Cannabis Use and Inhalational Anesthesia Administration in Older Adults: A Propensity Matched Retrospective Cohort Study.

BACKGROUND: Cannabis use is associated with higher intravenous anesthetic administration. Similar data regarding inhalational anesthetics are limited. With rising cannabis use prevalence, understanding any potential relationship with inhalational anesthetic dosing is crucial. We compared average intraoperative isoflurane/sevoflurane minimum alveolar concentration equivalents between older adults with and without cannabis use. METHODS: The electronic health records of 22,476 surgical patients ≥65 years old at the University of Florida Health System between 2018-2020 were reviewed. The primary exposure was cannabis use within 60 days of surgery, determined via i) a previously published natural language processing algorithm applied to unstructured notes and ii) structured data, including International Classification of Disease codes for cannabis use disorders and poisoning by cannabis, laboratory cannabinoids screening results, and RxNorm codes. The primary outcome was the intraoperative time-weighted average of isoflurane/sevoflurane minimum alveolar concentration equivalents at one-minute resolution. No a priori minimally clinically important difference was established. Patients demonstrating cannabis use were matched 4:1 to non-cannabis use controls using a propensity score. RESULTS: Among 5,118 meeting inclusion criteria, 1,340 patients (268 cannabis users and 1,072 nonusers) remained after propensity score matching. The median and interquartile range (IQR) age was 69 (67, 73) years; 872 (65.0%) were male, and 1,143 (85.3%) were non-Hispanic White. The median (IQR) anesthesia duration was 175 (118, 268) minutes. After matching, all baseline characteristics were well-balanced by exposure. Cannabis users had statistically significantly higher average minimum alveolar concentrations than nonusers [mean±SD: 0.58±0.23 versus 0.54±0.22, respectively; mean difference=0.04; 95% confidence limits, 0.01 to 0.06; p=0.020]. CONCLUSION: Cannabis use was associated with administering statistically significantly higher inhalational anesthetic minimum alveolar concentration equivalents in older adults, but the clinical significance of this difference is unclear. These data do not support the hypothesis that cannabis users require clinically meaningfully higher inhalational anesthetics doses.

Cannabis use and acute postoperative pain outcomes in older adults: a propensity matched retrospective cohort study.

INTRODUCTION: Cannabis use is increasing among older adults, but its impact on postoperative pain outcomes remains unclear in this population. We examined the association between cannabis use and postoperative pain levels and opioid doses within 24 hours of surgery. METHODS: We conducted a propensity score-matched retrospective cohort study using electronic health records data of 22 476 older surgical patients with at least 24-hour hospital stays at University of Florida Health between 2018 and 2020. Of the original cohort, 2577 patients were eligible for propensity-score matching (1:3 cannabis user: non-user). Cannabis use status was determined via natural language processing of clinical notes within 60 days of surgery and structured data. The primary outcomes were average Defense and Veterans Pain Rating Scale (DVPRS) score and total oral morphine equivalents (OME) within 24 hours of surgery. RESULTS: 504 patients were included (126 cannabis users and 378 non-users). The median (IQR) age was 69 (65-72) years; 295 (58.53%) were male, and 442 (87.70%) were non-Hispanic white. Baseline characteristics were well balanced. Cannabis users had significantly higher average DVPRS scores (median (IQR): 4.68 (2.71-5.96) vs 3.88 (2.33, 5.17); difference=0.80; 95% confidence limit (CL), 0.19 to 1.36; p=0.01) and total OME (median (IQR): 42.50 (15.00-60.00) mg vs 30.00 (7.50-60.00) mg; difference=12.5 mg; 95% CL, 3.80 mg to 21.20 mg; p=0.02) than non-users within 24 hours of surgery. DISCUSSION: This study showed that cannabis use in older adults was associated with increased postoperative pain levels and opioid doses.

Dosing Cefazolin for Surgical Site Infection Prophylaxis in Adolescent Idiopathic Scoliosis Surgery: Intermittent Bolus or Continuous Infusion?-A Pilot Study.

