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

Broens S, Boon M, Martini C, Niesters M, van Velzen M, Aarts L, Dahan A. Reversal of Partial Neuromuscular Block and the Ventilatory Response to Hypoxia. Anesthesiology. 2019;131:467–476.

The ventilatory response to hypoxia is a lifesaving chemoreflex originating at the carotid bodies that is impaired by nondepolarizing neuromuscular blocking agents. This single-center, randomized, controlled experimental study evaluated the effect of 3 strategies for reversal of a partial neuromuscular block on ventilatory control in 34 healthy male volunteers on the chemoreflex. The hypothesis was that the hypoxic ventilatory response is fully restored following the return to a train-of-four ratio of 1. Following full reversal, as measured at the thumb, there was persistent residual blunting of the hypoxic ventilatory response (0.45 ± 0.16 l · min−1 · %−1; train-of-four ratio, 1.0; p < .001). Despite full reversal of partial neuromuscular block at the thumb, impairment of the peripheral chemoreflex may persist at train-of-four ratios greater than 0.9 following reversal with neostigmine or sugammadex, or spontaneous recovery of the neuromuscular block.

Comment: Although train-of-four testing of the thumb indicated full recovery, the hypoxic chemoreflex was not fully restored following reversal of neuromuscular blockade. This phenomenon was observed regardless of the drug class of neuromuscular blocking drug used. In an accompanying editorial, Pandit and Eriksson¹ note evidence of potential synergism between neuromuscular blocking drugs and other anesthetic agents, including inhalational anesthetics, benzodiazepines, and opioids. This study demonstrates the importance of achieving full neuromuscular recovery while realizing the risk of impaired regulation of breathing and response to hypoxia may still be present during recovery despite complete neuromuscular blockade reversal.

Kim EM, Chung MH, Lee MH, Choi EM, Jun I-J, Y, Yun TH, Ko YK, Kim JH, Jun JH. Is Tube Thermosoftening Helpful for Videolaryngoscope-Guided Nasotracheal Intubation? Anesth Analg. 2019;129:812–818.

Thermosoftening of the cuffed endotracheal tube (ETT) and telescoping the ETT into a rubber catheter has been suggested as a method for reducing epistaxis during nasotracheal intubation (NTI). Simultaneously, the study evaluated whether this approach when combined with the cuff-inflation technique reduced the need for using Magill forceps to navigate the ETT. This randomized, controlled trial of 140 adults compared nasal intubations performed with this technique to nasal intubations performed without thermosoftening and a telescoped rubber catheter. The incidence and severity of epistaxis was significantly lower (7% vs 51%; p < .001), and the ETT passed through the nasal cavity with lower resistance (p = .001) and less time (p < .001) when compared with the control group. In both groups, all ETTs could be navigated into the trachea without the use of Magill forceps. These results suggest thermosoftening provides a substantial benefit during videolaryngoscope-guided NTI.

Comment: Epistaxis is the most common complication of NTI. Previously published studies report an incidence of 18 to 77%.² Thermosoftening is a common, well-established technique known to reduce the incidence of epistaxis.³ This paper demonstrates that addition of a rubber catheter to prevent contact of the Murphy eye and tip of the ETT with the mucosa provides further reduction of the risk of epistaxis. Although use of the catheter in itself may provide shielding for an unsoftened tube, the technique is further optimized when thermosoftening is combined with use of the rubber catheter.

Urman R, Rajan N, Belani K, Gayer S, Joshi G. Malignant Hyperthermia–Susceptible Adult Patient and Ambulatory Surgery Center: Society for Ambulatory Anesthesia and Ambulatory Surgical Care Committee of the American Society of Anesthesiologists Position Statement. Anesth Analg. 2019;129:347–349.

This position statement presents expert opinion on the identification and management of patients susceptible to malignant hyperthermia (MH) in a free-standing ambulatory surgical care facility (ASC). MH-susceptible patients are defined as those with a personal or family history suggestive of MH or an MH-like event that may or may not be confirmed by genetic-testing or muscle biopsy. The incidence of MH episodes in all patients is estimated to be approximately 1 in 500,000. Given the low risk of developing MH with a nontriggering agent, MH-susceptible patients may safely undergo procedures using a nontriggering anesthetic technique in a free-standing ASC. Based on a lack of supporting evidence, pretreatment of MH-susceptible patients with dantrolene is not recommended. Anesthetic plans for MH-susceptible patients should avoid MH triggering agents, and additional core temperature monitoring beyond that recommended in basic intraoperative standards should be implemented. Preparations need to ensure that dantrolene can be administered within 10 minutes from the first signs of MH. An effective and efficient means of transferring patients in the event of an MH crisis needs to be in place. Additional, useful details regarding patients with predisposing neuromuscular disorders, preparation of the anesthetic work station, and the relevance of point-of-care blood gas analyzers are found within the statement.

Comment: This document represents the joint effort of the Society for Ambulatory Anesthesia (SAMBA) and the Ambulatory Surgical Care Committee (ASCC) of the American Society of Anesthesiologists. This group recently collaborated for a statement on the use of succinylcholine for airway management in class B ambulatory facilities.⁴

Görges M, Poznikoff A, West N, Brodie S, Brant R, Whyte S. Effects of Dexmedetomidine on Blood Glucose and Serum Potassium Levels in Children Undergoing General Anesthesia: A Secondary Analysis of Safety Endpoints During a Randomized Controlled Trial. Anesth Analg. 2019;129:1093–1099.

