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

Meethil AP, Saraswat S, Chaudhary PP, Dabdoub SM, Kumar PS. Sources of SARS-CoV-2 and other microorganisms in dental aerosols. J Dent Res. 2021;100(8):817–823.

The COVID-19 pandemic has generated a high degree of concern about aerosols generated during dental procedures and the potential for transmission of respiratory pathogens harbored in saliva. Current knowledge of the pathogens found in dental aerosols is mostly gleaned from case reports and poorly controlled studies. A 2020 review found several studies described the radius of contamination following aerosol-generating dental procedures in the operatory; however, few characterized the type of organisms found, and none identified their source. Therefore, we tracked the origins of microbiota in aerosols generated during ultrasonic scaling, implant osteotomy, and restorative procedures by combining reverse transcriptase quantitative polymerase chain reaction (to identify and quantify SARS-CoV-2) and 16S sequencing (to characterize the entire microbiome) with fine-scale enumeration and source tracking. Saliva was sampled from 28 patients undergoing dental treatment in an enclosed dental operatory measuring 10.5ft × 10ft × 20ft with 5 dental team members and a ventilation rate of 6 exchanges per minute. Following the procedure, condensate was collected from the face shields of dental team members, the patient's chest, and an area 6 ft distant from the site of the operation. We found that 78% of the microbiota in condensate could be traced to the dental irrigant, whereas saliva contributed to a median of 0% of aerosol microbiota. We also identified low copy numbers of the SARS-CoV-2 virus in the saliva of several asymptomatic patients but none in aerosols generated from these patients. Together, the bacterial and viral data encouraged us to conclude that when infection control measures are used, such as preoperative mouth rinses and intraoral high-volume evacuation, dental treatment is not a factor for increasing the risk of SARS-CoV-2 transmission in asymptomatic patients and that standard infection control practices are sufficiently capable of protecting personnel and patients from exposure to potential pathogens.

Comment: This study is the first to report that irrigant fluid contributes to the majority of the bioload in dental aerosols. This is consistent with earlier studies that report irrigant flow dilutes the saliva 20- to 200-fold, which most likely explains the absence of SARS-CoV-2 in the aerosols sampled in this study. It also validates recent reports of very low SARS-CoV-2 transmission among dental personnel and identifies dental irrigants as the primary and major source of microorganisms during aerosol-generating dental procedures.

This study contributes important, new quantitative information regarding the potential for SARS-CoV-2 transmission from routine dental aerosols. It does not address the risk of transmission during other activities commonly performed when deep sedation and general anesthesia are performed. Endotracheal intubation and extubation, noninvasive ventilation, manual ventilation, and open suctioning of airways are all considered aerosol-generating procedures that might create uncontrolled respiratory secretions.¹

Midazolam premedication immediately before surgery is not associated with early postoperative delirium. Anesth Analg. 2021;133(3):765–771.

Postoperative delirium is common among older surgical patients and may be associated with anesthetic management during the perioperative period. Midazolam, a common premedication, has a short half-life of 1.5 to 2.5 hours; however, that time may be doubled in the elderly population. This study examined whether preoperative intravenous midazolam increased the incidence of postoperative delirium. A total of 1266 patients were included in the study, which used propensity score matching to analyze an existing database of patients 65 years and older who underwent elective, major noncardiac surgery. Intravenous midazolam was administered as premedication in 909 patients (72%), and 357 patients did not receive midazolam. Those who did and did not receive midazolam significantly differed in age, comorbidity scores, preoperative cognitive status, preoperative use of benzodiazepines, type of surgery, and year of surgery. After propensity score matching, all standardized differences in preoperative patient characteristics ranged from −0.07 to 0.06, indicating good balance on baseline variables between the 2 exposure groups. No association was found between premedication with midazolam and incident delirium on the morning of the first postoperative day in the matched data set, with an odds ratio of 0.91 (95% CI, 0.65–1.29), P = .67, leading the investigators to conclude that premedication using midazolam was not associated with higher incidence of delirium on the first postoperative day in older patients undergoing major noncardiac surgery.

Comment: Propensity score matching is a statistical technique in which researchers create an artificial control group by matching the characteristics of treated and nontreated patients with similar characteristics. It is often used to study nonrandomized investigations, such as observational studies, in which randomization would not be ethical. This is the first study to investigate the effect of midazolam premedication on postoperative delirium in older surgical patients. The results suggest the pathophysiology of postoperative delirium is most likely multifactorial and complex, not simply a function of preoperative exposure to a small premedication midazolam dose.

Cho EA, Huh J, Lee SH, et al. Gastric ultrasound assessing gastric emptying of preoperative carbohydrate drinks: a randomized controlled noninferiority study. Anesth Analg. 2021;133(3):690–697.

