Intravenous amino acids for renal protection in patients receiving temporary mechanical circulatory support: a secondary subgroup analysis of the PROTECTION study

OBJECTIVES: In cardiac surgery patients, acute kidney injury (AKI) frequently occurs in the setting of haemodynamic instability and treatment with temporary mechanical circulatory support (tMCS). Recent evidence suggests amino acids (AA) infusion may reduce AKI rate. However, the effect of AA infusion in patients requiring tMCS may be less effective. METHODS: We performed a secondary analysis of the PROTECTION multicentre randomized controlled trial including all patients treated with tMCS. Patients undergoing elective cardiac surgery with cardiopulmonary bypass were randomized to receive 2 g/kg ideal body weight/day of intravenous AA to a maximum of 100 g/day or matching placebo from operating room admission until up to 3 days, receipt of renal-replacement therapy, discharge from ICU or death. The primary outcome of the PROTECTION study was the rate of AKI, as in this secondary analysis. A total of 3511 patients were randomized in the study. RESULTS: We studied 232 patients who received tMCS, 112 randomized to AA infusion and 120 to placebo. The median preoperative serum creatinine value was significantly higher among AA group patients (AA: 1.08, interquartile range 0.90-1.26; placebo: 0.98, interquartile range 0.85-1.15; P = 0.02). The rate of AKI, however, was lower in patients randomized to AA (44.6% vs 60.8%; relative risk 0.73; 95% confidence interval (0.57-0.94); P = 0.01; number needed to treat = 6). We found no significant differences in secondary outcomes. CONCLUSIONS: Short-term AA infusion appears to reduce rate of AKI among patients requiring tMCS. Use of AA in this population at high-risk for renal failure appears justified.