The Journal of Thoracic and Cardiovascular Surgery, Vol 89, 107-114, Copyright © 1985 by The American Association for Thoracic Surgery and The Western Thoracic Surgical Association
Improved red blood cell survival after cardiac operations with administration of urea during cardiopulmonary bypass
D Roberts, B Bake and G William-Olsson
The plasma hemoglobin and red blood cell survival (half-life of 51Cr) was
studied in 48 patients undergoing single valve replacement or coronary
artery bypass graft. Urea or placebo was administered during
cardiopulmonary bypass in a prospective, randomized, double-blind manner to
test the potential effect on mechanical hemolysis. The mean plasma
hemoglobin level at the end of extracorporeal circulation was significantly
lower in the urea-treated groups (coronary artery bypass 342 mg/L; valve
replacement 364 mg/L) than in the control groups (coronary artery bypass
635 mg/L, p less than 0.05; valve replacement 518 mg/L, p less than 0.01).
The half-life of 51Cr was significantly longer in the urea-treated patients
(coronary artery bypass 18 days; valve replacement 16 days) than in the
control groups (coronary artery bypass 12.4 days, p less than 0.01; valve
replacement 12.7 days, p less than 0.001) but still below the normal
reference value (29 +/- 4 days). The plasma hemoglobin returned to near
normal values (50 mg/L) the day after operation (day 1) and remained low
with no differences between control and urea-treated groups. The total
blood hemoglobin was followed for 2 weeks after operation and showed
significantly less anemia in the urea-treated group. The lowest mean blood
hemoglobin level was noted between days 5 and 9-114 (coronary artery
bypass) and 107 (valve replacement) gm/L in the urea-treated patients
compared to 92.3 (coronary artery bypass, p less than 0.01) and 92.2 (valve
replacement, p less than 0.01) gm/L in the control subjects. The reduction
in the severity of the anemia led to less transfusion in the urea-treated
patients (approximately 0.5 unit/patient) than in the control subjects
(approximately 1 unit/patient, p less than 0.05) between days 3 and 14.