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A 64-year-old patient is scheduled for cardiac surgery with cardiopulmonary bypass, and the surgical team asks if you will be performing acute normovolemic hemodilution (ANH) during the case. Based on a recently published trial comparing ANH with usual care, which of the following outcomes is MOST likely with the use of ANH?
(A) Reduced allogeneic red blood cell transfusion requirements X
(B) Similar risk of mortality after cardiac surgery ✔
(C) Lower risk of reoperation for bleeding X
Gain insight on this topic, and many others, with Summaries of Emerging Evidence (SEE) 2026 – Volume 42B, now available. The content is aggregated from 30 international medical journals to streamline your learning and improve your practice.
Patients undergoing cardiac surgery commonly require allogeneic blood product transfusion during their hospital stay. However, transfusion during cardiac surgery has been shown to be a risk factor for adverse perioperative outcomes and mortality. Acute normovolemic hemodilution (ANH) is a technique intended to reduce allogeneic blood transfusions. Evidence to support its use has been accumulating, including the 2024 European Guidelines on Patient Blood Management in Adult Cardiac Surgery, which state that ANH may be considered to reduce postoperative transfusions (class of recommendation IIb, level of evidence A). Investigators recently performed a multicenter randomized controlled trial to test the hypothesis that ANH would reduce allogenic red blood cell transfusions during cardiac surgery.
A total of 2,010 adult patients from 32 centers across 11 countries scheduled to undergo elective cardiac surgery were enrolled and randomized to receive either ANH (withdrawal of ≥650 mL of whole blood and crystalloid replacement if needed) or usual care. Patients were excluded from the trial if they had unstable coronary disease, hemodynamic instability, inadequate preoperative cessation of antiplatelet therapy (other than low-dose aspirin), or if development of hemodynamic instability after ANH blood withdrawal was anticipated. Patients in the ANH group had their blood withdrawn before the administration of heparin, and a crystalloid infusion of up to 3 mL of crystalloid per 1 mL of withdrawn whole blood was permitted at the discretion of the anesthesiologist. The ANH blood was stored at room temperature and reinfused after patient separation from cardiopulmonary bypass (CPB) and reversal of heparin with protamine. Allogeneic red blood transfusion for the following hematocrit thresholds was recommended (but not required) for all study patients: hematocrit less than 28% before CPB, less than 20% during CPB, less than 25% immediately after CPB, and less than 27% during the postoperative hospital stay.
The primary outcome of the study was transfusion of at least 1 unit of allogeneic red blood cells between randomization and hospital discharge. The median volume of blood that was withdrawn for a patient in the ANH group was 650 mL. A median volume of 1,000 mL of crystalloid was administered before cardiopulmonary bypass in the ANH group compared to 700 mL in the usual-care group. The results of the trial revealed that by hospital discharge, 27.3% of patients in the ANH group and 29.2% of patients in the usual-care group received at least 1 unit of allogenic red blood (relative risk [RR], 0.93; 95% CI, 0.81 to 1.07). Patients in the ANH group received a median of 2 units of allogeneic red blood cells (IQR, 1–4) versus a median of 2 units (IQR, 1–3) in the usual-care group (RR, 0.5; 95% CI, –0.03 to 1.03). No difference was found between the ANH and usual-care groups in the rates of 30-day mortality after surgery (1.4% vs 1.6%, respectively; RR, 0.87; 95% CI, 0.42 to 1.76), postoperative bleeding (3.8% vs 2.6%, respectively; RR, 1.45; 95% CI, 0.89 to 2.37), or acute kidney injury (8.5% vs 8.9%, respectively; RR, 0.95; 95% CI, 0.71 to 1.26).
In summary, the authors of this multicenter randomized controlled trial concluded that ANH for adult patients undergoing elective cardiac surgery did not reduce the likelihood of receiving at least 1 unit of allogeneic red blood cell transfusion before hospital discharge. The trial also did not demonstrate any adverse impact on postoperative bleeding, acute kidney injury, or 30-day mortality.
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Date of last update: June 26, 2026
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