- This laboratory study aimed to generate a rational strategy for treating otolaryngology patients with unknown COVID-19 status while simultaneously protecting the health care team
- During simulated diagnostic endoscopy on a cadaver head, a "sneezing event" generated aerosols that settled up to 66 cm from the nare
- Spread of these aerosols was prevented by both an intact surgical mask and a mask modified to enable passage of an endoscope while maintaining a tight seal
- Cold non-powered endonasal surgical procedures conferred a low risk of aerosol generation
- The use of a high-speed drill caused aerosolization of droplets, the greatest risk factor for potential infection during endonasal surgery, even when activated for only several seconds
According to the latest guidelines from the World Health Organization (WHO), the new coronavirus SARS-CoV-2, is primarily transmitted through respiratory droplets and contact with surfaces. There's no strong evidence of airborne transmission, even within households or hospitals. However, the WHO does recommend airborne precautions during aerosol-generating health care procedures for COVID-19 patients.
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The guidance doesn't specifically address risks related to endonasal instrumentation. This is a major gap in knowledge because endonasal surgery differs fundamentally from other aerosol-generating procedures—it occurs in the setting of an occluded lower airway. There's great uncertainty about whether endonasal procedures generate aerosols and whether those aerosols could transmit coronavirus.
In laboratory experiments, researchers at Massachusetts General Hospital determined that endonasal surgery using a high-speed drill, even for short periods of time, has significant potential to generate aerosols. In collaboration with Benjamin S. Bleier, MD, FACS, and Alan D. Workman, MD, MTR, of the Department of Otolaryngology at Massachusetts Eye and Ear, Bob S. Carter, MD, PhD, chief of the Neurosurgery Department, and William T. Curry, MD, co-director of Mass General Neuroscience, and colleagues propose risk-mitigation strategies in the International Forum of Allergy & Rhinology.
The researchers passed an atomizer through the posterior cribriform plate of a cadaver head. The atomizer produced particles of fluorescein solution and an endoscopic camera was used to detect fluorescein-labeled aerosols.
Simulation of Outpatient Nasal Endoscopy
With the head upright, the fluorescein solution was atomized to mimic an irritative patient sneeze under four conditions:
- No mask on the cadaver head: Aerosol droplet contamination was evident up to 66 cm from the nare
- Surgical mask: No droplets were detected
- Surgical mask with perforation for passage of an endoscope: Aerosol droplet contamination was evident up to 42 cm from the nare
- Surgical mask with a piece of non-latex glove stapled over the perforation and a narrow slit cut just large enough to accommodate an endoscope: No droplets were detected
Simulation of Endoscopic Endonasal Surgery
With the head supine, the atomizer was used to coat the nasal cavity with fluorescein solution.
- Non-powered cold instrumentation: No aerosol droplets were observed in any of three conditions: posterior nasal endoscopy, nasal suctioning or endoscopic through-biting of the middle turbinate
- Powered suction microdebrider: No aerosol droplets were observed when a microdebrider was applied for 10 seconds to the posterior or anterior septum with debridement of tissue or activated external to the nare after tissue soilage
A high-speed drill was used to remove bone at the sphenoid rostrum and nasal beak, and was activated external to the nare after tissue soilage, for 10 seconds in each condition. In all conditions, aerosol droplets were observed in multiple regions between 6 and 30 cm from the nare.
The high-speed drill caused aerosolization of droplets to a significant degree whether the drill was activated at multiple sites inside the nasal or sinus cavities, or if it was smothered in nasal debris and activated externally.
Suggestions for Risk Mitigation
Diagnostic nasal endoscopy could be performed more safely with the patient wearing a surgical mask, and practitioners should wear personal protective equipment (PPE) when the patient's COVID-19 status is unknown.
Endoscopic skull base procedures should be reclassified as aerosol-generating surgery, and PPE protocols should reflect the dangers of prolonged proximity to the patient.
When patients have tested positive for COVID-19 or their status is unknown, surgical strategies to minimize or even eliminate high-speed drill use may be prudent. Continuous nasopharyngeal suction using a flexible catheter may be advantageous to reduce fluid accumulation and direct aerosols posteriorly.
Microdebriders appear to confer less risk, but they should be used in the closed position and deactivated prior to removal from the nare.
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Refer a patient to the Department of Neurosurgery at Mass General