The role of accidental hypothermia in drowning patients with out-of-hospital cardiac arrest: A nationwide registry-based cohort study

Abstract

Aim: This study aimed to investigate the associations between hypothermia and mortality or poor neurological outcome in a nationwide cohort of drowning patients with out-of-hospital cardiac arrest (OHCA).

Methods: This nationwide, registry-based cohort study reported in-hospital data on drowning patients with OHCA following the Utstein Style For Drowning. Drowning patients with OHCA were identified in the Danish Cardiac Arrest Registry from 2016 to 2021. The primary outcome was the rate of mortality or poor neurological outcome (corresponding to a modified Rankin Scale [mRS] score > 3) at 180 days after the drowning incident in patients with OHCA and accidental hypothermia (<35 °C) vs normothermia (≥35 °C).

Results: This study identified 118 drowning patients with OHCA and found an increased rate of mRS > 3 at 180 days after the drowning incident in the hypothermic group compared to the normothermic group (74% vs 18%, p < 0.001). The 180-day mortality (mRS = 6) was 69% in the hypothermic group compared to 16% in the normothermic group (p < 0.001). The hypothermic group had higher rates of ongoing CPR at hospital admission (45% vs 7%, p < 0.001), intensive care unit admission (70% vs 41%, p = 0.003), and mechanical ventilation during hospitalisation (78% vs 32%, p < 0.001) compared to the normothermic group.

Conclusion: Hypothermic drowning patients with OHCA had a higher risk of mortality or poor neurological outcome at 180 days compared to normothermic drowning patients with OHCA. This association may likely be explained by confounding factors such as prolonged submersion and cardiac arrest. Further research is warranted.

Keywords: Accidental hypothermia; Cohort, Extracorporeal Life Support; Danish Cardiac Arrest Registry; Danish Drowning Cohort; Danish Drowning Formula; Drowning; Out-of-hospital cardiac arrest; Registry-based.