Pitt EPIDEM 2670 - Measuring Injury Severity

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1Measuring Injury SeverityA brief introductionThomas Songer, PhDUniversity of [email protected] severity is an integral component in injury research and injury control. This lecture introduces the concept of injury severity and its use and importance in injury epidemiology. Upon completing the lecture, the reader should be able to:1. Describe the importance of measuring injury severity for injury control2. Describe the various measures of injury severityThis lecture combines the work of several injury professionals. Much of the material arises from a seminar given by Ellen MacKenzie at the University of Pittsburgh, as well as reference works, such as that by O’Keefe.Further details are available at:“Measuring Injury Severity” by Ellen MacKenzie. Online at:http://www.circl.pitt.edu/home/Multimedia/Seminar2000/Mackenzie/Mackenzie.htmO’Keefe G, Jurkovich GJ. Measurement of Injury Severity and Co-Morbidity. In Injury Control. Rivara FP, Cummings P, Koepsell TD, Grossman DC, Maier RV (eds). Cambridge University Press, 2001.2Degrees of Injury SeverityHouseholdsEmergency Dept.HospitalizationInjury DeathsPhysician VisitMaterial in the lectures before have spoken of the injury pyramid. It illustrates that injuries of differing levels of severity occur at different numerical frequencies. The most severe injuries occur less frequently. This point raises the issue of how do you compare injury circumstances in populations, particularly when levels of severity may differ between the populations.3InjuryPoliceHospitalSelf-TreatRobertson, 1992doctorEMSRehab CenterTrauma CenterMorgueEmergency Dept.For this issue, consider that injuries are often identified from several different sources. These sources are likely to capture events of differing severity between them, and also within them. Hospital admissions, for example, may include injuries of maximal severity requiring intensive care and those of lower levels of severity that involve an overnight observation period.4Major Areas of Application on Injury Severity Indices Triage  Prognostic Evaluation  Research and EvaluationInjury severity scales are used in three primary applications. These include triage applications to set priorities for patient treatment, prognostic evaluations to predict or manage injury outcomes, and research applications to compare groups on injury outcomes or treatment effects.5Is there potential for improvement in the care of injured patients?As an example, consider the question posed here; can we improve the care of injured patients? The obvious answer is to say yes! There are studies and anecdotal reports that indicate that not all trauma care is optimal, and that patterns of care differ by institution or geographic region of the country.However, to begin the process of answering this question, a researcher must define trauma care, but also who is receiving trauma care. Injury severity scales fit into the picture here by providing a structure to classify patients based upon the severity of their injuries.6Improvements in outcomes related to injury may be achieved by:• Enhancing pre-hospital care• Adopting ATLS principles• Integrating trauma care within and between hospitals• Investing in rehabilitation servicesImproving care to enhance injury outcomes can take many forms, such as those outlined here. Pre-hospital, or emergency medical services (paramedics) can be improved. This may involve training or guidelines on the transfer of patients to the most appropriate facility. The principles of ATLS (Advanced Trauma Life Support) may also be adopted. Other examples that may improve care would include the integration of trauma care services within and between hospitals, and the development of a plan to enhance the use of these services. Long-term care provision may also improve injury outcomes with respect to the quality of life of the person injured.Studies to evaluate the success of these interventions to improve injury outcomes will require comparisons between groups. Injury severity can be an important confounding variable in such an evaluation. Thus, adjustment for injury severity is central to the assessment of treatment interventions for injuries.7Measuring the Burden of Injuries• Fatal– Counts and rates– Years of Potential Life Lost• Non-fatal– Short term• Health care use– Hospitalization rates• Functional limitations• Severity–AIS–RTS, etc•PathologySegui-GomezInjury severity scales may also be used to characterize the burden of injury in descriptive studies. This slide illustrates that injury severity is one of a number of measures on the significance of non-fatal injury.8Injury Severity ScalesHow do you measure and score injury severity? The remainder of the lecture will overview several scales that have been developed to quantify injury severity.9Impact of the Injury will depend on...Extent of tissue damage Physiological response to the injury Host factors that mediate the responseThe development of injury severity scales has been influenced by three factors. The first two factors are the basis for the majority of the existing scales; (a) the area of the injury and its nature of damage, and (b) the physiologic state of the body in response to the injury. The third issue, host factors, has recently been recognized as potential variables that mediate injury outcome, and attempts are now underway to consider them in the assessment of injury severity. More details follow….10Aspects of Injury SeverityAnatomical InjuryPhysiological MeasurementsAgeBlunt/PenetratingProbability of survival of individual patientsComparisons between groupsWhile anatomy, physiology, and host factors may influence the manner in which injury severity is assessed, these variables do not occur in a vacuum. This slides illustrates a model which is meant to emphasise that these variables ultimately work together to determine the outcome of a patient following an injury. Thus, they are all important in assessing injury severity.However, several of the injury severity scales are based only on one aspect of this model. For example, the anatomical injury aspect. These one dimensional scales have been criticised on this basis.11INJURY SEVERITYAlphabet SoupSeveral injury severity scales exist in practice and in the literature. They represent, literally, an alphabet soup of assessment. The sheer number of scales arises from the markedly different


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