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

What is known and objective Low-dose ketamine can reduce the minimum alveolar concentration of sevoflurane necessary to block the adrenergic response (MAC(BAR)) in animals. However, the effects of low-dose ketamine on the sevoflurane MAC(BAR)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 MAC(BAR)of sevoflurane in patients undergoing laparoscopic cholecystectomy. Methods 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 0.5 mg/kg ketamine followed by a continuous infusion of 5 (K(1)group), 10 (K(2)group) and 20 mu g/kg/min (K(3)group). The target concentration of end-tidal sevoflurane was maintained for at least 20 minutes before carbon dioxide pneumoperitoneum stimulus. The MAC(BAR)of sevoflurane in each group was determined by using an up-and-down sequential allocation technique. Results and discussion Seventy-one patients completed the study. The values of MAC(BAR)for sevoflurane were 5.3% in the K-0, 4.8% in K-1, 3.3% in K(2)and 3.2% in K(3)groups. The use of ketamine significantly reduced the MAC(BAR)of sevoflurane compared to sevoflurane alone. The K(2)and K(3)groups showed significantly lower values of MAC(BAR)than that in the K(1)group. However, a higher dose of ketamine in the K(3)group did not further reduce the sevoflurane MAC(BAR). The mean arterial blood pressure (MAP) values before pneumoperitoneum in the K(2)and the K(3)groups were significantly higher compared to those in the K(0)and K(1)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. What is new and conclusion A loading dose of 0.5 mg/kg ketamine followed by a continuous infusion of 10.0 mu g/kg/min led to a significant decrease in the MAC(BAR)of sevoflurane in patients undergoing laparoscopic cholecystectomy.