Dexmedetomidine is a highly selective α²-adrenergic agonist, which is increasingly used in pediatric anesthesia and intensive care. This randomized, controlled trial examined 64 children between the ages of 3 and 10 years, undergoing elective surgery. Two doses of dexmedetomidine, 0.5 and 0.75 mcg/kg, were compared with controls receiving no dexmedetomidine. Both dexmedetomidine and control boluses were administered over a 60-second period following induction. Changes in plasma glucose and serum potassium concentrations were measured in venous blood sampled before and at 15 and 30 minutes after study drug administration. Forty-nine children completed the study. A small dose-dependent elevation in glucose was detected 15 minutes after administration of dexmedetomidine, but the small decreases observed in potassium levels appear to be unrelated to dexmedetomidine administration. These preliminary findings warrant further investigation.

Comment: The effect of dexmedetomidine on blood glucose concentrations is poorly defined. Physiologic models predict hypoinsulinemia and hyperglycemia following administration; however, published reports suggest cortisol levels are decreased, resulting in reduced blood glucose levels. Hypokalemia has been observed in over 2% of adults receiving dexmedetomidine in intensive care sedation studies and 9% of neonates receiving long-term infusions; however, the effects of dexmedetomidine on plasma potassium levels in healthy children have not been studied. Given the increasing popularity of dexmedetomidine in pediatric sedation and anesthesia, this study provides timely information.

Kawakami H, Nakajima D, Mihara T, Sato H, Goto T. Effectiveness of Magnesium in Preventing Shivering in Surgical Patients: A Systematic Review and Meta-analysis. Anesth Analg. 2019;129:689–700.

Clinical trials regarding the antishivering effect of perioperative magnesium have produced inconsistent results. The authors conducted a broad systematic review and meta-analysis with Trial Sequential Analysis to evaluate the effect of perioperative magnesium on prevention of shivering. PubMed, EMBASE, Web of Science, Cochrane Central Register of Controlled Trials, and 2 registry sites were searched for randomized clinical trials that compared the administration of magnesium to a placebo or no treatment in patients undergoing surgeries. The primary outcome of this meta-analysis was the incidence of shivering. The incidence of shivering was combined as a risk ratio with 95% CI using a random-effect model. The effect of the route of administration was also evaluated in a subgroup analysis. Sixty-four trials and 4303 patients (2300 and 2003 patients in magnesium and control groups, respectively) were included. The overall incidence of shivering was 9.9% in the magnesium group and 23.0% in the control group. Subgroup analysis revealed that the incidence of shivering was lower with intravenous (IV), epidural, and intrathecal administration. Trials with a low risk of bias were included for Trial Sequential Analysis. No increase in adverse events was reported. The authors concluded perioperative IV administration of magnesium effectively reduced shivering, and Trial Sequential Analysis suggested that no more trials are required to confirm that IV magnesium effectively reduces shivering.

Comment: The authors note that perioperative magnesium is a desirable intraoperative adjunct as it may reduce the need for anesthetic agents, neuromuscular blockade, and opioids. Previous meta-analysis of 3 trials showed a decrease in the incidence of shivering, but dosing and route of administration were not defined. This study confirmed the effectiveness of IV magnesium for reducing postoperative shivering. Intravenous doses greater than 60 mg/kg were not shown to result in any further reduction of shivering, whereas doses below 300 mg of magnesium sulfate did not result in statistically significant decreases in shivering. No serious adverse effects were reported in any of the trials examined in this study, leading the authors to conclude that intravenous magnesium should be considered in patients who are young, undergoing long surgeries, patients with limited cardiac reserve, and others at increased risk of shivering.

Greene N, Jooste E, Thibault D, Wallace A, Wang A, Vener D, Matsouaka R, Jacobs M, Jacobs J, Hill K, Ames W. A Study of Practice Behavior for Endotracheal Intubation Site for Children With Congenital Heart Disease Undergoing Surgery: Impact of Endotracheal Intubation Site on Perioperative Outcomes—An Analysis of the Society of Thoracic Surgeons Congenital Cardiac Anesthesia Society Database. Anesth Analg. 2019;129:1061–1068.

In adults undergoing cardiopulmonary bypass surgery, oral intubation is typically preferred over nasal intubation due to reduced risk of sinusitis and infection. In children, nasal intubation is more common and sometimes preferred due to perceived benefits of less postoperative sedation and a lower risk for accidental extubation. This study examined the practice of nasal intubation in the pediatric population undergoing cardiopulmonary bypass surgery to assess the risks/benefits of a nasal route against an oral route. Cases logged into the Society of Thoracic Surgeons Congenital Heart Surgery Database (STS-CHS) were used for this study of 26,754 studies recorded between 2010 and 2015. Nasal intubation was used in 41% of operations in neonates, 38% in infants, 15% in school-aged children, and 2% in adolescents. Nasal intubation appeared protective for accidental extubation only in neonates (p = .02). Although older children undergoing nasal intubation displayed an increased risk of infection, nasal intubation in neonates and infants did not appear to carry a similar risk. Nasal intubation in neonates and infants may also be associated with a shorter intubation length but not a shorter length of stay. Although this study represented data from 50 individual centers spanning 6 years, the authors found it difficult to draw definitive conclusions due to suboptimal statistical power. A nasal route of intubation may lead to decreased intubation length in neonates and infants undergoing cardiopulmonary bypass surgery and may be associated with postoperative infection after the first year of life.

Comment: This comparative study of nasal and oral intubation is noteworthy in that the database collects data from approximately 96% of all US centers performing congenital heart surgery and includes 98% of all operations. Although providing useful information, it displays limitations inherent in retrospective database queries, even with large data sources.

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