Effect of a Subanesthetic Dose of Intravenous Ketamine and/or Local Anesthetic Infiltration on Hemodynamic Responses to Skull-Pin Placement

Abstract

Insertion of cranial pins for stabilization of the head can result in a marked hypertensive response, which may adversely affect cerebral hemodynamics. The efficacy of a subanesthetic dose of intravenous ketamine (0.5 mg/kg) and/or lidocaine infiltration (1%) at pin fixation sites before pinning was studied in a prospective, double-blind, placebo-controlled, randomized trial of 40 patients. The subjects were divided into four groups of 10. Patients belonging to the placebo and lidocaine groups received intravenous normal saline (NS), followed by local infiltration with NS at pin insertion sites in the placebo group and 1% lidocaine in the lidocaine group. Patients belonging to the ketamine and ketamine-lidocaine groups received intravenous ketamine followed by local infiltration with NS in the ketamine group, and lidocaine infiltration in the ketamine-lidocaine group. Heart rate (HR) and invasive mean blood pressure (MBP) were recorded before intravenous medication and then at various time intervals until 15 minutes after pin fixation. Intergroup comparison of MBP and HR by 2-way analysis of variance revealed a significant difference between the groups and various time points (P < .05). Post hoc analysis revealed maximum increase in MBP each hour in the placebo group. Mean blood pressure response in the ketamine group was similar to the placebo group. Significant attenuation of MBP and HR was observed in the lidocaine and ketamine-lidocaine groups (P < .05). A minimal increase in HR was observed in the lidocaine-ketamine group. The current study demonstrates maximum attenuation of hemodynamic responses when a subanesthetic dose of intravenous ketamine (0.5 mg/kg) is administered with 1% lidocaine infiltration.