Scoring Systems in Trauma Patients

 Abstract:

            Evaluating the prognosis of traumatized patients is an established part of medical responsibility.  Diagnosis and treatment, given the top priority, are performed first as the chance of “meaningful recovery’ is mostly a clinical probability.

            Trauma scoring systems deal with a variety of injuries requiring complex treatment.  The assessment of these systems is a major challenge in clinical measurement and audit.  The effects of injuries can be defined in terms of physiological and/ or anatomical components versus the responses of the patients.

            Trauma scoring systems can aid decision-making for detecting individual discrimination or patient population calibration respectively.  They play a complementary role and are not substitutes for deciding patient outcome.  However, they may play an important role in patient triaging.

            Important trauma scores and their suggested roles in patient triaging and outcome will be discussed.

Introduction:

Over the past four decades, trauma has been clearly identified as a disease entity and subsequently developed as a separate specialty. Evaluating the prognosis of traumatized patients has thus become an established part of medical responsibility. Diagnosis and treatment, given the top priority, are performed first as the chance of “meaningful recovery” is mostly a clinical probability.

The concept of preventable trauma deaths has been documented in retrospective post-mortem studies from the 1960s, but it was not until the early 1970s that trauma systems were developed in USA ⁽¹⁾.  In England and Wales, a retrospective study of trauma deaths reported a similarly high incidence as in the USA ^(2). The subsequent adoption of trauma systems was followed by a dramatic reduction in preventable trauma deaths ^{(3, 4)}.

Trauma deaths occur in a trimodal distribution ⁽⁵⁾.  Immediate deaths are due to brain or heart lacerations and are not amenable to medical therapy. The second peak of trauma deaths such as patients who bleed to death from visceral injuries can be prevented by appropriate care by highly trained personnel in a trauma centre.  Late deaths such as secondary to sepsis or multiorgan failure peak about two weeks following injury. Much effort is now being focused on improved early resuscitation to prevent these late deaths.

Trauma scoring systems deal with trimodal injuries that require complex management. Assessment of such systems represents a major challenge in clinical measurement and audit. The effects of injuries can be defined in terms of physiological and/ or anatomical components versus patient responses.

Trauma scoring systems can aid decision-making for detecting individual or population patient outcome, in the form of patient discrimination or calibration respectively.  They play complementary roles and are not substitutes for deciding patient outcome. 

Field trauma scores play an important role in the process of patient triaging.  Triaging of a group of traumatized patients denotes their sorting out according to severity of injury to increase their survival rate. First priority triaging is given to patients who might survive only if treated, leaving until later those expected to die even if treated and those expected to survive even without treatment.  Colour coded labels with details of injury are attached to each patient according to priorities of triaging.

First priority triaged patients need rapid transfer with immediate treatment.  Second priority patients need urgent treatment after stabilization of their conditions.  Third priority patients are those described as “the walking wounded” with minor injuries. Patients of the fourth or the lowest priority are those expected to die. Triaging can be achieved by different trauma scoring systems or specific triaging systems as the Baxt Trauma Triage Rule or the score of Air Medical Evacuation System.

Triaging can be repeated at different stages of management of the traumatized patients, e.g. at the scene of the accident, at the emergency area of the hospital or the trauma centre and at the ward.  This is because priorities may change as circumstances change.

Trauma scores, when used properly for patient triaging can improve outcome of the traumatized patients.  Improved pre-hospital care together with rapid patient transfer leads to stabilization at the scene of the accident and encouraging “the scoop and run” concept.

Classification:

Scoring systems for trauma patients are classified on physiological and/ or anatomical basis into the following examples:

(I)               Physiological scores:

1-       Trauma score for adults.

2-       Revised trauma score for adults.

3-       Trauma score for children.

4-       Glasgow Coma Scale for adults.

5-       Glasgow Coma Scale for children.

6-       APACHE scores.

(II)            Anatomical scores:

1-       Abbreviated Injury Score.

2-       Injury Severity Score.

(III)         Combined physiological and anatomical scores:

1-       Trauma Injury Severity Score.

2-       Trauma Index Score.

3-       Circulation, Respiration, Abdomen/ thorax, Motor and Speech Score.

