Effect of low-dose ketamine on MACBAR of sevoflurane in laparoscopic cholecystectomy: A randomized controlled trial.

Abstract

Low-dose ketamine can reduce the minimum alveolar concentration of sevoflurane necessary to block the adrenergic response (MACBAR ) in animals. However, the effects of low-dose ketamine on the sevoflurane MACBAR in patients undergoing laparoscopic surgery are unclear. The aim of this study was to investigate the effects of three different low doses of ketamine on the MACBAR of sevoflurane in patients undergoing laparoscopic cholecystectomy. One hundred patients who underwent laparoscopic cholecystectomy were enrolled. After general anaesthesia induction and tracheal intubation, patients received sevoflurane anaesthesia in combination with a loading dose of saline followed by infusion or a loading dose of 0.5mg/kg ketamine followed by a continuous infusion of 5 (K1 group), 10 (K2 group) and 20μg/kg/min (K3 group). The target concentration of end-tidal sevoflurane was maintained for at least 20minutes before carbon dioxide pneumoperitoneum stimulus. The MACBAR of sevoflurane in each group was determined by using an up-and-down sequential allocation technique. Seventy-one patients completed the study. The values of MACBAR for sevoflurane were 5.3% in the K0 , 4.8% in K1 , 3.3% in K2 and 3.2% in K3 groups. The use of ketamine significantly reduced the MACBAR of sevoflurane compared to sevoflurane alone. The K2 and K3 groups showed significantly lower values of MACBAR than that in the K1 group. However, a higher dose of ketamine in the K3 group did not further reduce the sevoflurane MACBAR . The mean arterial blood pressure (MAP) values before pneumoperitoneum in the K2 and the K3 groups were significantly higher compared to those in the K0 and K1 groups. Compared with the values before pneumoperitoneum, the heart rate and MAP after pneumoperitoneum were significantly increased. Overall, the haemodynamics remained stable during the study period in all groups. A loading dose of 0.5mg/kg ketamine followed by a continuous infusion of 10.0μg/kg/min led to a significant decrease in the MACBAR of sevoflurane in patients undergoing laparoscopic cholecystectomy.