A Review of Current Literature of Interest to the Office-Based Anesthesiologist

Hyman J, Park C, Lin H-M, et al. Olanzapine for the prevention of nausea and vomiting after ambulatory surgery: a randomized controlled trial. Anesthesiology. 2020;132:1419–1428.

Postdischarge nausea and vomiting after ambulatory surgery is a common problem that is not adequately addressed in current practice. This prospective, randomized, double-blind, parallel-group, placebo-controlled study was designed to test the hypothesis that oral olanzapine is superior to placebo at preventing postdischarge nausea and vomiting. In a single-center trial of 140 patients, the authors compared a single preoperative dose of olanzapine 10 mg to a placebo, in adult female patients 50 years old or less, undergoing ambulatory gynecologic or plastic surgery with general anesthesia. All patients received standard antiemetic prophylaxis with dexamethasone and ondansetron. The primary composite outcome was nausea and/or vomiting in the 24-hour period after discharge. Secondary outcomes included severe nausea, vomiting, and side effects. The primary outcome occurred in 26 of 69 patients (38%) in the placebo group and in 10 of 71 patients (14%) in the olanzapine group. Severe nausea occurred in 14 patients (20%) in the placebo group and 4 patients (6%) in the olanzapine group. Vomiting occurred in 8 patients (12%) in the placebo group and 2 patients (3%) in the olanzapine group. The median score for sedation (scale 0–10, with 10 being highest) in the 24 hours after discharge was 4 (interquartile range, 2–7) in the placebo group and 6 (interquartile range, 3–8) in the olanzapine group (p = .023). When combined with ondansetron and dexamethasone, the addition of olanzapine relative to placebo decreased the risk of nausea and/or vomiting in the 24 hours after discharge from ambulatory surgery by approximately 60% with a slight increase in reported sedation.

Comment: Nausea and vomiting continue to be the most objectionable postoperative adverse effects reported by patients. All the patients in this study received perioperative antiemetic prophylaxis with dexamethasone and ondansetron, yet over one-third of patients in the placebo group still experienced nausea and vomiting after discharge, when intravenous rescue medications were no longer available. Olanzapine is an atypical antipsychotic drug that has activity involving many of the receptors involved in the pathogenesis of nausea and vomiting, including dopaminergic, serotonergic, histaminic, adrenergic, and muscarinic receptors. An important feature of olanzapine is its delayed peak plasma level at 6 hours and long half-life of 30 hours. This compares favorably to the 3-hour half-life of ondansetron. This study suggests a single dose of olanzapine may reduce the risk of postdischarge nausea and vomiting in adult oral surgical and dental patients undergoing treatment in the ambulatory setting. Although a significant reduction in nausea and vomiting was demonstrated, future studies are needed to determine if lower doses maintain antiemetic effectiveness while reducing sedation.

Dexter F, Parra M, Brown J, Loftus R. Perioperative COVID-19 defense: an evidence-based approach for optimization of infection control and operating room management. Anesth Analg. 2020;131:37–42.

Confirmed modes of viral transmission are typically contact with contaminated environmental surfaces and aerosolization. This review of the literature identifies 8 evidence-based practices for preventing and controlling operating room infections. Steps 1 through 4 include designation of clean and dirty workplace areas and containers for receiving used instruments and careful surface disinfection, double gloving prior to induction, disinfection of the surgical site and oral cavity before surgery, and use of a closed lumen intravenous delivery system. Step 5 includes environmental monitoring for the presence of Staphylococcus aureus, Enterococcus, Klebsiella, Acinetobacter, Pseudomonas, and Enterobacter transmission; Steps 6 through 8 include minimizing the number of perioperative personnel, limiting each operating room to 1 case with terminal cleaning using ultraviolet light or equivalent, and avoiding communal postoperative care environments. These 8 programmatic recommendations stand on a substantial body of empirical evidence characterizing the epidemiology of perioperative transmission and infection development.

