Indications for Extracorporeal Membrane Oxygenation in Older Adult Patients with Accidental Hypothermia and Hemodynamic Instability

Accidental hypothermia (AH) is a life-threatening condition, particularly in older adults, leading to multisystem failure, coagulopathies, and hemodynamic instability. While extracorporeal membrane oxygenation (ECMO) is recommended for rewarming in severe cases, its effectiveness in patients with hemodynamic instability before cardiac arrest remains uncertain. This study aims to clarify whether ECMO provides survival benefits in such cases by analyzing data from the ICE-CRASH study, a multicenter, prospective, observational study conducted in Japan between 2019 and 2022.

Study Design and Methodology

The ICE-CRASH study enrolled 499 patients with AH (core temperature < 32°C) across 36 tertiary care centers. Of these, 175 patients with hemodynamic instability but no cardiac arrest were analyzed in this post-hoc study. Hemodynamic instability was defined as a systolic blood pressure (SBP) ≤ 60 mmHg or an unmeasurable BP upon arrival at the emergency department (ED), or a heart rate ≤ 50 bpm. Patients were divided into ECMO (N = 17) and non-ECMO (N = 158) groups.

The primary outcome was 28-day mortality. Secondary outcomes included rewarming rate, ICU-, ventilator-, and catecholamine-free days, and complications such as bleeding, pneumonia, pancreatitis, and acute kidney injury. Statistical analyses included a restricted cubic spline model to identify potential predictors of mortality.

Key Findings

1. Survival Outcomes: The 28-day survival rate was similar between the ECMO (77%) and non-ECMO (76%) groups, indicating no significant survival benefit from ECMO.
2. Rewarming Rate: Patients in the ECMO group had a significantly higher rewarming rate (2.5°C/h vs. 1.3°C/h, p < 0.001).
3. Complications: The ECMO group experienced significantly higher bleeding complications (77% vs. 26%, p < 0.001). Other complications, including pneumonia and renal injury, were comparable between groups.
4. ICU-Free Days and Ventilator-Free Days: The non-ECMO group had significantly more ICU-free days and ventilator-free days, suggesting that ECMO treatment prolonged hospitalization and intensive care needs.

Subgroup Analysis and Predictive Factors

• A key finding was that a Glasgow Coma Scale (GCS) score ≤ 8 was associated with higher mortality, but no direct correlation was found between mortality and low SBP, core temperature, lactate levels, or pH.
• No specific subgroup (age <80 vs. ≥80, independent vs. assisted ADLs, core temperature ≥26°C vs. <26°C, SBP ≥60 mmHg vs. <60 mmHg) showed a statistically significant survival benefit from ECMO.
• The study challenges current guidelines that prioritize ECMO for patients with SBP < 90 mmHg, as hypothermia-induced metabolic suppression may allow for adequate oxygenation at lower BP levels.

Discussion

The results suggest that ECMO may not be the optimal treatment for hemodynamically unstable older adults with AH. While ECMO effectively increases rewarming speed, it does not improve survival and is associated with significant complications, particularly bleeding. The findings contrast with previous studies that reported ECMO benefits in younger, outdoor-exposed AH patients, likely due to differences in baseline health status and comorbidities.

One major implication is the need to reconsider current ECMO indications. Given the high mortality associated with AH despite ECMO, alternative rewarming strategies, such as endovascular catheters, may be more effective and safer for older patients. A randomized trial (ICE-CRASH II) is currently underway to evaluate these alternatives.

Study Limitations

• Small Sample Size: Only 17 patients received ECMO, limiting statistical power.
• Post-Hoc Analysis: The study was not originally designed to evaluate ECMO’s efficacy, requiring cautious interpretation of results.
• Generalizability: The cohort consisted mainly of older, indoor-exposed patients, making it difficult to apply findings to younger populations with outdoor hypothermia.

Conclusion

ECMO does not significantly improve survival outcomes in older adults with AH and hemodynamic instability. The study challenges the use of SBP as a primary indicator for ECMO initiation and suggests a need for alternative, less invasive rewarming techniques. Future research should focus on refining hypothermia management protocols to improve outcomes while minimizing risks.

Study Ranking = 4 (high-quality observational study, but not a randomized controlled trial).