Mathematical and computer modeling of acute normovolemic hemodilution
- 28 February 1994
- journal article
- research article
- Published by Wiley in Transfusion
- Vol. 34 (2), 176-179
- https://doi.org/10.1046/j.1537-2995.1994.34294143950.x
Abstract
Background: Advocates of acute normovolemic hemodilution (ANH) frequently neglect to consider the decreasing hematocrit of the patient during both hemodilution and the subsequent operative procedure and the need to begin transfusion at some minimal hematocrit. Study Design and Methods: For more accurate prediction of the efficacy of ANH, equations were derived and a computer model developed that allowed accounting for the decreasing hematocrit due to blood loss in an isovolemic patient and calculating the red cell volume on a minute-by-minute basis; the model also began the transfusion of ANH blood on a mL-for-mL basis when the minimal hematocrit was reached and transfused any remaining blood following completion of the case. The red cell volume saved by performing ANH for a given estimated blood volume (EBV) was expressed as either the fraction of the red cell volume of a routinely banked unit of blood (red cells stored in additive solution: volume 350 mL, hematocrit 0.65) or the number of units saved. Results: The number of units saved in a typical example–EBV, 5000 mL; pre-ANH hematocrit, 0.40; minimal hematocrit at which transfusion was begun, 0.25 over a range of estimated blood losses (500–2500 mL); and 1 to 5 ANH units drawn–never exceeded 0.6. Even with extensive hemodilution, as in a child (EBV, 1500 mL; pre-ANH hematocrit, 0.40; minimal hematocrit at which transfusion was begun, 0.15; 5 units drawn; and estimated blood losses, 2500, 1500, and 1000 mL) with a postdilution hematocrit of 0.16, the savings would have been only 0.29, 0.44, and 0.49 units, respectively. Conclusion: Because of the decreasing hematocrit in a bleeding isovolemic patient and the need to begin transfusion at some minimal hematocrit, the theoretic savings in red cell volume attributable to ANH is less than had previously been appreciated, and additional ANH does not necessarily result in additional patient benefit.Keywords
This publication has 11 references indexed in Scilit:
- Perioperative Indications for Red Blood Cell Transfusion—Has the Pendulum Swung Too Far?Mayo Clinic Proceedings, 1993
- Transfusion practice should be audited for both undertransfusion and overtransfusionTransfusion, 1992
- A randomized trial of perioperative hemodilution versus transfusion of preoperatively deposited autologous blood in elective surgeryTransfusion, 1992
- Acute normovolemic hemodilutionTransfusion, 1991
- EFFECT OF HAEMODILUTION ON TRANSFUSION REQUIREMENTS IN LIVER RESECTIONThe Lancet, 1989
- Intraoperative normovolemic hemodilutionJournal of Surgical Research, 1981
- COMPARATIVE EFFECTS OF INDUCED HYPOTENSION AND NORMOVOLAEMIC HAEMODILUTION ON BLOOD LOSS IN TOTAL HIP ARTHROPLASTYBritish Journal of Anaesthesia, 1980
- Regional Lung Function Following Hip Arthroplasty and Preoperative Normovolemic HemodilutionActa Anaesthesiologica Scandinavica, 1979
- Acute haemodilutional autotransfusion in the surgical management of scoliosisThe Journal of Bone and Joint Surgery. British volume, 1978
- Estimating Allowable HemodilutionAnesthesiology, 1974