Postoperative Anaemia Severity as a Superior Predictor of Short-Term Adverse Outcomes Following Vascular Surgery: A Retrospective Cohort Study at a UK Teaching Hospital Trust

Background Perioperative anaemia is highly prevalent in vascular surgery, yet the independent prognostic significance of postoperative anaemia severity remains poorly characterised compared with preoperative anaemia. This study evaluated the association between postoperative anaemia severity and short-term adverse outcomes and compared its predictive utility with preoperative and persistent perioperative anaemia models. Methods A retrospective single-centre cohort study was conducted at Nottingham University Hospitals NHS Trust. All patients undergoing inpatient vascular surgical procedures between July and October 2024 were identified. After excluding day-case procedures and patients with incomplete perioperative haemoglobin (Hb) data, 196 patients were included. Anaemia severity was categorised using World Health Organisation (WHO) sex-specific thresholds into four levels: no anaemia, mild (Hb 110-129 g/L), moderate (Hb 80-109 g/L), and severe (<80 g/L). The primary outcome was a 30-day composite of prolonged hospitalisation (seven days or more), unplanned readmission, and all-cause mortality. Three binomial logistic regression models were compared using Akaike Information Criterion (AIC), Nagelkerke R², and area under the receiver operating characteristic curve (AUC). Results Among 196 patients (mean age 69±15.4 years), the 30-day composite adverse outcome occurred in 158 (80.6%), including prolonged hospitalisation in 140 (71.4%), unplanned readmission in 50 (25.5%) and mortality in 16 (8.2%). A clinically significant perioperative haematological shift was observed: mean Hb declined from 115±18.9 g/L preoperatively to 105±17.9 g/L postoperatively, while moderate anaemia increased from 60 (30.6%) to 99 (50.5%) and severe anaemia doubled from 9 (4.6%) to 19 (9.7%). Subgroup comparisons revealed that baseline demographics and comorbidities had no significant association with the 30-day composite adverse outcome, including gender X2(1, N=196)=0.30, p=0.583, Cramer’s V=0.039 and major comorbidities X2(1, N=196)=0.49, p=0.483, Cramer’s V=0.050. Conversely, the operative approach was a highly significant predictor, X2(1, N=196)=11.26, p<0.001, Cramer’s V=0.240. The postoperative anaemia severity model demonstrated superior predictive performance (AUC=0.69; Nagelkerke R²=0.13; AIC=184.10; p=0.001) compared with the preoperative model (AUC=0.67; R²=0.10; AIC=188.10; p=0.005) and the persistent perioperative model (AUC=0.60; R²=0.04; AIC=191.74; p=0.025). A significant dose-response relationship was identified between postoperative anaemia severity and 30-day adverse outcomes: mild anaemia conferred no significant additional risk (OR 1.18; 95% CI 0.45-3.00; p=0.749), whereas moderate anaemia was associated with a 4.3-fold increase in odds (OR 4.31; 95% CI 1.75-10.63; p=0.002) and severe anaemia with a 9.7-fold increase (OR 9.69; 95% CI 1.17-80.41; p=0.035). Conclusions Postoperative anaemia severity is a critical, independent predictor of 30-day composite adverse outcomes in vascular surgery, demonstrating a clear dose-dependent risk acceleration at moderate and severe levels. This trajectory is heavily driven by procedural trauma, particularly open interventions. The synergistic impact of an open surgical approach and severe postoperative anaemia dictates poor short-term recovery, highlighting the postoperative period as a vital target for clinical optimisation.