CLINICAL INVESTIGATIONS

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1 808 Sokolove et al. d SEAT BELT SIGN AND ABDOMINAL INJURY IN CHILDREN CLINICAL INVESTIGATIONS Association between the Sign and Intraabdominal Injury in Children with Blunt Torso Trauma Peter E. Sokolove, MD, Nathan Kuppermann, MD, MPH, JamesF.Holmes,MD,MPH Abstract Objectives: To determine the association between an abdominal seat belt sign (SBS) and intra-abdominal injury (IAI) in children presenting to the emergency department (ED) after blunt trauma. Methods: The authors performed a prospective, observational study of children at risk for IAI who presented to a Level 1 trauma center following a motor vehicle collision (MVC) during a two-year period. Physical examination findings were recorded prior to abdominal imaging or surgery. The SBS was defined as an area of erythema, ecchymoses, and/or abrasions across the patient s abdominal wall resulting from a seat belt restraint. Patients were divided into two cohorts based on the presence or absence of an SBS, then further subdivided based on abdominal tenderness or pain. The authors compared patients with and without SBS, and those with and without abdominal pain or tenderness for the presence of IAI. Results: Three hundred ninety children, of whom 46 (12%, 95% CI = 9% to 15%) had an SBS, were enrolled. IAIs were more common in patients with, versus without, an SBS (14/46 vs. 36/344, relative risk 2.9; 95% CI = 1.7 to 5.0; p, 0.001). Patients with an SBS were more likely to have gastrointestinal injuries than those without an SBS (12/46 vs. 7/344, relative risk 12.8; 95% CI = 5.3 to 31; p = 0.001). Pancreatic injuries were also more common among patients with an SBS (3/46 vs. 1/344, relative risk 22; 95% CI = 2.4 to 211; p = 0.006). There was no difference in the prevalence of solid organ injuries between those with and without an SBS (4/46 vs. 34/344, relative risk 0.9, 95% CI = 0.3 to 2.4; p = 1.00). None of the six patients (0%, 95% CI = 0 to 39%) with an SBS, but without abdominal pain or tenderness, had IAIs. Conclusions: Patients with an SBS after an MVC are more likely to have IAIs than patients without an SBS, predominately due to a higher rate of gastrointestinal injuries. Patients with an SBS but without abdominal pain or tenderness appear to be at low risk for IAI. Key words: blunt abdominal trauma; seat belt sign; restraint; pediatric; motor vehicle collisions. ACADEMIC EMERGENCY MED- ICINE 2005; 12: Seat belts were first introduced into motor vehicles in 1960, marking a major advance in injury prevention. When lap and shoulder belts are used properly, the risk of fatal injury to occupants is reduced by 45% to 60%, and the risk of moderate to critical injury is reduced by 50% to 65%. 1 It has been estimated that seat belt use saves society an estimated $50 billion annually in medical care, lost productivity, and other injury-related costs. 2 Young children improperly restrained with seat belts, due to either incorrect choice of restraint or improper positioning, are at increased risk of injury. 3 Lap belts should be positioned low, across the From the Departments of Emergency Medicine (PES, NK, JFH) and Pediatrics (NK), University of California, Davis, School of Medicine, Sacramento, CA. Received November 27, 2004; revisions received April 15, 2005, and April 19, 2005; accepted May 2, Presented in part at the SAEM annual meeting, San Francisco, CA, May Address for correspondence and reprints: Peter E. Sokolove, MD, Department of Emergency Medicine, UC Davis Medical Center, 4150 V Street, PSSB 2100, Sacramento, CA Fax: ; pesokolove@ucdavis.edu. doi: /j.aem thighs, rather than across the abdomen. 4 A number of studies of adult patients have noted an association between the presence of the seat belt sign and intraabdominal injury, particularly involving injuries to the intestines or mesentery. 5 7 While prospective studies have confirmed this association in adult patients, pediatric studies of this topic have consisted of either case series or retrospective reviews The objective of this study was to prospectively evaluate the association between the abdominal seat belt sign and intra-abdominal injury in pediatric patients presenting to the emergency department (ED) after sustaining blunt torso trauma from a motor vehicle collision (MVC). We also sought to determine the rate of intra-abdominal injuries among the subset of children who have a seat belt sign but who do not have abdominal pain or tenderness. METHODS Study Design. This was a prospective, observational study performed in the ED of a single academic medical center. The study was reviewed and approved by the human subjects research committee at the participating institution with waiver of informed consent.

