Mary M. Lawnick

The Injury Severity Score revisited.

The injury severity score (5) (iss) is a scalar (single number) measure of anatomic injury, widely used in and an important contribution to trauma research. The iss is the sum of squares of the highest abbreviated injury scale (1-3) (AIS) grade in each of the three most severely injured body regions. Thus the iss is a summary measure of trauma to single or multiple body regions. Per cent mortality for blunt injured patients has been shown to be related to iss (based on AIS-76) and patient age (4-6). Patients used to establish those relationships were treated in 1961 and 1967-1968. Similar relationships for penetrating injuries have not been prepared because, until the 1985 version, the AIS provided severity grades for blunt injuries only. The iss is frequently used to assess or compare the injury severity of patient populations (7, 10, 13, 16) and as the anatomic component of trauma patient characterizations used in evaluation of care and quality assurance methods (8). The AIS first published in 1971, was developed to classify anatomic injury from motor vehicle-related trauma. It has been revised and broadened in scope in 1976, 1980, and 1985. Changes in injury coding, trauma care delivery, and clinical management mandate the updating of relationships between severity measures and mortality from which conclusions regarding patient management or healthcare policy issues may be drawn. The present study uses the most recent AIS version (AIS-85) to derive relationships between mortality rate and the iss for comtemporary patients with blunt or penetrating injuries and identifies important properties of the iss which should be considered when the measure is used to compare case mix severity in different populations.(Author/TRRL)

A New Characterization of Injury Severity

ASCOT (A Severity Characterization of Trauma) is a physiologic and anatomic characterization of injury severity which combines emergency department admission values of Glasgow Coma Scale, systolic blood pressure, respiratory rate, patient age, and AIS-85 anatomic injury scores in a way that obviates ISS shortcomings. ASCOT values are related to survival probability using the logistic function and regression weights reaffirm the importance of head injury and coma to the prediction of patient outcome. The ability of TRISS and ASCOT to discriminate survivors from non-survivors and the reliability of their predictions, as measured by the Hosmer-Lemeshow statistic, were compared using Major Trauma Outcome Study (MTOS) patient data. ASCOT performance matched or exceeded TRISSs for blunt-injured patients and for penetrating-injured patients. ASCOT performance gains were modest for blunt-injured patients. The Hosmer-Lemeshow statistics suggest that ASCOT reliably predicts patient outcome for penetrating-injured patients and nearly so for blunt-injured patients. Statistically reliable predictions were not achieved by TRISS for either set. ASCOT provides a more precise description of patient physiologic status and injury number, location, and severity than TRISS. The ASCOT patient description may be useful in relating to other important outcomes not highly correlated with TRISS or the Injury Severity Score (ISS) such as disability, length of stay, and resources required for treatment.

Progress in characterizing anatomic injury

A three-valued description of anatomic injury is presented. Anatomic profile (AP) components A, B, and C summarize serious injuries (greater than AIS 2) to the head/brain or spinal cord; to the thorax or front of the neck; and all remaining serious injuries. Relationships between AP components and survival rate reaffirm the seriousness of head injury. Logistic function models relating AP components and the Injury Severity Score (ISS) to survival probability were based on 20,946 Major Trauma Outcome Study (MTOS) patients (9.2% mortality rate) submitted through 1986. Model performance comparisons were based on 5,939 MTOS patients (7.8% mortality rate) submitted during 1987. The AP better discriminated survivors from nonsurvivors and provided a 31% increase in sensitivity when compared with the ISS. Neither the ISS nor the AP alone reliably predict patient outcome. The predictive power of methods for estimating patient survival probability which include physiologic indices or profiles, patient age, and an anatomic profile should be compared with current methods. The AP, which is based on the severity and location of all serious injuries, provides a more rational basis for comparing patient samples than the ISS.

