Surgical smoke not a source of transmission of COVID-19 virus in health care workers: JAMA
Ontario, Canada: Electrocautery or surgical smoke is an unlikely source for the transmission of the SARS-CoV-2 virus for health care workers, according to a research letter published in the journal JAMA Surgery.
"Despite the high viral titers used, SARS-CoV-2 was not detectable in aerosol cautery plume generated from electrocautery under any of the study conditions. By mimicking surgery on a patient with a high SARS-CoV-2 load, there was a minimum of a 9 log reduction of viral RNA with any of the electrocautery methods," wrote the authors.
The SARS-CoV-2 virus has been detected in sputum, saliva, blood, bile, and feces and been shown to remain viable in aerosols for at least 3 hours. Several colleges have raised direct transmission to surgical staff from aerosolized virus in an electrocautery plume as a particular safety concern. Cautery performed in areas of high potential viral load could be risky to those in the operating room. Also, there is a possibility that sinonasal pathologies can mimic the symptom profile of COVID-19 and contribute to false-negative nasopharyngeal screening results, further increasing potential perioperative risk and exposure.
SARS-CoV-2 is more susceptible to higher temperatures due to the presence of a lipid bilayer. Inhalation of even small amounts of aerosolized virus appears sufficient to establish infection. However, tip temperatures of electrocautery range from 100 to 1200 °C, and as such, the temperature is potentially sufficient to inactivate SARS-CoV-2 in the plume.
Against the above background, Leigh J. Sowerby, University of Western Ontario, London, Ontario, Canada, and colleagues aimed to investigate the presence of live SARS-CoV-2 in electrocautery plumes after an institutional review board waiver and approval was received from Lawson Health Research Institute.
For this purpose, the researchers applied electrocautery at 25 W using 3 different methods for 1 minute on raw chicken breast with an added 4 mL of Dulbecco modified eagle medium (DMEM) or a DMEM:blood mixture containing 1 × 105.7 median tissue culture infectious dose (TCID50) per mL of SARS-CoV-2 which was similar to the viral load in pulmonary sputum of a patient with symptoms.
For positive control, approximately 0.3 mL of both viral media and blood with SARS-CoV-2 was aerosolized (without heat) into the chamber and collected in the same fashion. The gelatin filters were solubilized in phosphate-buffered saline and added in undiluted and 1:10 serial dilutions to VeroE6 cells to determine the TCID50 value of the vaporized virus following electrocautery.
Key findings of the study include:
- Using a cell titer glow measurement for replicating virus,6 we observed no virus recovered from any electrocautery performed.
- Collected aerosolized blood or media containing SARS-CoV-2 (approximately 0.3 mL) resulted in a recovery at least 3 or 4 base 10 logs higher than electrocautery or the negative control.
- The maximal theoretical recovery of SARS-CoV-2 on the gelatin filter was approximately 1 × 106.2 units (or 1 × 109.2 viral cytopathic effect units, from the cell titer glow measurement).
- Viral RNA was readily detected in the control aerosols of both fluids in the absence of cautery.
- The lack of SARS-CoV-2 was also confirmed by the lack of viral RNA on quantitative real-time polymerase chain reaction with undiluted vapor collected on the filter.
"This suggests that electrocautery smoke is an unlikely source of SARS-CoV-2 transmission for health care workers. This study is limited by the in vitro nature of the experiment, and collecting cautery plumes from airway surgery in patients with active SARS-CoV-2 would be definitive," wrote the authors.
"Future work investigating the plume associated with lower-temperature thermal surgery (such as coblation or carbon dioxide laser) and different tissue substrates is warranted."
Reference:
The study titled, "Assessing the Risk of SARS-CoV-2 Transmission via Surgical Electrocautery Plume," is published in the journal JAMA Surgery.
DOI: https://jamanetwork.com/journals/jamasurgery/fullarticle/2780434
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