Anesthesiology Clin 25 (2007) 91–98

Management of the Obese Trauma Patient Yuval Meroz, MD, Yaacov Gozal, MD* Department of Anesthesiology & CCM, Hadassah Hebrew University School of Medicine, Hadassah Medical Organization, Kiryat Hadassah, P.O. Box 12000, Jerusalem 91120, Israel

Trauma and obesity are large-scale epidemics, causing significant morbidity and mortality. About 35% of Americans are overweight, with a body mass index (BMI) of 25 to 29 kg/m2; about 25% are obese (BMI of 30– 39); and 5% are morbidly obese (BMI R 40) [1]. This increasing population of overweight and morbidly obese persons will undoubtedly cause an increasing population of obese trauma victims. Despite the abundance of studies about trauma and morbid obesity, there are few studies about the impact of morbid obesity on type of injury, complications, and outcome. Thus, the aim of this article is to review the literature about the following subjects: Are obese patients at a higher risk for trauma? Do they suffer different types of injury? Are they more prone to complications after injury? Should treatment be modified when obese trauma victims are involved?

Before the trauma: risk of injury Obesity has been found to be associated with a higher rate of overall injuries among children [2] and adults [3]. Obesity’s effect on serious injuries, especially motor vehicle accidents, is less clear. Sleep apnea is a proven risk factor for vehicle accidents. Findley and colleagues [4] found that persons with sleep apnea had a sevenfold risk for vehicle accidents, compared with persons without sleep apnea. Teran-Santos and colleagues [5] performed a sleep test on 102 drivers who were involved in traffic accidents

* Corresponding author. E-mail address: [email protected] (Y. Gozal). 0889-8537/07/$ - see front matter Ó 2007 Elsevier Inc. All rights reserved. doi:10.1016/j.atc.2006.11.005 anesthesiology.theclinics.com

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and compared the results to those of 152 matched controls. They found that persons with significant sleep apnea had an odds ratio of 6.3 of being involved in a traffic accident. Although sleep apnea is not a synonym for obesity, there is a very strong correlation between both diseases. About 70% of sleep apnea patients are obese and about 40% of obese persons suffer from sleep apnea [6,7]. In a cohort study from New Zealand, Whitlock and colleagues [8] investigated the association between driver’s risk of injury and BMI. This half-prospective and half-retrospective study included 10,525 persons whose records were analyzed for a mean follow-up period of 10.3 years. Obesity (BMI R 28.7) was associated with a twofold risk for injury in a traffic accident, even after adjustment for other variables. Prehospital: type of injury Several works have evaluated the difference in injury patterns between obese and nonobese patients. The question about different types of injury arises not only because of different body habitus, but also because vehicles are designed to fit and provide safety to passengers with an average height and weight. In 1992, Boulanger and colleagues [9] analyzed the data on 6368 adults admitted to a level 1 trauma center because of blunt trauma over a 4-year period. They found that obese victims (BMI O 31) had significantly more rib fractures, pulmonary contusions, pelvic fractures, and extremity fractures, and fewer head and liver injuries. Moran and colleagues [10] searched the National Automotive Sampling System Crashworthiness Data System from 1995 to 1999. Their hypothesis was that if a driver’s body habitus diverges from the 50% percentile male Hybrid III Crash Dummy, the pattern of injury changes. Their results showed similar results to those of Boulanger and colleagues [9], with significantly fewer head and abdominal injury in patients with a BMI higher than 31. Another large retrospective study, by Mock and colleagues [11], based on the National Automotive Sampling System data from 1993 to 1996, showed increased risk of chest injuries among overweight vehicle crash victims. In a relatively small prospective work, Arbabi and colleagues [12] analyzed the data of 189 patients over 13 years old who were injured at a motor vehicle crash and transported to a level 1 trauma center. They found that overweight (BMI of 25–30) victims had a lower Injury Severity Score (ISS), increased severity of lower extremity injuries, and reduced severity of abdominal injuries. Obese patients (BMI O 30) also suffered a greater severity of lower extremity injury, but their ISS and abdominal injury severity were comparable to their lean counterparts, and there was no difference regarding head injury. The importance of this work was the introduction of the ‘‘cushion effect’’ hypothesis. The cushion effect is the increased protection given by the thicker abdominal fat layer of obese people to the internal organs, therefore reducing abdominal injuries. The cushion effect can protect overweight but not obese patients, because obese patients’ high mass and kinetic energy can