Background: Cefazolin may minimize the risk of surgical site infection (SSI) following posterior spinal fusion (PSF) for adolescent idiopathic scoliosis (AIS). Cefazolin dosing recommendations vary and there is limited evidence for achieved tissue concentrations. Methods: We performed a randomized, controlled, prospective pharmacokinetic pilot study of 12 patients given cefazolin by either intermittent bolus (30 mg/kg every 3 h) or continuous infusion (30 mg/kg bolus followed by 10/mg/kg per hour) during PSF for AIS. Results: Patients were well matched for demographic and perioperative variables. While total drug exposure, measured as area-under-the-curve (AUC), was similar in plasma for bolus and infusion dosing, infusion dosing achieved greater cefazolin exposure in subcutaneous and muscle tissue. Using the pharmacodynamic metric of time spent above minimal inhibitory concentration (MIC), both bolus and infusion dosing performed well. However, when targeting a bactericidal concentration of 32 µg/mL, patients in the bolus group spent a median of 1/5 and 1/3 of the typical 6 h operative time below target in subcutaneous and muscle tissue, respectively. Conclusions: We conclude that intraoperative determination of cefazolin tissue concentrations is feasible and both bolus and infusion dosing of cefazolin achieve concentrations in excess of typical MICs. Infusion dosing appears to more consistently achieve bactericidal concentrations in subcutaneous and muscle tissues.

Neurobehavioral Abnormalities in Offspring of Young Adult Male Rats With a History of Traumatic Brain Injury.

Children of parents with traumatic brain injury (TBI) are more likely to develop psychiatric disorders. This association is usually attributed to TBI-induced changes in parents' personality and families' social environment. We tested the hypothesis that offspring of young adult male rats with TBI develop neurodevelopmental abnormalities in the absence of direct social contact with sires. Male Sprague-Dawley rats (F0 generation) in the TBI group underwent moderate TBI via a midline fluid percussion injury that involved craniectomy under sevoflurane (SEVO) anesthesia for 40 min on post-natal Day 60 (P60), while F0 rats in the control group were placed in a new cage, one per cage, for the equivalent time duration. A subset of F0 rats was sacrificed on P66 to assess acute changes in hypothalamic-pituitary-adrenal (HPA) axis and inflammation markers. The remaining F0 males were mated with naive females on P90 to generate offspring (F1 generation). The F0 males and F1 males and females were sequentially evaluated in the elevated plus maze, for pre-pulse inhibition of acoustic startle, in the Morris water maze, and for resting and stress levels of serum corticosterone starting on ∼P105 (F0) and ∼P60 (F1), followed by tissue collection for further analyses. Acutely, the F0 TBI males had messenger RNA (mRNA) transcripts altered to support an increased hypothalamic and hippocampal Na+-K+-Cl- (Slc12a2) Cl- importer / K+-2Cl- (Slc12a5) Cl- exporter ratio and decreased hippocampal glucocorticoid receptors (Nr3c1), as well as increased serum levels of corticosterone, interleukin-1ß (IL-1ß), and biomarkers of activated hippocampal microglia and astrocytes. Long-term, F0 TBI rats exhibited increased corticosterone concentrations at rest and under stress, anxiety-like behavior, impaired sensory-motor gating, and impaired spatial memory. These abnormalities were underpinned by reduced mRNA levels of hypothalamic and hippocampal mineralocorticoid receptors (Nr3c2), hippocampal Nr3c1, and hypothalamic brain-derived neurotrophic factor (Bdnf), as well as elevated serum levels of IL-1ß, and biomarkers of activated hippocampal microglia and astrocytes. F1 male offspring of TBI sires exhibited abnormalities in all behavioral tests, while their F1 female counterparts had abnormal pre-pulse inhibition responses only. F1 male offspring of TBI sires also had reduced mRNA levels of hippocampal Nr3c1 and Nr3c2, as well as hypothalamic and hippocampal Bdnf, whereas increases in inflammatory markers were more profound in F1 females. These findings suggest that offspring of sires with a history of a moderate TBI that involved craniectomy under SEVO anesthesia for 40 min, develop sex-dependent neurobehavioral abnormalities in the absence of direct social interaction between the sire and the offspring.

Analyzing the value of IONM as a complex intervention: The gap between published evidence and clinical practice.

