title: Trends in intensive care unit cardiac arrest admissions and mortality in Australia and New Zealand.
abstract: OBJECTIVE
  To develop methods for distinguishing patients with in-hospital cardiac arrest (IHCA) from patients with out-of-hospital cardiac arrest (OHCA) in routinely collected intensive care unit registry data, and to explore the utility of the methods for describing trends in adult ICU cardiac arrest (CA) admissions and outcomes.
  
  
  METHODS
  A retrospective observational analysis of all ICU admissions entered in the Australian and New Zealand Intensive Care Society adult patient database between 2000 and 2011. Trends in admission and survival rates to hospital discharge over time were examined using eight different methods of classifying patients with IHCA and OHCA.
  
  
  RESULTS
  There were 1 001 754 admissions to the ICUs between 2000 and 2011. Of these, postarrest admissions comprised 23 857 (2.4%), and increased annually by an average of 135 admissions (95% CI, 120-150 admissions). The annual volume of patients with IHCA as a fraction of total admissions declined by 0.4 patients/1000 admissions (95% CI, 0.3-0.5 patients/1000 admissions). In contrast, for patients with OHCA, each year was associated with an additional 0.2 patients/1000 admissions (95% CI, 0.1-0.4 patients/1000 admissions). This increase occurred in tertiary ICUs and declined in non-tertiary ICUs. Survival to hospital discharge for both groups improved, increasing annually by 1.2% (95% CI, 0.8%-1.6%) for patients with IHCA, and by 1.1% (95% CI, 0.7%-1.4%) for patients with OHCA.
  
  
  CONCLUSIONS
  Use of routinely collected registry data uncovered important trends in adult ICU admission and survival rates for patients with IHCA and OHCA. The improved survival rates and increased number of admissions to tertiary centres requires further study to understand mechanisms and related factors.
authors.affiliation: Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, VIC, Australia. lahn.straney@monash.edu.
authors.forename: Lahn D
authors.initials: LD
authors.lastname: Straney
authors.affiliation: Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, VIC, Australia.
authors.forename: Janet E
authors.initials: JE
authors.lastname: Bray
authors.affiliation: Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, VIC, Australia.
authors.forename: Judith
authors.initials: J
authors.lastname: Finn
authors.affiliation: Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, VIC, Australia.
authors.forename: Stephen
authors.initials: S
authors.lastname: Bernard
authors.affiliation: Department of Intensive Care, Alfred Hospital, Melbourne, VIC, Australia.
authors.forename: David
authors.initials: D
authors.lastname: Pilcher
mesh_terms: D001315:Australia / Q000453:epidemiology; D005260:Female; D006323:Heart Arrest / Q000453:epidemiology* / Q000401:mortality; D017052:Hospital Mortality / Q000639:trends; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D009520:New Zealand / Q000453:epidemiology; D058687:Out-of-Hospital Cardiac Arrest / Q000453:epidemiology; D012042:Registries; D012189:Retrospective Studies