Interaction effects between hypothermia and diabetes mellitus on survival outcomes after out-of-hospital cardiac arrest.

OBJECTIVES: Mild therapeutic hypothermia (MTH) is the core hospital intervention to enhance neurological outcome after out-of-hospital cardiac arrest (OHCA). Diabetes mellitus (DM) has been known to be a harmful risk factor on survival after OHCA. This study aimed to investigate whether the effect of MTH on brain recovery after OHCA differed between patients with or without DM.

METHODS: We used a Korean national OHCA database composed of hospital and ambulance data. We included adult OHCA patients who survived to admission with presumed cardiac etiology during the study period from 2009 to 2013. We excluded cases without hospital outcome data. The primary exposure was MTH, which included all kinds of cooling methods that had been initiated within 6h after return of spontaneous circulation. DM was coded positive when the patient had a clinical history diagnosed by a physician before an OHCA event. The endpoints were discharge with good neurological recovery (cerebral performance category 1 or 2) and survival to discharge. We compared outcomes between MTH vs. non-MTH groups using multivariable logistic regression with an interaction term between MTH and DM for calculating adjusted odds ratios (AORs) and 95% confidence intervals (CIs) after adjusting for potential confounders.

RESULTS: Among 9735 patients following OHCA survived to hospital admission with cardiac etiology, MTH was performed in 16.5%. History of DM was observed in 25.4% among MTH group and 27.4% in non-MTH group (p=0.09). MTH group showed better outcomes than non-MTH group; 23.6% vs. 15.7% for good neurological recovery (p<0.01). AOR (95% CI) of MTH for good neurological recovery for all study groups was 1.23 (1.03-1.47). In the interaction model, AOR (95% CI) of MTH for good neurological recovery was 1.40 (1.16-1.70) in patients without DM vs. 0.69 (0.46-1.04) in patients with DM. For survival to discharge, the effects of MTH were different in patients without DM (1.97 (1.70-2.29)) and patients with DM (1.23 (0.96-1.57)).

CONCLUSION: DM modified the effect of MTH on survival and neurological outcomes for OHCA survivors. MTH is significantly associated with good neurological recovery in patients without DM, but not in patients with DM.