OBJECTIVE: Intraoperative neurophysiological monitoring (IONM) was investigated as a complex intervention (CI) as defined by the United Kingdom Medical Research Council (MRC) in published studies to identify challenges and solutions in estimating IONM's effects on postoperative outcomes. METHODS: A scoping review to April 2022 of the influence of setting on what was implemented as IONM and how it influenced postoperative outcomes was performed for studies that compared IONM to no IONM cohorts. IONM complexity was assessed with the iCAT_SR tool. Causal graphs were used to represent this complexity. RESULTS: IONM implementation depended on the surgical procedure, institution and/or surgeon. "How" IONM influenced neurologic outcomes was attributed to surgeon or institutional experience with the surgical procedure, surgeon or institutional experience with IONM, co-interventions in addition to IONM, models of IONM service delivery and individual characteristics of the IONM provider. Indirect effects of IONM mediated by extent of tumor resection, surgical approach, changes in operative procedure, shorter operative time, and duration of aneurysm clipping were also described. There were no quantitative estimates of the relative contribution of these indirect effects to total IONM effects on outcomes. CONCLUSIONS: IONM is a complex intervention whose evaluation is more challenging than that of a simple intervention. Its implementation and largely indirect effects depend on specific settings that are usefully represented in causal graphs. SIGNIFICANCE: IONM evaluation as a complex intervention aided by causal graphs and multivariable analysis could provide a valuable framework for future study design and assessments of IONM effectiveness in different settings.

Intergenerational Perioperative Neurocognitive Disorder.

Accelerated neurocognitive decline after general anesthesia/surgery, also known as perioperative neurocognitive disorder (PND), is a widely recognized public health problem that may affect millions of patients each year. Advanced age, with its increasing prevalence of heightened stress, inflammation, and neurodegenerative alterations, is a consistent contributing factor to the development of PND. Although a strong homeostatic reserve in young adults makes them more resilient to PND, animal data suggest that young adults with pathophysiological conditions characterized by excessive stress and inflammation may be vulnerable to PND, and this altered phenotype may be passed to future offspring (intergenerational PND). The purpose of this narrative review of data in the literature and the authors' own experimental findings in rodents is to draw attention to the possibility of intergenerational PND, a new phenomenon which, if confirmed in humans, may unravel a big new population that may be affected by parental PND. In particular, we discuss the roles of stress, inflammation, and epigenetic alterations in the development of PND. We also discuss experimental findings that demonstrate the effects of surgery, traumatic brain injury, and the general anesthetic sevoflurane that interact to induce persistent dysregulation of the stress response system, inflammation markers, and behavior in young adult male rats and in their future offspring who have neither trauma nor anesthetic exposure (i.e., an animal model of intergenerational PND).

The Enhanced Recovery After Surgery pathway for posterior cervical surgery: a retrospective propensity-matched cohort study.

OBJECTIVE: The Enhanced Recovery After Surgery (ERAS) protocol is a comprehensive, multifaceted approach aimed at improving postoperative outcomes. It incorporates a range of strategies to promote early and more effective recovery, including reducing pain, complications, and length of stay, without increasing readmission rate. To date, ERAS for spine surgery patients has been primarily limited to lumbar surgery and anterior cervical decompression and fusion (ACDF). ERAS has not been previously studied for posterior cervical surgery, which may present a greater opportunity for improvement in patient outcomes with ERAS than ACDF. This single-institution, multi-surgeon study assessed the impact of an ERAS protocol in patients undergoing posterior cervical decompression surgery. METHODS: This study included a retrospective consecutive patient cohort with controls that were propensity matched for age, body mass index, sex, home opioid use, surgical levels, Nurick grade, and smoking status. In addition, consecutive patients who underwent posterior cervical decompression surgery for degenerative disease from December 2014 to December 2021 were included. ERAS was implemented in December 2018. Demographic, perioperative, clinical, and radiographic information was gathered. Regression models were created to evaluate length of stay, physiological function, pain levels, and opioid use. The primary focus was length of stay, with secondary outcomes including timing of ambulation, bowel movement, and voiding; daily pain scores; opioid consumption; discharge status; 30-day readmission rates; and reoperation rates. RESULTS: There were 366 patients included in the study, all of whom were included in multivariate models, and 254 (127 in each cohort) were included on the basis of matching. After propensity matching, patient characteristics, operative procedures, and operative duration were similar between groups. The ERAS cohort had a significantly improved length of stay (3.2 vs 4.7 days, p < 0.0001) and home discharge rate (80% vs 50%, p < 0.001) without an increase in readmission rate. The ERAS cohort had an earlier day of the first ambulation (p = 0.003), bowel movement (p = 0.014), and voiding (p = 0.001). ERAS demonstrated a significantly lower composite complication rate (1.1 vs 1.8, p < 0.0001). ERAS resulted in better maximum pain scores (p = 0.043) and trended toward improved mean pain scores (p = 0.072), although total opioid use was similar. CONCLUSIONS: Implementing a novel ERAS protocol significantly improved length of stay, return of physiological function, home discharge, complications, and maximum pain score after posterior cervical surgery.