I. Physiological scoring systems:

Physiological scoring systems for traumatized patients are examplified by the trauma scores (TS) for adults and children, the revised trauma score (RTS), the Glasgow Coma Scale (GCS) for adults or children and the APACHE scoring systems.

1. Trauma score for adults

The TS for adults was based on an original scoring system depending on respiratory effort, capillary refill and GCS.  For improving this 3-parameter triaging score, Champion et al ⁽⁶⁾elucidated the 5-parameter TS (table 1) by adding two other parameters; the respiratory rate (RR) and the systolic blood pressure (SBP).

Table (1): Trauma score for adults

The TS for adults includes 1-16 points and is of prognostic value with decreasing the chance of patient survival at 12 points or less (table 2). The TS for adults is also of value for comparing the performance of different trauma centres or the same trauma centre over-time ⁽⁶⁾.

Table (2) : Survival rate from trauma score for adults

2. Trauma score for children

Anatomical differences make the adult TS not suitable for children. Children are more prone to head injuries because of the relative disproportion of their head and body sizes and because of the relatively loose ligaments of their cervical spines.  Jubevirer et al ⁽⁷⁾ have designed the TS for children which includes 6 variables and 12 points (table 3). A score of less than 8 points denotes more probability of death.

Table (3) Trauma score for children

SBP = Systolic blood pressure, CNS= central nervous system

3. Revised trauma score for adults

Out of the 5-parameters TS for adults, the 3-parameters RTS includes RR, SBP and GCS.  It includes a complex calculation combining coded (c) factors of the parameters multiplied by weighting values which are coefficients derived from a large database through regression analysis⁽⁸⁾.  These values aim to emphasize the increased impact of head injury on the total score (table 4). The coded RTS is calculated as follows:

RTSc = 0.2908RRc+0.7326 SBPc + 0.9368 GCSc

Table (4): Revised trauma score for adults

The RTS ranges between 0 and 7.84, with a lower score denoting a more serious injury.  A patient with less than 4 score needs an urgent transport to a trauma centre. The score is useful for prehospital triage, outcome assessment and quality assurance of critical care service.

However, the RTS is unable to accurately score patients who are intubated and mechanically ventilated, as determining the verbal component of the GCS and the RR are difficult in these patients.  An alternative approach in such a situation is to use the best motor and the eye opening responses of the GCS to calculate or to predict the verbal response.  Substitution of the best motor response for the total GCS can also maintain its predictive power.

4. Glasgow Coma Scale for adults

The GCS for adults monitors behaviours of eye opening (4 points), verbal responses (5 points) and motor responses (6 points), of the injured patient (table 5). So, the total score ranges between 3 and 15 points. Mild, moderate and severe head injuries are accounted for by 13-15, 9-12 and 8 or less scoring points respectively.

Table (5): The Glasgow Coma Scale for adults

5. Glasgow Coma Scale for children

The children version of the GCS was designed by Reilly et al ⁽¹¹⁾, where verbal responses were reported as appropriate words, or social smiles, cries, irritability or restlessness and agitation with the same numerical description for the severity of head injury as in adults (table 6).

Table (6): Glasgow Coma Scale for children

The GCS’s for adults or children can be used separately for describing the severity of head injury or as a component of other scoring systems as the APACHE systems.

6. APACHE scoring systems

The original APACHE scoring system was developed at the George Washington University Medical Centre as a way to measure disease severity ⁽¹²⁾. It consisted of two parts: the APS (acute physiology score) representing the degree of acute illness and the CHE (chronic health evaluation) indicating physiological reserve before the acute illness.  The APS component was developed by a panel of physicians from medicine, surgery and anaesthesia.  Thirty-four variables (neurologic, cardiovascular, respiratory, renal, gastrointestinal, metabolic, hematologic) were selected and relative weights (0-4) were assigned to the variables according to the clinicians’ clinical experience and a review of the literature. The worst value of each variable within the first 32 hr after admission was used.

