Variation in Time in Therapeutic Range for Cooling for Out-of-Hospital Cardiac Arrest

Introduction: For comatose survivors of out-of-hospital cardiac arrest (OHCA), targeted temperature management (TTM) is strongly recommended with a goal temperature of 32-36C for a period of at least 24 hours. However, adherence to this target in clinical practice remains unknown. We developed time-in-therapeutic range (TTR) as a treatment metric for patients receiving TTM and evaluated patient- and site-level variation in TTR. Methods: We used data from the Resuscitation Outcomes Consortium-CCC trial which included patients with OHCA across 10 North American sites during 2011-2015. We identified patients who underwent TTM for >12 hours. Serial temperature measures were evaluated between hypothermia start and end times with temperatures between consecutive measures imputed using a linear interpolation method. TTR was defined as percent of time between 32C and 36C during TTM (Fig A). Site was defined based on trial clusters, which represented hospitals served by the same EMS agency. Site-level variation in TTR<90% was evaluated in hierarchical logistic regression using median odds ratio (OR), after adjustment for patient-level factors. Results: A total of 2,695 patients across 49 clusters were included with a median of 45 (IQR: 34 - 52) patients per cluster. The median duration of hypothermia was 23 (IQR: 21 - 24) hours with a median time outside therapeutic range of 0.9 (IQR: 0.0 - 4.2) hours. The median TTR was 96.1% but 1,654 (61%) patients had at least one temperature outside the therapeutic range and 991 (37%) patients had a TTR <90%. There was large variation across sites in the proportion of patients with TTR<90%, ranging from 10% to 68%, with a median OR of 1.74 (Fig B). Conclusions: Within a large randomized controlled trial, more than 1 in 3 OHCA patients treated with TTM had a TTR <90%, with large variation in TTR across sites. These findings highlight an urgent need to focus on improving quality of TTM in clinical practice.