Prognostic value of arterial carbon dioxide tension during cardiopulmonary resuscitation in out-of-hospital cardiac arrest patients receiving extracorporeal resuscitation

Current guidelines on extracorporeal cardiopulmonary resuscitation (ECPR) recommend careful patient selection, but precise criteria are lacking. Arterial carbon dioxide tension (PaCO₂) has prognostic value in out-of-hospital cardiac arrest (OHCA) patients but has been less studied in patients receiving ECPR. We studied the relationship between PaCO₂ during cardiopulmonary resuscitation (CPR) and neurological outcomes of OHCA patients receiving ECPR and tested whether PaCO₂ could help ECPR selection.

This single-centre retrospective study enrolled 152 OHCA patients who received ECPR between January 2012 and December 2020. Favorable neurological outcome (FO) at discharge was the primary outcome. We used multivariable logistic regression to determine the independent variables for FO and generalised additive model (GAM) to determine the relationship between PaCO₂ and FO. Subgroup analyses were performed to test discriminative ability of PaCO₂ in subgroups of OHCA patients.

Multivariable logistic regression showed that PaCO₂ was independently associated with FO after adjusting for other favorable resuscitation characteristics (Odds ratio [OR] 0.23, 95% Confidence Interval [CI] 0.08–0.66, p-value = 0.006). GAM showed a near-linear reverse relationship between PaCO₂ and FO. PaCO₂ < 70 mmHg was the cutoff point for predicting FO. PaCO₂ also had prognostic value in patients with less favorable characteristics, including non-shockable rhythm (OR, 3.78) or low flow time > 60 min (OR, 4.66).

PaCO₂ before ECMO implementation had prognostic value for neurological outcomes in OHCA patients. Patients with PaCO₂ < 70 mmHg had higher possibility of FO, even in those with non-shockable rhythm or longer low-flow duration. PaCO₂ could serve as an ECPR selection criterion.