PROGNOSTIC VALIDITY AND RELIABILITY OF THE SOFA SCORE IN MULTIPLE TRAUMA PATIENTS

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1 3 PROGNOSTIC VALIDITY AND RELIABILITY OF THE SOFA SCORE IN MULTIPLE TRAUMA PATIENTS Ahmed S. Okasha, M.D.*, Ayman S.H. Rofaeel, M.D., Said M. El-Medany, M.D.* Sameh M. Shaker, MB. BCh. # *Department of Anesthesia and Critical Care Medicine, Faculty of Medicine, Alexandria University. Department of Anesthesia and Surgical Intensive Care, Faculty of Medicine, Mansoura University. # Department of Critical Care, Emergency Hospital, Mansoura University. ABSTRACT Background: This study evaluated the reliability of the SOFA score in prediction of outcome in multiple traumatized patients. Methods: 44 multiple traumatized patients admitted to surgical ICU were prospectively enrolled. The SOFA score was evaluated daily throughout the first seven days of ICU stay and at ICU discharge, whereas the total maximum SOFA score was recorded as the worst of all daily recorded scores. Glasgow Outcome Scale (GOS) was used to assess outcome at time of ICU discharge. The quality of outcome was categorized as survival with either good outcome (good recovery and moderate disability) or poor outcome (severe disability and vegetative state), and non-survival. All recorded scores were analyzed in relation with both GOS and quality of outcome. Results: No significant correlation was found between SOFA score at the first and second days of ICU stay with either GOS or the quality of outcome. The correlation between SOFA score with GOS and quality of outcome exhibited the earliest significance at the third day (P <0.05), and then showed a trend of progressive improvement with subsequent daily scores till became maximum at the seventh day, at ICU discharge, and for the total maximum SOFA score. At the third day of ICU stay, survival was associated with median SOFA score of 5 for good outcome, and 7 for poor outcome, whereas, non-survival was associated with median SOFA score of 9. Conclusion: The SOFA score provides valid and reliable prognostic information in multiple trauma patients. While the best prognostic capability was achieved for the SOFA score at the seventh day of ICU stay, at ICU discharge, and for the total maximum SOFA score, SOFA score at the third day exhibited the earliest reliable outcome prediction with efficient discrimination among survivors with good outcome or poor outcome versus non-survivors. INTRODUCTION Multiple trauma victims are exposed to a potential risk for developing multiple organ dysfunction and/or failure, which represent major causes of morbidity and mortality in these patients (1,2). Organ dysfunction after multiple trauma is a process rather than an event, hence it should be seen as a continuum and should not be described simply as present or absent. The time factor is fundamental as the development of organ failure may take some time (3). The Sequential Organ Failure Assessment (SOFA) score has been applied to improve the understanding of the pathogenesis of organ dysfunction/failure and the inter-relation between failure of various organs (4). Since mortality is directly related to the degree of organ dysfunction (5), we hypothesized that the SOFA score could provide reliable prognostic information in multiple traumatized patients, and hence, it may aid the judgment of patient s quality of outcome. Also, as the SOFA score is designed for sequential assessment of the dynamic course of organ dysfunction, the collection of data on daily basis may adequately reflects the progression of organ dysfunction/failure during a complex clinical course in the intensive care unit (ICU). This study was designed to test the validity and reliability of the SOFA score, as an organ dysfunction/failure assessment score, in prediction of outcome in multiple traumatized critically ill patients through daily evaluation during ICU stay. Also, the study aimed to evaluate the ability of SOFA score to discriminate among different qualitative categories of outcome of multiple traumatized patients; mainly the quality of survival versus non-survival. PATIENTS AND METHODS This prospective