title: Intraoperative bleeding: a mathematical model for minimizing hemoglobin loss.
abstract: BACKGROUND
  The rationale for intraoperative blood transfusion is often based on incorrect concepts and criteria.
  
  
  METHODS
  A mathematical model based on physiologic measures and describing the usual pattern of surgical blood loss is presented, and a theoretical means of minimizing intraoperative hemoglobin loss with hypervolemic hemodilution is proposed.
  
  
  RESULTS
  Intraoperative hemoglobin loss is often overestimated especially in connection with high-volume blood loss. The model of intraoperative hypervolemic hemodilution shows significant improvement in hemoglobin concentration in the immediate postoperative period, compared with normovolemic conditions. The difference is most marked at a high volume of blood loss and a high degree of maintained hypervolemia.
  
  
  CONCLUSIONS
  The practice of intraoperative blood transfusion according to volume of blood lost is to be discouraged, and regular monitoring of the hematocrit is necessary to avoid unnecessary transfusion. The theoretical advantages of hypervolemic hemodilution warrant further testing of the model in a clinical setting.
authors.affiliation: Department of Anaesthesiology, Hillbrow Hospital, Joubert Park, South Africa.
authors.forename: Y
authors.initials: Y
authors.lastname: Smetannikov
authors.forename: D
authors.initials: D
authors.lastname: Hopkins
mesh_terms: D016063:Blood Loss, Surgical; D001803:Blood Transfusion / Q000379:methods*; D003198:Computer Simulation; D006438:Hemodilution; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D008962:Models, Theoretical; D013514:Surgical Procedures, Operative / Q000379:methods*
chemical_list: D006454:Hemoglobins