Māori Health Outcomes in Intensive Care Following Cardiac Surgery in Aotearoa New Zealand

Māori, the indigenous peoples of Aotearoa New Zealand (NZ) experience disproportionately worse outcomes in cardiovascular health compared to non-Māori. Waikato Hospital provides tertiary cardiothoracic services to the Midland region of NZ, and has instituted an official policy to eliminate ethnic inequity in health. We aimed to audit the outcomes of our cardiothoracic intensive care unit (ICU) against this standard.

We analysed data from the prospectively-entered Australia and NZ Intensive Care Society database for all planned cardiothoracic ICU admissions from 2014 to 2018 at Waikato Hospital for patients aged 15-years and older (n=2,736). Outcomes measured were in-ICU, in-hospital, and 1-year mortality.

Māori were under-represented in this cohort (17.9%) compared to the general Midland population. Māori patients were younger (median 60 vs 68-years old, p<0.001), were more commonly female (34.8% vs 23.6%, p<0.001), domiciled in more deprived areas (2018 NZ Index of Deprivation of 9 vs 6, p<0.001), and more likely to have rheumatic heart disease (35.6% vs 16.6%, p<0.001). More non-Māori required coronary vessel only surgery (57.4% vs 45.2%), whilst more Māori required valvular only surgery (41.1% vs 31.2%) (p<0.001 overall). Baseline Acute Physiology and Chronic Health Evaluation (APACHE) III risk of death score was higher for Māori (1.53% vs 0.89%, p<0.001), as was the European System for Cardiac Operative Risk Evaluation (EuroSCORE) II (2.04% vs 1.55%, p<0.001). Unadjusted mortality was higher for Māori in-ICU (3.1% vs 1.3%, p=0.005) and at 1-year (7.1% vs 3.8%, p=0.002). Adjusted in-ICU mortality, however, was predicted by combined coronary-valvular surgery (adjusted odds ratio, AOR 25.5 [95% confidence interval (CI) 3.30-348.46], p=0.005), Australia and New Zealand Risk of Death (ANZROD) score (AOR 1.11 [CI 1.05-1.19] p<0.001), and renal replacement therapy requirement (AOR 154.56 [CI 30.86-1,107.17] p<0.001), but not by Māori ethnicity (AOR 0.27 [CI 0.03-1.43] p=0.156).

Our audit has identified significant inequity for Māori at our cardiothoracic ICU. Māori are sicker on presentation for planned cardiac surgery, as evidenced by higher admission severity scores, and experience higher unadjusted mortality up to 1-year compared to non-Māori. Māori also appear under-represented despite a greater burden of cardiovascular disease in the community. Further study is required to identify if upstream risk factors, including failure of early detection and referral for disease, contribute to these findings.