Intergenerational Perioperative Neurocognitive Disorder in Young Adult Male Rats with Traumatic Brain Injury.

BACKGROUND: The authors tested the hypothesis that the effects of traumatic brain injury, surgery, and sevoflurane interact to induce neurobehavioral abnormalities in adult male rats and in their offspring (an animal model of intergenerational perioperative neurocognitive disorder). METHODS: Sprague-Dawley male rats (assigned generation F0) underwent a traumatic brain injury on postnatal day 60 that involved craniectomy (surgery) under 3% sevoflurane for 40 min followed by 2.1% sevoflurane for 3 h on postnatal days 62, 64, and 66 (injury group). The surgery group had craniectomy without traumatic brain injury, whereas the sevoflurane group had sevoflurane only. On postnatal day 90, F0 males and control females were mated to generate offspring (assigned generation F1). RESULTS: Acutely, F0 injury rats exhibited the greatest increases in serum corticosterone and interleukin-1ß and -6, and activation of the hippocampal microglia. Long-term, compared to controls, F0 injury rats had the most exacerbated corticosterone levels at rest (mean ± SD, 2.21 ± 0.64 vs. 7.28 ± 1.95 ng/ml, n = 7 - 8; P < 0.001) and 10 min after restraint (133.12 ± 33.98 vs. 232.83 ± 40.71 ng/ml, n = 7 - 8; P < 0.001), increased interleukin-1ß and -6, and reduced expression of hippocampal glucocorticoid receptor (Nr3c1; 0.53 ± 0.08 fold change relative to control, P < 0.001, n = 6) and brain-derived neurotrophic factor genes. They also exhibited greater behavioral deficiencies. Similar abnormalities were evident in their male offspring, whereas F1 females were not affected. The reduced Nr3c1 expression in F1 male, but not female, hippocampus was accompanied by corresponding Nr3c1 promoter hypermethylated CpG sites in F0 spermatozoa and F1 male, but not female, hippocampus. CONCLUSIONS: These findings in rats suggest that young adult males with traumatic brain injury are at an increased risk of developing perioperative neurocognitive disorder, as are their unexposed male but not female offspring.

Frailty Assessment and Prehabilitation Before Complex Spine Surgery in Patients With Degenerative Spine Disease: A Narrative Review.

Degenerative spine disease increases in prevalence and may become debilitating as people age. Complex spine surgery may offer relief but becomes riskier with age. Efforts to lessen the physiological impact of surgery through minimally invasive techniques and enhanced recovery programs mitigate risk only after the decision for surgery. Frailty assessments outperform traditional tools of perioperative risk stratification. The extent of frailty predicts complications after spine surgery such as reoperation for infection and 30-day mortality, as well as elements of social cost such as hospital length of stay and discharge to an advanced care facility. Symptoms of spine disease overlap with phenotypic markers of frailty; therefore, different frailty assessment tools may perform differently in patients with degenerative spine disease. Beyond frailty, however, cognitive decline and psychosocial isolation may interact with frailty and affect achievable surgical outcomes. Prehabilitation, which has reduced perioperative risk in colorectal and cardiac surgery, may benefit potential complex spine surgery patients. Typical prehabilitation includes physical exercise, nutrition supplementation, and behavioral measures that may offer symptomatic relief even in the absence of surgery. Nonetheless, the data on the efficacy of prehabilitation for spine surgery remains sparse and barriers to prehabilitation are poorly defined. This narrative review concludes that a frailty assessment-potentially supplemented by an assessment of cognition and psychosocial resources-should be part of shared decision-making for patients considering complex spine surgery. Such an assessment may suffice to prompt interventions that form a prehabilitation program. Formal prehabilitation programs will require further study to better define their place in complex spine care.

Utility of evoked potentials during anterior cerebral artery and anterior communicating artery aneurysm clipping.

