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

Khanna P, Saini K, Sinha R, Nisa N, Kumar S, Maitra S. Correlation between duration of preoperative fasting and emergence delirium in pediatric patients undergoing ophthalmic examination under anesthesia: a prospective observational study. Pediatr Anesth. 2018;28:547–551.

Preoperative fasting in children can increase anxiety; however, no previously published data are available to determine whether duration of preoperative fasting correlates with postoperative emergence delirium. The aim of this study was to identify any correlation between the duration of preoperative fasting and emergence delirium in children undergoing ophthalmic examination under anesthesia. A total of 100 children between the ages of 2 and 6 years, of American Society of Anesthesiologists physical status I or II, and scheduled for examination of the eye under general anesthesia with sevoflurane were studied. Data regarding preoperative fasting were recorded, and the presence of emergence delirium was assessed by the Pediatric Anesthesia Emergence Delirium (PAED) scale. No premedication was used in any patients, but parental presence was allowed for all of them. Mean (standard deviation) duration of fasting to clear liquid was 6.3 ± 1.7 hours. Twenty-four children (24%) had at least 1 recorded PAED score >10 at any time point in the postoperative period. PAED scores at 15 and 25 minutes were significantly correlated with duration of fasting. No correlation was found between duration of fasting and blood glucose level or between fasting blood glucose and PAED score at any time point. The authors conclude that increased preoperative fasting duration may be a risk factor for postoperative emergence delirium in children undergoing ophthalmic examination under general anesthesia

Comment: Emergence delirium and the risk of perioperative pulmonary aspiration are two adverse events of significant concern to pediatric anesthesiologists. One expert recently suggested the presence of postoperative delirium or agitation should documented for every child, as if it were a “vital sign.”¹ This study by Khanna and colleagues may provide a strategy for reducing the incidence of emergence delirium, but this idea must be balanced by concerns about the potential perioperative aspiration which underlies existing NPO guidelines. A recently published comprehensive review and a large observational outcomes study reported that aspiration during procedural sedation and anesthesia outside of the operating room is a rare event.^2,3 This study also raises questions about the practice of encouraging parents to keep their children fasted several hours longer than the 2-hour recommendation for clear liquids. It is much easier to move a child into an earlier spot in the schedule that has been vacated on the day of surgery if there is no doubt about the new patient's npo status. Working to achieve the minimum allowable fasting period requires staff who are willing and able to communicate well with the child's parents at the preoperative evaluation. This process is time-consuming, and some parents may not be able or willing to follow detailed instructions. It much easier to simply instruct parents to keep the child fasted from midnight on the previous day or sooner.⁴ The solution of this emerging issue is complex, as anesthesia providers balance optimum npo status and the need to maintain an efficient anesthesia practice.

Selb CD, Rochefort H, Chomsky-Higgins K, Gosnell JE, Suh I, Shen WT, Duh QY, Finlayson E. Association of patient frailty with increased morbidity after common ambulatory general surgery operations. JAMA Surg. 2018;153:160–168.

Frailty is a measure of decreased physiological reserve that is associated with morbidity and mortality in major surgery and emergency operations. Prior to this study, the association of frailty with outcomes following ambulatory surgery had not been established. The outcomes of 140,828 patients undergoing common, elective ambulatory surgery (hernia, breast, thyroid, or parathyroid surgery) with a mean age of 59.3 years were examined. Seventy-seven percent of the patients underwent general anesthesia, while 20% received local anesthesia and monitored anesthesia care. In all surgeries, intermediate and high frailty index scores were significantly correlated with both any type of complication and serious complications. Local anesthesia with monitored anesthesia care was the only covariate associated with decreased odds of serious complications. The authors concluded that frailty is associated with increased perioperative morbidity in this sample of common, seemingly low-risk operations. Surgeons and anesthesiologists should consider frailty, rather than chronological age, when counseling and selecting patients for elective ambulatory surgery. Informed consent should be adjusted to consider frailty to ensure patients have an accurate assessment of the risk of surgery.

Comment: The assessment of frailty is commonly based on the presence of some combination of 5 domains: unintentional weight loss over the past year, self-reported exhaustion, diminished grip strength (weakness), slow walking speed, and low physical activity. The presence of 3 or more of these constitutes frailty, while 1 or more indicates a prefrail state. In approximately 10 years, the number of people older than 65 years will exceed the number of children for the first time in United States history.⁵ Over the next 30 years, the population of adults in the United States is expected to nearly double from the 43.1 million reported in 2012 to approximately 84 million.⁶ Accurate, evidence-based assessment of frailty is expected to become an increasingly integral part of office-based anesthesia and surgery soon.

Hoshijima H, Mihara T, Maruyama K, et al. McGrath videolaryngoscope versus Macintosh laryngoscope for tracheal intubation: a systematic review and meta-analysis with trial sequential analysis. J Clin Anesth. 2018;46:25–32.

