Detection of human coronavirus RNA in surgical smoke generated by surgical devices

Abstract

Background: Gaseous by-products generated by surgical devices - collectively referred to as 'surgical smoke' - present the hazard of transmitting infective viruses from patients to surgical teams. However, insufficient evidence exists to evaluate and mitigate the risks of SARS-CoV-2 transmission via surgical smoke.

Aim: To demonstrate the existence and infectivity of human coronavirus RNA in surgical smoke using a model experiment and to evaluate the possibility of lowering transmission risk by filtration through a surgical mask.

Methods: Pelleted HeLa-ACE2-TMPRSS2 cells infected with human coronavirus were incised by electric scalpel and ultrasonic scalpel, separately. A vacuum system was used to obtain surgical smoke in the form of hydrosol. Reverse transcription-quantitative polymerase chain reaction was used to analyse samples for the presence of viral RNA, and infectivity was determined through plaque assay. Furthermore, a surgical mask was placed centrally in the vacuum line to evaluate its ability to filter viral RNA present in the surgical smoke.

Findings: In this model, 1/10⁶ to 1/10⁵ of the viral RNA contained in the incision target was detected in the collected surgical smoke. The virus present in the smoke was unable to induce plaque formation in cultured cells. In addition, filtration of surgical smoke through a surgical mask effectively reduced the amount of viral RNA by at least 99.80%.

Conclusion: This study demonstrated that surgical smoke may carry human coronavirus, though viral infectivity was considerably reduced. In clinical settings, surgical mask filtration should provide sufficient additional protection against potential coronavirus, including SARS-CoV-2, infection facilitated by surgical smoke.

Keywords: Coronavirus; Electric scalpel; Infectivity; Plaque assay; Surgical smoke; Ultrasonic scalpel.

Figure 1

Sampling system for surgical smoke. Schematic and photograph of the sampling system.

Figure 2

Amount of viral RNA in surgical smoke generated by different types of surgical devices, and the effect of filtration through a surgical mask. The presence or absence of a mask filter is indicated as (+) or (–), respectively. Student's t-test was used to analyse the statistical significance of differences between the groups with or without mask filtration (N = 5; ∗P < 0.05).

Figure 3

Time-dependent change of mask filtering effect. (A) Schematic of the study protocol in chronological order. (B) Viral load in surgical smoke generated by different types of surgical devices and filtered through a surgical mask for 2 h. The viral load that passed through the mask did not change significantly during the 2 h (N = 3).

Figure 4

Amount of human coronavirus-229E RNA in surgical smoke generated from the targets containing different viral concentrations. The limit of detection was 10 copies/mL. The results are based on the mean of 10 samples. The error bars show the standard error.

Figure 5

Plaques of human coronavirus-229E on HeLa-ACE2-TMPRSS2 cell monolayers. No plaques were observed in the plate incubated with the sample that had absorbed the surgical smoke.

Figure 6

Amount of human coronavirus-229E RNA in the cultured cell supernatant after 4 days of incubation with smoke-containing media. The amount of RNA in the medium adsorbed with the smoke generated by an electric scalpel decreased by >97% after 4 days of incubation, while the amount of RNA incubation of intact virus without cells reduced the amount of viral RNA by approximately 33%. By contrast, the amount of RNA in the medium adsorbed with the smoke generated by an ultrasonic scalpel increased during incubation.