Response entropy is more reactive than bispectral index during laparoscopic gastric banding

Benefits of dexmedetomidine on postoperative analgesia after bariatric surgery: a systematic review and meta-analysis

INTRODUCTION

Anesthetic management of morbidly obese patients is challenging, particularly in those undergoing bariatric surgery. Dexmedetomidine is a α2-adrenergic receptor agonist that is increasingly used in the perioperative setting for its beneficial properties including sedation, anxiolysis, analgesia with opioid-sparing effects, and minimal impact on respiration. The objective of this study was to evaluate the effect of dexmedetomidine on postoperative analgesia and recovery-related outcomes among patients undergoing bariatric surgery.

EVIDENCE ACQUISITION

We conducted a systematic review and meta-analysis of MEDLINE, EMBASE, and CENTRAL databases from conception to September 2021 for randomized controlled trials (RCTs) using dexmedetomidine in bariatric patients on postoperative outcomes. Outcomes were pooled using random effects model and presented as relative risks (RR) or mean differences (MD) with 95% confidence intervals (CI).

EVIDENCE SYNTHESIS

In total, 20 RCTs with 665 patients in the dexmedetomidine group and 671 patients in the control groups were included. Among RCTs, the dexmedetomidine group had significantly lower opioid usage at 24-hours postoperatively (MD: -5.14, 95%CI: -10.18 to -0.10; moderate certainty), reduced pain scores on a 10-point scale at PACU arrival (MD: -1.69, 95%CI: -2.79 to -0.59; moderate certainty) and 6 hours postoperatively (MD: -1.82, 95%CI: - 3.00 to -0.64; low certainty), and fewer instances of nausea (RR: 0.59, 95%CI: 0.45 to 0.75; moderate certainty) and vomiting (RR: 0.25, 95%CI: 0.15 to 0.43; moderate certainty), compared to control groups.

CONCLUSIONS

Dexmedetomidine is an efficacious anesthesia adjunct in patients undergoing bariatric surgery. These benefits of dexmedetomidine may be considered in the multi-modal analgesic management and enhanced recovery pathways in this high-risk population.

Light levels of anaesthesia after relaxation for tracheal intubation - comparison of succinylcholine and cis-atracurium

BACKGROUND

Use of a single bolus of a hypnotic together with non-depolarizing muscle relaxants for anaesthesia induction may cause inappropriate light levels of anaesthesia (ILLA). The purpose of this study was to compare the incidence of ILLA during anaesthesia induction using either cis-atracurium (CIS) or succinylcholine (SUC).

METHODS

Patients (n = 65) received fentanyl and propofol. Relaxants were randomly chosen and were either CIS 0.15 mg/kg, or SUC 1 mg/kg. After achieving relaxation, ILLA were assessed double-blinded by the isolated forearm technique and electroencephalogram -derived values.

RESULTS

Time from induction to complete relaxation was 335 ± 55 s with CIS and 141 ± 26 s with SUC. Nine patients in the CIS group (26%), but no patient in the SUC group responded to commands before endotracheal intubation (P < 0.01). During the entire induction up to 1 min after intubation in the CIS group, 24 of 35 patients (68%) showed 31 episodes of ILLA, as defined as responsiveness to commands and spontaneous movements. With SUC, 8 of 30 patients (27%) showed 11 episodes of ILLA (P < 0.01). In patients with ILLA, state entropy (SE) and spectral edge frequency (SEF) were 68 ± 10 (mean ± standard deviation) and 17 ± 4 Hz, respectively, and in patients without ILLA, SE and SEF were 40 ± 14 and 12 ± 3 Hz, respectively (P < 0.01).

CONCLUSION

The onset time of a muscle relaxant has substantial impact on the incidence of ILLA during induction of anaesthesia. Entropy and SEF may indicate the presence of ILLA.

Comparison of spectral entropy and BIS VISTA™ monitor during general anesthesia for cardiac surgery

OBJECTIVES

We compared the primary metrics of the Spectral entropy M-ENTROPY™ module and BIS VISTA™ monitor-i.e., bispectral index (BIS), state entropy (SE), and response entropy (RE) in terms of agreement and correlation during general anesthesia for cardiac surgery. We also evaluated responsiveness of electroencephalogram (EEG)-based and hemodynamic parameters to surgical noxious stimulation, skin incision, and sternotomy, hypothesizing that RE would be a better responsiveness predictor.

METHODS

BIS and entropy sensors were applied before anesthesia induction in 32 patients having elective cardiac surgery. Total intravenous anesthesia was standardized and guided by the BIS index with neuromuscular blockade tested with train-of-four monitoring. Parameters included SE, RE, BIS, forehead electromyography (EMG), and hemodynamic variables. Time points for analyzing BIS, entropy, and hemodynamic values were 1 min before and after: anesthesia induction, intubation, skin incision, sternotomy, cannulation of the aorta, cardiopulmonary bypass (CPB), cross-clamping the aorta, de-clamping the aorta, and end of CPB; also after starting the re-warming phase and at 10, 20, 30, and 40 min following.

RESULTS

The mean difference between BIS and SE (Bland-Altman) was 2.14 (+16/- 11; 95% CI 1.59-2.67), and between BIS and RE it was 0.02 (+14/- 14; 95% CI 0.01-0.06). BIS and SE (r(2) = 0.66; P = 0.001) and BIS and RE (r(2) = 0.7; P = 0.001) were closely correlated (Pearson's). EEG parameters, EMG values, and systolic blood pressure significantly increased after skin incision, and sternotomy. The effect of surgical stimulation (Cohen's d) was highest for RE after skin incision (-0.71; P = 0.0001) and sternotomy (-0.94; P = 0.0001).

CONCLUSION

Agreement was poor between the BIS index measured by BIS VISTA™ and SE values at critical anesthesia time points in patients undergoing cardiac surgery. RE was a good predictor of arousal after surgical stimulation regardless of the surgical level of muscle relaxation. Index differences most likely resulted from different algorithms for calculating consciousness level.

Does spectral entropy reflect the response to intubation or incision during propofol-remifentanil anesthesia?

BACKGROUND

Spectral entropy is an electroencephalogram-based monitoring technique with a frequency band enlarged to include the electromyogram spectrum, which is intended to help to assess analgesia. Although its correlation with hypnosis has been shown, its performance during a noxious stimulation and the influence of neuromuscular blockade have not been described.

METHODS

In this prospective, open, multicenter study, 105 patients received propofol then remifentanil target-controlled infusion for induction of anesthesia, with randomized remifentanil targets ranging from 2 to 8 ng/mL. Half of the patients received neuromuscular blockade. Intubation and incision were used as standard noxious stimulations, motor or hemodynamic responses were recorded, and spectral entropy values before and after stimulations were compared between responders and nonresponders.

RESULTS

No difference was found in response entropy (RE), state entropy (SE), or (RE - SE) between patients with or without hemodynamic response to stimulations. Patients with motor response to intubation had higher values of RE, SE, and (RE - SE) both before and after the intubation than patients with no response. These results were confirmed by a prediction probability analysis, showing a significant but weak predictive value of entropy for motor response only.

CONCLUSIONS

Entropy predicted a motor response to noxious stimulations but not a hemodynamic response, which limits its usefulness for assessing the analgesic component of anesthesia in paralyzed patients. High values (RE >55) before the stimulation should be avoided in order to decrease the risk of motor response, but lower values might not prevent this response when the opioid concentration is insufficient, despite an adequate hypnosis.