Effects of different target remifentanil concentrations on MACBAR of sevoflurane and catecholamineRAR in gynecological patients undergoing laparoscopic surgery

Abstract

Objective To investigate the effects of different targeted plasma remifentanil concentrations on the minimum alveolar concentration of sevoflurane (MACBAR) and minimum plasma catecholamine concentration for blocking adrenergic response (CatecholamineBAR: NEBR, EBAR) in gynecological patients undergoing laparoscopic surgery using carbon dioxide pneumoperitoneum.Methods Seventy five gynecological patients undergoing laparoscopic surgery, ASA physical status Ⅰ -Ⅱ, were randomly assigned to three groups: control group (R0) and 2 remifentanil groups (R1, R2). Anesthesia was induced by target controlled infusion with remifentanil (plasma concentration 2 μg/L), and intravenous infection with 0.3 mg/kg etomidate. Vecuronium 0.1 mg/kg was administered to facilitate tracheal intubation. After intubation anesthesia was maintained with sevoflurane in all groups. But in R0, R1and R2, the targeted plasma concentration of remifentanil was adjusted to 0, 1 μg/L and 2 μg/L, respectively. The MACBAR of sevoflurane was determined by using a sequential design and pneumoperitoneum stimulation in each group, while blood samples were collected at corresponding time points to determinate catecholamine concentrations and the values of NEBAR, EBAR were calculated.Results In group R0, R1 and R2, the MACBARs of sevoflurane were (4.60±0.30)％, (2.37±0.21) ％ and(1.70±0.28) ％, respectively.No significant differences were found in NEBAR, EBAR and minimum MAP among the three groups. Conclusion The targeted plasma concentrations of remifentanil at 1 μg/L and 2 μg/L can significantly reduce MACBAR of sevoflurane by 48％ and 63％ respectively in gynecological patients undergoing laparoscopic surgery. However, the value of catecholamineBAR was not influenced by the changes of remifentanil's target plasma concentration and the end-tidal sevoflurane concentration. Key words: Sevoflurane; Remifentanil; MAC ; Adrenergic response; Catecholamine; Pneumoperitoneum