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overwhelm the protective effect of the abdominal fat. It is unclear if this cushion effect is effective in other types of trauma besides vehicle crashes. A larger, but retrospective, study was done by Byrens and colleagues [13], who analyzed the files of 1877 adult patients admitted to a level 1 trauma center during 1 year. Only 1179 patients were included because of a lack of data. This large study did not show any difference in injury patterns between patients with a BMI higher than 35 and those with a BMI less than 35. Some conflicting results came from another large retrospective study by Brown and colleagues [14] that included 1153 patients, all of whom suffered blunt trauma that required admission to an ICU at a level 1 trauma center. Patients were classified as obese (BMI R 30) or nonobese (BMI ! 30). Obese patients had significantly fewer head injuries (42% versus 55%), but suffered significantly more lower extremity fractures (53% versus 38%). Recently, this group examined the impact of obesity on children and adolescents [15]. Obese patients (BMI R 95th percentile for age) suffered significantly fewer severe head injuries (20% AIS R 3) than nonobese patients (38%), despite similar ISS for both groups. The results showed a tendency toward fewer overall head injuries, but without statistical significance. In summary, obese patients tend to have fewer head injuries and more lower extremity, pelvic, and rib fractures. Overweight, but not obese, patients involved in motor vehicle accidents may have some abdominal protective or cushion effect. However, these findings should not justify a different approach to obese patients at the prehospital stage or at the emergency room. The findings should be considered, however, when designing safety devices to give obese persons an adequate level of protection that is comparable to that given to their lean counterparts.

In hospital: complications, morbidity, and mortality Overweight patients are prone to develop more complications following trauma than lean patients. The first work to show a worse outcome in overweight patients was the study by Choban and colleagues [16] in 1991. This retrospective work analyzed the charts of 351 patients suffering blunt trauma. Unfortunately, only 184 records had height and weight data. The main findings showed significantly high mortality rates (42.1% for the severely overweight group [BMI O 31], compared with 8.0% for the overweight group [BMI of 27–31], and 5.0% for the average weight group [BMI ! 27]). The severely overweight patients suffered more complications, mainly pulmonary in nature. The clinical course of the severely overweight nonsurvivors was characterized by a significantly shorter length of stay at hospital (8.62 days versus 26.6 days for the average weight group) and a rapid deterioration, unresponsive to intervention. Increased BMI and ISS were found to be independent determinants of outcome. Mock and colleagues [11] found that increased weight and a higher BMI were strong

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predictors of 30-days mortality. The odds ratios of risk of death were 2.57 for a body weight of 100 to 119 kg, and 4.48 for a body weight above 119 kg. For increased BMI, the odds ratios were 3.18 for a BMI of 35 to 39 and 3.34 for a BMI above 39, all statistically significant. The investigators speculated that increased mortality could be attributed at least partially to a higher rate of comorbidities among the obese patients. Increased body weight and increased BMI remained associated with increased mortality after a multivariate logistic regression analysis that included adjustment for age, gender, seatbelt use, seating position, and vehicle weight. Arbabi and colleagues [12] found that for the lean patients, the mean ISS was 26.3 and the mortality rate was 11.3%. For the overweight patients, the mean ISS was 19.4 and the mortality rate was 4.9%. The mean ISS of the obese patients was 23.1, similar to the ISS of their lean counterparts, but the mortality rate was significantly higher (20% versus 11.3%, OR ¼ 4.2). Therefore, the increased mortality rate appears to be related to the increased BMI, and not to severity of injury. The nonlinear association (reduced mortality rate for overweight patients compared with either lean or obese patients) probably was caused by the cushion effect described previously. Wang and colleagues [17] analyzed the data of 67 patients who were involved in motor vehicle collisions and underwent abdominal CT. Increased depth of subcutaneous fat was associated with decreased severity of abdominal injury. The influence of the victim’s gender was not examined until Zhu and colleagues [18] analyzed National Automotive Sampling System data between the years 1997 and 2001. A total of 30,667 victims were enrolled, of whom 8230 were excluded. The end point was 30-days mortality. Although men had a nonlinear J-shaped association between their BMI and mortality, with lowest risk at a BMI of 28, women’s’ risk had no association with their BMI. Additionally, women with elevated BMIs had a lower risk, compared with men with elevated BMIs. The pattern of the men can be explained by the cushion effect, but the pattern of the women is unclear and might be associated with different body shape or different distribution of subcutaneous fat. Byrens and colleagues [13] found that the overall mortality rate of obese (BMI R 35) patients was 10.7%, compared with 4.1% for patients with a BMI of less than 35. The mortality rate of obese patients with an ISS of at least 20 was 56.3%, compared with 20.2% for nonobese patients. The rate of complications was also significantly higher. Generally, 27% of the obese patients had at least one complication, compared with 17.6% of the lean patients. More specifically, obese patients had more pulmonary complications, such as adult respiratory distress syndrome, found in 6.5% of the obese group versus 2% of the lean patients, and the need for mechanical ventilation (14.7% of obese patients versus 9% of lean patients). These findings cannot be explained by pre-existing diseases only, because both groups had a similar percentage of chronic obstructive pulmonary disease. The obese patients also suffered a higher rate of renal complications,