Objective: To investigate the optimal combination of somatosensory- and transcranial motor-evoked potential (SSEP/tcMEP) modalities and monitored extremities during clip reconstruction of aneurysms of the anterior cerebral artery (ACA) and its branches. Methods: A retrospective review of 104 cases of surgical clipping of ruptured and unruptured aneurysms was performed. SSEP/tcMEP changes and postoperative motor deficits (PMDs) were assessed from upper and lower extremities (UE/LE) to determine the diagnostic accuracy of each modality separately and in combination. Results: PMDs were reported in 9 of 104 patients; 7 LE and 8 UE (3.6% of 415 extremities). Evoked potential (EP) monitoring failed to predict a PMD in 8 extremities (1.9%). Seven of 8 false negatives had subarachnoid hemorrhage. Sensitivity and specificity in LE were 50% and 97% for tcMEP, 71% and 98% for SSEP, and 83% and 98% for dual-monitoring of both tcMEP/SSEP. Sensitivity and specificity in UE were 38% and 99% for tcMEP, and 50% and 97% for tcMEP/SSEP, respectively. Conclusions: Combined tcMEP/SSEP is more accurate than single-modality monitoring for LE but is relatively insensitive for UE PMDs. Significance: During ACA aneurysm clipping, multiple factors may confound the ability of EP monitoring to predict PMDs, especially brachiofacial hemiparesis caused by perforator insufficiency.

Enhanced recovery after surgery (ERAS) improves return of physiological function in frail patients undergoing one- to two-level TLIFs: an observational retrospective cohort study.

BACKGROUND CONTEXT: The enhanced recovery after surgery (ERAS) protocol is a multimodal approach which has been shown to facilitate recovery of physiological function, and reduce early post-operative pain, complications, and length of stay (LOS) in open one- to two-level TLIF. The benefit of ERAS in specifically frail patients undergoing TLIF has not been demonstrated. Frailty is clinically defined as a syndrome of physiological decline that can predispose patients undergoing surgery to poor outcomes. PURPOSE: This study primarily evaluated the benefit of an ERAS protocol in frail patients undergoing one- or two-level open TLIF compared to frail patients without ERAS. Secondarily, we assessed whether outcomes in frail patients with ERAS approximated those seen in nonfrail patients with ERAS. STUDY DESIGN: Retrospective consecutive patient cohort with controls propensity-matched for age, body mass index, sex, and smoking status. PATIENT SAMPLE: Consecutive patients that underwent one- or two-level open TLIF for degenerative disease from August, 2015 to July, 2021 by a single surgeon. ERAS was implemented in December 2018. OUTCOME MEASURES: Primary outcome measure was return of postoperative physiological function defined as the summation of first day to ambulate, first day to bowel movement, and first day to void. Additional outcome measures included LOS, daily average pain scores, opioid use, discharge disposition, 30-day readmission rate, and reoperation. METHODS: A retrospective analysis of frail patients > 65 years of age undergoing one- to two-level open TLIF post-ERAS were compared to propensity matched frail pre-ERAS patients. Frailty was assessed using the Fried phenotype classification (score >1). Patient demographics, LOS, first-day-to-ambulate (A1), first-day-to-bowel movement (B1), first-day-to-void (V1) were collected. Return of physiological function was defined as A1+B1+V1. Primary analysis was a comparison of frail patients pre-ERAS versus post-ERAS to determine effect of ERAS on return of physiologic function with frailty. Secondary analysis was a comparison of post-ERAS frail versus post-ERAS nonfrail patients to determine if return of physiologic function in frail patients with ERAS approximates that of nonfrail patients. RESULTS: In the primary analysis, 32 frail patients were included with mean age ± standard deviation of 72.8±4.4 years, mean BMI 28.8±5.5, 65.6% were male, 15 pre-ERAS and 17 post-ERAS. Patient characteristics were similar between groups. After ERAS implementation, return of physiological function improved by a mean 3.2 days overall (post-ERAS 3.4 vs. pre-ERAS 6.7 days) (p<.0001), indicating a positive effect of ERAS in frail patients. Additionally, length of stay improved by 1 day (4.8±1.6 vs. 3.8±1.9 days, p<.0001). Total daily intravenous morphine milligram equivalent (MME) as well as average daily pain scores were similar between groups. Secondarily, 26 nonfrail patients post ERAS were used as a comparison group with the 17 post-ERAS frail cohort. Mean age of this cohort was 73.4±4.6 years, mean BMI 27.4±4.9, and 61.9% were male. Return of physiologic function was similar between cohorts (post-ERAS nonfrail 3.5 vs. post-ERAS frail 3.4 days) (p=.938), indicating the benefit with ERAS in frail patients approximates that of nonfrail patients. CONCLUSIONS: ERAS significantly improves return of physiologic function and length of stay in patients with frailty after one- to two-level TLIF, and approximates improved outcomes seen in non-frail patients.

Enhanced recovery after surgery (ERAS) for open transforaminal lumbar interbody fusion: a retrospective propensity-matched cohort study.

