Albumin after cardiac surgery is often chosen for volume therapy, but does it protect the kidneys? A systematic review and Bayesian meta-analysis by Darlison and colleagues found that perioperative albumin was unlikely to reduce acute kidney injury (AKI) in adults undergoing cardiopulmonary bypass. The review included 14 randomized trials, while seven trials supplied the kidney-injury data central to its conclusion.
What Was Studied?
The authors evaluated 14 randomized trials involving 3,304 adults undergoing on-pump cardiac surgery. Eligible interventions included albumin-containing fluids given intraoperatively or postoperatively, compared with crystalloid, other colloids, or standard-care fluid regimens. Albumin concentrations ranged from 4–5% to 20–25%.
The review followed a prospectively registered protocol (PROSPERO CRD42024580170), with duplicate independent assessment of study eligibility, data extraction, risk of bias, and certainty of evidence. Searches were performed in September 2024, and the investigators obtained additional aggregate data directly from trial authors. The primary analysis used a Bayesian random-effects model, supported by sensitivity analyses and a frequentist comparison.
Trials comparing fluids used only for bypass priming were excluded. Some included regimens did incorporate priming alongside other perioperative fluid administration. This distinction matters: the review addresses broader perioperative albumin strategies, rather than isolating albumin in the pump prime. Off-pump surgery and pediatric populations were outside its scope.
Albumin After Cardiac Surgery: Main Kidney Findings
| Measure | Reported finding |
|---|---|
| Trials contributing to the primary AKI outcome | 7 trials; 2,690 patients |
| AKI events in albumin groups | 323/1,348 (24.0%) |
| AKI events in comparator groups | 299/1,342 (22.3%) |
| Pooled risk ratio for AKI | 1.09; 95% credible interval 0.86–1.34 |
| Posterior probability of any AKI reduction | 18.3% |
| Authors’ GRADE certainty for the AKI outcome | High |
The point estimate did not favor renal protection with albumin. Its credible interval included both a reduction and an increase in AKI risk. The results therefore do not establish that albumin causes kidney injury, but they offer little support for selecting it specifically to prevent AKI.
The 18.3% posterior probability describes the probability of any risk reduction under the authors’ statistical model and assumptions. It is not a patient’s probability of avoiding AKI, and it does not quantify the chance of a clinically important benefit. Sensitivity analyses using alternative priors, low-risk-of-bias studies, and frequentist methods were consistent with the primary result.
Other Outcomes Did Not Show a Clear Benefit
Mortality was uncommon: 15 of 1,528 patients in albumin groups and 13 of 1,633 in comparator groups died across the 12 contributing trials. The pooled mortality risk ratio was 1.09 (95% credible interval 0.65–1.82). Renal replacement therapy also showed no clear difference, with a risk ratio of 1.15 (95% credible interval 0.68–1.95).
No statistically significant differences were identified in ICU or hospital length of stay, mechanical ventilation duration, or vasopressor-support duration. Certainty for these secondary outcomes was moderate or low. Rare deaths and dialysis events, wide intervals, and differences between studies mean that an absence of statistical significance should not be read as proof of equivalent outcomes.
Concentration and Timing Did Not Identify a Beneficial Subgroup
Prespecified subgroup analyses did not detect significant differences according to albumin concentration, administration timing, comparator-fluid category, procedural grouping, or trial risk of bias. These findings do not demonstrate that every concentration or dosing strategy has identical effects; subgroup comparisons may have limited power.
The planned subgroup analysis for patients with preoperative estimated glomerular filtration rate below 60 mL/min/1.73 m² could not be performed because suitable data were unavailable. The review therefore does not settle whether a narrowly defined renal-risk population might respond differently.
Relevance for Perfusion Practice
The findings support reassessing the rationale for routine perioperative albumin when the stated goal is kidney protection. A decision to use albumin for a particular volume-management problem should be distinguished from a claim that it prevents postoperative AKI. This review did not establish an optimal fluid protocol, an albumin dose, or a target serum albumin concentration.
For perfusion teams reviewing local practice, useful questions include when albumin is administered, whether its purpose is priming or subsequent volume therapy, which comparator fluid would otherwise be used, and how postoperative kidney outcomes are defined. These are implementation considerations prompted by the evidence, rather than interventions tested by the meta-analysis.
The study does not directly answer the separate question of albumin used exclusively in the bypass prime. It also cannot be generalized automatically to off-pump surgery, children, or targeted correction of hypoalbuminemia in populations not represented by the included trials.
Strengths, Limitations, and Disclosures
Four of the seven AKI trials were judged at low overall risk of bias and accounted for 96.3% of the participants contributing to that outcome. The inclusion of recent large randomized trials and consistency across sensitivity analyses strengthen the primary finding.
Nevertheless, AKI definitions and assessment timing differed, fluid regimens and comparator solutions varied, and some standard-care arms permitted albumin exposure. Individual-patient data were unavailable, limiting investigation of clinically important patient subgroups. The September 2024 search also means this is not a review of every trial published through 2026.
Several review authors participated in the ALBICS-AKI or HASFLAIR II trials. The disclosures include institutional funding from Commonwealth Serum Laboratories for those trials, and one author’s associate-editor role at Critical Care Science. These relationships are relevant when appraising the synthesis.
The clinical message is focused: perioperative albumin is unlikely to reduce AKI after adult on-pump cardiac surgery. The evidence supports reviewing kidney-protection claims while preserving individualized assessment of the reason for fluid administration.
Original Article
Darlison PR, Shehabi Y, Walker HGM, et al. Perioperative albumin versus other fluids to prevent cardiac surgery-associated kidney injury: a systematic review and meta-analysis of randomized trials. Critical Care Science. 2026;38:e20260353. doi:10.62675/2965-2774.20260353.
The source article is available under a Creative Commons Attribution license (CC BY 4.0). The PDF is unchanged. The cover is an AI-generated editorial illustration.