study included forty four multiple injured patients, 18 to 65 years old, who were admitted to the surgical intensive care unit (ICU) at the Emergency Hospital, Mansoura University. The study protocol was approved by the institutional research and ethics committee and an informed consent was secured from the patient s next of kin. Patients with preexisting systemic disease of clinical significance and those with a length of ICU stay less than 2 days were excluded. Standard ICU monitoring was applied, including continuous electrocardiogram, noninvasive blood pressure, oxygen saturation, end tidal carbon dioxide tension, temperature, central venous pressure, and urine output. Patients' management followed a standard protocol for management of head injury, whereas associated systemic injuries were managed through appropriate consultation of

2 4 the corresponding surgical specialties. Hemodynamicaly unstable patients were managed with increasing the rate of intravenous fluid administration, followed by continuous infusion of vasoactive drugs (dopamine, dobutamine, or epinephrine) according to a pre-adjusted infusion rate. Evaluation of organ dysfunction was performed according to the set of clinical (respiratory support, mean arterial blood pressure, Glasgow Coma Scale and urine output) and laboratory (arterial blood gas analysis, platelets count, bilirubin concentration, serum creatinine) parameters of the SOFA score. The most abnormal value for each parameter in every 24 hours period was recorded, and the total score was interpreted as shown in table 1 (4,6). The SOFA score was recorded at ICU admission (first day), then daily throughout the first seven days of ICU stay, and at time of ICU discharge. The total maximum SOFA score was recorded as the worst score of all daily recorded SOFA scores throughout the whole period of the study. For every organ system, organ dysfunction was defined as SOFA score of 1-2, meanwhile organ failure was defined as SOFA score of 3-4. Glasgow Outcome Scale (GOS) was used to assess outcome at time of ICU discharge. For the purpose of assessing the quality of outcome, the five components of GOS [good recovery (GR), moderate disability (MD), severe disability (SD), persistent vegetative state (PVS), and death] were categorized into three qualitative outcome categories. Outcome was classified as survival and non-survival (death). The quality of survival was further categorized into either good outcome (GR and MD) or poor outcome (SD and PVS). All daily recorded SOFA scores were analyzed in relation to GOS and the quality of outcome. STATISTICAL ANALYSIS Data were analyzed with Statistical Package for Social Sciences program (SPSS, version 10), and were presented as median (SD), or as indicated elsewhere. Spearman Rank Correlation Analysis was used to test the relationship between daily SOFA scores with GOS, and with the quality of outcome. For the purpose of analysis, GOS was ranked as 5 to 1 for GR to death, respectively. Pearson Chi-square test was used to test the degree of conditional distribution/response of qualitative variables; the distribution of values of the quality of outcome (as the dependent variable) across different values of all recorded SOFA scores (as the independent variable). A probability (P) value was considered to be statistically significant if < 0.05, and highly significant if < Table (1): The Sequential Organ Failure Assessment (SOFA) score (4,6). SOFA score Respiration PaO 2 /FiO 2 (mmhg) > with respiratory support 100 with respiratory support Coagulation Platelets ( 10 3 /mm 3 ) > Liver Bilirubin (mg/dl) (µmol/l) < 1.2 (< 20) (20-32) (33-101) ( ) > 12.0 (>204) Cardiovascular Hypotension No hypotension MAP < 70 mmhg Dopamine 5 or dobutamine (any dose)* Dopamine > 5 or epinephrine 0.1 or norepinephrine 0.1* Dopamine > 15 or epinephrine > 0.1 or norepinephrine > 0.1* Central nervous system Glasgow Coma Score < 6 Renal Creatinine (mg/dl) (µmol/l) < 1.2 (< 110) ( ) ( ) ( ) > 5 (> 440) or urine output or < 500 ml/day or < 200 ml/day *Adrenergic agents administered for at least 1 hour (doses given are in µg/kg/min). MAP; mean arterial pressure.

