Blood loss in total knee arthroplasty: an analysis of risk factors

The amount of blood loss in a primary cemented total knee arthroplasty (TKA) seems to vary in different reported studies. We carried out a prospective study to determine the factors affecting the peri-operative blood loss, hidden blood loss and blood transfusion requirements in a primary cemented total knee arthroplasty. The factors analysed were gender, diagnosis, tourniquet time and body mass index (BMI). We included a total of 66 consecutive patients who underwent primary TKA by a single surgeon (A.M). There was significantly more peri-operative blood loss in male patients than in females (p=0.001, Student's t test). The patients with rheumatoid arthritis did not show any statistical difference in peri-operative blood loss compared with that in patients with osteoarthritis. The tourniquet time and the surgical time showed a positive correlation with peri-operative blood loss. The BMI did not show any correlation with peri-operative blood loss. The incidence of blood transfusion was significantly higher in patients with rheumatoid knees as their pre-operative haemoglobin value was low. The amount of hidden blood loss in our series was 38%. We concluded that gender and tourniquet time plays a role in blood loss in TKA, but diagnosis (advanced osteoarthritis [OA] or rheumatoid arthritis (RA) does not. The blood transfusion depends on both pre-operative haemoglobin value and intra-operative blood loss. The post-operative transfusion trigger can be brought to 8.0 g% in a haemodynamically stable patient.