392 TRANSFUSION Volume 46, March 2006 Blackwell Publishing IncMalden, USATRFTransfusion0041-11322006 American Association of Blood BanksMarch 2006463392397Original Article RCV DURING CARDIAC SURGERYSLIGHT ET AL. ABBREVIATIONS: AVR = aortic valve replacement; BSA = Body surface area; BV = blood volume; CABG = coronary artery bypass grafting; CPB = cardiopulmonary bypass; ITU = intensive therapy unit; MVR = mitral valve replacement; PV = plasma volume; RCV = red cell volume. From the Department of Cardiothoracic Surgery, The Royal Infirmary of Edinburgh, Little France Crescent, Edinburgh, Scotland, United Kingdom. Address reprint requests to: Robert D, Slight, MB ChB, Department of Cardiothoracic Surgery, The Royal Infirmary of Edinburgh, Little France Crescent, Old Dalkeith Road, Edinburgh, Scotland, UK, EH16 4SU; e-mail: rdslight@btopenworld.com. Received for publication July 5, 2005; revision received August 11, 2005, and accepted August 11, 2005. doi: 10.1111/j.1537-2995.2006.00734.x TRANSFUSION 2006;46:392-397. TRANSFUSION PRACTICE Perioperative red cell, plasma, and blood volume change in patients undergoing cardiac surgery Robert D. Slight, Norzeihan J. Bappu, Onyekwelu C. Nzewi, D. Brian L. McClelland, and Pankaj S. Mankad BACKGROUND: Current blood prescription in cardiac surgery is based largely on hemoglobin (Hb) concentra- tion. Hb may not provide a reliable guide to the patient’s red cell (RBC) volume (RCV) during cardiac surgery as a consequence of the high fluid loads infused. This study provides estimates of the perioperative changes in RCV, plasma volume (PV), and blood volume (BV) with a view to developing a more accurate way of assessing a patient’s need for transfusion. STUDY DESIGN AND METHODS: Thirty adult elective cardiac surgery patients were recruited to the study. The preoperative RCV was calculated by use of a standard nomogram. Losses and gains in RCV at several time points were added or subtracted from the baseline value. Estimates of PV and BV were derived from patient hematocrit level and RCV for each time point. RESULTS: The greatest perioperative loss of RCV occurred during cardiopulmonary bypass (CPB); however, half of this loss was returned to the patient at the end of CPB. A net gain of RCV occurred during the period of intensive care management. PV and BV showed two distinct peaks, immediately after CPB and at 16 hours after intensive therapy unit return. CONCLUSIONS: PV and BV expansion are significant factors that may lead to a Hb value that is misleadingly low in that it overestimates the decrease in RCV. This effect could lead to unnecessary transfusion if the RBC transfusion threshold is based only on Hb concentration. ardiac surgery, with extracorporeal circulation, is associated with a heavy fluid load both in relation to the pump priming solution and the administration of intravenous fluids. Such hemodilution may have a profound effect on hemoglobin (Hb) concentration or hematocrit (Hct). 1,2 The decision to transfuse red cells (RBCs) is based largely on the Hb con- centration on the assumption that this is a good predictor of systemic oxygenation. Hb is a good predictor of the ability of the blood to deliver oxygen but not necessarily systemic oxygenation due to other factors such as cardiac output. If Hb concentration is depressed by fluid loading, then RBCs may be transfused unnecessarily, exposing the patient to an avoidable risk. This study has been designed to record changes in RBC volume (RCV) as opposed to Hb or Hct level. Esti- mates were also made of plasma volume (PV) and blood volume (BV) at the various time points from patient Hct level. It is anticipated that the results obtained can be used, in part, to develop a more rational system for the prescription of blood products. C