BACKGROUND: A hypertensive response is seen when a skull pin is inserted for a craniotomy. The risk of morbidity and mortality is high in patients with intracranial pathology. Many methods have been introduced to overcome the problem. We compared the hemodynamic effects and changes of intracranial pressure when we used lidocaine or fentanyl for blunting the hypertensive response. METHODS: Thirty-two patients scheduled for a craniectomy were divided into two groups: an IV (intravenous) bolus of fentanyl (2micro gram/kg) group or lidocaine (1.5 mg/kg) group. An anesthesia was induced with fentanyl (2micro gram/kg), thiopental (5-7 mg/kg), lidocaine (1.5 mg/kg) and vecuronium (0.1 mg/kg), and was maintained with isoflurane 1 MAC (minimum alveolar anesthetic concentration) in nitrous oxide 50% and oxygen. After induction of anesthesia, a lumbar subarachnoid catheter was inserted for CSFP (cerebrospinal fluid pressure) measurement. An IV bolus of either fentanyl (2micro gram/kg) or lidocaine (1.5 mg/kg) was administered prior to insertion of the skull pin by a randomized method. CSFP, MAP (mean arterial pressure), and HR (heart rate) were measured before and 5 min after induction of anesthesia, immediately before and each mininute for five measurements after skull pin insertion. RESULTS: There were no intergroup differences in the values of CSFP and HR. The MAP increased 9+/-14 (mean+/-SD) mmHg and 4+/-12 (mean+/-SD) mmHg 1 min after the skull pin insertion compared with immediately before skull pin insertion in the fentanyl group and lidocaine group respectively. The MAP recovered 2 min after the skull pin insertion in both groups. CPP (cerebral perfusion pressure) recovered 3 min and 2 min after the skull pin insertion in the fentanyl group and lidocaine group respectively. CONCLUSIONS: An IV bolus of either fentanyl or lidocaine before skull pin insertion resulted in a stable value of CSFP, CPP and HR.