BACKGROUND: Extracorporeal membrane oxygenation (ECMO) indications in patients with accidental hypothermia (AH) and hemodynamic instability before cardiac arrest (CA) are unclear. We aimed to identify a subgroup of these patients who would benefit from ECMO rewarming. METHODS: This study was a post-hoc analysis of the ICE-CRASH study (2019-2022), a prospective, multicenter, observational study throughout Japan. Among the 499 patients (core temperature <
32 °C, age >
18 years), 175 with AH and hemodynamic instability were selected. The primary outcome was 28-day mortality. We examined the effect of ECMO on 28-day mortality after risk stratification based on age, activities of daily living (ADLs), core temperature, Glasgow coma scale (GCS) score, systolic blood pressure (SBP), arrhythmia, pH, and lactate levels. The secondary outcomes were rewarming rate, event-free days (ICU-, ventilator-, and catecholamine-free days), and complications. RESULTS: The patients were divided into ECMO (N = 17) and non-ECMO (N = 158) groups. No significant difference was observed in the 28-day survival rates between the ECMO (13/17, 77%) and non-ECMO (120/158, 76%) groups (p = 0.96). The restricted cubic spline curve showed that the 28-day mortality increased with a GCS score ≤ 8
no relationship was observed between 28-day mortality and decreased SBP or core temperature. No significant difference was observed in the effectiveness of ECMO based on age (<
80 vs. ≥ 80 years), ADLs (independent vs. assistance needed/unknown), core temperature (≥ 26 vs. <
26 °C), GCS (>
8 vs. ≤ 8), SBP (≥ 60 vs. <
60 mmHg), arrhythmia (sinus rhythm vs. arrhythmia), pH (≥ 7.1 vs. <
7.1), and serum lactate level (<
3.0 vs. ≥ 3.0 mmol/L). The rewarming rate was significantly higher in the ECMO group than in the non-ECMO group (2.5 °C/h vs. 1.3 °C/h, p <
0.001), and ICU-, ventilator-, and catecholamine-free days were significantly higher in the non-ECMO group than in the ECMO group. Bleeding complications were significantly more common in the ECMO group than in the non-ECMO group (77% vs. 26%, p <
0.001). CONCLUSIONS: We were unable to identify a subgroup of older adult patients with AH and hemodynamic instability who would benefit from ECMO. The ICE-CRASH study was registered with the University Hospital Medical Information Network Clinical Trial Registry on April 1, 2019 (UMIN-CTR ID: UMIN000036132).