ISS: Injury severity score

ISS: Injury severity score

Définition

L'ISS est un système d'évaluation de la gravité d'un patient polytraumatisé, en fonction du siège des lésions. Il a été défini par l'American Association for Automotive Medicine.

Application: Polytraumatisé

Description et pondération des lésions présentes sur Le corps, divisé en 6 régions anatomiques distinctes : tête et cou, face, thorax, abdomen / organes pelviens, extrémités / ceinture pelvienne et atteintes superficielles.

Calcul:

· Pour chacune des 6 parties du corps considérées, Les Lésions constatées sont notées de 0 à 5, c'est L'AIS (Tableau I).

IL existe une échelle permettant de coter les Lésions fermées et une échelle pour les lésions ouvertes.

· L'AIS Le plus élevé est déterminé pour chacune des régions.

· Le score ISS est calculé à partir des 3 régions anatomiques Les plus lésées, qui vont faire le pronostic du patient, c'est-à-dire celles dont L'AIS est Le plus élevé.

· L'ISS est La somme du carré de chacune de ces trois valeurs les plus élevées d'AIS.

· Le score ne peut dépasser 75.

Plus Le score est élevé, plus Le traumatisme est grave. Si le score AIS est à 5 pour chacune des 6 régions, Le décès ne fait pas de doute et on notera d'emblée un ISS égal à 75.

· IL existe une corrélation entre L'ISS et la durée du traitement, de la ventilation assistée, de L'hospitalisation et l'importance des séquelles.

· Le score est excellent pour Le polytraumatisé, mais il sous estime Les traumatisme crâniens graves isolés.

Tableau I : AIS

I - Tête et cou	0 point: Pas de Lésion
2- Face	1 point: Blessure légère
3- Thorax	2 points: Blessure modérée
4- Abdomen,	3 points: Blessure sérieuse
organes pelviens	4 points: Blessure grave
5- Extrémités,ceinture pelvienne	5 points Lésions mettant en jeu Le pronostic vital
6- Atteintes superficielles

Prendre les trois régions les plus touchées

Si les trois régions donnent 5 points l'ISS est par définition à 75

ISS = (AISa)² + (AISb)² + (AISc)²

a, b, c = Les trois zones anatomiques Le plus gravement atteintes.

(AIS a, b, c,) = degré de sévérité AIS le plus élevé pour chacune des régions a, b, c.

Adapté de:

Baker SP, O'Neill B, Haddon W Jr, Long WB - The injury severity score: a method for describing patients with multiple injuries and evaluating emergency care. J Trauma 1974;14(3):187-96

Lecture suggérée sur le sujet:

Morris JA Jr, Auerbach PS, Marshall GA, Bluth RF, Johnson LG, Trunkey DD - The Trauma Score as a triage tool in the prehospital setting. JAMA 1986 Sep 12;256(10):1319-25

Implementation of a regional trauma care system requires a field triage toolthat identifies the severely injured patient and transports him to a trauma center, while preserving the flow of minimally injured patients to community hospitals. We prospectively tested the Trauma Score (TS) as a field triage tool and evaluated its accuracy against that of the Injury Severity Score (ISS), calculated after the patients' injuries were fully defined. During an 18-month period, 1106 patients admitted to the trauma center at San Francisco General Hospital had a TS determined in the field (TS1) and on arrival at the emergency department. A TS1 of 14 or less defined a subgroup of 222 patients in whom 93% of the deaths occurred. Using an ISS of 20 or more as an indicator of life-threatening injury, we determined the predictive value of TS1. There were 66 false-negatives (ISS, greater than or equal to 20; TS1, 15 or 16) and 107 false-positives (ISS, less than 20; TS1, less than or equal to 14). Using a prehospital TS of 14 or less as an indicator of serious injury, only 20% of amajor urban trauma population would qualify for diversion to a trauma center.

Rutledge R, Fakhry S, Rutherford E, Muakkassa F, Meyer A -Comparison of APACHE II, Trauma Score, and Injury Severity Score as predictors of outcome in critically injured trauma patients. Am J Surg 1993 Sep;166(3):244-7

Trauma Score (TS), APACHE II score, and Injury Severity Score (ISS) have been utilized to quantitate severity of illness in various groups of patients. The purpose of this study was to compare the relationship of the APACHE II score, TS, and "computer-derived" ISS with outcome in critically injured trauma patients. Data were recorded prospectively in a computer database for 428 consecutive trauma admissions. Stepwise discriminate analysis was utilized to determine the best predictor of both intensive care unit (ICU) and hospital outcome. Forty-two patients died in the ICU (10%), and another 18 patients died after leaving the ICU (4%), for a total mortality rate of 14%. The mean p value and partial R2 value obtained from stepwise discriminant analysis of the relationships between APACHE II score, TS, and ISS to ICU and hospital survival are shown. APACHE II score was the best predictor of both ICU and hospital outcome in these critically ill trauma patients. However, when combining all

three measures (APACHE II score, TS, and ISS), only a portion of the variance in outcome is explained by the scores (R2 < 0.05). We conclude that scoring systems for outcome prediction should be utilized only as an adjunct to clinical assessment in the evaluation of the severity of illness and mortality risk in critically ill trauma patients.

Collopy BT, Tulloh BR, Rennie GC, Fink RL, Rush JH, Trinca GW - Correlation between injury severity scores and subjective ratings of injury severity: a basis for trauma audit. Injury 1992;23(7):489-92

A retrospective review of 1900 road accident victims attending the emergency departments of two Melbourne hospitals was undertaken to identify Injury Severity Score levels which could distinguish between minor, moderate, severe and critical injury. Injuries scoring ISS 6 or below were designated 'minor' because they were associated with a low risk of requiring admission to hospital. Case notes of patients scoring above ISS 6 were then reviewed by a panel of clinicians, who independently rated each patient's overall injury severity as moderate, severe or critical according to what was recorded in the notes and their 'clinical' judgement. ISS values were compared with clinicians' ratings. Measures of each clinician's individual rating consistency, and correlation between pairs of clinicians with respect to inter-rater consistency, were made. By combining data from both hospitals it emerged that 'moderate' injury corresponded to ISS 8-13, 'severe' to ISS 14-20 and 'critical' to ISS 21 and above. These ISS breakpoints will be useful in selecting groups of injured patients for future trauma audit studies.