2 ACAD EMERG MED d September 2005, Vol. 12, No. 9 d Study Setting and Population. All patients were enrolled and treated at an urban academic ED. The hospital is a Level 1 trauma center with approximately 60,000 ED patient visits per year, including approximately 12,000 pediatric ED patient visits per year. We studied children 16 years of age or younger with blunt trauma at risk for intra-abdominal injury, who presented to the ED following an MVC between April 1996 and September This study was conducted as part of a larger study of intra-abdominal injuries among 1,095 children sustaining blunt trauma. 24 Study Protocol. The methods of patient identification and enrollment have been previously described. 24 In brief, patients underwent a complete physical examination by the faculty emergency physician, the results of which were documented on a data form prior to definitive abdominal imaging or surgery, if performed. We defined the seat belt sign as an area of erythema, ecchymoses, and/or abrasions extending across the patient s abdomen resulting from a seat belt restraint. We considered abdominal pain to be present if the child complained of pain in or over the abdomen. We considered abdominal tenderness to be present if the child stated that palpation caused pain, or if the patient grimaced on palpation of the abdomen during physical examination. We considered peritoneal signs to be present if the patient had rebound tenderness on abdominal examination. We defined an intra-abdominal injury to be present if an International Classification of Diseases, Ninth Revision (ICD-9)-coded injury was documented involving the spleen, liver, pancreas, urinary tract, adrenal glands, or gastrointestinal tract during the patient s ED stay or hospitalization. Gastrointestinal injuries included any injury to the intestines or associated mesentery. We defined solid organ injuries as those involving the liver, kidneys, or spleen. Intra-abdominal injuries were identified by abdominal computed tomography (CT) scanning, by laparotomy, or at autopsy. Patients discharged to home after ED evaluation were contacted by telephone at least one week after ED discharge to determine clinical status. Patients without symptoms of intra-abdominal injury at the telephone follow-up were considered not to have a clinically important intra-abdominal injury. Measurements. We recorded patient demographics, use and type of occupant restraint, physical examination findings, Pediatric Trauma Score (ranging from 26 to 112, reflecting more severe to less severe injury), and presence of abdominal pain onto a data form prior to imaging or laparotomy (if performed). We also recorded the use and type of diagnostic studies (e.g., CT scan, ultrasound) obtained to evaluate for intra-abdominal injury (if obtained). We measured the rate of hospital admission and the presence and types of intra-abdominal injuries identified in hospitalized patients, and the rate of successful telephone follow-up of patients discharged to home from the ED. Finally, we calculated the rate of improper restraint use (i.e., lack of car-seat use) among children younger than 4 years of age. We defined this as the proportion of children in this age range who were either unrestrained or known to be restrained in any manner other than in a car seat. Data Analysis. We divided patients into two cohorts based on the presence or absence of the seat belt sign, and further subdivided the group of patients with the seat belt sign into those with and those without complaints of abdominal pain, or abdominal tenderness on physical examination. We compared rates of intra-abdominal injury and organ-specific injury using Fisher s exact test, and we calculated 95% confidence intervals (95% CIs) for differences in these rates between cohorts. We analyzed the data using STATA 8.0 for Windows statistical software. 25 RESULTS Of the 1,095 children sustaining blunt torso and abdominal trauma in the original study, patients were involved in an MVC, and therefore served as the study population of the current study. Fifty (13%) of these 390 patients had intra-abdominal injuries. Characteristics of the two study cohorts (i.e., those with and those without the seat belt sign) are reported in Table 1. Overall, the mean age (6 standard deviation [SD]) of patients in this study was 8.7 (65.0) years (range 11 days to 16 years), and the median pediatric trauma score was 11 (interquartile range 9 to 11). Of the 390 patients, 203 (52%) were known to be restrained, including 59 (29%) with a lap belt, 70 (34%) with a lap and shoulder belt (three-point restraint), and 38 (19%) in a car seat. A restraint of unknown type was used in 36 (18%) patients, and it was unclear whether the patient was restrained in 58 (15%). Of the 92 study patients younger than 4 years of age, restraint type was known for 78 (85%) patients. Forty-two (54%) of these 92 patients were improperly restrained, including 22 (27%) who were completely unrestrained. Abdominal TABLE 1. Characteristics of the 390 Study Patients Sign Present (n = 46) Sign Absent (n = 344) Age mean 7.9 years 8.5 years Restrained 46 (100%) 186 (54%) Diagnostic abdominal evaluation performed* 40 (87%) 201 (58%) Hospital admission 37 (80%) 189 (55%) Intra-abdominal injury 14 (30%) 36 (10%) Laparotomy 11 (24%) 13 (4%) *Abdominal CT, abdominal ultrasound, diagnostic peritoneal lavage, and/or laparotomy.