Comment: The dental office, and even the dental operating room environment, differ in fundamental, important ways from the standard hospital operating room. Regardless, the amount of published evidence regarding viral transmission in the context of dental treatment is relatively sparse and superficial compared with literature examining the operating room environment. Although direct comparison of the 2 environments may only yield limited information, this paper provides an excellent, evidence-based resource for those planning studies on infection transmission and control in the dental operatory.

Fischer M, Grass B, Kemper M, Weiss M, Dave M, Ungern-Sternberg B. Cuffed pediatric endotracheal tubes—Outer cuff diameters compared to age-related airway dimensions. Pediatr Anesthesia. 2020;30:424–434.

This study compared the residual cuff diameters of pediatric endotracheal tubes. Cuff diameters of 5 common tracheal tubes with internal diameters of 3 to 7 mm were measured at a cuff pressure of 20 cm H₂0 and compared with cuffed diameters claimed by their manufacturers. Cuffs made from polyurethane possessed less variation (91%–118%) from manufacturer-claimed values for outer diameter than those made from polyvinylchloride (91%–146%). Cuff diameters claimed by the manufacturer varied significantly (86%–188%) from the median diameter of the corresponding age range. Significant variation (68%–157%) from the maximum mid-tracheal lateral diameter for the corresponding age was also found. The authors concluded that significant heterogeneity exists between the cuff diameters of identically sized tubes of different brands. The authors also noted many commonly produced pediatric endotracheal tubes appear to lack anatomic rationale for their design.

Comment: Suboptimal cuff inflation is associated with inconsistent end-tidal carbon dioxide readings, environmental anesthetic gas pollution, and incomplete sealing of the trachea. Overinflation is associated with an increased risk of ischemia and tissue damage to the tracheal mucosa. Inconsistencies in the design of pediatric endotracheal tubes has been shown in many past studies. This study is unique in that it provides the first comprehensive comparison of cuff diameters in several currently marketed brands while proposing refinements to improve the anatomical correctness of pediatric endotracheal tubes.

Ji H, Kim A, Ebinger JE, et al. Sex differences in blood pressure trajectories over the life course. JAMA Cardiol. 2020;5:255–262.

This large longitudinal study of blood pressure (BP) measures collected data from 32,833 men and women for a period of 43 years (1971–2014) in 4 community-based US cohort studies, spanning the ages of 5 to 98 years. In contrast with the notion that important vascular disease processes in women lag behind men by 10 to 20 years, this sex-specific analysis indicates that BP measures actually progress more rapidly in women, beginning early in life. This early-onset sexual dimorphism may set the stage for later-life cardiovascular diseases that tend to present differently, not simply later, in women compared with men.

Comment: The authors view BP as the single most accessible metric of vascular aging as well as the largest contributor to ischemic heart disease and heart failure risks in both sexes. This large, longitudinal study reinforces other published studies that suggest vascular physiology is fundamentally different between men and women. Women, compared with men, clearly exhibit a steeper increase in BP that begins as early as the third decade and continues throughout the course of life. Hormonal variations are not sufficient to account for these differences, as women also possess smaller hearts, smaller blood vessel caliber, and total body size, even after adjusting for body surface area. The authors suggest these findings will contribute to a new understand of the progression and development of cardiovascular disease.

Matava C, Kovatsis P, Lee J, et al. Pediatric airway management in COVID-19 patients: consensus guidelines from the Society for Pediatric Anesthesia's Pediatric Difficult Intubation Collaborative and the Canadian Pediatric Anesthesia Society. Anesth Analg. 2020;131:61–73.

