Effects of different remifentanil target concentrations on MAC BAR of sevoflurane in gynaecological patients with CO2 pneumoperitoneum stimulus

Abstract

To investigate the effects of different target plasma remifentanil concentrations on the minimum alveolar concentration of sevoflurane (MAC) for blocking adrenergic response (BAR) during laparoscopic gynaecological surgery with carbon dioxide insufflation. Seventy-five gynaecological patients with ASA I-II undergoing laparoscopic surgery were randomly assigned to three groups. Anaesthesia was induced by sevoflurane, and 0.1 mg kg(-1) of vecuronium i.v. was injected to facilitate tracheal intubation. After intubation the target plasma concentrations of remifentanil in Groups 1, 2, and 3 were adjusted to 0, 1, and 2 ng ml(-1), respectively. The changes in haemodynamics were observed before and after the creation of carbon dioxide pneumoperitoneum. The MAC BAR of sevoflurane in each group was determined by using an up-and-down sequential-allocation technique, and blood samples were collected at corresponding time points to determine the concentrations of remifentanil, norepinephrine, and epinephrine. In Groups 1, 2 and 3, the MAC BAR of sevoflurane was 4.6% (CI 95%: 4.3-4.9%), 2.4% (CI 95%: 2.2-2.6%), and 1.7% (CI 95%: 1.4-2.1%), respectively. No significant differences were found in the increase of norepinephrine, epinephrine, and mean arterial pressure after compared with before insufflation of pneumoperitoneum among the three groups. Remifentanil can effectively decrease the sevoflurane concentration to block sympathetic adrenergic response to CO2 pneumoperitoneum stimulus. At similar MAC BAR the haemodynamic and adrenergic response is not affected by the infused remifentanil concentration. The number of this clinical trial registry is ChiCTR-TRC-13004005, and the Universal Trial Number is U1111-1151-5630.