3 810 Sokolove et al. d SEAT BELT SIGN AND ABDOMINAL INJURY IN CHILDREN CT, abdominal ultrasound, diagnostic peritoneal lavage, and/or laparotomy were performed in 241 (62%) patients. The diagnostic studies obtained in these 241 patients included: abdominal CT in 199, abdominal ultrasound in 84, diagnostic peritoneal lavage in 12, and laparotomy in 24. Seventy-six patients had multiple abdominal studies. Telephone follow-up was achieved successfully in 141 (86%) of the 164 patients who were discharged home from the ED, and all of these patients were without clinical evidence of intraabdominal injury at the time of follow-up. Forty-six (12%) patients had a seat belt sign. The mean age (6SD) of these patients was 8.5 (64.1) years (range 10 months to 16 years), and the median pediatric trauma score was 11 (interquartile range 10 to 12). Of these patients, 23 (50%) were restrained with a lap belt, 15 (33%) with a lap and shoulder belt, and two (5%) in a car seat. Type of restraint was not known in six (15%) of these patients. Of the 46 patients with a seat belt sign, 40 (87%) underwent abdominal CT, abdominal ultrasound, diagnostic peritoneal lavage, and/or laparotomy. Abdominal studies obtained in these 40 patients included: abdominal CT in 32, abdominal ultrasound in 13, and laparotomy in 11; multiple studies were performed in 15 patients. None of the patients underwent diagnostic peritoneal lavage. Thirty-seven (80%) of the 46 patients were admitted to the hospital and evaluated for intraabdominal injuries with serial physical examinations and hematocrit measurements for at least 24 hours. The remaining nine patients were discharged to home from the ED. Telephone follow-up was achieved successfully in seven (78%) of these nine patients, and all of these seven patients were asymptomatic at the time of follow-up. There were no apparent cases of missed intra-abdominal injuries among patients in this study on review of the trauma registry and continuing quality improvement records at our institution. Of the 50 study patients with intra-abdominal injuries, 19 patients had gastrointestinal injuries. Of these 19 patients with gastrointestinal tract injuries, 18 (95%) underwent laparotomy, including 11 of the 12 (92%) patients with a seat belt sign. Table 2 describes the types of intra-abdominal injuries observed among the study patients, both with and without a seat belt sign. Overall, intra-abdominal injuries were more likely to occur in those patients with a seat belt sign (14/46, 30%) than those without a seat belt sign (36/344, 10%) (relative risk 2.9, 95% CI = 1.7 to 5.0; p = 0.001). Patients with a seat belt sign were also more likely to have a gastrointestinal tract injury (12/46, 26%) than those without a seat belt sign (7/344, 2%) (relative risk 12.8, 95% CI = 5.3 to 31; p = 0.001). There was no difference in the prevalence of solid organ injuries between those with a seat belt sign (4/46, 9%) and those without a seat belt sign (34/344, 10%) (relative risk 0.9, 95% CI = 0.3 to 2.4; p = 1.00). In a subanalysis of the 241 patients who underwent abdominal CT, abdominal ultrasound, diagnostic peritoneal lavage, and/or laparotomy, intra-abdominal injuries were more likely to occur in those patients with a seat belt sign (14/40, 35%) than those without a seat belt sign (36/201, 18%) (relative risk 2.0, 95% CI = 1.2 to 3.3; p = 0.02). Patients with a seat belt sign who underwent a diagnostic abdominal test were also more likely to have a gastrointestinal tract injury (12/ 40, 30%) than those without a seat belt sign (7/201, 3.5%) (relative risk 8.6, 95% CI = 3.6 to 20.5; p, 0.001). To eliminate the potential bias of increased risk of intra-abdominal injury in unrestrained patients, we also performed a subanalysis limited to the 204 patients known to be restrained. In this subanalysis, the rate of intra-abdominal injury among patients with a seat belt sign (14/46, 30%) was also higher than patients without a seat belt sign (15/158, 8%) (relative risk 3.2; 95% CI = 1.7 to 6.1; p, 0.001). Patients known to be restrained and who had a seat belt sign were also more likely to have a gastrointestinal tract injury (12/46, 26%) than those known to be restrained but who did not have a seat belt sign (1/158, 0.6%) (relative risk 41, 95% CI = 5.5 to 309; p, 0.001). Six (13%) of the 46 patients with a seat belt sign were initially without abdominal pain or tenderness. None (0%, 95% CI = 0% to 39%) of the six patients with a seat belt sign but who did not have abdominal pain or tenderness was diagnosed as having an intraabdominal injury. Table 3 lists the clinical characteristics of these six patients. Two of these patients were admitted to the hospital, and four were discharged home after observation in the ED. All four of these TABLE 2. Types of Intra-abdominal Injuries in the 390 Study Patients Sign Present (n = 46) Sign Absent (n = 344) Relative Risk (95% CI) p-value Gastrointestinal tract 12 (26%) 7 (2%) 12.8 (5.3, 31) Pancreas 3 (7%) 1 (0.3%) 22.4 (2.4, 211) Adrenal glands 1 (2%) 3 (1%) 2.5 (0.3, 23) 0.40 Solid organ 4 (9%) 34 (10%) 0.9 (0.3, 2.4) 1.00 Spleen 1 (2%) 19 (6%) 0.4 (0.1, 2.9) 0.49 Liver 3 (7%) 15 (4%) 1.5 (0.5, 5.0) 0.46 Kidney 1 (2%) 7 (2%) 1.1 (0.1, 8.5) 1.00

