Perioperative red cell, plasma, and blood volume change in patients undergoing cardiac surgery.
BACKGROUND
Current blood prescription in cardiac surgery is based largely on hemoglobin (Hb) concentration. 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.


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.
Slight
Robert D
RD
Department of Cardiothoracic Surgery, The Royal Infirmary of Edinburgh, Little France Crescent, Edinburgh, Scotland, United Kingdom. rdslight@btopenworld.com
Bappu
Norzeihan J
NJ
Nzewi
Onyekwelu C
OC
McClelland
D Brian L
DB
Mankad
Pankaj S
PS
D000368:Aged; D001811:Blood Volume Determination / Q000379:methods; D002315:Cardiopulmonary Bypass; D017558:Elective Surgical Procedures; D004911:Erythrocyte Volume; D005260:Female; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D008297:Male; D008875:Middle Aged; D010953:Plasma Volume
D006454:Hemoglobins