Effect of Small-dose Ketamine on Hemodynamic Changes during Lower Extremity Surgery Using a Tourniquet under General Anesthesia

Kim, Jin Mo; An, Youn Jeong; Kim, Jun Woo

Abstract

BACKGORUND: A tourniquet is commonly used to achieve bloodless field in surgery of the extremities. However, use of tourniquet occasionally has been associated with intraoperative hypertension, but the mechanism of this tourniquet-induced hypertension is unknown. We investigated the effect of preoperative ketamine on tourniquet-induced changes of arterial blood pressure (BP), heart rate (HR), cardiac index (Ci), and systemic vascular resistance index (SVRi).
METHODS
Twenty-two patients of ASA physical status class 1 and 2, scheduled for lower extremity surgery using a tourniquet, were randomly assigned into two groups. Anesthesia was maintained with 1.5-2.0 vol% enflurane and 50% N2O in O2 with endotracheal intubation. The changes of BP, HR, Ci, and SVRi were measured (1) at 10 minutes after induction, (2) at 10 minutes after injection of normal saline (control group) or ketamine 0.25 mg/kg, i.v. (ketamine group) before skin incision and tourniquet inflation, (3) at immediately and 5, 10, 15, 20, 30, and 40 minutes after inflation of tourniquet, and (4) immediately after deflation of tourniquet.
RESULTS
During tourniquet inflation, BP and HR were not significantly changed in each group and there was no significant differences between the two groups. However, Ci decreased during inflation of the tourniquet in both groups, and it significantly decreased in the control group at the time of 5 and 40 minutes after inflation of tourniquet. SVRi significantly increased during inflation of the tourniquet, and decreased immediately after deflation of the tourniquet in the control group.
CONCLUSiONS
We concluded that preoperative iV ketamine, 0.25 mg/kg can prevent tourniquet-induced hemodynamic changes in patients under general anesthesia.