Quantifying the Effect of Anemia on Major Lower Limb Amputation

Abstract

Introduction: Major Lower limb amputation (MLLA) for end stage vascular disease are unfortunately common. Approximately 4000 are performed each year within the UK. These patients have often suffered years of chronic disease and as such many are anaemic. A 2017 Delphi consensus identified that improving outcomes for amputees are included in the top ten research priorities in the UK. This tertiary center cohort study evaluates the impact of anaemia on the outcome of MLLA to help understand if there is a role in optimization of haemoglobin (Hb) to improve outcomes. Methods: A prospectively maintained database was reviewed. All MLLA between 2015 and 2018 were identified. Anaemia was defined as a pre-operative Hb of less than 120g/dL as per WHO guidance. In addition, a ROC analysis was performed to identify the most sensitive and specific 'critical Hb'. Groups were stratified accrodingly into non-anaemics, moderate anaemia (Hb of < 120-100) and severe anaemia (Hb < 100). Pre-, intra- and post-operative metrics were analyzed to understand if anaemia impacted on clinical outcome. Inter-group comparative statistics and regression analyses were performed. Results: 337 MLLA patients were included. 98 were not anaemic with an average Hb of 133(13.7) g/dL, 111 were mildly anaemic; Hb of 109(5.73) g/dL and 128 were severely anaemic with a mean Hb of 87.8(7.3) g/dL. Mean follow-up period was 22 months. Baseline comparisons were equivalent for age, gender, co-morbidity and medications, as were intra-operative blood loss for all groups. Length of stay was significantly longer with progressive anaemia with the non-anaemic group staying 26.7(25) days, for the moderate group 36.5(42) days and the severely anaemic group 36.6 (30) days (P=0.003). Overall anaemia was associated with a greater 22-month mortality (P=0.021), this was most significant in the severely anaemic group (P< 0.001). The non-anaemics had a probability of survival of 76% compared to the anaemic groups. Regression analysis also demonstrated that an incremental increase of Hb by 1g/dL leads to 2% increase in survival probability. The severely anaemic group fared worse for overall complications but there was no statistical difference in the specific wound complication or revision surgery rates in either anaemia group compared to the non-anaemics. Myocardial events were greatest in the mildly-anaemic group compared to the non-anaemic patients. ROC analysis revealed that 111g/dL to be the most sensitive and specific Hb level to predict, complications and long-term mortality. Conclusion: Pre-operative anaemia significantly increases the length of hospital stay following MLLA. It is also associated with higher long-term mortality and a lower Hb equates to a greater probability of death. Consequently, optimisation of baseline Hb may improve these outcomes in this high risk non-elective group of patients. More work is being undertaken to fully appreciate this relationship. Disclosure: Nothing to disclose