3 5 RESULTS Patients' characteristics and the duration of ICU stay are displayed in table 2. All patients sustained trauma to the head plus one or more of other anatomical sites/systems (chest, abdomen or orthopedic trauma). Patients were distributed according to their outcome at ICU discharge (GOS and quality of outcome; table 3). No significant correlation was found between SOFA score evaluation over the first and second days of ICU stay, with either GOS or the quality of outcome (table 4). The correlations between SOFA scores at subsequent days of follow up with GOS and the quality of outcome were significant (P <0.05; table 4), and showed a trend of progressive improvement starting from the third day through SOFA score at discharge. SOFA score at the third day was the earliest significant predictor of the quality of outcome (P <0.05; table 4). Survival was associated with median SOFA score of 5 for good outcome, and 7 for poor outcome, whereas, non-survival was associated with median SOFA score of 9 (figure 1). The best correlation with outcome was achieved with SOFA score at the seventh day of ICU stay, at discharge, and with the total maximum SOFA score (P <0.01; table 4). For both the SOFA score at the seventh day and at discharge, good outcome was associated with a median value of 2, poor outcome was associated with median value of 7 and 5 respectively, whereas, non-survival was associated with a median value of 11 and 12 respectively (figure 1). For the total maximum SOFA score, survival was associated with median SOFA score of 7 for good outcome, and 11 for poor outcome, whereas, the median SOFA score associated with non-survival was 12 (figure 1). Table (2): Patients characteristics. median ± SD range Age (years) 34 ± Initial GCS score 8 ± Initial SOFA score 7 ± Total duration of ICU stay 20 ± N (%) Gender Male Female (75%) (25%) Extent of trauma 2 sites/systems 3 sites/ systems 4 sites/ systems (18.2%) (72.7%) (9.1%) Data are presented as median ± SD or number (n) and percent (%). Table (3) Distribution of patients according to Glasgow Outcome Scale (GOS) and the quality of outcome. GOS Quality of outcome Good recovery 10 (22.7%) Survival Moderate disability 10 (22.7%) Good outcome 20 (45.4%) Severe disability 2 (4.55%) Persistent vegetative state 3 (6.85%) Poor outcome 5 (11.4%) Death 19 (43.2%) Non-survival 19 (43.2%) Data are presented as number and percent (%). Table (4): Serial SOFA scores in correlation with Glasgow Outcome Scale (GOS), and the quality of outcome. GOS Quality of outcome r value P value r value P value SOFA N.S N.S. SOFA N.S N.S. SOFA < < 0.05 SOFA < < 0.05 SOFA < < 0.05 SOFA < < 0.05 SOFA < < 0.01 SOFA-D < < 0.01 SOFA-M < < 0.01 SOFA 1-7; SOFA score at the first through the seventh days of ICU stay respectively. SOFA-D; SOFA score at ICU discharge, SOFA-M; total maximum SOFA score. r value = correlation coefficient between daily SOFA scores and GOS/quality of outcome. P value >0.05 = non-significant (N.S.), <0.05 = significant, <0.01 = highly significant.

4 Good outcome Poor outcome Nonsurvival 14 SOFA score SOFA 1 SOFA 2 SOFA 3 SOFA 4 SOFA 5 SOFA 6 SOFA 7 SOFA D SOFA M Figure 1. Trend of daily SOFA scores in relation to the quality of outome SOFA 1-7; SOFA score at the first through the seventh days of ICU stay respectively SOFA D; SOFA score at discharge SOFA M; total maximum SOFA score DISCUSSION The present study demonstrated that the SOFA score represents a reliable outcome prediction model in multiple traumatized patients. Since all patients in our study sustained head trauma, which is considered a major contributor in predicting outcome in multiply injured patients (7), outcome was assessed by the Glasgow Outcome Scale (GOS); a specific model for detection of outcome after brain injury (8). The persistent correlation between daily SOFA scores and GOS in our study represents a novel approach in prediction of outcome in multiple traumatized patients, which would improve the appreciation and extend the validation of the prognostic capability of the SOFA score to include those patients with head injury. Previous studies have used several outcome end points rather than the GOS. When mortality was considered the sole outcome measure, the SOFA score has been described as a reliable