The influence of pre-operative anaemia on clinical outcomes following infra-inguinal bypass surgery.

INTRODUCTION: Anaemia is associated with a greater mortality and complications in cardiovascular surgery. Within chronic limb-threatening ischaemia (CLTI) the effect of anaemia is becoming apparent. This study aimed to further understand the influence of anaemia in patients undergoing surgical revascularisation for lower-limb ischaemia.

METHODS: A retrospective review of all patients undergoing infra-inguinal surgical revascularisation between 2016 and 2018 at a tertiary centre was performed. Anaemia was defined as a haemoglobin (Hb) of less than 120g/L. Primary outcome was overall survival by Kaplan-Meier analysis. Secondary outcomes included, length of hospital stay, blood-transfusion requirements, wound infection, myocardial infarction, limb-loss and all-cause mortality. Cox-proportional hazard analysis and receiver operator characteristics (ROC) were performed.

RESULTS: 124 patients were followed up for a mean of 23(8) months. 45 patients were anaemic. There were comparable baseline demographics, comorbidity and severity of symptoms. Overall survival was significantly worse (Log rank p<0.01) in the anaemic group as was the duration of stay; 27(23) days vs. 14(16) days (P=0.001). Anaemic patients received more blood transfusions; 19 (42%) compared to 13 (16.5%) (p=0.001) and had more cardiac complications (11.1% vs 3.8%) (P=0.02). Surgical Site infection rates were also higher (20% vs. 6.3% P=0.036). There was no difference in graft patency or subsequent ipsilateral major lower extremity amputation. 30-day mortality was comparable between the anaemic versus the non-anaemic; 3 (6.7%) vs. 1 (1.3%) (P=0.132). At 1-year there was a greater mortality in the anaemic group of 8 (18%) vs. 4 (5%) in the non-anaemic group (P=0.037) which persisted into the long-term. Anaemia was independently associated with mortality; Hazard Ratio 4.0 (1.14-12.1). A 'cut-off' Hb of 112g/L was identified by ROC analysis.

CONCLUSION: Pre-operative anaemia in infra-inguinal bypass surgery has a significant association with mortality and morbidity. Pre-operative anaemia should prompt the vascular team to consider these patients as higher risk and consider optimisation of haemoglobin.