Improved characterization of combat injury

BACKGROUND Combat injury patterns differ from civilian trauma in that the former are largely explosion-related, comprising multiple mechanistic and fragment injuries and high-kinetic-energy bullets. Further, unlike civilians, U.S. armed forces combatants are usually heavily protected with helmets and Kevlar body armor with ceramic plate inserts. Searchable databases providing actionable, statistically valid knowledge of body surface entry wounds and resulting organ injury severity are essential to understanding combat trauma. METHODS Two tools were developed to address these unique aspects of combat injury: (1) the Surface Wound Mapping (SWM) database and Surface Wound Analysis Tool (SWAT) software that were developed to generate 3D density maps of point-of-surface wound entry and resultant anatomic injury severity; and (2) the Abbreviated Injury Scale (AIS) 2005-Military that was developed by a panel of military trauma surgeons to account for multiple injury etiology from explosions and other high-kinetic- energy weapons. Combined data from the Joint Theater Trauma Registry, Navy/Marine Combat Trauma Registry, and the Armed Forces Medical Examiner System Mortality Trauma Registry were coded in AIS 2005-Military, entered into the SWM database, and analyzed for entrance site and wounding path. RESULTS When data on 1,151 patients, who had a total of 3,500 surface wounds and 12,889 injuries, were entered into SWM, surface wounds averaged 3.0 per casualty and injuries averaged 11.2 per casualty. Of the 3,500 surface wounds, 2,496 (71%) were entrance wounds with 6,631 (51%) associated internal injuries, with 2.2 entrance wounds and 5.8 associated injuries per casualty (some details cannot be given because of operational security). Crude deaths rates were calculated using Maximum AIS-Military. CONCLUSION These new tools have been successfully implemented to describe combat injury, mortality, and distribution of wounds and associated injuries. AIS 2005-Military is a more precise assignment of severity to military injuries. SWM has brought data from all three combat registries together into one analyzable database. SWM and SWAT allow visualization of wounds and associated injuries by region on a 3D model of the body.

A comparison of Abbreviated Injury Scale 1980 and 1985 versions.

The 1980 and 1985 versions of the Abbreviated Injury Scale (AIS) are quantitatively and qualitatively compared based on experience gained during the recent coding of nearly 115,000 injuries from more than 33,000 seriously injured patients using both AIS versions. Quantitative comparisons are based on differences in AIS scores and Injury Severity Score (ISS) values which result under the two schemes. Qualitative comparisons concern the completeness and clinical usability of the two scales in a trauma center setting.

Combat Injury Coding: A Review and Reconfiguration

BACKGROUND The current civilian Abbreviated Injury Scale (AIS), designed for automobile crash injuries, yields important information about civilian injuries. It has been recognized for some time, however, that both the AIS and AIS-based scores such as the Injury Severity Score (ISS) are inadequate for describing penetrating injuries, especially those sustained in combat. Existing injury coding systems do not adequately describe (they actually exclude) combat injuries such as the devastating multi-mechanistic injuries resulting from attacks with improvised explosive devices (IEDs). METHODS After quantifying the inapplicability of current coding systems, the Military Combat Injury Scale (MCIS), which includes injury descriptors that accurately characterize combat anatomic injury, and the Military Functional Incapacity Scale (MFIS), which indicates immediate tactical functional impairment, were developed by a large tri-service military and civilian group of combat trauma subject-matter experts. Assignment of MCIS severity levels was based on urgency, level of care needed, and risk of death from each individual injury. The MFIS was developed based on the casualty’s ability to shoot, move, and communicate, and comprises four levels ranging from “Able to continue mission” to “Lost to military.” Separate functional impairments were identified for injuries aboard ship. Preliminary evaluation of MCIS discrimination, calibration, and casualty disposition was performed on 992 combat-injured patients using two modeling processes. RESULTS Based on combat casualty data, the MCIS is a new, simpler, comprehensive severity scale with 269 codes (vs. 1999 in AIS) that specifically characterize and distinguish the many unique injuries encountered in combat. The MCIS integrates with the MFIS, which associates immediate combat functional impairment with minor and moderate-severity injuries. Predictive validation on combat datasets shows improved performance over AIS-based tools in addition to improved face, construct, and content validity and coding inter-rater reliability. Thus, the MCIS has greater relevance, accuracy, and precision for many military-specific applications. CONCLUSION Over a period of several years, the Military Combat Injury Scale and Military Functional Incapacity Scale were developed, tested and validated by teams of civilian and tri-service military expertise. MCIS shows significant promise in documenting the nature, severity and complexity of modern combat injury.

