Abstract
Total hip arthroplasty (THA) patients often require peri-operative blood transfusion. Variables that predict transfusion requirement may allow us to target cross-matching of individual patients.
153 patients underwent primary unilateral THA for osteoarthritis or rheumatoid arthritis during 2002 in our institution. 75 casenotes from these subjects were reviewed. Age, sex, diagnosis, weight, height, pre-operative haemoglobin (Hb) and haematocrit (Hct), anticoagulation type and timing were recorded, along with post-operative Hb and timing and quantity of any blood transfusion. Potential predictors of transfusion were examined using logistic regression analysis. ROC analysis was used to compare the relative predictive value of significant variables.
Mean (±SD) age at surgery was 67±11 years (53% females). Mean pre-operative Hb was 13.8±1.4g/dl, mean post-operative Hb was 10.2±1.0g/dl. 27 patients (36%) needed a transfusion; the most frequently given volume was 2 units and the mean number of units given was 0.85. The most common reason for transfusion was an asymptomatic low Hb (< 8.0g/dl). Pre-operative Hb and Hct were predictive of post-operative transfusion (logistic regression analysis P< 0.01). Age, gender, diagnosis and anticoagulation were not predictive. Using ROC analysis the optimal ‘cut-off’ value of pre-op Hb as a predictor was 12.7 g/dl, giving a sensitivity of 41% and a specificity of 88% for blood transfusion requirement. The optimal ‘cut-off’ for Hct was 0.41, sensitivity 74% and specificity 61%. There was no significant difference in the overall predictive value between these variables (comparison of area under ROC curves, P> 0.05).
In summary, subjects with a pre-operative Hb< 12.7 or Hct < 0.41 are more likely to require a blood transfusion after unilateral primary THA than those with an Hb or Hct above these values. In treatment centres where cross-matched blood is not available at short notice on demand, pre-operative cross-match of patients with blood counts below these values may be appropriate.
The abstracts were prepared by Mr Peter Kay, Editorial Secretary. Correspondence should be addressed to British Hip Society, The Hip Centre, Wrightington Hospital, Appley Bridge, Wigan, Lancashire WN6 9EP.
