Decreases in out of hospital cardiac arrest (OHCA) outcome metrics persist when known COVID patients are excluded from analysis.

Objective: A decline in OHCA performance metrics during the pandemic has been reported in the literature but the cause is still not known. The Montgomery County Fire and Rescue Service (MCFRS) observed a decline in both the rate of return of spontaneous circulation (ROSC) and the proportion of resuscitations that resulted in cerebral performance category (CPC) 1 or 2 discharge of the patient beginning in March of 2020. This study examines whether the decline in these performance metrics persists when known COVID positive patients are excluded from the analysis.

Methods: Two samples of OHCA patients for similar time periods (one year apart) before and after the start of the COVID pandemic were developed. A database of known COVID positive patients among EMS encounters was used to identify and exclude COVID positive patients. OHCA outcomes in these two groups were then compared using a Chi-square test and Fisher's exact test for difference in proportions and Analysis of Variance (ANOVA) for difference in means. A two-stage multivariable logistic regression model was used to develop odds ratios for achieving ROSC and CPC 1 or 2 discharge in each period.

Results: After excluding known COVID patients, 32.5% of the patients in the pre-COVID period achieved ROSC compared to 25.1% in the COVID period (p = 0.007). 6% of patients in the pre-COVID period were discharged with CPC 1 or 2 compared to 3.2% from the COVID era (p = 0.026). Controlling for all available patient characteristics, patients undergoing OHCA resuscitation prior to be beginning of the pandemic were 1.2 times more likely to achieve ROSC and 1.6 times more likely to be discharged with CPC 1 or 2 than non-COVID patients in the pandemic era sample.

Conclusions: When known COVID patients are excluded, pre-pandemic OHCA resuscitation patients were more likely to achieve ROSC and CPC 1 or 2 discharge. The prevalence of known COVID positive patients among all OHCA resuscitations during the pandemic was not sufficient to fully account for the marked decrease in both ROSC and CPC 1 or 2 discharges. Other causative factors must be sought.