Injury Severity Score Worksheet

What is an Injury Severity Score Worksheet?

An Injury Severity Score (ISS) Worksheet is a tool used by medical professionals, particularly in the fields of trauma and emergency care, to assess the overall severity of a patient's injuries. It serves as a standardized method for scoring the injuries that a patient has sustained, based on a system that classifies injuries by body region and assigns severity scores.

Here’s how it generally works:

1. Classification of injuries: Injuries are classified according to the Abbreviated Injury Scale (AIS), which rates each injury on a scale from 1 (minor) to 6 (maximal, currently untreatable). The AIS is a globally recognized coding system that details hundreds of injuries and describes the type, location, and severity of damage.
2. Calculation of ISS: The worksheet involves calculating the ISS by squaring the AIS scores of the three most severely injured body regions and then summing these squares. The highest possible score is 75, indicating very severe injuries, usually including at least one critical injury. Scores are only taken from the three most severely injured body regions to ensure that multiple injuries in one body region do not disproportionately influence the overall score.
3. Utility and importance: The ISS is crucial for evaluating the potential outcomes and treatment approaches for trauma patients. It helps triage patients, predict mortality rates, and assess hospital resources needed for trauma care. This scoring system also plays a significant role in the research and development of safety regulations and measures.

What are the levels of injury severity?

The levels of injury severity are primarily categorized using the Abbreviated Injury Scale (AIS), which provides a numerical score to describe the severity of individual injuries. This score is then used to compute broader assessments like the ISS.

The AIS uses a scale of 1 to 6, with each level reflecting the potential threat to life and the probable need for medical intervention. Below is an extensive breakdown of each AIS level:

AIS 1: Minor

Injuries classified as AIS 1 are minor and usually do not require extensive medical treatment. Examples include small cuts, minor bruises, and sprains. These injuries typically heal with basic first aid and seldom lead to significant functional impairment.

AIS 2: Moderate

Moderate injuries, or AIS 2, involve more significant damage but are still not life-threatening. Examples might include non-complicated fractures, deep lacerations, or minor head injuries without loss of consciousness. These injuries often require medical treatment, such as stitches or casting, but full recovery is expected.

AIS 3: Serious

Serious injuries fall under AIS 3. These are injuries that pose a potential threat to life and definitely require professional medical attention. Examples include complicated fractures, injuries with potential blood loss, or small organ injuries. Such injuries might lead to some degree of permanent disability.

AIS 4: Severe

AIS 4 injuries are severe and pose a significant threat to life. They typically involve extensive organ damage or injuries that significantly impair bodily functions. Examples include severe head trauma with prolonged unconsciousness, injuries requiring surgical intervention to prevent death, or injuries that result in permanent functional impairment.

AIS 5: Critical

Critical injuries, classified as AIS 5, are life-threatening and require immediate and aggressive medical intervention. These injuries often involve major trauma to vital organs, body system or multiple body systems. Examples are severe head injuries with irreversible brain damage or extensive and critical internal injuries.

AIS 6: Maximal

Finally, AIS 6 represents injuries that are currently considered untreatable and invariably fatal, such as severe whole-body trauma or decapitation. This level indicates that survival is not expected regardless of medical intervention.

Utility of the AIS

Understanding the AIS levels helps medical professionals accurately assess the severity of injuries, prioritize treatment accordingly, and predict potential outcomes. This scale also facilitates communication among healthcare providers and aids in the research and development of safety regulations and measures. It's a critical tool in the fields of trauma assessment and emergency medicine.

_{Are the AIS and ISS the same?}

No, the Abbreviated Injury Scale (AIS) and the Injury Severity Score (ISS) are not the same, although they are closely related. The AIS is a coding system that classifies and describes the severity of individual injuries on a scale from 1 (minor) to 6 (maximally fatal). Each injury is assigned an AIS score based on its potential threat to life, its location, and the type of injury.

The ISS, on the other hand, is a scoring system used to assess the overall severity of trauma in patients who have sustained multiple injuries. It is calculated using the AIS scores from the patient's injuries. The ISS is specifically designed to give an overview of the total impact of all injuries sustained by a patient, which is useful in determining the level of medical response needed, predicting mortality rates, and evaluating the outcomes of trauma care.

How do you calculate ISS?

To calculate ISS, follow these steps:

Step 1: Identify the AIS score

Determine the AIS score for each injury the patient sustained. The AIS scale ranges from trauma score of 1 to 6, with higher scores indicating more severe injuries.

Step 2: Select the highest scores

From all the injuries, identify the three scores with highest AIS scores in each of the three major body regions (head or neck, face, chest, abdominal or pelvic contents, extremities or pelvic girdle, and external). Regardless of the number of injuries in that region, only the highest score in each body region is considered.

Step 3: Calculate

Square each of the three highest AIS scores from the different body regions, and then sum these squared values. The formula for ISS is:

ISS = (AISbodyregion1)2 + (AISbodyregion2)2 + (AISbodyregion3)2

where AISbodyregion1, AISbodyregion2, and AISbodyregion3​ are the highest AIS scores from three different body regions.

Step 4: Interpreting the score

The resulting sum is the ISS, which ranges from 1 to 75. If any injury receives an AIS score of 6 (maximally fatal), the ISS is automatically set to 75, indicating extreme or severe injury severity.

Does the ISS score correlate well with mortality?

Yes, the Injury Severity Score (ISS) correlates strongly with mortality, particularly in the context evaluating emergency care of trauma patients. It is widely used in trauma centers and hospitals to help predict the likelihood of survival following severe injuries. The relationship between the ISS and mortality is well-established, serving as a critical metric in both clinical settings and research.

Several studies have validated the utility of the ISS in predicting mortality. For example, patients with an ISS of 25 or more are generally at high risk for complications and death, whereas those with scores under 15 tend to have much lower mortality rates. The predictive power of the ISS is particularly valuable in emergency medical settings, where quick and accurate assessments are crucial for directing resources and prioritizing care based on the severity of injuries.