Objective
Preoperative anemia in elderly patients undergoing surgery is prevalent and associated with adverse events; however, the interaction with other risk factors in patients with chronic limb-threatening ischemia (CLTI) is not well described. The purpose of this study was to assess the association between lower hematocrit (HCT) on admission and postoperative outcomes after infrainguinal bypass surgery.
Methods
Patients with CLTI undergoing non-emergent infrainguinal bypass were identified in the targeted vascular NSQIP 2011–2014. Thirty-day outcomes were compared across preoperative HCT levels: severe (HCT ≤29%), moderate (HCT 29.1–34%), mild (HCT 34.1–39%), or no anemia (HCT >39%), with no anemia serving as the reference group for all analyses. Independent associations between levels of anemia and postoperative outcomes were established using multivariable logistic regression. A sensitivity analysis was performed to assess interactions between preoperative anemia and blood transfusions.
Results
We identified 5,081 patients undergoing bypass, of which 741 (15%) had severe, 1,317 (26%) moderate, 1,516 (30%) mild, and 1,507 (30%) no anemia. Anemic patients were older and more commonly suffered from tissue loss and comorbidities (e.g. hypertension, diabetes, and renal insufficiency) (all P<.001). After adjustment for baseline conditions, mortality was higher in those with severe (3.1%, OR: 2.8, [95% CI: 1.3–6.3]) and moderate anemia (3.0%, OR: 2.6 [1.2–5.5]) compared to those without anemia (0.7%). Severe anemia was independently associated with major amputation (6.9% vs. 3.3%, OR: 1.6 [1.01–2.6]) compared to no anemia. Anemia on admission was additionally associated with several other adverse outcomes, such as major adverse cardiovascular event (MACE) (severe: OR: 1.9 [1.1–3.0]; moderate: OR: 1.9 [1.3–2.9]; mild: OR: 1.6 [1.1–2.4]) and unplanned return to the operating room (severe: OR: 1.6 [1.2–2.1]; moderate: OR: 1.5 [1.2–1.8]; mild: OR: 1.3 [1.03–1.6]). Moreover, mortality associated with preoperative anemia was not different in patients receiving postoperative blood transfusions compared to those who did not, while MACE was significantly higher in patients with preoperative anemia and blood transfusions (interaction; P < .001)
Conclusions
Mortality and major adverse events in CLTI patients undergoing infrainguinal bypass are inversely associated with preoperative hematocrit levels, with the highest event rates in the most severely anemic patients. The correlation between anemia and MACE – but not mortality – was stronger in those patients receiving postoperative blood transfusions. Further research is needed to define an appropriate transfusion threshold and attention should be focused on how to best optimize anemic CLTI patients prior to intervention.