Acute kidney injury after out-of-hospital cardiac arrest

BACKGROUND: Acute kidney injury (AKI) is a significant risk factor associated with reduced survival following out-of-hospital cardiac arrest (OHCA). Whether the severity of AKI simply serves as a surrogate measure of worse peri-arrest conditions, or represents an additional risk to long-term survival remains unclear. METHODS: This is a sub-study derived from a randomized trial in which 789 comatose adult OHCA patients with presumed cardiac cause and sustained return of spontaneous circulation (ROSC) were enrolled. Patients without prior dialysis dependent kidney disease and surviving at least 48 h were included (N = 759). AKI was defined by the kidney disease: improving global outcome (KDIGO) classification, and patients were divided into groups based on the development of AKI and the need for continuous kidney replacement therapy (CKRT), thus establishing three groups of patients-No AKI, AKI no CKRT, and AKI CKRT. Primary outcome was overall survival within 365 days after OHCA according to AKI group. Adjusted Cox proportional hazard models were used to assess overall survival within 365 days according to the three groups. RESULTS: In the whole population, median age was 64 (54-73) years, 80% male, 90% of patients presented with shockable rhythm, and time to ROSC was median 18 (12-26) min. A total of 254 (33.5%) patients developed AKI according to the KDIGO definition, with 77 requiring CKRT and 177 without need for CKRT. AKI CKRT patients had longer time-to-ROSC and worse metabolic derangement at hospital admission. Overall survival within 365 days from OHCA decreased with the severity of kidney injury. Adjusted Cox regression analysis found that AKI, both with and without CKRT, was significantly associated with reduced overall survival up until 365 days, with comparable hazard ratios relative to no AKI (HR 1.75, 95% CI 1.13-2.70 vs. HR 1.76, 95% CI 1.30-2.39). CONCLUSIONS: In comatose patients who had been resuscitated after OHCA, patients developing AKI, with or without initiation of CKRT, had a worse 1-year overall survival compared to non-AKI patients. This association remains statistically significant after adjusting for other peri-arrest risk factors. TRIAL REGISTRATION: The BOX trial is registered at ClinicalTrials.gov: NCT03141099.