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

Brown J, Gregson FKA, Shrimpton A, et al. A quantitative evaluation of aerosol generation during tracheal intubation and extubation. Anaesthesia . 2021;76(2):174–181. doi: 10.1111/anae.15292. PMID: 33022093; PMCID: PMC7675579.

In response to the COVID-19 pandemic, guidance issued from the World Health Organization and the Centers for Disease Control and Prevention recommend minimizing aerosol generating procedures (AGPs) and adopting personal protective equipment and engineering practices when AGPs must be performed. Tracheal intubation and extubation have been classified as AGPs; however, the underlying evidence for this classification is weak and based upon data from studies of other viral respiratory infections. Using mean airborne particles as a surrogate for infection risk, this study quantified the number of aerosolized particles generated in the intubation field using high resolution, real-time monitoring. Tracheal intubation, including face mask ventilation, produced very low quantities of aerosolized particles compared with a volitional cough. Tracheal extubation, particularly when associated with coughing, produced particle levels 15-fold greater than intubation but 35-fold less than volitional coughing. Thus, the study does not support the designation of tracheal intubation as an AGP. Extubation without coughing was found to be quantitatively different than extubation with coughing. Acknowledging that coughing is sometimes interpreted as an indicator of the return of protective reflexes after extubation, practices to reduce aerosolization and coughing following extubation are warranted. The authors caution that no broad conclusions about the risk of actual SARS-CoV-2 infection can be drawn from this study due to several limitations, including the relatively small number of observations, the limited spatial area of aerosolization studied, and the absence of known COVID-19 patients in the study.

Comment: This study raises several considerations for the dental anesthesia provider. Intubation appears to have several advantages for limiting and controlling exposure to potentially infectious aerosol in the intraoperative period. Extubation and recovery appear to carry the highest risk of infection particularly when associated with coughing. Patients with a reactive airway and other conditions are known to be more prone to experience coughing, laryngospasm, and other complications associated with extubation. Nonintubated airway management techniques are often viewed as providing less mechanical irritation to the trachea than endotracheal intubation; however, coughing and other respiratory complications are more likely to occur in the minimally protected, nonintubated airway during the perioperative period. This is especially true during lighter levels of sedation or following stimulation from oral secretions, bleeding, and manipulation of the head. Deeper levels of sedation and anesthesia, such as those achieved during anesthesia induction, as well as the use of opioids help to control coughing. A recent review of the risks of extubation and coughing in the COVID-19 era by Sibert et al¹ may be of interest to many dental anesthesia providers. (Saxen MA)

Allison JR, Currie CC, Edwards DC, et al. Evaluating aerosol and splatter following dental procedures: addressing new challenges for oral health care and rehabilitation. J Oral Rehabil . 2020;48:61–72. https://doi.org/10.1111/joor.13098

This in vitro study evaluated the distribution and persistence of dental aerosol and splatter by introducing fluorescein dye into the irrigation reservoirs of a high-speed air-turbine handpiece, an ultrasonic scaler, and a triplicate air-water syringe. Filter paper was placed throughout the area surrounding the chair while 3 simulated procedures were performed on mannequins: an anterior crown preparation, ultrasonic scaling, and irrigation. Simultaneous high-speed suction was provided either by an assistant or by the operator. Samples were analyzed by spectrofluorometric analysis and photographic image analysis. The mannequin, operator, and assistant all sustained heavy contamination, particularly within 1.0 to 1.5 m of the operating field, although detectable contamination was found within a 4-m radius. Suction reduced contamination by 65 to 75% in the 1.0- to 1.5-m zone. Contamination remained in the air but was effectively cleared from operating area within 30 minutes.

Comment: Dental procedures produce aerosol and splatter with the potential to transmit SARS-CoV-2, although the viral load and the degree of infectivity of dental aerosols and splatters remain unknown.² This study provides a robust quantitative analysis of physical aspects of dental aerosol and splatter while performing commonly accepted aerosol generating dental procedures (AGDPs) with and without the presence of suction in real-world simulations. Although this study provides valuable information, it was performed in a large 308-m² teaching laboratory in a hospital with 6.5 air exchanges per hour. The ideal dental operatory has been estimated at approximately 12 m² with highly variable air-exchange rates.³ At the time of this writing, other investigations are emerging that evaluate the impact of environmental factors (room size, air-exchange rate, open vs closed operatory design) on the distribution and persistence of dental aerosol and splatter.⁴ The degree to which environmental factors affect aerosol and splatter in the dental operatory setting will likely be challenging to define, given the high variability of dental office designs. By comparison, operating rooms, which are often constructed to meet minimum specifications of accrediting bodies, display less design variability. (Saxen MA)

Moon TS, Van de Putte P, De Baerdemaeker L, Schumann R. The obese patient: facts, fables, and best practices. Anesth Analg . 2021;132(1):53–64. doi: 10.1213/ANE.0000000000004772

