Introduction: Off-hours in-hospital cardiac arrest (IHCA) is associated with lower odds of acute resuscitation survival than on-hours IHCA; however, this disadvantage appeared to diminish between 2000 and 2014. No study has investigated nighttime IHCA survival in the United States using more recent data than 2014, and it is unknown if outcomes have changed. We aimed to investigate whether a nighttime survival disadvantage remains using contemporary data and hypothesized improvement with ongoing quality improvement efforts. Methods: This was an observational cohort study using Get With The Guidelines-Resuscitation, a prospectively collected IHCA registry in the United States. We included index IHCA from 2015-2024 and excluded pediatric patients, pediatric/outpatient IHCA locations, and patients without hospital data. Our exposure variable was the time of IHCA (daytime: 07:00-22:59; nighttime: 23:00-06:59). Our primary outcomes were acute resuscitation survival (return of circulation ≥ 20 minutes), survival to discharge, and post-resuscitation survival (survival to discharge among those with acute resuscitation survival). We used a multi-level mixed-effects logistic regression model with hospital as a random effect and demographics, comorbidities, and pre-IHCA illness severity as fixed effects. We performed a sensitivity analysis excluding COVID years. Results: Of 290,698 IHCAs, 97,535 (34.8%) were during nighttime. Nighttime IHCA had lower adjusted odds of acute resuscitation survival (unadjusted 70.9% vs. 75.0%; aOR 0.87; 95% CI: 0.86, 0.89), survival to discharge (unadjusted 19.5 vs. 24.4%; aOR0.83; 0.81, 0.85), and post-resuscitation survival (unadjusted 27.8% vs. 33.0%; aOR 0.86; 95% CI: 0.84, 0.88). Our sensitivity analysis excluding 2020-2021 also demonstrated lower adjusted odds of acute resuscitation, overall, and post-resuscitation survival. Conclusions: Our study identified a nighttime survival disadvantage for patients experiencing IHCA, with no evidence of improvement over time. The absolute difference in survival to discharge between night and daytime of 4.9% is higher than a previously reported on-hours/off-hours difference of 2.8% in 2014, suggesting that the disadvantage remains. Future research should identify ways to improve care for patients experiencing IHCA at nighttime.
Dodi et al. (Sun,) studied this question.