The purpose of this study was to show that the risk of pulmonary aspiration is not increased with the consumption of carbohydrate drinks before surgery. Sixty-four patients between the ages of 18 and 65 scheduled for elective laparoscopic benign gynecologic surgery were enrolled and randomly assigned to the NPO group (n = 32) or the NO-NPO group (n = 32). After having a regular meal until midnight before surgery, the NPO group fasted until surgery, whereas the NO-NPO group ingested 400 mL of a carbohydrate drink at midnight and freely up to 2 hours before anesthesia. The primary outcome was the gastric antral cross-sectional area (CSA) as measured by gastric ultrasound. Noninferiority was defined as a mean difference of CSA < 2.8 cm².

No significant difference was seen in the cross-sectional antral area between the NPO group (6.25 ± 3.79 cm²) and the NO-NPO group (6.21 ± 2.48 cm²; P = .959. The authors concluded that preoperative carbohydrates ingested up to 2 hours before anesthesia do not delay gastric emptying compared with midnight fasting, as evaluated with gastric ultrasound.

Comment: Preoperative carbohydrate drinks have been shown to reduce anxiety, thirst, and postoperative nausea and vomiting and lessen insulin resistance. Prior studies have supported the belief that carbohydrate drinks can be consumed up to 2 hours prior to surgery without increasing the risk of pulmonary aspiration. However, direct quantitative measurement of gastric volume had not been used to verify the concept because the available assessment methods were either invasive, exposed patients to radiation, or were not well tolerated by conscious patients. This study accomplished that verification using gastric ultrasound, a noninvasive method. It also demonstrated the potential for using gastric ultrasound as a practical way to quickly assess gastric volume in the preoperative period.

Disma N, Frykholm P, Cook-Sather SD, Lerman J. Pro-con debate: 1- vs 2-hour fast for clear liquids before anesthesia in children. Anesth Analg. 2021;133(3):581–591.

Perioperative fasting guidelines are designed to minimize the risk of pulmonary aspiration of gastrointestinal contents. The current recommendations from the American Society of Anesthesiologists and the European Society of Anaesthesiology and Intensive Care are for a minimum 2-hour fast after ingestion of clear liquids before general anesthesia, regional anesthesia, or procedural sedation and analgesia. Nonetheless, in children, fasting guidelines can also have consequences regarding child and parent satisfaction, hemodynamic stability, the ability to obtain vascular access, and perioperative energy balance. Although current guidelines recommend a relatively short 2-hour fasting time for clear fluids, the actual duration of fasting time can be significantly longer. Prolonged fasting can result in children arriving to the operating room for an elective procedure being thirsty, hungry, and generally in an uncomfortable state. Furthermore, prolonged fasting may adversely affect hemodynamic stability and can result in parental dissatisfaction with the perioperative experience. In this PRO and CON presentation, the authors debate the premise that reducing the nominal minimum fasting time from 2 hours to 1 hour can reduce the incidence of prolonged fasting and provide significant benefits to children, with no increased risks.

Comment: In an accompanying editorial to this Pro-Con debate, Drs Nguyen and Davis challenge the premise that a 2-hour clear liquid fast is too onerous when comparable conditions seem to be achievable with a 1-hour fast in healthy patients.² The authors claim the real issue is prolonged fasting for periods significantly greater than 2 hours, which create conditions for both NPO violations and the deleterious perioperative and postoperative physiologic consequences of excessive fasting. In the author's opinion, this issue is caused primarily by institutional policies, lack of communication with patients, and other easily correctable conditions.

Tom J. Sedation strategies and techniques for painful dental procedures. In: Mason KP, ed. Pediatric Sedation Outside of the Operating Room. Switzerland AG: Springer Nature;2021:533–544.

Providing various levels of sedation to pediatric patients undergoing invasive, complex, and otherwise painful dental procedures involves treatment planning for a variety of consequences, including intraoperative bleeding, significant surgical stimulation, and impaired access to the pediatric airway. The judicious use of local anesthesia can facilitate surgery and reduce the anesthetic and analgesic demands; however, the proximity of the surgical field to the pediatric airway necessitates informed and careful planning to assure safe operating conditions. This chapter explores some of the more common painful and invasive pediatric dental procedures with accompanying precautions and specific sedation and anesthetic considerations.

Comment: This is a chapter from Sedation Outside of the Operating Room, a book written for a wide spectrum of anesthesia providers, including physician anesthesiologists, nurse anesthetists, nonanesthesiologist physicians, dentists, and dental specialists. The author does an excellent job of describing the underlying physiological considerations and providing literature citations to support his work. The text is written in a way that requires only a basic familiarity with the oral cavity and clinical dental techniques, making it an excellent choice for nondental providers or dental students. It does not address advanced topics, such as the anatomical variation of the mandibular nerve or detailed pharmacologic considerations of local anesthetic agents, that would be desired by dentist anesthesiologists and other dental specialists. Still, this chapter provides an excellent resource for the clinician in need of an introduction to safe and effective local anesthesia for the pediatric dental patient.

Summaries and comments provided by

Mark A. Saxen, DDS, PhD

Indiana Office-Based Anesthesia

Indiana University School of Dentistry

Indianapolis, IN