[Wearing surgical masks in the operation theatre: yes or no?]

In the Netherlands, the surgical mask is part of the standard surgical attire even for the non-sterile personnel in the operation theatre. Solid evidence on the effect on postoperative infection rates is missing. Due to a national scarcity in surgical masks during the first wave of the COVID-19 crisis the usage of these masks was decreased. In our tertiary referral centre for Surgical Oncology, this led to the decision that, for a period of ten weeks, the surgical masks were only being used by the sterile surgical team and not by non-sterile operation theatre personnel. This retrospective study evaluates the influence of this intervention in terms of postoperative wound infection rates.

Retrospective cohort study.

Consecutive patients undergoing surgery during the first COVID-19 wave (2-3-2020 until 11-05-2020) were compared with patients undergoing surgery in the same period a year earlier. Patients undergoing surgery for soft-tissue malignancies were included. Intra-abdominal surgery was excluded. Primary outcome measurement was wound infection rate within 30 days following surgery. Secondary, a cost reduction analysis was made.

In the COVID-19 wave, a total of 219 patients underwent surgery for soft-tissue malignancies, compared to 241 a year earlier. The incidence of postoperative wound infection was 58/460 (12.6%) for the total cohort. There was no difference in infection rate between the COVID-19 period and the same period in 2019; 25/219 (11,4%; 95% CI: 7,8-16,4)) vs. 33/241 (13,7%; 95% CI: 9,8-18,6), p = 0,46) respectively. During the COVID-19 wave, a total of 6.400 of surgical masks were used by the personnel in the operation theatre complex, compared to a total of 11.000 in the same period in 2019. This resulted in a reduction of 42% in usage of surgical masks.

Based on this mono-centric, explorative retrospective cohort study, it seems that omitting the surgical mask for the non-sterile operation theatre personnel does not influence the postoperative wound infection rate. Despite the fact that our sample size is small, the impressive reduction in usage of 42% demands further research initiatives on a larger scale.