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

## TL;DR

This study finds that checking post-surgery blood levels the day after hip or knee replacement is rarely needed, as severe drops are uncommon.

## Contribution

The study identifies specific risk factors for post-operative anaemia and questions the routine use of day 1 haemoglobin testing in THA/TKA patients.

## Key findings

- Over half of patients had post-operative haemoglobin levels classified as anaemic.
- Female gender and pre-operative anaemia were significant risk factors for post-operative anaemia.
- Use of a drain in TKA and anterolateral approach in THA were associated with greater haemoglobin drops.

## Abstract

Background: 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.

Methods: 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.

Results: 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).

Conclusion: 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.