Clinical Implications of Post-operative Haemoglobin Levels in Total Hip and Knee Arthroplasty

Current trends towards minimally invasive surgery and enhanced recovery encourage patients to mobilise and be discharged on the same day following total hip and knee arthroplasty (THA/TKA). The aim was to evaluate the value of current practice in measuring day 1 postoperative haemoglobin levels and stratify patient groups for whom this may be useful.

Three hundred and five patients who underwent elective THA or TKA, over six months (June-December 2023 inclusive), at a single trust, were included. Variables including age, sex, pre-operative and post-operative haemoglobin, American Society of Anaesthesiologists classification, approach, tourniquet time and the use of a drain were recorded. Odds ratio analysis was used to assess factors that may increase the risk of post-operative anaemia.

A total of 157 THAs and 148 TKAs were included; 156/305 (51%) were found to have haemoglobin levels that would be defined as anaemic post-operatively. Risk factors identified corresponding to post-operative anaemia include female gender and pre-operative anaemia. The use of a drain in TKA was associated with a statistically significant increase in the drop in haemoglobin (-14.7 vs. -11.7 g/L, p = 0.034), whereas the use of a tourniquet and patient age made no statistically significant difference. In the THA cohort, the anterolateral approach resulted in a greater drop in haemoglobin than the posterior approach (-15.7 vs. -11 g/L; p = 0.017). Only one patient in each group underwent transfusion (0.6% THA, 0.7% TKA).

Our data show that drops in haemoglobin that require intervention are rare and therefore carrying out day 1 post-operative haemoglobin levels is unnecessary for most patients. Pre-operative patient variables such as pre-existing anaemia and female gender are predictive of risk.