Preoperative hemoglobin levels and the need for transfusion after prosthetic hip and knee surgery: analysis of predictive factors.

Background: Several studies have established a relationship between the preoperative hemoglobin level and the need for postoperative blood transfusion. We analyzed the relationship between preoperative hemoglobin levels, as well as other factors such as age, gender, weight, height, type and duration of the total joint replacement surgery, and the need for postoperative blood transfusion.

Methods: A retrospective study of 296 patients treated with 370 procedures (209 total hip arthroplasties [56.5%] and 161 total knee arthroplasties [43.5%]) from 1994 to 1998 was carried out. A univariate analysis was performed to establish the relationship between all independent variables and the need for postoperative transfusion. Variables that were determined to have a significant relationship were included in a multivariate analysis.

Results: The univariate analysis revealed a significant relationship between the need for postoperative blood transfusion and preoperative hemoglobin levels (p = 0.0001), duration of surgery (p = 0.0001), weight (p = 0.002), height (p = 0.019), and gender (p = 0.0056). However, the multivariate analysis identified a significant relationship only between the need for transfusion and the preoperative hemoglobin level (p = 0.0001) and weight (p = 0.011); height (p = 0.776) and gender (p = 0.122) were discounted as significant factors. Patients with a preoperative hemoglobin level of <130 g/L had a four times greater risk of having a transfusion than did those with a hemoglobin level between 130 and 150 g/L and a 15.3 times greater risk than did those with a hemoglobin level of >150 g/L.

Conclusions: The preoperative hemoglobin level (p = 0.0001) and weight of the patient (p = 0.011) were shown to predict the need for blood transfusion after hip and knee replacement.