BACKGROUND: The enhanced recovery after surgery (ERAS) protocol is a multidisciplinary, multimodal approach which has been shown to facilitate recovery of physiological function, and reduce postoperative pain, complication rates, and length of stay without adversely affecting readmission rates. Design and implementation of ERAS protocols in the recent spine surgery literature has primarily focused on patients undergoing minimally invasive lumbar surgery. However, conventional open transforaminal lumbar interbody fusion (TLIF) remains a common procedure and to date there are no studies assessing an ERAS protocol in this patient population. PURPOSE: This study presents a single surgeon experience implementing an ERAS protocol in patients undergoing 1- or 2-level open TLIF. STUDY DESIGN/SETTING: Retrospective consecutive patient cohort with controls propensity-matched for age, body mass index, sex, and smoking status. PATIENT SAMPLE: Consecutive patients that underwent 1- or 2-level open TLIF for degenerative disease from 12/2018 - 02/2021 and controls from 12/2011-12/2017 by a single surgeon. ERAS was implemented in December 2018. OUTCOME MEASURES: Primary: length of stay; Secondary: first day to ambulate, first day to bowel movement, first day to void, daily average and maximum pain scores, opioid use, discharge disposition, 30-day readmission rate, and re-operations. METHODS: Demographic, perioperative, clinical, radiographic data were collected. Multivariate mixed-linear regression models were developed for length of stay, physiological function, pain scales, and opiate use. RESULTS: There were 114 patients included with 57 in each cohort. After propensity matching, patient characteristics were similar between groups. Operative time decreased significantly after institution of ERAS (170±44 vs. 141±37 minutes, p <.0001) as did length of stay (4.6±1.7 vs. 3.6±1.6 days, p<.0001). First day of ambulation, bowel movement, and bladder voiding improved by 0.8 (p<.0001), 0.7 (p=.008), and 0.8 (p<.0001) days, respectively, in the ERAS cohort. Total daily intravenous morphine milligram equivalent (MME) (8±9 vs. 36±38, p<0.0001) and total 72-hour MME consumption (53±33 vs. 68±48, p<.0001) was significantly lower in the ERAS cohort; however, 72-hour MME consumption was not found to be significantly different in a sensitivity analysis controlling for preoperative MME. Average daily pain scores were similar between groups. CONCLUSIONS: Consistent with other studies demonstrating benefit of an ERAS protocol for minimally invasive spine procedures, ERAS was associated with decreased operative time, reduced length of stay, decrease in IV opioid consumption, and improved physiological outcomes for open 1- and 2-level TLIF. ERAS can be a potentially effective strategy for improving patient outcome and efficiency of healthcare resources for common conventional spinal surgeries such as open TLIF.

Best Practices in Facial Nerve Monitoring.

OBJECTIVES/HYPOTHESIS: Facial nerve monitoring (FNM) has evolved into a widely used adjunct for many surgical procedures along the course of the facial nerve. Even though majority opinion holds that FNM reduces the incidence of iatrogenic nerve injury, there are few if any studies yielding high-level evidence and no practice guidelines on which clinicians can rely. Instead, a review of the literature and medicolegal cases reveals significant variations in methodology, training, and clinical indications. STUDY DESIGN: Literature review and expert opinion. METHODS: Given the lack of standard references to serve as a resource for FNM, we assembled a multidisciplinary group of experts representing more than a century of combined monitoring experience to synthesize the literature and provide a rational basis to improve the quality of patient care during FNM. RESULTS: Over the years, two models of monitoring have become well-established: 1) monitoring by the surgeon using a stand-alone device that provides auditory feedback of facial electromyography directly to the surgeon, and 2) a team, typically consisting of surgeon, technologist, and interpreting neurophysiologist. Regardless of the setting and the number of people involved, the reliability of monitoring depends on the integration of proper technical performance, accurate interpretation of responses, and their timely application to the surgical procedure. We describe critical steps in the technical set-up and provide a basis for context-appropriate interpretation and troubleshooting of recorded signals. CONCLUSIONS: We trust this initial attempt to describe best practices will serve as a basis for improving the quality of patient care while reducing inappropriate variations. LEVEL OF EVIDENCE: 4 Laryngoscope, 131:S1-S42, 2021.

Transcranial Motor Evoked Potential Monitoring in a Patient With a Deep Brain Stimulator: A Case Report.

