Relationship between time to target temperature and outcome in patients treated with therapeutic hypothermia after cardiac arrest

Abstract

Introduction: Our purpose was to study whether the time to target temperature correlates with neurologic outcome in patients after cardiac arrest with restoration of spontaneous circulation treated with therapeutic mild hypothermia in an academic emergency department.

Methods: Temperature data between April 1995 and June 2008 were collected from 588 patients and analyzed in a retrospective cohort study by observers blinded to outcome. The time needed to achieve an esophageal temperature of less than 34°C was recorded. Survival and neurological outcomes were determined within six months after cardiac arrest.

Results: The median time from restoration of spontaneous circulation to reaching a temperature of less than 34°C was 209 minutes (interquartile range [IQR]: 130-302) in patients with favorable neurological outcomes compared to 158 min (IQR: 101-230) (P < 0.01) in patients with unfavorable neurological outcomes. The adjusted odds ratio for a favorable neurological outcome with a longer time to target temperature was 1.86 (95% CI 1.03 to 3.38, P = 0.04).

Conclusions: In comatose cardiac arrest patients treated with therapeutic hypothermia after return of spontaneous circulation, a faster decline in body temperature to the 34°C target appears to predict an unfavorable neurologic outcome.

Figure 1

Time to Target Temperature (T2TT) correlated to the best cerebral perforemance catergory (CPC). Temperature data between April 1995 and June 2008 were collected from 588 patients. The best cerebral performance category achieved within 6 months after cardiac arrest was used. A CPC of 1 indicates good cerebral performance (the patient is alert and has normal cerebral function). A CPC of 2 indicates moderate disability (the patient is alert and has sufficient cerebral function to live independently and work part-time). Such patients might have hemiplegia, seizures, ataxia, dysarthria, dysphasia or permanent memory loss, or other mental changes. A CPC of 3 indicates severe cerebral disability (the patient is conscious but dependent on others for daily support because of impaired brain function). A CPC of 4 indicates a vegetative state. Time is expressed in minutes from restoration of spontaneous circulation (ROSC) to hospital admission (admission), to first monitored esophageal temperature (T_es 1st), to start of cooling (Cool Start), and to esophageal temperature (T_es) of less than 34°C, 33.5°C, and 33°C. Data are presented as median and interquaritle range from the 25th to the 75th percentile.