TL;DR: 🟡 Positive but limited — IV amino acids reduced cardiac-surgery AKI occurrence, but the benefit was concentrated in early/mild stages with no effect on RRT use or mortality.
1. Publication
- Title: A Randomized Trial of Intravenous Amino Acids for Kidney Protection
- Acronym: PROTECTION
- Year & Journal: New England Journal of Medicine, published June 12, 2024 (391(8):687-698)
- Citation: Landoni G, Monaco F, Ti LK, et al; PROTECTION Study Group. N Engl J Med. 2024;391(8):687-698. doi:10.1056/NEJMoa2403769
2. Context & Rationale
Background: Amino acid infusion increases renal blood flow and glomerular filtration by inducing a state of "renal reserve recruitment," a mechanism distinct from other AKI-prevention strategies. Cardiac surgery-associated AKI remains a common, morbid complication of cardiopulmonary bypass.
Research Question/Hypothesis: In adults undergoing cardiac surgery with CPB, does perioperative IV amino acid infusion reduce AKI occurrence compared with balanced crystalloid (Ringer's lactate)?
3. Design & Methods
- Study Type: Multinational, double-blind, randomized, placebo-controlled trial
- Setting & Centers: 22 centers, 3 countries (Italy, Singapore, Croatia)
- Population: Adults undergoing cardiac surgery with CPB, expected duration ≥1h
- Intervention: IV amino acid infusion, commencing at time of surgery
- Comparator: Balanced crystalloid (Ringer's lactate)
- Statistical Power & Follow-Up: Primary: AKI occurrence (KDIGO creatinine criteria). Secondary: AKI severity, RRT use/duration, 30-day all-cause mortality.
4. Key Results
Outcome | Amino Acids | Placebo (Crystalloid) | Notes |
AKI occurrence (primary) | Reduced | — | Significant reduction |
AKI severity | Reduction primarily in early/mild stages | — | Per NephJC critique: benefit was primarily reduction of early-stage AKI |
RRT use/duration, 30-day mortality | No significant difference | No significant difference | Hard clinical outcomes unaffected |
5. Internal Validity Assessment
Multinational, double-blind, placebo-controlled RCT across 22 centers. Overall: Moderate-to-strong — statistically significant reduction in the primary AKI-occurrence endpoint, but independent commentary (NephJC) specifically notes the benefit was "primarily reduction in early stages of AKI without decreases in hard clinical outcomes" (RRT, mortality) — an important limitation on clinical significance despite statistical significance.
6. External Validity Assessment
Italian, Singaporean, and Croatian cardiac surgery population with CPB — reasonably representative of international cardiac surgery practice.
7. Strengths & Limitations
Strengths: Rigorous double-blind, placebo-controlled, multinational design; statistically significant primary result; mechanistically plausible rationale (renal reserve recruitment).
Limitations: Benefit concentrated in early/mild AKI stages without corresponding reduction in RRT use or mortality, per independent (NephJC) critique; a separate single-center trial (Journal of Thoracic and Cardiovascular Surgery) found IV amino acid therapy did NOT alter duration of renal dysfunction, an important discordant data point; control-group characteristics reportedly included longer CPB times in some analyses, a potential confounder noted by reviewers.
8. Interpretation & Practice Impact
Supports considering perioperative IV amino acid infusion to reduce AKI occurrence in cardiac surgery, though the benefit is concentrated in milder AKI stages without demonstrated impact on RRT need or mortality — independent reviewers (NephJC) conclude amino acid infusion is "unlikely to find a mainstream audience based upon the current study" given this limitation.
9. Controversies & Subsequent Evidence
An accompanying NEJM editorial and independent NephJC commentary ("Trial by Combat: Do Amino Acids provide PROTECTION to the Kidneys?") directly question the clinical significance of a benefit limited to milder AKI stages without hard-outcome improvement. A subsequent meta-analysis (Pruna et al., J Cardiothorac Vasc Anesth 2024) pooling PROTECTION with other amino-acid-for-renal-protection trials found a discordant single-center trial showing no effect on renal dysfunction duration — reflecting genuine, ongoing uncertainty about amino acids' true clinical value for kidney protection.
10. Summary & Executive Takeaway
Summary: PROTECTION, a multinational double-blind RCT across 22 centers in 3 countries, randomized cardiac surgery patients to perioperative IV amino acid infusion or placebo (crystalloid). AKI occurrence was significantly reduced, but this benefit was concentrated in early/mild AKI stages, with no significant difference in RRT use or 30-day mortality.
Overall Takeaway: IV amino acid infusion reduces AKI occurrence after cardiac surgery, but the benefit appears limited to milder AKI stages without translating into reduced dialysis need or improved survival — independent reviewers have concluded this is unlikely to become mainstream practice based on current evidence, pending further confirmatory data with hard clinical outcomes.
11. Bibliography
- Losiggio R, Redaelli MB, Landoni G, Bellomo R. Intravenous Amino-acid Infusion to Prevent AKI after Cardiac Surgery: Review of the Evidence. Ann Thorac Surg. 2025;120(2):256-266.
- Pruna A, Losiggio R, Landoni G, et al. Amino Acid Infusion for Perioperative Functional Renal Protection: A Meta-analysis. J Cardiothorac Vasc Anesth. 2024;38(12):3076-3085.