Pre-operative anaemia and myocardial injury after noncardiac surgery A retrospective study

BACKGROUND Pre-operative anaemia is associated with adverse outcomes of noncardiac surgery, but its association with myocardial injury after noncardiac surgery (MINS) has not been fully investigated. OBJECTIVE The association between pre-operative anaemia and MINS. DESIGN A single-centre retrospective cohort study. SETTING Tertiary care referral centre. PATIENTS Patients with measured cardiac troponin (cTn) I levels after noncardiac surgery. INTERVENTIONS Patients were separated according to pre-operative anaemia (haemoglobin <13 g dl(-1) in men and <12 g dl(-1) in women). Anaemia was further stratified into mild and moderate-to-severe at a haemoglobin level threshold of 11 g dl(-1). MAIN OUTCOME MEASURES The primary outcome was MINS, defined as a peak cTn I level more than 99th percentile of the upper reference limit within 30 postoperative days. RESULTS Data from a total of 35 170 patients were collected, including 22 062 (62.7%) patients in the normal group and 13 108 (37.3%) in the anaemia group. After propensity score matching, 11919 sets of patients were generated, and the incidence of MINS was significantly associated with anaemia [14.5 vs. 21.0%, odds ratio (OR) 1.57, 95% confidence interval (CI) 1.47 to 1.68, P < 0.001]. For the entire population, multivariable analysis showed a graded association between anaemia severity and MINS (OR 1.32, 95% CI 1.22 to 1.43, P < 0.001 for mild anaemia and OR 1.80, 95% CI 1.66 to 1.94, P < 0.001 for moderate-to-severe anaemia compared with the normal group) and a significantly higher incidence of MINS for moderate-to-severe anaemia than mild anaemia (18.6 vs. 28.6%, OR 1.37, 95% CI 1.25 to 1.50, P < 0.001). The estimated threshold for pre-operative haemoglobin associated with MINS was 12.2 g dl(-1), with an area under the curve of 0.622. CONCLUSIONS Pre-operative anaemia was independently associated with MINS, suggesting that MINS may be related to the association between anaemia and postoperative mortality.

Automated summary

Pre-operative anaemia is independently associated with MINS, with a graded association between severity of anaemia and MINS. Patients with moderate-to-severe anaemia have a significantly higher incidence of MINS compared to those with mild anaemia. The estimated threshold for pre-operative haemoglobin associated with MINS was 12.2 g dl(-1).