Impact of Mild Hypercapnia on Renal Function After Out-of-Hospital Cardiac Arrest

Background: Acute kidney injury (AKI) is a serious complication of out-of-hospital cardiac arrest (OHCA). Post-resuscitation cardiogenic shock (CS) is a key contributing factor. Targeting a higher arterial carbon dioxide tension may affect AKI after OHCA in patients with or without CS.

Methods: Pre-planned exploratory study of a multi-national randomised trial comparing targeted mild hypercapnia or targeted normocapnia. The primary outcome was AKI defined by Kidney Disease: Improving Global Outcomes (KDIGO) criteria with modifications. Secondary outcomes included use of renal replacement therapy (RRT) and favourable neurological outcome (Glasgow Outcome Scale Extended, score 5-8) at six-months according to AKI. Exploratory objectives included evaluation of secondary outcomes in patients with both CS and AKI.

Results: We studied 1668 of 1700 TAME patients. AKI occurred in 1203 patients (72.1%) with 596 (49.6%) in the targeted mild hypercapnia group and 607 (50.4%) in the targeted normocapnia group. Stage 3 AKI occurred in 193 patients (23.3%) and 196 patients (23.4%), respectively and RRT in 82 (9.9%) vs 75 patients (8.9%), respectively. At six-months, 237 of 429 no-AKI patients (55.2%) had a favourable neurological outcome compared to 445 of 1111 AKI patients (40.1%) (p <0.0001). AKI occurred more frequently (P<0.001) in patients with CS, affecting 936 patients (77.8%). For CS and AKI patients, there were no significant differences any secondary outcome.

Conclusions: AKI occurred in approximately two-thirds and RRT in approximately one in ten TAME patients without differences according to treatment allocation. CS significantly increased the prevalence of AKI but this effect was not modified by carbon dioxide allocation.