The CHE component consisted of a questionnaire inquiring about the number of recent physician visits, activities of daily living and the presence of carcinoma.  Patients were then classified into A for excellent health to D for severely failing health.  Probability calculations were not a part of the original APACHE system. However, results for the initial study group indicated a direct relationship between the APS and the probability of death.  With the CHE component, only class D patients were found to be independently associated with mortality. The predictive ability of the original APACHE score was subsequently validated in new population of patients.  Criticism included the large number of variables and the 32 hr allowed for data collection. Further analysis and modifications led to the development of the APACHE II scoring system⁽¹³⁾.

The APACHE II system incorporated important modifications. The number of APS variables was reduced from 34 to only 12 through multivariate analysis of a large database.  So, infrequently measured (e.g. osmolality) and redundant (e.g. BUN) variables were eliminated. In addition, the weights of variables were modified according to their statistical correlation to hospital mortality. The GCS was given an increased weight of 12 and acute renal failure was double-weighted with a maximum score of 8.  The most abnormal APS values within the first 24 hr of ICU admission were used (table 7). Again, CHE points were assigned for only 7 organ system dysfunctions. Non-operative and emergency surgery were given additional weights and age was incorporated into the APACHE II score.

Table (7) Acute physiology score (APS) in APACHE II

With these modifications, APACHE II consisted of 3 parts: APS (12 variables; creatinine: 0-8 points, GCS: 0-12 points, other 10 variables 0-4 point each; maximum 60 points), age points (0-6) and CHE points (2-5) for a maximal total score of 71.  The patients were given a specific diagnosis according to the principal reason for ICU admission.

By multivariate analysis of the APACHE II data, an equation allowing calculation of an estimate of an individual patient's hospital mortality was derived. The 3 variables of this equation were the APACHE score, the disease category (D) and the presence or absence of emergency surgery (S) to calculate the risk of hospital death (R) using Ln Loge):

Ln (R/1-R) = -3.517 + (APACHE II score x 0.146) + D + S

By this equation, the decision criterion for patient risk of death equals 0.5 with expected mortality if its exceeds 0.5 and expected survival if it is 0.5 or less.

The APACHE III scoring system is a further refinement with 17 variables for the APS component and reweighting of age and CHE components ⁽¹⁴⁾. The total score ranges between 0 and 299 (table 8 a,b).  The equation for risk of hospital death (R) includes an added parameter (L) for patient location before admission.

Ln (R/1-R)= (APACHE III score x 0.053) + S+D+L

Both APACHE II and III systems were shown to be useful with different degrees of success for evaluation of patient discrimination (the probability of individual patient death) or calibration (the probability of death of patient population).  They may be also useful for comparing performance of ICU's or trauma centres in different locations or the same establishments over-time.

Researchers have shown that APACHE scores are inferior to other trauma scores for predicting mortality in traumatized patients.  Poor performance is related largely to the absence of anatomic components in APACHE systems.

Table 8 (a): Acute physiology score (APS) in APACHE III scoring system

Table (8b): APACHE III Physiologic Scoring For Acid Base Abnormalities

II. Anatomical scoring systems

In addition to specific organ trauma scores (e.g. severity of liver trauma score, pancreatic injury scale, renal injury scale), the main pure anatomical scoring system for an individual patient is the Injury Severity Score (ISS).

The actual measurement of injury severity began in 1969 when researchers developed the Abbreviated Injury Scale (AIS) to grade the severity of individual injuries. ⁽¹⁵⁾

1. Abbreviated Injury Scale

Since the introduction of the AIS, it has been modified in 1990 (AIS-90), as a simple numerical method for grading and comparing injury severity. Although originally intended for use with vehicular injuries, its scope has increased for use with other injuries.

For calculating the AIS, the body is divided into 6 regions and each is weighted according to injury severity up to 6 degrees (table 9).

Table (9): The Abbreviated Injury Scale

2. Injury severity score

Baker et al ⁽¹⁶⁾ deduced the ISS from the original AIS of the injured patients as a means of summarizing multiple patient injuries.