The Pediatric Difficult Intubation Collaborative (PeDI-C) currently includes 35 hospitals from 6 countries. The consensus guidelines on pediatric airway management in this paper are based on expert opinion and early data about the features of COVID-19. The overarching goals during care include minimizing aerosolized respiratory secretions, minimizing the number of clinicians in contact with a patient, and recognizing that undiagnosed asymptomatic patients may shed the virus and infect healthcare workers. Recommendations include administering anxiolytic medications, intravenous anesthetic inductions, tracheal intubation using video laryngoscopes and cuffed tracheal tubes, use of in-line suction catheters, and modifying workflow to recover patients from anesthesia in the operating room. Importantly, PeDI-C recommends that anesthesiologists consider using appropriate personal protective equipment when performing aerosol-generating medical procedures in asymptomatic children, in addition to known or suspected children with COVID-19. Airway procedures should be done in negative pressure rooms when available. Adequate time should be allowed for operating room cleaning and air filtration between surgical cases. Research using rigorous study designs is urgently needed to inform safe practices during the COVID-19 pandemic. Until further information is available, PeDI-C advises that clinicians consider these guidelines to enhance the safety of healthcare workers during airway management when performing aerosol-generating medical procedures. These guidelines have been endorsed by the Society for Pediatric Anesthesia and the Canadian Pediatric Anesthesia Society.

Comment: This Collaborative strongly supports the use of precautions while treating asymptomatic children. Some have noted a recently published comparison of N95 masks to surgical masks for preventing the transmission of the influenza virus¹ and concluded surgical masks may be sufficient for treating asymptomatic children in the dental office setting. The authors caution against this argument, noting SARS-CoV-2 is 2 to 3 times more contagious than influenza and may aerosolize and remain longer than influenza virus.^2,3

Krause M, McWilliams S, Bullard K, et al. Neostigmine versus sugammadex for reversal of neuromuscular blockade and effects on reintubation for respiratory failure or newly initiated noninvasive ventilation: an interrupted time series design. Anesth Analg. 2020;131:141–151.

Pulmonary complications related to residual neuromuscular blockade are associated with postoperative morbidity and mortality. Using an interrupted time series design, these examiners tested whether proportions of reintubation for respiratory failure or new noninvasive ventilation were changed after a system-wide transition of the standard reversal agent from neostigmine to sugammadex. Of 13,031 screened patients, a total of 7316 adult patients undergoing a procedure with general anesthesia that included pharmacologic reversal of neuromuscular blockade and admission ≥1 night were studied. Two groups were identified: the presugammadex and the postsugammadex groups. The primary outcome was defined as a composite of reintubation for respiratory failure or new noninvasive ventilation. The composite respiratory outcome occurred in 6.1% of the nonsugammadex group versus 4.2% of the sugammadex group. The authors concluded the system-wide transition of the standard pharmacologic reversal agent from neostigmine to sugammadex was associated with a reduction in the odds of the composite respiratory outcome

Comment: In addition to a lower experience rate of re-intubation and new noninvasive ventilation, reversal with sugammadex was associated with an immediate reduction in the odds for hypoxic events.

Also of interest:

Chen X, Liu Y, Gong Y, et al. Perioperative management of patients infected with the novel coronavirus: recommendation from the Joint Task Force of the Chinese Society of Anesthesiology and the Chinese Association of Anesthesiologists. Anesthesiology. 2020;132:1307–1316.

The recommendations in this document are based upon the practice and experience of anesthesiologists providing care during the COVID-19 outbreak in Wuhan, China.

Grassi L, Kacmarek R, Berra L. Ventilatory mechanics in the patient with obesity. Anesthesiology. 2020;132:1246–1256.

This focused review discusses the effect of abdominal fat on airway management and the mechanics of ventilation in the context of both spontaneous and mechanical ventilation.

Schwartz A, Low D, Hunter S, Lockman J. Don't let your student fall asleep. Anesthesiology. 2020;132:1556.

This annotated graphic provides an excellent illustration for anesthesiologists teaching nasal intubation to learners. The rational for and use of Magill forceps and a tube bender are discussed, along with the importance of patient positioning.

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