysis was done using Wilkoxon ranksum test and the repeated measures of ANOVA. The value of p < 0.05 was considered significant. RESULTS A significant rise in the intracranial pressure and cerebral perfusion pressure along with the hemodynamic parameters was noted during the tunneling phase in both groups. The changes were of longer clinical duration in the butorphanol group. CONCLUSION Butorphanol must be used with caution in neurosurgical patients. The ventricular end of the shunt catheter should preferably be put before the tunneling phase to avoid rise in intracranial pressure.