Now, for the calculation of the ISS, the highest AIS grades in the three most severely injured regions are summed and the total is then squared, giving a total score ranging between 1 and 75 points.  A score of 75 denotes the worst patient outcome. It has been shown logic to consider that if any region is graded as 6 which means incompatibility with life, the ISS is considered to be 75 points. Depending on patient age, 30-40 out of 75 scoring points can predict 50% probability of patient death ⁽¹⁷⁾.  The ISS has also been proved useful for patient triaging and to compare the performance of different trauma centres or the same centre over-time.

The most obvious limitation of the ISS is that it limits the total number of contributing injuries to only three which impairs the usefulness of the score in penetrating injuries. Another important limitation of the score is that it weights the injuries to each body region equally, ignoring the seriousness of head injury due to trauma ⁽¹⁸⁾.

Osler et al ⁽¹⁹⁾ in 1997 has reported a modified ISS or a new ISS (NISS), based on the three most severe injuries regardless of the body region. This simple but significant modification of the ISS avoids an important limitation. By preserving the AIS as the framework of injury severity, the NISS remains a user friend, and becomes a more accurate predictor of mortality than the ISS, particularly in penetrating injuries. Balogh et al ⁽²⁰⁾ in 2000 reported the ability of the NISS to predict post-injury multiple organ failure.

III. Physiological and anatomical scoring systems

The combined physiological and anatomical scoring systems are examplified by the Trauma Injury Severity Score (TRISS), the Trauma Index Score (TIS) and the Circulation, Respiration, Abdomen/ thorax, Motor and Speech (CRAMS) score.

1. Trauma Injury Severity Score

The TS and the ISS form the physiological and anatomical components of the TRISS respectively. Age of the traumatized patient is a third component, and each of the three components is assigned a coefficient.  The probability of survival of the traumatized patient can be estimated using a special TRISS chart ⁽²¹⁾.

The TRISS is considered to be a good prognostic tool for the evaluation of the traumatized patient outcome.  It is also considered valuable for patient triage.  However, although the TRISS became a standard assessment methodology in traumatized adults and children, it has been recently criticized ⁽²²⁾.  Firstly, it includes no information about the patient condition as a cardiovascular disease.  Secondly, it cannot include intubated patients where RR and verbal responses cannot be evaluated. Thirdly, it includes the TS, not its revised version.

2. Trauma Index Score

The TIS was developed by Kirkpatric and Youmans ⁽²³⁾. It considers physiological organ grades and anatomical regional components. It also escalates the type of injury (table 10).  Each parameter of the score is divided into 1-4 scoring points.  The maximum score is 20 points with less than 7 points denoting a mild condition and less than 18 points denoting the severest condition.

Table (10): Trauma Index Score

BP= blood pressure, HR= heart rate, CNS= central nervous system

3. Circulation, Respiratin, Abdomen/ thorax, Motor and Speech score

The CRAMS score has been developed by Gormicon ⁽²⁴⁾.  It includes a mixture of physiological and anatomical parameters with a maximum of 10 scoring points (table 11).  A traumatized patient with a lower score has a more serious condition.  The score can discriminate between survivors and non-survivors and is useful for patient triaging. It can compare different trauma centres at different locations or the same centre over-time.

Table (11): Circulation, Respiration, Abdomen/ thorax, Motor and Speech score

BP = blood pressure

Determinants of outcome of the traumatized patient

The traumatized patient outcome is of multimodal and multi-factorial nature through integration of the diagnosis of his/ her condition, the severity and chronicity of his/ her illness and the biological reserves added to the amount of monitoring and therapy s/he receives. For example ABG showing ABE of more than -15 mmol/L predicts very poor prognosis ⁽²⁵⁾.

Although decision-making of the traumatized patient is mostly clinically based, it can be fortified by information given by the scoring systems. This is because decision-making cannot depend on a numerical score only. Again, the ideal scoring system for the traumatized patient is far from being reached. If low scoring points denote patient outcome, the enthusiasm of the treating physician may fade away and s/he may not continue the same level of care. S/he may decrease the inotropic support of the circulation or even withhold the mechanical ventilatory support. I think that it is a mercy from Allah that determination of patient outcome cannot be determined by severity scoring systems. This is because the act of death is actually not known except soon before its occurrence when nothing can be done, while early prognosis of mortality may deprive the patient from many supportive measures that may be effective and may even lead to an unexpected survival.

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