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Brief Report

Characteristics and outcomes of adults admitted to New Zealand ICUs following a cardiac arrest by ethnicity: a brief report

James Moore, Rinaldo Bellomo, Michael Bailey, Carol Hodgson, Paul J Young, for the ANZICS CORE Management Committee

Crit Care Resusc 2021; 23 (4): 418-422

  • Author Details
  • Competing Interests
    None declared
  • References
    1. Dicker B, Wyawahare P, Howie G, Davey P. Out-of-Hospital Cardiac Arrest Registry: Annual Report 2014/15. New Zealand: Clinical Audit and Research, St John; 2015. (viewed Oct 2021).
    2. National Health Board. National Minimum Dataset (hospital events) data dictionary. Wellington: Ministry of Health, 2014. (viewed Oct 2021).
    3. Hart GK; ANZICS Centre for Outcomes and Resources Evaluation (CORE) Management Committee. The ANZICS CORE: an evolution in registry activities for intensive care in Australia and New Zealand. Crit Care Resusc 2008; 10: 83-8.
    4. D’Hoore W, Bouckaert A, Tilquin C. Practical considerations on the use of the Charlson comorbidity index with administrative data bases. J Clin Epidemiol 1996; 49: 1429-33.
There are significant ethnic disparities in the risk of developing and dying from heart disease in New Zealand. While the incidence of cardiac arrest is higher for the Māori compared with the non-Māori population, 1 the intensive care unit (ICU) admission rates after cardiac arrest and outcomes for major New Zealand ethnic groups have not been reported. Many patients who have a cardiac arrest require a period of supportive care in the ICU), and, accordingly, ICU care is a critical link in the chain of survival.
We conducted a retrospective cohort study using data from the New Zealand Ministry of Health National Minimum Dataset matched to the Australian New Zealand Intensive Care Society Centre for Outcome and Resource Evaluation Adult Patient Database (ANZICS CORE APD). This study was submitted to the Health and Disability Ethics Committee of New Zealand (20/CEN/86) and deemed out of scope due to minimal risk. The National Minimum Dataset is a centralised data collection system containing all New Zealand hospital admissions, organised using a patient’s National Health Index number and administered by the New Zealand Ministry of Health. 2  The ANZICS CORE APD is an established binational voluntary intensive care registry database, which has been described previously. 3
We used data relating to ICU admissions in New Zealand hospitals following cardiac arrest from 1 July 2009 to 30 June 2018 inclusive. We included all admissions where the ICU admission diagnosis was cardiac arrest and all admissions where a cardiac arrest occurred in the 24 hours before ICU admission, even when this was not the ICU admission diagnosis. We evaluated the association between ethnicity and outcomes (day 180 mortality, ICU mortality, hospital mortality, and discharge home) using European ethnicity as the reference category. We used logistic regression and performed analyses using four models. First, we evaluated the raw association between ethnicity and each of the binomial outcomes. Second, we evaluated these same associations incorporating adjustment for deprivation status. Third, we evaluated these associations adjusting for all variables that were known before ICU admission (ie, deprivation status, age, sex, site of admission, year of admission, and chronic comorbidities as measured using the Charlson Comorbidity Index 4 ). Finally, we adjusted for illness severity using the Australian and New Zealand Risk of Death (ANZROD) assessment, which includes data from the first 24 hours in the ICU. This final analysis also incorporated adjustment for deprivation status, site, sex, year, and comorbidity as included in the ANZROD model. Comparison of outcomes by ethnic group are reported as odds ratios (ORs) along with 95% confidence intervals (CIs), with an OR of more than 1 corresponding to a greater risk of an adverse outcome for non-European patients.
A total of 3308 of 61 873 ICU admissions (5.3%) occurred after a cardiac arrest. There were highly statistically significant differences in post-cardiac arrest ICU admission rates by ethnicity, with 2039 of 42 871 European (4.8%), 667 of 9681 Māori (6.9%), 325 of 4603 Pacific peoples (7.1%), and 194 of 3435 Asian (5.6%) ICU patients, respectively, admitted following a cardiac arrest (< 0.001). European patients were older, had fewer comorbidities, had markedly lower rates of diabetes, and had lower illness severity (Table 1).
Notably, for day 180 mortality, the OR for death adjusting for pre-ICU baseline confounders (deprivation status, age, sex, site of admission, year of admission, and chronic comorbidities) was significantly higher for Māori, Pacific peoples and Asian patients compared with European patients (Table 2 and Figure 1). While Asian patients appeared to have worse outcomes than European patients when accounting for ICU illness severity, the illness severity-adjusted outcomes for other ethnic groups were similar to those of European patients (Table 2).
Our data show that, after accounting for illness severity, Asian patients had worse outcomes, and Māori and Pacific peoples patients had similar outcomes to European post-cardiac arrest patients admitted to the ICU. Thus, they suggest that for Māori and Pacific peoples patients there may not be major inequities in relation to the provision of ICU care in these patients. Nevertheless, because Māori, Pacific peoples and Asian patients have higher mortality rates than European patients, post-cardiac arrest interventions provided in the ICU that produce a given overall relative reduction in mortality will result in greater absolute reductions in mortality and a smaller number needed to treat for such ethnic minorities. Moreover, as cardiac arrest before ICU admission is more common in non-European patients, the population-level effects of such improvements will disproportionately benefit non-European patients. Accordingly, these data provide support for prioritisation of ICU research investigating improvements in cardiac arrest treatments in order to reduce inequities in this aspect of New Zealand public health delivery.

Acknowledgements: We acknowledge the Australian New Zealand Intensive Care Society Centre for Outcome and Resource Evaluation (ANZICS CORE), which provided the data for this study, and the staff from Christchurch Hospital ICU, Dunedin Hospital ICU, Tauranga Hospital ICU, Wellington Hospital ICU, Southland Hospital ICU, Taranaki Health ICU, Timaru Hospital ICU, Hawkes Bay Hospital ICU, Nelson Hospital ICU, Waikato Hospital ICU, Rotorua Hospital ICU, Whangarei Area Hospital ICU, Hutt Hospital ICU, Auckland City Hospital cardiac and vascular ICU, Auckland City Hospital Department of Critical Care Medicine, North Shore Hospital ICU, and Middlemore Hospital ICU, who collected the data and submitted them to ANZICS CORE. We also acknowledge Chris Lewis who provided the data from the New Zealand Ministry of Health National Minimum Dataset for this study. This research was conducted during the tenure of a Health Research Council Clinical Practitioner Fellowship held by Paul Young. The Medical Research Institute of New Zealand is supported by independent research organisation funding from the Health Research Council of New Zealand.