Among in-hospital cardiac arrest survivors not treated with therapeutic hypothermia, a postresuscitation maximum temperature of 36.8 to <37.3°C was associated with the highest survival rate, with temperatures at both high and low extremes associated with the lowest survival in an inverted U-shaped relationship.
Key Findings
Results
An inverted U-shaped relationship existed between maximum postresuscitation temperature and survival to hospital discharge, with the optimal range being 36.8 to <37.3°C.
The highest survival rate (72.7%) was observed in the 36.8 to <37.3°C group, which served as the reference category.
All other temperature ranges had lower rates of survival to hospital discharge.
The worst outcomes were seen at the lowest (<36.3°C) and highest (≥38.8°C) temperature extremes.
A similar inverted U-shaped relationship was observed for favorable neurological survival.
Analysis used multivariable hierarchical logistic regression to evaluate associations.
Results
Patients with the lowest postresuscitation maximum temperature (<36.3°C) had significantly reduced odds of survival to hospital discharge.
Survival rate in the <36.3°C group was 48.4%.
Adjusted odds ratio for survival to hospital discharge was 0.42 (95% CI, 0.37–0.46) compared to the reference group.
This represents one of the two worst-performing temperature categories.
Results
Patients with the highest postresuscitation maximum temperature (≥38.8°C, i.e., fever) had similarly reduced odds of survival to hospital discharge.
Survival rate in the ≥38.8°C group was 51.5%.
Adjusted odds ratio for survival to hospital discharge was 0.40 (95% CI, 0.36–0.44) compared to the reference group.
The magnitude of harm associated with high fever was comparable to that seen with low temperatures (<36.3°C).
Methods
The study population consisted of 36,514 adult in-hospital cardiac arrest patients with return of spontaneous circulation who survived at least 24 hours, drawn from the GWTG-Resuscitation registry from 2015 to 2024.
Mean age was 64.2 ± 16.6 years.
61.8% were men and 69.4% were White individuals.
Patients who received therapeutic hypothermia after return of spontaneous circulation were excluded to better understand the natural history of postresuscitation temperature.
Only index in-hospital cardiac arrest events were included.
Results
The median maximum temperature in the 24 hours after return of spontaneous circulation was 37.2°C, and the overall survival to discharge rate was 66.3%.
Median maximum temperature was 37.2°C (interquartile range, 36.8–37.8°C).
66.3% of patients survived to hospital discharge.
57.0% had favorable neurological survival.
Temperature was categorized in 0.5°C intervals from <36.3°C to ≥38.8°C.
What This Means
This research suggests that after a patient's heart is successfully restarted following a cardiac arrest that occurs inside a hospital, their body temperature in the following 24 hours is meaningfully associated with whether they survive and recover neurologically. Using data from over 36,000 patients across nearly a decade, the study found that patients whose maximum temperature stayed in a narrow normal range — roughly 36.8 to 37.3°C (about 98.2 to 99.1°F) — had the best outcomes, with nearly 73% surviving to hospital discharge. Patients whose temperatures were either lower or higher than this range fared progressively worse.
Notably, the harm associated with very low temperatures (below 36.3°C or about 97.3°F) was nearly as large as the harm from high fever (38.8°C or above, roughly 101.8°F). Both extremes were associated with survival rates around 48–52%, compared to 72.7% in the optimal range. This inverted U-shaped pattern held for favorable neurological recovery as well, not just survival. Importantly, patients who received therapeutic hypothermia — a deliberate cooling treatment — were excluded, so these findings reflect what happens naturally when temperature is not actively manipulated.
This research matters because it challenges a one-directional view that 'cooler is safer' after cardiac arrest, at least in the in-hospital setting where resuscitation tends to be rapid. It suggests that both fever and abnormally low temperatures after resuscitation are associated with worse outcomes, and that maintaining a near-normal body temperature may be an important goal in postresuscitation care. These findings could inform how hospitals monitor and manage temperature in patients who survive cardiac arrest.
Cantu-Martinez O, Jawad M, Kennedy K, Girard A, Ikemura N, Spertus J, et al.. (2026). Association Between Maximum Temperature 24 Hours After Resuscitation and Survival for In-Hospital Cardiac Arrest.. Journal of the American Heart Association. https://doi.org/10.1161/JAHA.125.048549