The concentration of desflurane preventing spectral entropy change during surgical stimulation: A prospective randomized trial

Abstract Study objective To determine the concentration of desflurane necessary to blunt changes in spectral entropy during surgical incision when two different target-controlled effect-site concentrations of remifentanil (1 and 3 ng/ml) were infused. Design Prospective, randomized controlled study. Setting Operating room of a university hospital. Interventions Forty-two patients undergoing general anesthesia for elective surgery were enrolled and randomly allocated to the R1 (1 ng/ml of remifentanil, n = 21) or R3 (3 ng/ml of remifentanil, n = 21) group. After at least a 10-min administration of target-controlled remifentanil concentration and predetermined end-tidal desflurane following endotracheal intubation, changes in spectral entropy in response to surgical incision were evaluated. Measurements Concentration of desflurane necessary to blunt changes in spectral entropy during surgical incision for each group was determined using Dixon's up-and-down method. Hemodynamic variables including mean arterial pressure (MAP) and heart rate (HR) were measured. Main results Concentration of desflurane necessary to blunt changes in spectral entropy during surgical incision in 50% of patients (EC50 ) was 4.1% (95% CI: 3.5–4.7%) for the R1 group and 3.4% (95% CI: 3.0–3.8%) for the R3 group ( P = 0.033). Additionally, the calculated EC95 values using the logistic regression analysis for the R1 and R3 groups were 5.8% (95% CI: 5.0–10.8%) and 5.1% (95% CI: 4.3–10.6%), respectively. MAPs and HRs were significantly higher in the R1 than in the R3 group after surgical incision. Conclusions Desflurane 4.1% with remifentanil 1 ng/ml and desflurane 3.4% with remifentanil 3 ng/ml significantly blunt the change in spectral entropy after surgical incision in 50% of patients.