Association between postoperative haemoglobin concentrations and composite of non-fatal myocardial infarction and all-cause mortality in noncardiac surgical patients: post hoc analysis of the POISE-2 trial

BACKGROUND: Myocardial infarction is the most common postoperative major vascular complication. Perioperative anaemia may contribute to cardiac supply-demand mismatch, and therefore myocardial injury. We therefore tested the hypothesis that the lowest in-hospital postoperative haemoglobin concentration is associated with a composite of non-fatal myocardial infarction and all-cause mortality within the first 30 days after noncardiac surgery. METHODS: We conducted a retrospective analysis of patients enrolled in the PeriOperative Ischemic Evaluation-2 (POISE-2) trial. We assessed the association between the lowest postoperative haemoglobin concentration during the initial hospitalisation and a composite of non-fatal myocardial infarction (Third Universal Definition) and all-cause mortality within 30 postoperative days, using a multivariable logistic regression model. RESULTS: We analysed 7227 patients from POISE-2, of whom 7.8% developed myocardial infarction; 1.5% died within 30 days. The composite primary outcome of non-fatal myocardial infarction and all-cause mortality occurred in 8.9% patients overall, ranging from 16% in patients with postoperative haemoglobin concentrations <88 g L^-1 to 4.1% in patients with postoperative haemoglobin >113 g L^-1. After adjusting for baseline factors, in patients with a lowest postoperative haemoglobin concentration <110 g L^-1, each 10 g L^-1 reduction in the lowest postoperative haemoglobin concentration was associated with a 1.46 (95% confidence interval: 1.37-1.56; P<0.001) fold increase in the odds of the composite outcome. In contrast, there was no significant relationship amongst patients with lowest postoperative haemoglobin concentration >110 g L^-1. CONCLUSIONS: Postoperative anaemia may be a modifiable risk factor for non-fatal myocardial infarction and all-cause mortality.