prediction model for mortality risk in diverse categories of critically ill patients (9-14). This demonstrates an agreement with the reliable prediction of nonsurvival by the SOFA score in the present study. The importance of the analysis of morbidity is increasingly recognizable, since mortality alone is considered insufficient for assessing ICU outcome, as functional health and quality of life cannot be ignored (15-17). Despite the primary aim of the SOFA score was not to predict outcome but to determine the degree of organ dysfunction, an increase in the mortality rate is associated with a greater SOFA score for each organ (18). A relationship exists between organ failure and death, and thus between morbidity and mortality. Unlike most available scoring systems, the SOFA score has been applied to focus on morbidity (4). In order to extend the reliability of the SOFA score, not merely as a descriptive score but as a prognostic one as well, the quality of outcome after multiple trauma has received major consideration in our study. The prognostic validity of SOFA scores at the first (admission) and second days of ICU stay were not evident in the current study. Only SOFA score at the third day was the earliest reliable predictor of outcome, whereas the best prediction of outcome was achieved by SOFA score at the seventh day, at discharge and by the total maximum SOFA score. Besides non-survival, SOFA scores starting from the third day of ICU stay exhibited a predictive discrimination between patients who survived with good outcome and those who survived with poor outcome. Non-survivors had the highest scores, whereas survivors with good outcome had the lowest scores that followed a stable course and survivors with poor outcome had intermediary scores. In agreement with our study, the SOFA score on admission was reported to exhibit no predictive differentiation between survival and nonsurvival. Prognosis may be better estimated some time after ICU admission, and an increase in SOFA score over the first three days of ICU stay was reported to predict mortality better than the admission score (19-21). Unlike survivors, nonsurvivors tend to exhibit significant increase in score over time (4,18,22,23). This is not unexpected, as

5 7 organ dysfunction and hence, the SOFA score, may peak after admission. So, the sensitivity of SOFA score as a measure for cumulative organ dysfunction and progression of multiple organ dysfunction/failure seems to be improved with repeated daily follow up than with the admission score (24,25). This is particularly more evident in patients with prolonged ICU stays, as the course of ICU stay is unpredictable and can negatively influence the performance of the admission score (4). Furthermore, strategies directed at the prevention and/or limiting of further organ dysfunction will have a significant impact on prognosis, independent of the patient condition on ICU admission (26). Therefore, the SOFA score functions as an index for determining either sequential deterioration or improvement of the pathological condition during treatment (18,27,28). Early categorization of patients according to their expected outcome represents a major challenge; hence early prediction of outcome was considered another important target of application of the SOFA score in our patients' population. Although SOFA scores at the seventh day of ICU stay and at discharge were the strongest predictors of outcome, it seems clinically not feasible to wait for the whole first week to be able to judge the patient s outcome, while such prediction can be possible at the third day. Similarly, the total maximum SOFA score has been reported as a very reliable predictor of outcome (10,19,29,30), which is still valid in our study. In the current study, with a total maximum SOFA score of 12 or higher, mortality rate was 100%. This finding is in close similarity with previous studies which described best sensitivity and specificity for prediction of mortality with a cutoff value ranging from for the total maximum SOFA score (4,18,19). However, since multiple trauma follows a dynamic course, it is unexpected to determine when the maximum SOFA score will be encountered, or the patient's score will be followed indefinitely. So, when an