# Non-selective Day-1 Haemoglobin Monitoring Following Elective Primary Knee Arthroplasty: Clinical Value or Outdated Practice?

## TL;DR

This study finds that routine blood tests for anemia one day after knee replacement surgery offer little benefit due to modern techniques that reduce blood loss.

## Contribution

The study challenges the routine use of Day-1 haemoglobin monitoring in knee arthroplasty under modern surgical practices.

## Key findings

- Only 1.3% of patients had Day-1 haemoglobin levels below 80 g/L.
- Modern techniques reduced transfusion rates to 2.4% with no transfusion-related complications.
- No patients required reoperation for haemorrhage.

## Abstract

Background

Knee arthroplasty is one of the most commonly performed elective surgeries in the UK. Routine Day-1 postoperative haemoglobin (Hb) monitoring is standard practice, but its value is increasingly questioned. Improvements in perioperative care, surgical technique, and the use of adjuncts have significantly reduced blood loss and transfusion rates.

Objectives

The main objective of this study is to evaluate the need for universal, routine Day-1 Hb monitoring following elective primary knee arthroplasty by assessing the mean Hb drop, the rate of severe anaemia, and the rate of red blood cell (RBC) transfusions.

Methods

We conducted a retrospective audit of 452 consecutive total and unicondylar primary knee arthroplasties performed by a single surgeon between March 2013 and February 2020. Standardised surgical techniques were employed, including an anteromedial approach, universal tranexamic acid (TXA) and adrenaline administration, avoidance of surgical drains, controlled blood pressure management, and electrocautery haemostasis. A restrictive transfusion protocol was followed (transfusion for symptomatic anaemia or Hb <70 g/L). The primary outcomes were the mean Hb drop, the incidence of severe anaemia, and RBC transfusion rates.

Results

Mean preoperative Hb was 137.2 ± 14.2 g/L, decreasing to 113.8 ± 14.1 g/L on Day 1 (mean drop: 23.3 ± 9.0 g/L). Only six patients (1.3%) had Day-1 Hb levels below 80 g/L, and 12 patients (2.4%) required postoperative transfusion. No patients were required to return to theatre for haemorrhage control, and no transfusion-related complications occurred.

Conclusions

With modern blood conservation techniques, universal Day-1 Hb monitoring offers minimal clinical value in elective primary knee arthroplasty. We recommend selective Hb testing for patients with low preoperative Hb levels, relevant comorbidities, or clinical symptoms of anaemia, rather than routine testing for all patients. This approach maintains patient safety while reducing unnecessary interventions, healthcare costs, and environmental impact.