VOLUME 32, ISSUE 1
Kristina L. Goff, MD
Assistant Professor, Department of Anesthesiology & Pain Medicine
The University of Texas Southwestern Medical Center
Dallas, TX Baylor College of Medicine
Houston, TX
Understanding the Literature: A Summary of Recent Publications
Based on the lecture “From Print to Practice: Recent Publications and their Possible Impact on Anesthesia Care” presented by Dr. Girish P. Joshi at the September 2019 Texas Society of Anesthesiologists Annual Meeting
Each September at the Texas Society of AnesthesiologistseAnnual Meeting, Dr. Girish Joshi gives a presentation highlighting recent publications that he believes may have a significant impact on the practice of anesthesiology. In this article, we seek to summarize the most salient points of his talk, touching on the key studies he mentions and their potential influences on our clinical practice.
Monitoring Depth of Anesthesia
Wildes TS, Mickle AM, et al. ENGAGES Research Group. Effect of Electroencephalography-Guided Anesthetic Administration on Postoperative Delirium Among Older Adults Undergoing Major Surgery: The ENGAGES Randomized Clinical Trial. JAMA. 2019 Feb 5;321(5):473-483.
In an attempt to minimize exposure to anesthetic agents and, thereby, potentially improve postoperative outcomes, many physician anesthesiologists have incorporated the use of intraoperative electroencephalography to gauge and adjust anesthetic depth. But is this additional monitoring really providing patients a benefit? The ENGAGES trial, published in JAMA in 2019, indicates that EEG-guided anesthetics do not impact postoperative delirium in elderly patients undergoing major surgery, although intraoperative use of EEG does decrease the median end tidal volatile agent concentration as compared to standard practice. Of note, the median minimum alveolar concentration (MAC) value in the EEG-guided group was 0.69 (interquartile range [IQR] – 0.62-0.77), suggesting that MAC values of less than 1 are likely adequate to prevent awareness/recall.
Patient Blood Management
Mueller MM, Van Remoortel H, et al. ICC PBM Frankfurt 2018 Group. Patient Blood Management: Recommendations From the 2018 Frankfurt Consensus Conference. JAMA. 2019 Mar 12;321(10):983-997.
Optimal transfusion thresholds have been the subject of some debate, with new data suggesting lower hemoglobin values are often acceptable and may help decrease the incidence of transfusion-related adverse events. Recommendations from the 2018 Frankfurt Patient Blood Management Consensus Conference were published in JAMA in 2019. These guidelines suggest a hemoglobin threshold of 7 g/dL is acceptable for transfusion in hemodynamically stable patients without an acute coronary syndrome (ACS), as well as for clinically stable, critically ill patients without significant cardiovascular concerns. In patients with ACS or patients with significant cardiovascular comorbidities undergoing major surgery (e.g. repair of hip fracture), a higher threshold (8 g/dL) is recommended. For patients undergoing cardiac surgery, a transfusion trigger of 7.5 g/dL may be considered.
Nitrous Oxide
Buhre W, Disma N, et al. European Society of Anaesthesiology Task Force on Nitrous Oxide: a narrative review of its role in clinical practice. Br J Anaesth. 2019 May;122(5):587-604.
Nitrous oxide (N2O) is a useful anesthetic adjunct but its use has declined in recent years due to uncertain concerns about its safety and side effect profile. In 2019, the European Society of Anesthesiologists Task Force on Nitrous Oxide released a narrative summary of the existing data surrounding nitrous oxide use. They included findings from 319 observational and randomized controlled trials. Their review addresses many specific concerns, including the risk of postoperative nausea and vomiting, the potential risks of use during laparoscopic abdominal surgeries, the potential for cardiovascular and cerebrovascular ischemia related to N2O-induced elevations in plasma homocysteine levels, and the potential environmental effects of medical N2O use. Based on the available data, they conclude that “many perceived drawbacks of medical N2O administration have been exaggerated or misplaced.” Considering this and recognizing the benefits with regard to decreased opioid requirements and postoperative pain, they encourage the continued, but judicious, use of N2O and recommend further investigation into novel applications for N2O in the treatment of chronic conditions such as pain and depression.
Cricoid Pressure
Birenbaum A, Hajage D, et al. IRIS Investigators Group. Effect of Cricoid Pressure Compared With a Sham Procedure in the Rapid Sequence Induction of Anesthesia: The IRIS Randomized Clinical Trial. JAMA Surg. 2019 Jan 1;154(1):9-17.
Cricoid pressure (CP) is traditionally considered a key element of the rapid sequence intubation (RSI) process, yet, its practicality and efficacy are often questioned. Many continue to perform cricoid pressure during RSI for medicolegal reason, despite concerns that it can make intubation more challenging, and may induce relaxation of the lower esophageal sphincter. A recent, large sample, randomized, blinded, non-inferiority trial compared the effectiveness of cricoid pressure to a sham procedure to determine whether cricoid pressure decreases pulmonary aspiration. The relative risk of aspiration was found to be the same with both CP and the sham intervention, However, because the rate of aspiration was significantly lower than predicted, the study was underpowered to demonstrate noninferiority compared to the sham procedure. The time to successful intubation was longer and the intubation grade worse in the CP group. This study is certainly a building block in the argument against the routine use of cricoid pressure, although, notably, this study did not look at the obstetric population.