early prediction is achieved; e.g. at the third day, it also seems more favorable and desirable than prediction by the total maximum SOFA score. The SOFA score should be considered a tool which describes the severity of organ dysfunction, and not simply a global number giving no information on individual organ status (4). The number of organ dysfunction/failure significantly contributed to mortality, stressing the role of associated organ failure as an important prognostic determinant in critically ill patients (31-33). The description of organ dysfunction/ failure by the SOFA score is based on simple but objective and specific variables which are derived from standard monitoring of critically ill patients and are routinely available everywhere (34,35). Moreover, the power and utility of the SOFA score in trauma patients are supported by the use of the Glasgow Coma Scale, which represents a sensitive index for assessment of the neurologic status of brain trauma patients (36). The SOFA score remains a gross evaluation, but this is the best way to keep it simple and widely applicable. Using more sophisticated parameters may restrict its use to centers where such tests are routinely used, or may result in missing data (4). The simplicity of the SOFA score allows rapid bedside calculation, hence its repeated assessment can be considered as an easy task (21). The SOFA score also reflects the utilization of therapeutic resources use during ICU stay. Organ failure prolongs the length of ICU stay and involves increased use of resources, so assessment of morbidity is vital for the cost-effective analysis of therapeutic interventions (4,37). In conclusion, the SOFA score appeared to provide valid and reliable descriptive and prognostic information in multiple trauma patients, as it reflects the progression of multiple organ dysfunction/ failure in relation to prognosis of these victims. While the best prognostic capability was achieved by the SOFA score at the seventh day, at ICU discharge, and the total maximum SOFA score, the SOFA score at the third day of ICU stay was the earliest reliable outcome predictor. The SOFA score demonstrated good correlation with outcome assessed by GOS at ICU discharge, and also, provided efficient discrimination among different qualitative outcome categories; survival with good or poor outcome versus non-survival. As an easily applicable scoring system, the routine application of the SOFA score in follow-up and outcome prediction in multiple traumatized patients starting from the third day of ICU stay seems to be advisable. REFERENCES 1- Fry DE, Pearlstein L, Fulton RL, Polk HC: Multiple system organ failure. The role of uncontrolled infection. Arch Surg 1980;115: Beal AL, Cerra FB: Multiple organ failure syndrome in the 1990s. Systemic inflammatory response and organ dysfunction. JAMA 1994;271: Chang RW, Jacobs S, Lee B: Predicting outcome among intensive care unit patients using computerized trend analysis of daily APACHE II scores corrected for organ system failure. Intensive Care Med 1988;14: Vincent JL, de Mendonca A, Cantraine F, et al: Use of the SOFA score to assess the incidence of organ dysfunction/failure in intensive care units: results of a multicenter, prospective study. Crit Care Med 1998;26:

6 8 5- Deitch EA: Multiple organ failure. Pathophysiology and potential future therapy. Ann Surg 1992;216: Vincent JL, Moreno R, Takala J, et al: The SOFA (Sepsis-related Organ Failure Assessment) score to describe organ dysfunction/failure. Intensive Care Med 1996;22: Kaisers U, Kuchler I, Unterberg AW, et al: Secondary insults in sever head injury: Do multiple injured patients worse?. Crit Care Med 2001;29: Alberico AM, Ward JD, Choi SC, et al: Outcome after severe head injury. Relationship to mass lesions, diffuse injury, and ICP course in pediatric and adult patients. J Neurosurg 1987;67: Rosenberg AL: Recent innovations in intensive care unit risk-prediction models. Curr Opin Crit Care 2002;8: Halonen KI, Pettila V, Leppaniemi AK, et al: Multiple organ dysfunction associated with severe acute pancreatitis. Crit Care Med 2002;30: Paugam-Burtz C, Dupont H, Marmuse JP, et al: Daily organ-systems failure for diagnosis of persistent intra-abdominal sepsis after postoperative peritonitis. Intensive