SUMMARY: A major complication of surgical scoliosis correction is permanent injury of the spinal cord. Intraoperative neuromonitoring continually evaluates spinal cord function through monitoring sensory and corticospinal motor tracts. There is no literature or manufacturer recommendation on whether transcranial motor evoked potential (tcMEP) monitoring can be performed safely in the presence of a deep brain stimulator (DBS) system. A 17-year-old adolescent boy with severe neuromuscular scoliosis presented for a posterior spinal fusion. The patient suffered from generalized dystonia treated with a DBS terminating in the left and right globus pallidus internus. The competing goals of monitoring motor function during the spinal fusion and preserving the integrity of the DBS system were discussed preoperatively. The DBS system was deactivated for the duration of surgery, and tcMEPs were used sparingly at the lowest suitable stimulation voltage. Intraoperative management focused on facilitating neurophysiologic monitoring through a total intravenous anesthetic of propofol, methadone, and remifentanil. The tcMEPS remained unchanged throughout the operation and the patient emerged able to move his lower extremities to command. Postoperatively, the DBS system was turned back on and showed retained settings, normal functioning, and unchanged impedance of the DBS leads. Neither the patient nor his parents reported any subjective changes in the symptoms of dystonia. The authors conclude that monitoring tcMEPs in the presence of a DBS implant may be done safely, when the clinical circumstances suggest that the added information gained from tcMEPs outweighs the theoretical risk to the DBS system and the course of the medical condition treated by the DBS.

Methadone and a Clinical Pathway in Adolescent Idiopathic Scoliosis Surgery: A Historically Controlled Study.

STUDY DESIGN: Historically controlled clinical trial. OBJECTIVES: Patients presenting for correction of adolescent idiopathic scoliosis (AIS) by posterior spinal fusion may benefit from structured clinical pathways. We studied the effects of implementing a published clinical pathway for the perioperative care of patients with AIS that required intraoperative use of methadone at our institution. METHODS: We performed a historically controlled clinical trial of patients undergoing posterior spinal fusion for AIS by comparing a retrospectively collected control group of 25 patients with a prospective experimental group of 14 patients receiving methadone, gabapentin, propofol, and remifentanil as part of a new clinical pathway. RESULTS: Use of the pathway decreased average pain scores evaluated by the Numeric Rating Scale in the 24 hours following surgery (4.8 [4-6] to 3.4 [2-4], P = .03 [-2.6 to -0.2; t = -2.3]) and postoperative opioid consumption by 76% (41 [29-51] mg to 10 [4-17] mg, P < .001 [-45 to -15; Welch's t = 4.9]) during the same period. Improved analgesia and reduced reliance on opioids facilitated other postoperative elements of the clinical pathway and shortened the average hospital length of stay by 1 day (4 [3-6] days to 3 [3-5] days, P = .001 [-2 to -1; U = 67, Z = -3.3]). CONCLUSIONS: Multimodal analgesia and a clinical pathway add value in the perioperative care of patients undergoing posterior spinal fusion for AIS by improving analgesia and shortening hospitalization. The prospective arm of the trial was registered at clinicaltrials.gov under NCT02481570.

Neuroanesthesiologists as interoperative neurophysiologists: a collaborative cognitive apprenticeship model of training in a community of clinical practice.

Directing intraoperative neurophysiologic monitoring (IONM) is a patient care activity for which no formal training programs exist, even though the need for well-trained practitioners is readily evident while caring for patients with diseases of the brain, spinal cord, spinal column, or nervous system. Here, we present the theoretical basis and institutional experience for a successful model of learning a new and complex set of skills: the medical direction of IONM. In a major academic institution, a clinical community of practice absorbed new members with professional backgrounds ranging from a recent neuroanesthesia fellowship to several decades of neuroanesthesia practice and trained them in a collaborative cognitive apprenticeship model to medically direct IONM. Our community of practice comprises experienced technicians, a diplomate of the American Board of Neurophysiologic Monitoring (DABNM), and six neuroanesthesiologists. This group forms the base of the scaffolding or structure where the apprenticeship and learning take place. The clinical community of practice has trained eight new members in the medical direction of IONM. The group has also trained four outside anesthesiologists-one of whom went on to become certified as a DABNM-who went on to develop the IONM program at a major children's hospital. This collaborative cognitive apprenticeship in anesthesiology to learn the medical direction of IONM is quite innovative as it integrates new members and expands the range of existing ones. In our model, the entire community is elevated by the reciprocal interactions of master clinicians, novice apprentices, and the community of practice.

Intergenerational Effects of Sevoflurane in Young Adult Rats.

