Association among blood pressure, end-tidal carbon dioxide, peripheral oxygen saturation and mortality in prehospital post-resuscitation care

Aim: Post-resuscitation care is described as the fourth link in a chain of survival in resuscitation guidelines. However, data on prehospital post-resuscitation care is scarce. We aimed to examine the association among systolic blood pressure (SBP), peripheral oxygen saturation (SpO₂) and end-tidal carbon dioxide (EtCO₂) after prehospital stabilisation and outcome among patients resuscitated from out-of-hospital cardiac arrest (OHCA). Methods: In this retrospective study, we evaluated association of the last measured prehospital SBP, SpO₂ and EtCO₂ before patient handover with 30-day and one-year mortality in 2,611 patients receiving prehospital post-resuscitation care by helicopter emergency medical services in Finland. Statistical analyses were completed through locally estimated scatterplot smoothing (LOESS) and multivariable logistic regression. The regression analyses were adjusted by sex, age, initial rhythm, bystander CPR, and time interval from collapse to the return of spontaneous circulation (ROSC). Results: Mortality related to SBP and EtCO₂ values were U-shaped and lowest at 135 mmHg and 4.7 kPa, respectively, whereas higher SpO2 shifted towards lower mortality. In adjusted analyses, increased 30-day mortality and one year mortality was observed in patients with SBP < 100 mmHg (OR 1.9 [95% CI 1.4–2.4]) and SBP < 100 (OR 1.8 [1.2–2.6]) or EtCO2 < 4.0 kPa (OR 1.4 [1.1–1.5]), respectively. SpO2 was not significantly associated with either 30-day or one year mortality. Conclusions: After prehospital post-resuscitation stabilization, SBP < 100 mmHg and EtCO₂ < 4.0 kPa were observed to be independently associated with higher mortality. The optimal targets for prehospital post-resuscitation care need to be established in the prospective studies.