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including acute renal failure and acute renal insufficiency (6.6% of the obese patients versus 1% of the lean patients). Twenty-five percent of the obese patients with an ISS of at least 20 developed renal complications, compared with 2.2% of their lean counterparts. Obese patients had significantly higher rates of diabetes and hypertension, which could partially explain the high percentage of renal complications. On the other hand, the rate of cardiovascular complications was similar between the groups. One of the main results of this study is the definition of a BMI of greater than or equal to 35 as a cutoff point for increased risk for trauma victims. In a retrospective study of 242 blunt trauma victims admitted to a level 1 trauma center, Neville and colleagues [19] showed that patients with a BMI of greater than or equal to 30 suffered a twofold increase in mortality compared with lean patients (32% versus 16%) and a fourfold increase in the rate of multiple organ failure (13% versus 3%). In the work of Brown and colleagues [14], obesity was found to be an independent risk factor for mortality (odds ratio ¼ 1.6). Obese patients suffered more overall complications (42% versus 32%), more multiple system organ failure (19% versus 11%), more adult respiratory distress syndrome (11% versus 6%), and more renal failure requiring dialysis (8% versus 4%). In a short publication, Zein and colleagues [20] described 304 patients admitted to an ICU at a level 1 trauma center. Most of the patients were men (75%) and suffered blunt trauma (86%). Obese patients made up 33% of the study population and suffered an overall mortality rate of 11.3%, similar to the 12.1% rate of the nonobese patients. These findings contradict other published works. Brown and colleagues [15] examined the effect of obesity on children suffering trauma. The study included 316 patients, aged 6 to19, who were treated in an ICU in a level 1 trauma center. Patients were classified as obese (BMI R 9th percentile for age) or nonobese. The mortality rates were not statistically different between the obese (9%) and nonobese (15%) children. It seems that morbid obesity is an independent risk factor for mortality following severe trauma, and the risk may be a two- to fourfold increase. Obese patients suffer many more pulmonary and renal complications, with an increased need for prolonged mechanical ventilation. Patients of moderate weight, with a BMI of around 28, seem to have some protection, compared with lean and obese patients, and these patients are less prone to mortality and complications. The studies are mostly retrospective, and many patients, up to 50%, were omitted because of a lack of data. Some works included only vehicle crash victims, whereas others included all blunt trauma victims, or even penetrating trauma victims. The common BMI definitions for obesity might not be adequate for trauma patients. At least one large study suggests that the cutoff limit for increased risk should be a BMI higher than 35. As to specific treatment or approach, the authors recommend using increased BMI as a risk factor, especially while considering admission to an ICU.

