Effect of general anaesthesia with mechanical ventilation on biomarkers of lung inflammation/injury in COVID-19 survivors – A cohort study

Background: A rise in biomarkers of lung injury with intraoperative mechanical ventilation in patients with healthy lungs may herald postoperative pulmonary complications (POPC). However, perioperative cytokine responses to mechanical ventilation in patients with previous SARS-CoV-2 associated pulmonary involvement are unknown. Objectives: To monitor proinflammatory cytokine responses to intraoperative mechanical ventilation in Corona virus disease-19 (COVID-19) survivors with COVID-associated pulmonary involvement and determine utility of these biomarkers in predicting POPC. Design: A prospective cohort study. Setting: Operating room, postoperative recovery area. Methods: Twenty-four patients with previous COVID-related lung involvement (group 1) and 20 patients with no/presumably no COVID-19 infection (group 2) undergoing various surgeries under general anaesthesia were recruited. General anaesthesia and ventilation were managed similarly in two groups. Bronchoalveolar lavage fluid (BALF) samples were collected at onset of ventilation and at end of surgery. Serum samples were collected at same timepoints and 1-hour postoperatively. Main outcome measures: Concentrations of interleukin-8 (IL-8) and tumour necrosis factor α (TNFα) were measured using Enzyme-linked immunosorbent assay, interleukin-6 (IL-6) by Chemiluminescence immunoassay and C-Reactive protein (CRP) by immunoturbidimetry on automated analyzers. Results: Patient demographics were comparable in both groups except age and American society of Anaesthesiologists classification. Rise of BALF IL-6 and IL-8 was more significant in group 1 (P < 0.001), compared to group 2 (P < 0.05 for IL-6 and P < 0.01 for IL-8). A significant increase in serum IL-6 correlated well with serum CRP at several timepoints in group 1. In both groups, BALF and serum TNF α was below detection limit. Only one patient in group 1 developed POPC. Conclusions: Despite a significant perioperative elevation of IL-6 and IL-8 in BALF, when mechanically ventilated, incidence of POPC did not increase in COVID survivors with prior COVID-associated pulmonary involvement. However, this needs to be validated on a larger sample size.