The 'golden hour': an examination of mortality from major trauma in an informal, decentralised state-wide emergency medical system

Vivienne Tippett (2009). The 'golden hour': an examination of mortality from major trauma in an informal, decentralised state-wide emergency medical system PhD Thesis, School of Population Health, The University of Queensland.

       
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Author Vivienne Tippett
Thesis Title The 'golden hour': an examination of mortality from major trauma in an informal, decentralised state-wide emergency medical system
School, Centre or Institute School of Population Health
Institution The University of Queensland
Publication date 2009-04
Thesis type PhD Thesis
Supervisor Professor Andrew Wilson
Dr Leigh Tooth
Total pages 334
Total colour pages 7
Total black and white pages 327
Subjects 11 Medical and Health Sciences
Abstract/Summary ABSTRACT Key words: major trauma, mortality, emergency pre-hospital, performance indicators. Australian and New Zealand Standard Research Classifications: Division 11 (Medical and Health Sciences); Group 1117 (Public Health and Health Services) Background Response times are a common performance measure for many ambulance services and emergency medical response systems and are considered to be a standard measure of emergency medical services quality. The development of formalised Emergency Medical Systems in Australia and internationally have almost universally assumed a link between shorter response times and improved patient outcome measured by survival. While the evidence to support time-criticality for patients who experience a cardiac arrest is considered unequivocal, the assumption that response and scene times are universally important across all patient groups is not consistently supported by the research evidence. Little is known about whether or not the importance of time-dependent performance measures vary as a function of the Emergency Medical System arrangements to which they apply, the skill set of attending paramedics or the epidemiology of the target population. Despite this, response times continue to be one of the key performance measures for ambulance services regardless of the wider health services system in which they operate. Given the significant investment in paramedic training and increasing levels of clinical responsibility witnessed in the last decade, the development of a robust body of evidence about whether this investment and expertise alters outcomes for patients is yet to develop and there has been little shift in measures of performance. Major traumatic injury is associated with significant disease burden in Australia as elsewhere in the world. An estimated 1,500 Queenslanders die each year as a result of major traumatic injury and injury remains the single most common cause of death in Queenslanders between the ages of 1 and 35 years. As such, injury has a massive impact on the health of Queenslanders. Each year, around 10% of Queenslanders will suffer from an injury of some kind and it is known that injury results in 10% of all hospital admissions and 40-60% of attendances at hospital Emergency Departments. In Australia, injury is recognised as one of the seven National Health Priority Areas by the Australian Government. While this document provides for the setting of broad targets for reduction in injury and its social, economic and health corollaries, little advice is provided regarding health service performance with this target group. The emergency pre-hospital environment is absent in this and most strategic policy documents of this ilk in Australia. This thesis has two core aims: • to provide for the first time a descriptive analysis of major trauma in Queensland for the period 1998-2001 including description of the systemic factors influencing patient mortality; and in the light of these findings to • examine the utility of emergency pre-hospital time-dependent performance indicators as predictors of mortality in this patient group. The period of interest 1998-2001 was selected to provide a baseline for the development of the Queensland Trauma Plan implemented by government in 2007. Methods This thesis involved three key activities: (1) a review of the literature on the basis for time-dependent measures of pre-hospital performance in trauma, impacts of system design and emergency pre-hospital skill set on mortality from major trauma; (2) a descriptive quantitative analysis of linked patient data over a four year period (1998-2001) of the relationship between pre-hospital time and mortality; and (3) the theoretical development of alternative emergency pre-hospital performance measures for trauma. Results Of the 23,462 patients in the study population, 29.0% (n= 6,793) died as a consequence of their injuries. Fifteen percent (15.0%) of the patients died in the pre-hospital environment. After adjustment for age, sex and severity (GCS<9) and the presence or absence of co-morbidities, a response interval in excess of 10 minutes (the State benchmark for high acuity cases) did not affect all-cause, all-age mortality from major trauma (OR 1.03; 95%CI 0.93-1.13) compared to response times < 10 minutes. Similarly, no significant effect of response interval >10 minutes (OR 1.11; 95%CI 0.98-1.26) was noted in the pre-hospital period. Scene time >20 minutes (OR 0.75; CI 0.65-0.86) improved the chance of survival to hospital by comparison to scene times <20 minutes. At all times in the pre-hospital care continuum, the presence of an Intensive Care Paramedic improved survival (OR 1.29; 95%CI 1.13-1.48) when compared to solely Advanced Care Paramedic crews, however this effect was not sustained for overall mortality. Conclusions Traditional time-dependent emergency pre-hospital performance measures are not associated with pre-hospital survival from major traumatic injury in Queensland. This finding differs from the experience of similar systems in Canada and elsewhere and may be due to differences in trauma profile, system arrangements, skill sets and funding models. Alternatively, the system operating in Queensland may in fact be optimised in terms of response, scene and transfer times given the size and geography of the State. This study has confirmed the positive survival benefit associated with highly skilled paramedics in the field and demonstrates that time-dependent performance measures should not be considered proxy measures of survival. New performance indicators specifically targeted to patient outcomes need to be developed to monitor the performance of trauma systems in the pre-hospital sector.
Keyword major trauma, , , performance indicators.
mortality
emergency pre-hospital
Additional Notes 57, 144, 148, 151, 153, 176, 191

 
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Created: Thu, 11 Mar 2010, 10:31:59 EST by Aspr Vivienne Tippett on behalf of Library - Information Access Service