Prevalence of discordant elevations of state entropy and bispectral index in patients at amnestic sevoflurane concentrations: a historical cohort study.

BACKGROUND: Processed electroencephalogram (EEG) monitors help assess the hypnotic state during general anesthesia or sedation. Maintaining the bispectral index (BIS) or state entropy (SE) between 40 and 60 has been recommended to mitigate anesthesia awareness. Nonetheless, SEs > 70 were frequently observed at end-tidal sevoflurane concentrations unlikely to allow awareness. We sought to determine the prevalence of elevated discordant measurements during BIS and SE monitoring. METHODS: Electronic data collected over 11 months at two academic hospitals were retrospectively reviewed. At the hospital using SE, all cases were included with patients ≥ 18 yr and sevoflurane administered for at least 30 min during surgery. A cohort of cases propensity matched by age and American Society of Anesthesiologist Physical Status were selected from the hospital using BIS. Elevated discordant EEG indices were defined as values > 70 occurring during stable end-tidal sevoflurane concentrations > 1.5%. The odds ratio (OR) based on the probability of a case having at least one elevated discordant SE or BIS lasting ≥ two minutes (primary endpoint) was calculated. RESULTS: At each hospital, 3,690 cases were studied. The mean (95% confidence interval [CI]) incidence of cases with at least one interval of an elevated discordant EEG index lasting at least two minutes was 3.6% (2.8% to 4.4%) for SE compared with 0.24% (0.17% to 0.27%) for BIS (pooled OR, 17.0; 95% CI, 8.3 to 34.7; P < 0.001). CONCLUSIONS: The prevalence of an elevated discordant EEG index is much greater with SE than with BIS. Elevated index values occurring at anesthetic concentrations well above the awareness threshold need to be assessed to determine if they indicate an inadequate depth of anesthesia requiring treatment or if they simply reflect the underlying monitoring algorithm.

Perioperative use of bispectral (BIS) monitor for a pressure ulcer patient with locked-in syndrome (LIS).

The bispectral (BIS) monitor uses brain electroencephalographic data to measure the depth of sedation and pharmacological response during anaesthetic procedures. In this case, the BIS monitor was used for another purpose, to demonstrate postoperatively to the nursing staff that a patient with history of locked-in syndrome (LIS), who underwent pressure ulcer debridement, had periods of wakefulness and apparent sensation, even with his eyes closed. Furthermore, as patients with LIS can feel pain, despite being unable to move, local block or general anaesthesia should be provided for sharp surgical debridement and other painful procedures. This use of the BIS has shown that as a general rule, the staff should treat the patient as though he might be awake and sensate even if he does not open his eyes or move his limbs. The goal of this study was to continuously monitor pain level and communicate these findings to the entire wound team, i.e. anaesthesiologists, surgeons and nurses.

Development of an enhanced recovery protocol after laser ablation surgery protocol: a preliminary analysis.

Background: Enhanced recovery after surgery (ERAS) programs are a model of care that aim to improve patient outcomes, reduce complications, and facilitate recovery while reducing healthcare-associated costs and admission length. While such programs have been developed in other surgical subspecialties, there have yet to be guidelines published specifically for laser interstitial thermal therapy (LITT). Here we describe the first multidisciplinary ERAS preliminary protocol for LITT for the treatment of brain tumors. Methods: Between the years 2013 and 2021, 184 adult patients consecutively treated with LITT at our single institution were retrospectively analyzed. During this time, a series of pre, intra, and postoperative adjustments were made to the admission course and surgical/anesthesia workflow with the goal of improving recovery and admission length. Results: The mean age at surgery was 60.7 years with a median preoperative Karnofsky performance score of 90 ± 13. Lesions were most commonly metastases (50%) and high-grade gliomas (37%). The mean length of stay was 2.4 days, with the average patient being discharged 1.2 days after surgery. There was an overall readmission rate of 8.7% with a LITT-specific readmission rate of 2.2%. Three of 184 patients required repeat intervention in the perioperative period, and there was one perioperative mortality. Conclusions: This preliminary study shows the proposed LITT ERAS protocol to be a safe means of discharging patients on postoperative day 1 while preserving outcomes. Although future prospective work is needed to validate this protocol, results show the ERAS approach to be promising for LITT.

On the use of multivariable piecewise-linear models for predicting human response to anesthesia.

The standard modeling paradigm used to describe the relationship between input anesthetic agents and output patient endpoint variables are single-input single-output pharmacokinetic-pharmacodynamic (PK-PD) compartment models. In this paper, we propose the use of multivariable piecewise-linear models to describe the relations between inputs that include anesthesia, surgical stimuli and disturbances to a variety of patient output variables. Subspace identification methods are applied to clinical data to construct the models. A comparison of predicted and measured responses is completed, which includes predictions from PK-PD models, and piecewise-linear time-invariant models.