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Treating the obese trauma patient: clinical topics Because of the lack of studies and guidelines about the clinical approach to the obese trauma patient, it is necessary to rely on either small series and case reports or general articles about treating obese critical patients [21–24]. Securing the airway is the first priority. Using gum elastic bougie has been recommended for cases of difficult intubation [25], and the laryngeal mask [26] or Combitube [27] can be used as a rescue device. A combination of rigid laryngoscopy and fiberoptic bronchoscope can be used for tube exchanging [28], but fiberoptic intubation can be limited by the presence of blood and secretions. Securing the surgical airway can be challenging as well. Even after a period of time in the ICU, conversion from endotracheal tube to tracheostomy might be difficult. Rehm and colleagues [29] studied cases in which elective cricothyroidotomy was performed instead of tracheostomy in 18 morbidly obese trauma patients after prolonged intubation in the ICU. None of the patients suffered any major complications related to the procedure and the investigators found that cricothyroidotomy can be a reasonable and less demanding alternative to tracheostomy in ventilated patients with difficult neck anatomy. Weaning the injured obese patient might be challenging as well. Yoo and colleagues [30] reported their experience with a 69-year-old obese patient (BMI ¼ 39) suffering multiple rib fractures and pulmonary contusion. Weaning was successful only after abdominal lipectomy and omentectomy, with removal of 4.5 kg of abdominal fat. Another important issue in treating obese trauma patients is the risk of thromboembolic events. Both trauma and obesity are independent risk factors for such events [31]. Meissner and colleagues [32] conducted a prospective study that included 101 trauma patients with ISS greater than or equal to 15. Obesity, defined as a body weight higher than 120% of ideal body weight among men and higher than 130% among women, was found to be an independent risk factor for thromboembolic events. Although only 4.2% of the patients without venous thromboembolism were obese, as many as 26.7% of the patients suffering venous thromboembolism were obese. Rutherford and colleagues [33] studied the levels of anti-Xa in 18 critically ill trauma and surgical patients, both obese and nonobese. They found that a daily dose of enoxaparin, 40 mg, resulted in an inadequate level of anti-Xa in all but two patients. The investigators’ recommendation was a twice-daily regimen and the monitoring of anti-Xa in patients with either morbid obesity or renal failure. An essential part of treating trauma patients is metabolic and nutritional support, but hemodynamic monitoring can be challenging in obese trauma victims. Line placement can be technically difficult, and the standard equipment may be inadequate. Thompson and colleagues [34] reported a case of extravasation into subcutaneous tissues because the introducer of the pulmonary artery catheter was too short. Brown and colleagues [35] checked

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the usefulness of cardiac index measurement by thoracic bioimpedance. They compared thermodilution and bioimpedance measurements in 74 obese patients and 211 nonobese patients. All patients were trauma victims admitted to an ICU in a level 1 trauma center. The investigators found the bioimpedance results correlated well with thermodilution measurements in both groups. Summary Obese persons are more likely to be involved in vehicle accidents, probably because of the presence of sleep apnea. They are more likely to suffer chest, pelvis, and extremity fractures. Mildly overweight persons are less prone to intra-abdominal injury, because of the protective effect of the abdominal fat, known as the cushion effect. Obese trauma patients are far more likely to develop in-hospital complications, especially pulmonary, renal, and thromboembolic complications. The BMI is an independent risk factor for morbidity and mortality after trauma. Because only limited data exist about the correct clinical approach to obese trauma patients, it is necessary to rely on general knowledge about treating obese patients in the ICU. More research is definitely needed to improve the treatment of obese trauma patients. References [1] Hedley AA, Ogden CL, Johnson CL, et al. Prevelance of overweight and obesity among US children, adolescents, and adults, 1999–2002. JAMA 2004;291:2847–50. [2] Bazelmans C, Coppieters Y, Godin I, et al. Is obesity associated with injuries among young people? Eur J Epidemiol 2004;19:1037–42. [3] Xiang H, Smith GA, Wilkins JR III, et al. Obesity and risk of nonfatal unintentional injuries. Am J Prev Med 2005;29:41–5. [4] Findley LJ, Unverzagt MF, Suratt PM. Automobile accidents involving patients with obstructive sleep apnea. Am Rev Respir Dis 1988;138:337–40. [5] Teran-Santos J, Jimenez-Gomez A, Cordero-Guevara J. The association between sleep apnea and the risk of traffic accidents. N Engl J Med 1999;340:847–51. [6] Young T, Peppard PE, Gottlieb DJ. Epidemiology of obstructive sleep apnea: a population health perspective. Am J Respir Crit Care Med 2002;165:1217–39. [7] Malthora A, White DP. Obstructive sleep apnoea. Lancet 2002;360:237–45. [8] Whitlock G, Norton R, Jackson R, et al. Is body mass index a risk factor for motor vehicle driver injury? A cohort study with prospective and retrospective outcomes. Int J Epidemiol 2003;32:147–9. [9] Boulanger BR, Miltzman D, Mitchell K, et al. Body habitus as a predictor of injury patterns after blunt trauma. J Trauma 1992;33:228–32. [10] Moran SG, McGwin G, Metzger JS, et al. Injury rates among restrained drivers in motor vehicle collisions: the role of body habitus. J Trauma 2002;52:1116–20. [11] Mock CN, Grossman DC, Kauffman RP, et al. The relationship between body weight and risk of death and serious injury in motor vehicle crashes. Accid Anal Prev 2002;34:221–8. [12] Arbabi S, Wahl WL, Hemmila MR, et al. The cushion effect. J Trauma 2003;54:1090–3. [13] Byrens MC, McDaniel MD, Moore MB, et al. The effect of obesity on outcomes among injured patients. J Trauma 2005;58:232–7.

