[Application of Narcotrend-assisted anesthesia in-depth monitor during escharectomy and skin transplantation in burn patients with target-controlled infusion of remifentanil hydrochloride and propofol]

Abstract

Objective: To evaluate the feasibility and efficacy of Narcotrend (NT) monitor in monitoring the depth of anesthesia in severely burned patients with target-controlled infusion (TCI) of remifentanil hydrochloride and propofol during perioperative period.

Methods: Eighty patients with severe burn hospitalized from February to November 2011, to whom eschar excision was performed within one week after injury, were enrolled. They were classified into II to III grade according to the American Society of Anesthetists classification, and their total burn area ranged from 31% to 50%TBSA, or full-thickness burn area from 11% to 20% TBSA. Patients were divided into trial group (monitoring depth of anesthesia with routine method and NT monitor) and control group (monitoring depth of anesthesia with routine method) according to the random number table, with 40 cases in each group. All patients received TCI of remifentanil hydrochloride and propofol to induce and maintain anesthesia. During the operation, the anesthesia level of NT monitor used in the trial group was maintained from grade D1 to E0, while the fluctuation of mean arterial pressure (MAP) and heart rate of patients in control group was maintained around the basic values within a range of 20%, and on the basis of which, concentrations of two narcotics were adjusted. Concentrations of remifentanil hydrochloride and propofol during maintenance of anesthesia were recorded. The duration from drug withdrawal to waking from anesthesia (including the duration from drug withdrawal to eye opening by calling and the duration from drug withdrawal to orientation recovery) of patients was recorded. Values of MAP and heart rate at admission into the operation room, loss of consciousness, 2 min after intubation, before operation, 2, 15, and 30 min after the beginning of operation, and the end of operation were recorded. The prediction probability (P(k)) of NT stage (NTS) and NT index (NTI) in trial group, and that of MAP and heart rate in control group for two durations from drug withdrawal to waking form anesthesia were recorded. The administration of vasoactive drugs and intraoperative awareness of patients in two groups were recorded. Data were processed with t test, analysis of variance, and chi-square test, and the relationship between NTS, NTI, MAP, heart rate and their corresponding P(k) for the duration from drug withdrawal to orientation recovery was processed with Spearman correlation analysis.

Results: Maintained target effect-site concentration of remifentanil hydrochloride and target plasma concentration of propofol of patients were obviously lower in trial group [(2.62 ± 0.35) ng/mL, (3.84 ± 0.22) µg/mL] than in control group [(2.95 ± 0.21) ng/mL, (4.16 ± 0.31) µg/mL, with t values respectively -5.113 and -5.324, P values all below 0.01]. The duration from drug withdrawal to eye opening by calling and the duration from drug withdrawal to orientation recovery were obviously shorter in trial group [(10.2 ± 0.7) min, (11.1 ± 1.0) min] than in control group [(11.3 ± 1.0) min, (13.1 ± 0.7) min, with t values respectively -5.740 and -10.806, P values all below 0.01]. The MAP (except for 2 min after intubation) and the heart rate of patients in both groups were lower at the time points from loss of consciousness to the end of operation than at the time of entering operation room (with F values respectively 12.074, 36.425, P values all below 0.01 in trial group and F values respectively 21.776, 35.759, P values all below 0.01 in control group). The statistically significant difference between two groups in MAP level was only observed at the time of loss of consciousness (t = 3.985, P < 0.01). MAP level was close in two groups at other time points. Heart rates of patients in two groups were close during perioperative period. P(k) values of NTS and NTI for the duration from drug withdrawal to eye opening by calling (0.937 ± 0.025, 0.899 ± 0.049) were obviously higher than those of MAP and heart rate for this duration (0.579 ± 0.057, 0.536 ± 0.039, F = 900.337, P < 0.01). P(k) values of NTS and NTI for the duration from drug withdrawal to the orientation recovery (0.901 ± 0.031, 0.868 ± 0.046) were significantly higher than those of MAP and heart rate for this duration (0.532 ± 0.060, 0.483 ± 0.044, F = 890.895, P < 0.01). NTS, NTI, MAP, and heart rate were respectively negative, positive, positive and positive in correlation with their P(k) values for the duration from drug withdrawal to the orientation recovery (with r values from -0.734 to 0.682, P values all below 0.01). There was no statistically significant difference between two groups in administration of vasoactive drugs. No intraoperative awareness occurred.

Conclusions: Application of Narcotrend monitor in monitoring the depth of anesthesia in severely burned patients during perioperative period with TCI of remifentanil hydrochloride and propofol is beneficial to reducing dosage of narcotics and shortening duration of recovery from anesthesia, and it can accurately predict the level of consciousness of patients at the time of withdrawal of anesthesia.