SS06. Effect of Postoperative Anemia and Baseline Cardiac Risk on Adverse Outcomes After Vascular Surgery Interventions

Abstract

Published data suggest that permissive anemia strategies allowing nadir hemoglobin (nHb) 7 g/dL or lower are safe in a variety of clinical settings. The appropriateness of these strategies in patients at high risk for adverse postoperative cardiac events remains unclear. We sought to determine the combined effect of postoperative nHb and cardiac risk status on major complications after vascular surgical interventions. This was a single-institution retrospective analysis of patients who underwent elective open procedures for occlusive vascular disease or aneurysm repair, either open or endovascular. The Revised Cardiac Risk Index (RCRI) was used to assess baseline cardiac risk. Primary outcome was a composite end point (CE) of mortality or major ischemic events (myocardial infarction, stroke, acute kidney injury, or coronary revascularization) within 90 days from the index operation. Secondary outcomes included ICU length of stay (ICU LOS), and 90-day respiratory complications (pneumonia, ventilator dependence for >48 hours postoperatively, or reintubation). Hierarchical multivariable regression was used to model each outcome with adjustment for age, type of operation, comorbidities, and intraoperative covariates. We analyzed 2509 operations performed over 8 years in 1872 patients with mean age 65 (range, 43 to 94) years. In the fully adjusted multivariable model, higher values of nHb were strongly protective from the primary CE (OR, 0.79; P < .0001), representing 21% reduction in the odds of the CE per g/dL increase in nHb). In the same model, RCRI class II (OR, 1.8; P < .0001), class III (OR, 2.07; P < 0.0001), and class IV (OR, 2.38; P < 00001) were associated with progressively increasing odds of the CE compared with RCRI class I (Table). The curvilinear association between the probability of the primary end point occurring over a range of nHb and cardiac risk strata is demonstrated in the Fig. An interaction term between transfusion and nHb was not significant statistically, indicating that the harmful effect of anemia was independent of blood transfusion. Higher values of nHb were favorably associated with respiratory complications (OR, 0.7; P < .0001) and ICU LOS (average 0.47 day reduction per g/dL increase of nHb; P < .0001). Postoperative anemia increases the rate of early postoperative mortality and major ischemic events, particularly in patients at higher baseline cardiac risk. It also adversely affects respiratory complications and ICU LOS. Until a randomized trial definitively settles the issue, restrictive transfusion strategies should be practiced with caution in patients undergoing major vascular interventions.TableThe final fully adjusted multivariate model with the composite end point of 90-day mortality or ischemic events as the dependent variablePredictorOR95% CIP valueNadir hemoglobin0.79(0.74-0.85)<.0001RCRI Class IReferenceReferenceReference II1.76(1.29-2.42)<.0001 III2.06(1.45-2.93)<.0001 IV2.35(1.58-3.48)<.0001Intraoperative blood lossa1.03(1.00-1.06).05ACE inhibitors0.78(0.61-0.99).04ACE, Angiotensin converting enzyme; CI, confidence interval; OR, odds ratio; RCRI, Revised Cardiac Risk Index.aIntraoperative blood loss is modeled in increments of 100 mL, so the demonstrated OR indicates odds of the composite end point per 100-mL increase in blood loss. Open table in a new tab