Outcome improvement for anaemia and iron deficiency in ERAS hip and knee arthroplasty: a descriptive analysis.

Background and purpose: Preoperative anaemia including iron deficiency anaemia (IDA) is a well-established perioperative risk factor. However, most studies on iron therapy to treat IDA have been negative and few have been conducted within an enhanced recovery after surgery (ERAS) protocol. Furthermore, patients with IDA often have comorbidities not necessarily influenced by iron, but potentially influencing traditional study endpoints such as length of stay (LOS), morbidity, etc. The aim of this paper is to discuss patient-related challenges when planning outcome studies on the potential benefits of iron therapy in patients with IDA, based upon a large detailed prospective database in ERAS total hip (THA) and knee arthroplasty (TKA).

Methods: A prospective observational cohort study in ERAS THA and TKA from 2022 to 2023. Detailed complete follow-up through questionnaires and electronic medical records.

Results: Of 3655 included patients, 276 (7.6%) had IDA defined as a haemoglobin (Hb) of < 13.0 g/dL and transferrin saturation of 0.20, while 3379 had a Hb of ≥ 13.0. Patients with IDA were a median 5 years older than non-anaemics, with an increased fraction living alone (38.4% vs. 28.8%), using walking aids (54.3% vs 26.4%) and receiving home care (16.2% vs 4.7%). Fewer IDA patients were working (12.7% vs. 29.6%) and a median number of prescribed drugs was higher (10 vs. 6). Median LOS was 1 day in both IDA and non-anaemic patients, but a LOS of > 2 days occurred in 11.6% of patients with IDA vs. 4.3% in non-anaemics. The proportion with 30- or 90-day readmissions was 6.5% vs. 4.1% and. 13.4% vs6.0%, in patients with IDA and non-anaemics, respectively. However, potentially anaemia or iron deficiency-related causes of LOS > 2 days or 90-day readmissions were only 5.4% and 2.2% in patients with IDA and 1.9% and 1.0% in non-anaemics.

Conclusion: Conventional randomised trials with single or composite "hard" endpoints are at risk of being inconclusive or underpowered due to a considerable burden of other patient-related risk factors and with postoperative complications which may not be modifiable by correction of IDA per se. We will propose to gain further insights from detailed observational and mechanistic studies prior to initiating extensive randomised studies.