BACKGROUND: Sevoflurane administered to neonatal rats induces neurobehavioral abnormalities and epigenetic reprogramming of their germ cells; the latter can pass adverse effects of sevoflurane to future offspring. As germ cells are susceptible to reprogramming by environmental factors across the lifespan, the authors hypothesized that sevoflurane administered to adult rats could induce neurobehavioral abnormalities in future offspring, but not in the exposed rats themselves. METHODS: Sprague-Dawley rats were anesthetized with 2.1% sevoflurane for 3 h every other day between postnatal days 56 and 60. Twenty-five days later, exposed rats and nonexposed controls were mated to produce offspring. RESULTS: Adult male but not female offspring of exposed parents of either sex exhibited deficiencies in elevated plus maze (mean ± SD, offspring of both exposed parents vs. offspring of control parents, 35 ± 12 vs. 15 ± 15 s, P < 0.001) and prepulse inhibition of acoustic startle (offspring of both exposed parents vs. offspring of control parents, 46.504 ± 13.448 vs. 25.838 ± 22.866%, P = 0.009), and increased methylation and reduced expression of the potassium ion-chloride ion cotransporter KCC2 gene (Kcc2) in the hypothalamus. Kcc2 was also hypermethylated in sperm and ovary of the exposed rats. Surprisingly, exposed male rats also exhibited long-term abnormalities in functioning of the hypothalamic-pituitary-gonadal and -adrenal axes, reduced expression of hypothalamic and hippocampal Kcc2, and deficiencies in elevated plus maze (sevoflurane vs. control, 40 ± 24 vs. 25 ± 12 s, P = 0.038) and prepulse inhibition of startle (sevoflurane vs. control, 39.905 ± 21.507 vs. 29.193 ± 24.263%, P < 0.050). CONCLUSIONS: Adult sevoflurane exposure affects brain development in male offspring by epigenetically reprogramming both parental germ cells, while it induces neuroendocrine and behavioral abnormalities only in exposed males. Sex steroids may be required for mediation of the adverse effects of adult sevoflurane in exposed males.

Proof of principle: Preoperative cognitive reserve and brain integrity predicts intra-individual variability in processed EEG (Bispectral Index Monitor) during general anesthesia.

BACKGROUND: Preoperative cognitive reserve and brain integrity may explain commonly observed intraoperative fluctuations seen on a standard anesthesia depth monitor used ubiquitously in operating rooms throughout the nation. Neurophysiological variability indicates compromised regulation and organization of neural networks. Based on theories of neuronal integrity changes that accompany aging, we assessed the relative contribution of: 1) premorbid cognitive reserve, 2) current brain integrity (gray and white matter markers of neurodegenerative disease), and 3) current cognition (specifically domains of processing speed/working memory, episodic memory, and motor function) on intraoperative neurophysiological variability as measured from a common intraoperative tool, the Bispectral Index Monitor (BIS). METHODS: This sub-study included participants from a parent study of non-demented older adults electing unilateral Total Knee Arthroplasty (TKA) with the same surgeon and anesthesia protocol, who also completed a preoperative neuropsychological assessment and preoperative 3T brain magnetic resonance imaging scan. Left frontal two-channel derived EEG via the BIS was acquired preoperatively (un-medicated and awake) and continuously intraoperatively with time from tourniquet up to tourniquet down. Data analyses used correlation and regression modeling. RESULTS: Fifty-four participants met inclusion criteria for the sub-study. The mean (SD) age was 69.5 (7.4) years, 54% were male, 89% were white, and the mean (SD) American Society of Anesthesiologists score was 2.76 (0.47). We confirmed that brain integrity positively and significantly associated with each of the cognitive domains of interest. EEG intra-individual variability (squared deviation from the mean BIS value between tourniquet up and down) was significantly correlated with cognitive reserve (r = -.40, p = .003), brain integrity (r = -.37, p = .007), and a domain of processing speed/working memory (termed cognitive efficiency; r = -.31, p = .021). Hierarchical regression models that sequentially included age, propofol bolus dose, cognitive reserve, brain integrity, and cognitive efficiency found that intraoperative propofol bolus dose (p = .001), premorbid cognitive reserve (p = .008), and current brain integrity (p = .004) explained a significant portion of intraoperative intra-individual variability from the BIS monitor. CONCLUSIONS: Older adults with higher premorbid reserve and less brain disease were more stable intraoperatively on a depth of anesthesia monitor. Researchers need to replicate findings within larger cohorts and other surgery types.