Obesity alters anatomy and physiology, which complicates the evaluation and management of obese patients in the perioperative setting. This narrative review article summarized the current evidence for several aspects of perioperative anesthesia. Gastric point-of-care ultrasound (PoCUS) is a noninvasive tool that can be used to assess aspiration risk in the obese patient by evaluating the quantity and quality of gastric contents. An important perioperative goal is adequate end-organ perfusion. Standard noninvasive blood pressure (NIBP) is our best available routine surrogate measurement but is vulnerable to greater inaccuracy in patients with obesity compared with the nonobese population. Current NIBP methodologies are discussed. Obese patients are at risk for wound and surgical site infections, but few studies conclusively guide the exact dosing of intraoperative prophylactic antibiotics for these patients. Intubation and extubation of the patient with obesity can be complicated, and evidence-based strategies are discussed to mitigate danger during intubation and extubation.

Comment: According to the Centers for Disease Control and Prevention, the age-adjusted prevalence of obesity in adults increased from 30.5 to 42.4% in the period between 2000 and 2018. Data from a comparable time period estimate a prevalence of 13.9% in children aged 2 to 5 years.⁵ (Saxen MA)

Somers M, Tsakiris P, Isert P, Kim S. Management of total transection of nasoendotracheal tube during LeFort I Osteotomy. Case Rep Anesthesiol . 2020.

This case report presents the management of sudden airway loss when a nasoendotracheal was severed with an osteotome during the maxillary downfracture phase of the osteotomy. In addition to describing the clinical course of this emergency, the authors offer steps for the appropriate management and prevention of this rare but life-threatening complication.

Comment: The acute loss of airway control because of sudden total compromise of an endotracheal tube (ETT) can be catastrophic. Mechanical iatrogenic damage via drills, saws, and chisels coming into contact with the ETT is especially foreseeable during mid-face osteotomies utilizing nasal intubation. These occurrences have been reported for decades as the authors' references document, although the first paper dealing with this complication, published in Anesthesia Progress in 1978, was overlooked (Orr D. Airway compromise during oral & maxillofacial surgery: case report and review of potential causes. Anesth Prog. 1978;25:161–163). Prevention preparations include consultation between the anesthesiologist and surgeon, shielding the ETT from cutting instruments, and consideration of reinforced ETTs. Potential causes of such a complication could include anything from a defective ETT cuff to a cut pilot line to partial or total transection of the ETT proper. In perhaps the worst case, the distal portion of the ETT may become lodged in the patient's trachea. Several options for ventilation may be viable and include the following: successful removal of the remaining ETT and reintubation; jet insufflation with a tube placed inside a retained ETT; intentionally displacing the retained ETT into the right or left main stem bronchus, preserving the other side for ventilation with a new ETT; and establishing a surgical airway (ie, cricothyrotomy or tracheotomy) with enough access to drive the remaining ETT retrograde back into the oral cavity for removal if straightforward placement of the tracheostomy tube is impossible. Every piece of instrumentation for these and other corrective measures needs to be immediately available. This paper is a good source for review by anesthesiologists who manage such patients. (Orr DL)

Cassorla L. Decontamination and reuse of N95 filtering facepiece respirators: where do we stand? Anesth Analg . 2021;132(1):2–14. doi: 10.1213/ANE.0000000000005254

The COVID-19 pandemic created an extraordinary demand for N95 and similarly rated filtering facepiece respirators (FFR) that remains unmet due to limited stock, production constraints, and logistics. This discussion reviews the background of the current shortage, classification, structure, and functional aspects of FFR and potentially effective decontamination methods along with reference websites for those seeking updated information and guidance. The most promising techniques utilize heat, hydrogen peroxide, microwave-generated steam, or ultraviolet light. Many require special or repurposed equipment and a detailed operational roadmap specific to each setting. Although limited, research is growing. There is significant variation between models regarding the ability to withstand decontamination yet remain protective. The number of times an individual respirator can be reused is often limited by its ability to maintain a tight fit after multiple uses rather than by the decontamination method itself. There is no single solution for all settings; each individual or institution must choose according to their need, capability, and available resources.

Comment: At the time of this writing, a renewed shortage of N95 masks seems likely given the increasing momentum of the COVID-19 pandemic and the continuing demand that exceeds supply in all sectors of the US economy. 3M Company, the largest domestic manufacturer of N95 masks, reports monthly production of N95 respirators in the US alone increased from 22 million in 2019 to 95 million at the end of 2020.The need for dental anesthesia providers to maximize use of their personal protective equipment will almost certainly be present for the foreseeable future.⁶ (Saxen MA)

Summaries and comments provided by:

Mark A. Saxen, DDS, PhD

Indiana Office-Based Anesthesia

Indiana University School of Dentistry

Indianapolis, IN

Daniel L. Orr II, DDS, MS (Anesth), PhD, JD, MD

Professor Emeritus Anesthesiology and OMS

UNLV School of Dental Medicine

Las Vegas, NV