4 ACAD EMERG MED d September 2005, Vol. 12, No. 9 d TABLE 3. Clinical Characteristics of Six Patients with Signs but without Abdominal Pain or Tenderness at ED Presentation* Patient ID 10-year-old female 8-year-old male 7-year-old male 3-year-old male 4-year-old male 7-year-old male Mechanism of Injury Rollover MVC, front passenger Side-impact MVC, front passenger MVC at 25 mph, front passenger MVC with significant front-end damage Slow-speed MVC into pole, rear passenger Rollover MVC at highway speed Restraint Type Abdominal Imaging Studies Obtained Associated Injuries 3-point None Arm laceration, cephalohematoma Observation Period Hospitalized for 2 nights 3-point None Chest wall 5.5 hours in ED contusion Lap belt None Ear abrasion 3 hours in ED Car seat Abdominal Nasal abrasion Hospitalized CT scan for 2 nights 3-point None Chin abrasion 2.5 hours in ED Lap belt None Arm and nasal contusions 4 hours in ED *None of these six patients was determined to have an intra-abdominal injury. MVC = motor vehicle collision. Comments Developed lower-abdominal tenderness within 4 hours in ED patients were available for telephone follow-up and were clinically well at follow-up. DISCUSSION Our study confirms that children with seat belt signs following MVCs are almost three times as likely as those without a seat belt sign to suffer an intraabdominal injury, and are almost 13 times as likely to suffer a gastrointestinal injury. We also observed that pancreatic injury was 22 times more common among children with seat belt signs. We found, however, no increased risk of solid organ injury (spleen, liver, or kidney) among patients who had seat belt signs, compared with those who did not have a seat belt sign. Finally, we found no injuries in the few patients with seat belt signs who did not have abdominal pain or tenderness. Among children with seat belt signs, we found rates of intra-abdominal injuries similar to those reported by Jerby et al. 20 Exploratory laparotomy in our study, however, was performed in half the number of patients compared with the laparotomy rate reported by Campbell et al. 21 The differences in laparotomy rates may have been influenced by a number of factors, including study population (all ED patients versus admitted patients), potential ascertainment bias (prospective versus retrospective study design), and changing pediatric surgical practices in the setting of trauma. Despite these differences, both studies indicate that the seat belt sign is clearly a high-risk finding that should prompt clinicians to carefully evaluate patients for intra-abdominal injuries. The first description of the seat belt syndrome included a case of a belted driver who sustained a ruptured pancreas and duodenum. 26 Pancreatic injuries have since been described in association with thoracolumbar spinal fractures after motor vehicle collisions, occurring most commonly among patients with lumbar Chance-type fractures. 8,14,22 Pancreatic injuries have been reported to occur in about 3% to 4% of children with seat belt signs, 18,21 which is similar to our observed rate of 7%. While this association has been previously reported, our study demonstrated a higher rate of pancreatic injury among children who had seat belt signs, when compared with those who did not have seat belt signs. A prior study of mostly adult patients found no difference in pancreatic injury rates between seat-belted (0.1%) and unbelted (0.3%) patients; however, pancreatic injury rates were not reported for those with and without seat belt signs. 27 While there is an increased risk of intra-abdominal injury among patients with seat belt signs, prior studies have suggested that seat belt use does not by itself increase the risk of intra-abdominal injury. 27,28 Rather, seat belt use changes the spectrum of these injuries. The risk of intra-abdominal injury among restrained children involved in MVCs has also been shown to depend on the adequacy of the restraint system. In one study of more than 17,000 restrained children involved in almost 11,000 MVCs, only 59% of the children were optimally restrained. Suboptimally restrained children were more than three times as likely to sustain intra-abdominal injuries. 29 In a similar study of more than 13,000 restrained children involved in almost 9,000 MVCs, children with intra-abdominal injuries were about four times more likely to have hollow viscus injuries if suboptimal restraints were used. 30 Abdominal ultrasound has been investigated as a potential imaging modality for patients with seat belt signs. In a study of 23 patients having seat belt signs