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[14] Brown CVR, Neville AL, Rhee P, et al. The impact of obesity on the outcome of 1,153 critically injured blunt trauma patients. J Trauma 2005;59:1048–51. [15] Brown CVR, Neville AL, Salim A, et al. The impact of obesity on severely injured children and adolescents. J Pediatr Surg 2006;41:88–91. [16] Choban PS, Weireter LJ Jr, Maynes C. Obesity and increased mortality in blunt trauma. J Trauma 1991;31:1253–7. [17] Wang SC, Bednarski B, Patel S, et al. Increased depth of subcutaneous fat is protective against abdominal injuries in motor vehicle collisions. Annu Proc Assoc Adv Automot Med 2003;47:545–9. [18] Zhu S, Layde PM, Guse CE, et al. Obesity and risk for death due to motor vehicle crashes. Am J Public Health 2006;96:734–9. [19] Neville AL, Brown CVR, Weng J, et al. Obesity is an independent risk factor of mortality in severely injured blunt trauma patients. Arch Surg 2004;139:983–7. [20] Zein JG, Albrecht RM, Tawk MM, et al. Effect of obesity on mortality in severely injured blunt trauma patients remains unclear. Arch Surg 2005;140:1130–1. [21] Flanchbaum L, Choban PS. Surgical implications of obesity. Annu Rev Med 1998;49: 215–34. [22] Marik P, Varon J. The obese patient in the ICU. Chest 1998;113:492–8. [23] Grant P, Newcombe M. Emergency management of the morbidly obese. Emerg Med Australas 2004;16:309–17. [24] Pieracci FM, Barie PS, Pomp A. Critical care of the bariatric patient. Crit Care Med 2006;34: 1796–804. [25] Jabre P, Combes X, Leroux B. Use of gum elastic bougie for prehospital difficult intubation. Am J Emerg Med 2005;23:552–5. [26] Aye T, Milne B. Use of the laryngeal mask prior to definitive intubation in a difficult airway: a case report. J Emerg Med 1995;13:711–4. [27] Agro F, Frass M, Benumof J. The asophageal tracheal combitube as a non-invasive alternative to endotracheal tube. A review. Minerva Anestesiol 2001;67:863–74. [28] Hagberg CA, Westhofen P. A two-person technique for fiberoptic-aided tracheal extubation/reintubation in intensive care unit (ICU). J Clin Anesth 2003;15:467–70. [29] Rehm CG, Wanek SM, Gagnon EB, et al. Cricothyroidotomy for elective airway management in critically ill trauma patients with technically challenging neck anatomy. Crit Care 2002;6:531–5. [30] Yoo KY, Lim SC, Kim YH, et al. Successful weaning from mechanical ventilation after abdominal lipectomy and omentectomy in an obese patient with multiple rib fractures. Br J Anaesth 2006;96:269–70. [31] Kim V, Spandorfer J. Epidemiology of venous thromboembolic disease. Emerg Med Clin North Am 2001;19:839–59. [32] Meissner MH, Chandler WL, Elliot JS. Venous thromboembolism in trauma: a local manifestation of systemic hypercoagulability? J Trauma 2003;54:224–31. [33] Rutherford EJ, Schooler WG, Sredzinski E. Optimal dose of enoxaparin in critically ill trauma and surgical patients. J Trauma 2005;58:1167–70. [34] Thompson EC, Wilkins HE, Fox VJ, et al. Insufficient length of pulmonary artery introducer in an obese patient. Arch Surg 2004;139:794–6. [35] Brown CVR, Martin MJ, Shoemaker WC, et al. The effect of obesity on bioimpedance cardiac index. Am J Surg 2005;189:547–51.