THE USE OF A MAXIMUM ALLOWABLE BLOOD LOSS PROTOCOL TO REDUCE BLOOD TRANSFUSION REQUIREMENTS IN ELECTIVE PRIMARY LOWER LIMB ARTHROPLASTY

Abstract

The aim of our study was to demonstrate the safety of the use of a maximal allowable blood loss formula to reduce the transfusion requirements of elective primary arthroplasty patients.

In the UK, many arthroplasties are performed each year. Many patients will receive blood transfusion post operatively. Often these patients don’t predonate blood, and most units don’t use re-infusion drains. Blood is both costly, and potentially hazardous product to use; we felt it may be beneficial to patients to reduce the unnecessary use of allogenic blood.

We began with a prospective six-month audit, of transfusion requirements of our elective primary arthroplasty patients, establishing our blood use. Our results showed that 66% (58% knees, 73% hips) had at least one unit of blood post operatively, averaging 1.3 units per patient (1.1 knees, 1.5 hips).

Following this, we instituted a new protocol for postoperative blood transfusion. The protocol involved calculation of a maximum allowable blood loss (MABL) the patient could safely lose prior to the need for blood transfusion. This value is based on the patients weight and preoperative haematocrit. Blood loses up to this value would be made up with colloid replacement. When this MABL value is reached the patient has a bedside measurement of their haematocrit. If it has fallen below 0.3 for males and 0.27 for female patients then they are transfused blood, one unit at a time until it is at or above these reference values. As a ‘safety net’ all patients have a formal full blood count on days 1,2, and 3, and are transfused if their Hb is less than 8.5 g/dl.

This protocol was in place for one year (Feb. 2001-Feb. 2002). Our results show, on average a reduction of blood use from 1.3 units to 0.56 units per patient. The percentage transfused was reduced from 66% to 24% (11% knees, 34% hips).

Overall we had a significant reduction of 59% in units of blood transfused to patients following the new protocol. And feel that this method demonstrates a safe system to reduce transfusion requirements.