5 812 Sokolove et al. d SEAT BELT SIGN AND ABDOMINAL INJURY IN CHILDREN and requiring laparotomy for intestinal or mesenteric injury, 15 (65%) had negative focused assessment with sonography for trauma (FAST) examinations, and three (13%) others had equivocal studies. 31 Thus, abdominal sonography appears to be inadequate to exclude the intra-abdominal injuries most often seen in patients with seat belt signs. Stable patients with seat belt signs are generally evaluated with abdominal CT scanning. 7 While traditionally it has been reported that CT scans are insensitive for detecting hollow viscus injuries, newer-generation helical CT scans detect 83% to 94% of gastrointestinal injuries, including 91% of major gastrointestinal injuries. 38 After a negative abdominal CT scan, it is common clinical practice to observe patients with seat belt signs, but there are no data supporting a particular length of observation. In one study of children sustaining blunt abdominal trauma, 94% of those with intestinal injuries requiring laparotomy had tenderness on their initial physical examinations. 20 In managing patients with seat belt signs who have abdominal pain or tenderness, it is prudent and common practice to admit them for overnight observation, regardless of abdominal CT scan results, and consider the need for laparotomy. The current literature provides inadequate guidance regarding children with seat belt signs who lack abdominal pain or tenderness. In the current study, there appeared to be variability in ED attending physician management for this clinical scenario. We reported six such children in our study. The ED attending physicians elected to admit two of these patients, one of whom developed abdominal tenderness within four hours of ED arrival. The remaining four patients were observed in the ED from two and a half to five and a half hours prior to discharge home. None of these six patients was later determined to have an intra-abdominal injury. These data suggest that asymptomatic patients with an isolated seat belt sign might be considered for discharge from the ED following a several-hour period of observation, which includes serial abdominal examinations. Such patients should have an appropriate home situation prior to consideration for discharge home (e.g., reliable parents, acceptable distance from medical care, available telephone, and transportation). We emphasize, however, that our study was not intended to enroll a cohort of patients to adequately address this small subgroup. LIMITATIONS There are several limitations to this study. The study was conducted at a single institution that serves as a Level 1 trauma center; thus our findings may not be generalizable to all children seeking trauma care at different institutions. Thirty-eight percent of our overall study population and 13% of those with seat belt signs did not have radiologic or surgical evaluation for intra-abdominal injuries, beyond either hospitalization or telephone follow-up. Evaluation bias may have been introduced because patients with abnormal physical examination findings were more likely to undergo radiologic or surgical abdominal evaluation than patients without these findings. All patients, however, had either diagnostic testing or clinical follow-up in order to identify clinically important missed injuries. In addition, subanalyses of only those patients undergoing diagnostic testing for determining the presence or absence of intra-abdominal injury confirmed the increased risk of gastrointestinal injuries in those patients with seat belt signs. Finally, as noted above, only a small number of patients with seat belt signs lacked abdominal pain and tenderness, limiting our ability to make definitive management recommendations for such patients. CONCLUSIONS Pediatric patients with seat belt signs after motor vehicle collisions are more likely to have intraabdominal injuries than those patients without seat belt signs. This finding is predominately due to an increased risk of gastrointestinal tract injuries among patients with seat belt signs. Patients with seat belt signs but without abdominal pain or tenderness appear to be at low risk for clinically important intra-abdominal injuries, but further study is needed to confirm this finding and determine the optimal period of observation for such patients. The authors thank William E. Brant, MD, for interpreting the abdominal CT scans for this study. References 1. National Highway Traffic Safety Administration. 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