POSTOPERATIVE DRAINED BLOOD AS A MONITOR OF TOTAL BLOOD LOSS FOLLOWING KNEE ARTHROPLASTY.

Abstract

Background and goal of study: Although a great percentage of the total postoperative bleeding corresponds to a hidden blood loss in the tissues and joint, visible blood from the drainage is considered the gold standard for monitoring blood loss after a knee arthroplasty. Only one study was not able to find a consistent relationship between the total blood loss and postoperative drained blood. The aim of our study was to assess the usefulness of a postoperative drainage as a monitor of bleeding following a knee arthroplasty.

Material and methods: Fifty patients undergoing unilateral arthroplasty from March to November 2004, were prospectively followed until the fourth postoperative day. Drained red blood cells(RBC) loss was assessed by multiplying the drained blood volume by an haematocrit (Hct) of 30% from a pilot study. Total RBC loss and hidden RBC loss from each patient were calculated. Regression analysis was performed to assess the relationship between the total RBC loss and drained RBC loss.

Results and discussions: The average age of the fifty ASA 2 patients was 72 +− 7 years. Nearly all the procedures were performed under intradural anaesthesia. Cemented technique and tourniquet were used in all cases. The mean total RBC loss was 615 +−197ml. The mean drained RBC loss was 206+− 113ml, and mean hidden RBC loss was 414 +−194ml. Thus the hidden loss was 67% of the total blood loss. Regression analysis shown a poor correlation coefficient between the total RBC loss and drained RBC loss (r= 0.31, p< 0.03).