The McGrath laryngoscope is a self-contained videolaryngoscope that includes a single-use blade, camera, and light source, negating the need for separate cables, screens, and power units. Several randomized controlled trials have compared the McGrath laryngoscope to the traditional Macintosh laryngoscope; however, the overall result has been inconsistent. This article provides a systematic review of these studies to assess the relative effectiveness of the 2 laryngoscopes for tracheal intubation for general anesthesia in adults. An initial collection of 473 articles was considered. After excluding case reports, mannikin trials, review articles, studies of intubation during cardiopulmonary resuscitation, and comparison of unrelated laryngoscopes, 14 articles describing 15 randomized controlled trials were selected. A total of 1459 intubations were represented in the 15 selected trials. Meta-analysis of these trials failed to show a significant difference in the success rate between the 2 laryngoscopes. The incidence of soft-tissue bleeding was significantly lower with the McGrath versus the Macintosh. No significant differences were noted regarding sore throat or dental trauma. Overall, the McGrath was found to provide superior glottic visualization but was also associated with significantly longer intubation time. The authors concluded further studies were needed to confirm their finding of increased intubation time.

Comment: A comparison of McGrath and Macintosh laryngoscopes for nasoendotracheal intubation in patients undergoing oral and maxillofacial surgery was among the 14 articles selected for this analysis.⁷ That study of oral surgery patients found the time to intubation for nasotracheal intubation to be significantly shorter for the McGrath laryngoscope. The oral surgery study also found better visualization and lower frequency of Magill forceps use associated with the McGrath. A shortcoming of the oral surgery study was the small subject number, which included 35 adult patients.

Ramgolan A, Hall GL, Zang G, Hegarty M, Ungern-Sternberg BS. Inhalational versus intravenous induction of anesthesia in children with high risk of perioperative respiratory adverse events. Anesthesiology. 2018;128:1065–1074.

Limited evidence suggests children have a lower incidence of perioperative respiratory adverse events when intravenous propofol is used compared with inhalational sevoflurane for the induction of anesthesia. This single-center, open-label randomized controlled trial of 300 children, aged 0 to 8 years, assessed the impact of induction technique on the occurrence of adverse perioperative respiratory events. Children receiving propofol for induction were significantly less likely to experience adverse events compared with sevoflurane after adjusting for age, sex, American Society of Anesthesiologists physical status classification, and weight. The authors conclude that anesthesiologists should consider intravenous induction with propofol for high-risk children, when clinically appropriate.

Comment: In this study, high-risk children were defined as having any 2 of the following: upper respiratory infection within the past 2 weeks, wheezing within the past 12 months, wheezing upon exercise, nocturnal dry cough, past or present eczema, passive smoking, and family history of hay fever, asthma, or eczema. Intravenous propofol induction, initiated immediately upon intravenous access, was compared with inhalation of 66% nitrous oxide followed by 8% sevoflurane. A laryngeal mask was used for airway management in all patients. In an accompanying editorial to this article, Davidson noted the study excluded children requiring premedication and needle-phobic children and included only children who were deemed suitable for both induction methods by the anesthesiologist.⁸ While this study provides good evidence for the controlled “all else being equal scenario,” the results of this study may not necessarily be applicable to the broader range of situations clinicians encounter in daily practice.

Ryo K-H, Song K, Lim T-Y, Choic W-J, Kim Y-K, Kim H-S. Does equi-minimum alveolar concentration value ensure equivalent analgesic or hypnotic potency? A comparison of desflurane and sevoflurane. Anesthesiology. 2018;128:1092–1098.

Minimum alveolar concentration (MAC) has traditionally been used to as the standard measure to compare the potencies of volatile anesthetics. Ideal general anesthesia is achieved from an appropriate combination of analgesia, hypnosis, and immobility; however, analgesia and hypnosis are mediated by central mechanisms, while immobility is mediated through a spinal mechanism. It is possible that immobility could be achieved without adequate analgesia or hypnosis. This prospective randomized trial of 89 patients compared the surgical pleth index and bispectral index values produced by desflurane and sevoflurane at equi-MAC under standardized nociceptive stimuli. During a steady state of 1.0 MAC, desflurane and sevoflurane did not cause similar surgical pleth and bispectral index values, suggesting equi-MAC of these 2 agents may not ensure equivalent analgesic or hypnotic potency. The results of this study are consistent with previous studies that suggest that desflurane may have greater analgesic potency than sevoflurane at equi-MAC.

Comment: The practice of switching from sevoflurane induction to desflurane maintenance is a common practice that maximizes rapid awakening and early recovery. This study emphasizes the importance of adjusting adjuvant analgesics, nitrous oxide, and other drugs in the context of switching volatile agents, as part of a balanced anesthetic technique. The authors caution readers that the bispectral index and surgical pleth indices are surrogate markers for analgesic and hypnotic levels. Further studies are needed to confirm these findings.

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