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Mathematical considerations in the practice of acute normovolemic hemodilution
Author(s) -
Kick O.,
Daniel E.
Publication year - 1997
Publication title -
transfusion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.045
H-Index - 132
eISSN - 1537-2995
pISSN - 0041-1132
DOI - 10.1046/j.1537-2995.1997.37297203515.x
Subject(s) - hematocrit , nomogram , medicine , blood volume , blood loss , anemia , anesthesia , packed red blood cells , surgery , blood transfusion
BACKGROUND: Acute normovolemic hemodilution (ANH) is recommended as a simple and cost‐effective method of autologous transfusion. The present mathematical model, based on the current clinical practice of removing 2 to 3 units of fresh whole blood, defines the indications for ANH. STUDY DESIGN AND METHODS: A mathematical model and subsequent nomograms were developed to define patients for whom removal of 2 to 3 units (450 mL each) would allow a theoretical red cell savings equivalent to 1 unit of packed red cells (volume, 250 mL; hematocrit, 60%), that is, a successful application of the technique. Minimal safe target hematocrits were defined as 30, 26, and 22 percent. RESULTS: The minimal initial hematocrits required for given patient weights are displayed on nomograms derived from the mathematical model. The nomograms also indicate the surgical blood loss allowed without ANH: for example, a 75‐kg man, (2‐unit ANH, minimal safe hematocrit 22%) requires a minimal initial hematocrit of 42 percent (surgical blood loss of 0.64 × estimated blood volume = 3100 mL). CONCLUSION: ANH involving the removal of 2 to 3 units (450 mL each) may be useful in patients with anticipated blood loss exceeding 50 percent of estimated blood volume, high initial hematocrit, and a capacity to tolerate dilution‐induced anemia.