Cardiac arrest: two-tiered medical systems improved survival.

Clinical bottom line (level 4)

  1. Patients with an out-of-hospital cardiac arrest who were treated by a two-tier emergency medical service system, were more likely to survive until discharge than those treated by a one-tier system.
Nichol et al: Annals of Emergency Medicine 1996; 27: 700-710
Expires October 2003

The study

Systematic review of published, case series of
  • Patients: cardiac arrest
  • Intervention: two-tier basic (with or without defibrillation) and advanced life support (7526 patients) compared with one-tiered system with basic (with or without defibrillation) or advanced life support (15787 patients)
  • Outcome: survival


    • Articles found in English using MEDLINE, 1966 to August 1992 (search terms: keywords 'heart arrest'; subheadings 'therapy', 'resuscitation' and 'cardiopulmonary resuscitation' combined with 'prognosis' or 'survival' ) and manual search of bibliographies of all citations to check for previous unidentified articles, authors of primary studies were contacted to identify additional studies

    Selection criteria: as above
    Appraisal criteria: detailed in text
    Articles excluded if: emergency medical services system other than ambulance or fire companies, patient population of <100, inability to determine the total number of cardiac arrests, or reports detailing only ventricular fibrillation, or lack of data for survival to discharge

    36 articles describing 41 systems, mainly in USA.
    • A two-tier system has two types of responder, the first tier having quicker access with basic life support skills backed up with a secondary, more skilled supplier. A one-tier system has only one type of responder, but and they may be of any skill level (for the purpose of this report).
    • When subjects were included in more than one publication from a single centre, only the report with the largest number of subjects was included.
    • Different systems described in a single article were treated as separate studies because the systems were operating in different areas or times and did not involve the same patients.

    The evidence

    One-tier (control) vs two-tier (experimental) systems
    Outcome Time to outcome CEREERRRR
    (95% CI)    		ARR
    (95% CI)    		NNT
    (95% CI)
    absolute survival unknown 821
    (5.20%)    		 790
    (10.5%)    		 -102%
    (-122% to -84.0%)    		 -5.29%
    (-6.07% to -4.52%)    		 19
    (16 to 22)

    • The length of time it took the response unit to respond was found to be associated with survival.
    • There is no ability to separate the types of single-tier systems (basic, basic+defibrillator, and advanced life support crews)

    Comments

    1. Uncertain if the primary studies are merely case-series (with subsequent ascertainment bias), or systematic community-wide cohorts.
    2. Study does not address if changing from a one-tier to two-tier system actually improves outcomes.

    Citation

    1. Nichol G, Detsky AS, Stiell IG, et al: Effectiveness of emergency medical services for victims of out-of-hospital cardiac arrest: A metaanalysis. Annals of Emergency Medicine 1996; 27: 700-710
    Contributor: Clare Wotton and Bob Phillips, October 1999
    Reviewer:

    Clinical Question.
    Patient out-of-hospital cardiac arrest
    Intervention or Exposure medical care systems
    Outcome survival