Non-Operating Room Anesthesia
Smith ZL, Mullady DK, et al. A randomized controlled trial evaluating general endotracheal anesthesia versus monitored anesthesia care and the incidence of sedation-related adverse events during ERCP in high-risk patients. Gastrointest Endosc. 2019 Apr;89(4):855-862.
Non-operating room anesthesia (NORA) is an increasing area of focus in our field, as anesthesia services are requested in more varied environments. Many of these cases require procedural sedatio, and anesthesiologists must carefully balance the demands of patient comfort, procedural success, and rapid recovery. Indeed, these anesthetics frequently prove challenging, and, in a closed claims analysis published in Current Opinions in Anesthesiology, 50% of all anesthesia-related claims occurred in NORA cases. Endoscopic retrograde cholangiopancreatography (ERCP) cases are some of the more complex procedures performed in a non-operating room setting. Anesthesiologists often struggle with the decision between monitored anesthesia care (MAC) and general endotracheal anesthesia (GETA). Smith and colleagues published a randomize, controlled trial looking at outcomes in high risk patients undergoing ERCP with either MAC or GETA. They found a significantly higher rate of sedation-related adverse events (including the use of airway maneuvers, the incidence of hypoxia and/or respiratory failure, and the incidence of hemodynamic compromise) among patients receiving MAC. They reported a 10% incidence of the need to convert from MAC to GETA due to respiratory instability. This study suggests that, at least in patients with high risk for respiratory compromise, GETA may be the preferred anesthetic choice for ERCP.
Neuromuscular Blockade
Thevathasan T, Shih SL, et al. Association between intraoperative non-depolarising neuromuscular blocking agent dose and 30-day readmission after abdominal surgery. Br J Anaesth. 2017 Oct 1;119(4):595-605.
Broens SJL, Boon M, et al. Reversal of Partial Neuromuscular Block and the Ventilatory Response to Hypoxia: A Randomized Controlled Trial in Healthy Volunteers. Anesthesiology. 2019Sep;131(3):467-476.
Use of neuromuscular blockade and reversal agents has long been the subject of controversy among anesthesiologists. Deep paralysis and incomplete reversal with acetylcholinesterases are associated with depressed respiratory function and airway protection and may lead to poor postoperative pulmonary outcomes. But with the introduction of sugammadex to the American market, many wonder whether this is still a concern. A 2018 study published in the British Journal of Anesthesiology confirms previous findings, demonstrating increased risk of 30-day readmission for patients after abdominal surgery who receive high doses of neuromuscular blocking agents, despite the use of reversal agents prior to extubation. This was particularly true for patients who had surgery in the ambulatory setting. Another study published in 2019 in Anesthesiology seeks to understand why pulmonary outcomes may be worse, even when “full” reversal of neuromuscular blockade has been achieved with either neostigmine or sugammadex. The authors of this randomized controlled trial report impaired peripheral chemoreflexes (i.e. carotid body) which may result in depressed ventilatory response to hypoxia, even when the train of four ratio was >0.9. This impairment may be a significant contributor to the postoperative respiratory issues associated with the use of neuromuscular blocking agents.
Intraoperative Opioid Use
Long DR, Lihn AL, et al. Association between intraoperative opioid administration and 30-day readmission: a pre-specified analysis of registry data from a healthcare network in New England. Br J Anaesth. 2018 May;120(5):1090-1102.
Friedrich S, Raub D, et al. Effects of low-dose intraoperative fentanyl on postoperative respiratory complication rate: a pre-specified, retrospective analysis. Br J Anaesth. 2019 Jun;122(6):e180-e188.
Given the current awareness of the prevalence of opioid abuse among the general population, many anesthesiologists try to limit the use of these medications intraoperatively, favoring instead a multimodal approach using adjunctive pain medications. In fact, some anesthesiologists avoid opioid administration altogether. In some settings this may provide patient benefit. For example, a 2018 study by Long et. al. published in the British Journal of Anesthesia shows a dose dependent increase in 30-day readmission rates among ambulatory patients receiving intraoperative opioids. However, opioid dosing had a different effect among non-ambulatory patients: in this context, low doses actually corresponded with lower rates of readmission as compared to no opioid use at all or high dose opioid administration. This was supported by a later study in the same journal, which demonstrates a lower risk of postoperative respiratory complications for patients who received 1-2 mcg/kg of fentanyl intraoperatively as compared to no fentanyl or higher doses of fentanyl. In some cases, the addition of multiple preoperative and intraoperative non-opioid pain medications, intended to address discomfort while decreasing opioid requirements, may ultimately contribute to worsening postoperative cognitive dysfunction and increased length of stay.
I would like to thank Dr. Girish P. Joshi for his lecture and notes from which this article’s content was derived.
