From the Guidelines
Acute Normovolemic Hemodilution (ANH) should only be considered when the preoperative hemoglobin concentration is at least 110 g/liter, as recommended by the British Committee for Standards in Haematology Blood Transfusion Task Force 1. This guideline is crucial in ensuring that patients undergoing ANH have sufficient oxygen-carrying capacity to tolerate the procedure.
- The ideal candidate for ANH has a starting hemoglobin between 110-140 g/liter, which provides a sufficient reserve for blood removal while maintaining adequate oxygen delivery to tissues.
- During the procedure, blood is withdrawn while maintaining normovolemia with crystalloid or colloid solutions, with the goal of reducing the hemoglobin to a level that balances the benefits of hemodilution with the need to maintain adequate oxygen delivery.
- The safety of ANH depends on the maintenance of normovolaemia, and care must be taken to match the continuous replacement of volume with the removal of blood, especially in older patients and those with suspected cardiac disease 1.
- The volume of blood to be removed can be calculated using a formula that takes into account the estimated blood volume, initial haematocrit, desired haematocrit, and average haematocrit, ensuring that the procedure is tailored to the individual patient's needs.
From the Research
Hemoglobin Level for Acute Normovolemic Hemodilution (ANH)
- The initial hemoglobin concentration for considering ANH should be > or = 12 g/dl 2
- A target hematocrit of 20-25% (7.0-8.0 g/dl hemoglobin concentration) is feasible and safe for healthy subjects 2
- Intraoperative target hemoglobin concentrations of 5.0 g/dl and less have been tolerated by young surgical patients without adverse effects 2
- A target hemoglobin concentration of 11 g/dL was used in a study on aortic surgery 3
- Patients with preoperative hemoglobin >12 g/dl were included in a study on major orthopedic surgery 4
Considerations for ANH
- ANH should be considered for patients undergoing elective surgery with an anticipated blood loss of > or = 1500 ml 2
- The efficacy of ANH depends on the preoperative hematocrit, the target hematocrit, and the preset intra- and postoperative transfusion trigger 2
- The safety and efficacy of ANH in reducing homologous blood transfusion requirements have been demonstrated in various clinical studies 2, 5, 4, 6