Acute kidney injury (AKI) frequently complicates cardiac surgery and is more common among Black patients. We evaluated determinants of race-based differences in AKI rates.

Serum creatinine-based criteria was used to identify adult cardiac surgical patients developing post-operative AKI in the PERForm registry (7/1/2014-6/30/2019). Patient characteristics, operative details and outcomes were compared by race (Black versus White) after excluding patients with pre-operative dialysis, missing pre- or post-operative creatinine, or other races. A mixed effect model (adjusting for demographics, comorbidities, surgical factors) used hospital as a random effect to predict post-operative stage 2 or 3 AKI. Propensity score analyses were conducted to evaluate robustness of the primary analyses.

The study cohort included 34,520 patients (8% Black). More Black than White patients were female (43 versus 27%, p<.001), had hypertension (93 versus 87%, p<.001) and diabetes (51 versus 41%, p<.001). AKI >Stage 2 occurred among 1,780 (5%) patients, more often among Black than White patients (8 versus 5%, p<.001). Intra-operatively, Black patients had lower nadir hematocrits (23 versus 26, p<.001), and were more likely to be transfused (22 versus 14%, p<.001). After adjustment, Black (compared to White) race independently predicted odds for post-operative AKI (adjOR 1.50, 95% CI 1.26-1.78). The multivariable findings were similar in propensity score analyses.

Despite accounting for differences in risk factors and intra-operative practices, Black patients had a 50% increased odds for developing moderate-severe post-operative AKI compared to White patients. Additional evaluations are warranted to identify potential targets to address racial disparities in AKI outcomes.