Care Med 2002; 28: Silfvast T, Pettila V, Ihalainen A, Elonen E: Multiple organ failure and outcome of critically ill patients with haematological malignancy. Acta Anaesthesiol Scand 2003;47: Soliman HM, Mercan D, Lobo SS, et al: Development of ionized hypomagnesemia is associated with higher mortality rates. Crit Care Med 2003;31: Ceriani R, Mazzoni M, Bortone F, et al: Application of the Sequential Organ Failure Assessment Score to cardiac surgical patients. Chest 2003;123: Suter PM, Armaganidis A, Beaufils F, et al: Consensus conference organized by the ESICM and SRLF. Predicting outcome in ICU patients. Intensive Care Med 1994; 20: Gunning K, Rowan K: ABC of intensive care: Outcome data and scoring systems. BMJ 1999;319: Lizana GF, Peres Bota D, De Cubber M, Vincent JL: Long term outcome in ICU patients: what about quality of life. Intensive Care Med 2003;29: Oda S, Hirasawa H, Sugai T, et al: Comparison of Sepsis-related Organ Failure Assessment (SOFA) score and CIS (cellular injury score) for scoring of severity for patients with multiple organ dysfunction syndrome (MODS). Intensive Care Med 2000;26: Ferreira FL, Bota DP, Bross A, et al: Serial evaluation of the SOFA score to predict outcome in critically ill patients. JAMA 2001;286: Garnacho-Montero J, Garcia-Garmendia JL, Barrero-Almodovar A, et al: Impact of adequate empirical antibiotic therapy on the outcome of patients admitted to the intensive care unit with sepsis. Crit Care Med 2003;31: Janssens U, Graf C, Graf J, et al: Evaluation of the SOFA score: a single-center experience of a medical intensive care unit in 303 consecutive patients with predominantly cardiovascular disorders. Sequential Organ Failure Assessment. Intensive Care Med 2000,26: Evans L: Risk of fatality from physical trauma versus sex and age. J Trauma 1988;28: Zygun DA, Doig CJ, Gupta AK, et al: Nonneurological organ dysfunction in neurocritical care. J Crit Care 2003;18: Shime N, Kageyama K, Ashida H, Tanaka Y: Application of modified sequential organ failure assessment score in children after cardiac surgery. J Cardiothorac Vasc Anesth 2001;15: Engel JM, Junger A, Zimmer M, et al: Correlation of a computerized SOFA score and derived measures with length of stay at an operative ICU. Anasthesiol Intensivmed Notfallmed Schmerzther 2003;38: Moreno R, Vincent JL, Matos R, et al: The use of maximum SOFA score to quantify organ dysfunction/failure in intensive care. Results of a prospective, multicentre study. Intensive Care Med 1999;25: Vincent JL, Ferreira FL: Evaluation of organ failure: we are making progress. Intensive Care Med 2000;26: Timsit JF, Fosse JP, Troche G, et al: Calibration and discrimination by daily Logistic Organ Dysfunction scoring comparatively with daily Sequential Organ Failure Assessment scoring for predicting hospital mortality in critically ill patients. Crit Care Med 2002;30: Jacobs S, Zuleika M, Mphansa T: The Multiple Organ Dysfunction Score as a descriptor of patient outcome in septic shock compared with two other scoring systems. Crit Care Med 1999;27: Du B, Chen D, Liu D: Prediction of prognosis of patients with multiple organ dysfunction syndrome by sepsis-related organ failure assessment. Zhonghua Yi Xue Za Zhi 2001;81: De Mendonca A, Vincent JL, Suter PM, et al: Acute renal failure in the ICU: risk factors and outcome evaluated by the SOFA score. Intensive Care Med 2000;26: Durham RM, Moran JJ, Mazuski JE, et al: Multiple organ failure in trauma patients. J Trauma 2003;55:

7 9 33- Flaatten H, Gjerde S, Guttormsen AB, et al: Outcome after acute respiratory failure is more dependent on organ dysfunction in other vital organs than on the severity of the respiratory failure. Crit Care 2003;7:R Bernard GR, Doig BG, Hudson G, et al: Quantification of organ failure for clinical trials and clinical practice. Am J Respir Crit Care Med 1995;151:A Le Gall JR, Klar J, Lemeshow S, et al: The Logistic Organ Dysfunction system: a new way to assess organ dysfunction in the intensive care unit. ICU Scoring Group. JAMA 1996;276: Chestnut RM: Glasgow Coma Score versus severity systems in head trauma. Crit Care Med 1998;26: Holt AW, Bury LK, Bersten AD, et al: Prospective evaluation of residents and nurses as severity score data collectors. Crit Care Med 1992;20: