Authors: Okazawa et al.
Canadian Journal of Anesthesia, published April 15, 2026
Key Points
Acute normovolemic hemodilution is a blood conservation strategy used to reduce exposure to allogeneic blood transfusion.
Its use in cardiac surgery has been limited partly because of concerns about organ perfusion and renal oxygen delivery.
This retrospective cohort study evaluated whether acute normovolemic hemodilution was associated with less cardiac surgery-associated acute kidney injury.
The study included 19,387 elective cardiac surgery patients, of whom 1,644 received acute normovolemic hemodilution.
Acute normovolemic hemodilution was associated with a lower rate of postoperative renal replacement therapy and fewer allogeneic transfusion units on the day of surgery.
Summary
This retrospective cohort study examined whether acute normovolemic hemodilution was associated with a lower risk of acute kidney injury after elective cardiac surgery. Allogeneic blood transfusions are associated with increased postoperative morbidity and mortality, and blood conservation strategies remain important in cardiac surgery. Acute normovolemic hemodilution is one such strategy, but its adoption has been limited because clinicians have worried about whether hemodilution could compromise organ perfusion, especially renal oxygenation.
The investigators used the JMDC Hospital database in Japan and included patients undergoing elective cardiac surgery between April 2016 and May 2023. Patients were divided into two groups: those who received acute normovolemic hemodilution and those who did not.
The primary outcome was initiation of renal replacement therapy within 7 days after surgery. This was used as a marker of clinically significant cardiac surgery-associated acute kidney injury. Secondary outcomes included in-hospital mortality, length of hospital stay, and the number of allogeneic blood transfusion units given on the day of surgery.
The study included 19,387 patients. Of these, 1,644 patients, or 8%, received acute normovolemic hemodilution. To reduce confounding, the authors used marginal structural models with standardized mortality ratio weighting based on propensity scores.
After adjustment, patients who received acute normovolemic hemodilution had a lower incidence of postoperative renal replacement therapy than those who did not receive it. Renal replacement therapy occurred in 2% of patients in the hemodilution group compared with 3% in the non-hemodilution group. The acute normovolemic hemodilution group also required fewer allogeneic blood transfusion units on the day of surgery.
In-hospital mortality did not differ significantly between groups. This suggests that the observed benefit was related mainly to reduced postoperative renal replacement therapy and reduced transfusion exposure, rather than a measurable mortality difference in this study.
The authors concluded that acute normovolemic hemodilution was associated with reduced postoperative renal replacement therapy and lower allogeneic transfusion requirements in elective cardiac surgery. However, because this was a retrospective observational study, residual confounding may remain, and the findings should be confirmed in future prospective studies.
What You Should Know
This study supports acute normovolemic hemodilution as a potentially useful blood conservation strategy in elective cardiac surgery. The important finding is that, despite theoretical concerns about renal oxygenation, acute normovolemic hemodilution was associated with less need for postoperative renal replacement therapy.
For anesthesia providers, the study is clinically relevant because transfusion avoidance and kidney protection are both major priorities in cardiac surgery. If acute normovolemic hemodilution reduces allogeneic transfusion exposure without increasing kidney injury, it may be a valuable part of a patient blood management strategy.
The results should still be interpreted carefully. This was not a randomized trial, and patients selected for acute normovolemic hemodilution may have differed from those who did not receive it. Even with statistical adjustment, unmeasured confounding can remain.
Overall, the article suggests that acute normovolemic hemodilution may reduce transfusion needs and may be associated with lower risk of severe cardiac surgery-associated acute kidney injury requiring renal replacement therapy. Future prospective trials would help confirm whether the relationship is causal.
Thank you to the Canadian Journal of Anesthesia for allowing us to summarize and share this article.