Linking data from national trauma and rehabilitation registries

OBJECTIVE To evaluate te feasibility of retrospectively creating a data base useful in trauma systems evaluations. MATERIALS AND METHODS Records for 375 patients in both the Major Trauma Outcome Study and the Uniform Data System for Medical Rehabilitation were linked to create an injury-through-rehabilitation data base, including patients from four impairment groups: traumatic brain injury (TBI); spinal cord injury --paraplegic complete (SCI-PARA) and quadriplegic complete (SCI-QUAD); and hip fracture (HIP-FX). MEASUREMENTS AND MAIN RESULTS The average ages (25.1 years SCI-QUAD, 72.6 years HIP-FX); Injury Severity Score (10.2 HIP-FX, 31.7 SCI-PARA); Revised Trauma Score (5.9 TBI, 7.8 HIP-FX); and acute care lengths of stay (13.3 days HIP-FX, 24.2 days TBI) varied substantially over the four groups. On average, patients spent from approximately 20 days (HIP-FX) to nearly 100 days (SCI-QUAD) in rehabilitation. Functional gains during rehabilitation were primarily in motor skills, but TBI patients also made substantial cognitive gains. Nearly 90% of TBI and SCI patients were discharged to their homes; the percentage of HIP-FX patients discharged to their homes, however, was lower (74%). Across all impairment groups, more patients lived with their relatives after rather than before injury. The correlation between a summary Major Trauma Outcome Study-Functional Independence Measure assessed at acute care discharge and the complete Uniform Data System for Medical Rehabilitation-Functional Independence Measure assessed on admission to rehabilitation was significant for all study patients and for each impairment group except SCI_PARA. CONCLUSIONS Linking records to create the study data base was arduous and could not be practically accomplished on a large scale or on a continuing basis. Because of the growing emphases on trauma system evaluations and outcomes beyond survival at acute care discharge, we recommend the routine inclusion of rehabilitation data in hospital-based trauma registries.

Applying modeling and simulation to predict human injury due to a blast attack on a shipboard environment

Computer models simulating blast effects on ship personnel are needed, but thus far, development of models has focused on simulating blast effects on ship structure and equipment. Thus, capability gaps exist in predicting the type and severity of injuries from surface or underwater weapon impact, estimating medical response requirements, and determining outcomes of patients. The Human Injury & Treatment (HIT) model addresses these gaps. Algorithms are utilized for scoring the type and severity of injuries predicted, using a variety of existing and developing injury models. Additional algorithms determine the post-injury level of incapacitation by evaluating how a physical impairment can impact performance of a task. A manning model simulates movement of personnel aboard the ship (Young, Allen, & Minks, 2011). It functions iteratively with the Tactical Medical Logistics (TML+) code, a medical response model predicting resource utilization and patient outcomes (Mitchell, 2004). Impact: HIT will help the Navy and commercial maritime interests anticipate medical response requirements resulting from blast attacks to a ship, and understand the impact of personnel loss on the crew’s ability to perform damage control.

Multi-Injury Casualty Stream Simulation in a Shipboard Combat Environment.

Accurate forecasts of casualty streams are essential for estimating personnel and materiel requirements for future naval combat engagements. The scarcity of recent naval combat data makes accurate forecasting difficult. Furthermore, current forecasts are based on single injuries only, even though empirical evidence indicates most battle casualties suffer multiple injuries. These anticipated single-injury casualty streams underestimate the needed medical resources. This article describes a method of simulating realistic multi-injury casualty streams in a maritime environment by combining available shipboard data with ground combat blast data. The simulations, based on the Military Combat Injury Scale, are expected to provide a better tool for medical logistics planning.