Morbid Obesity's Silver Lining: An Armor for Hollow Viscus in Blunt Abdominal Trauma

An evaluation of the "Obesity Paradox" in isolated blunt abdominal trauma in the United States

BACKGROUND

The obesity paradox theorizes a survival benefit in trauma patients secondary to the cushioning effect of adiposity. We aim to evaluate the impact of body mass index (BMI) on abdominal injury severity, morbidity, and mortality in adults with isolated, blunt abdominal trauma in the United States.

METHODS

We reviewed the National Trauma Data Bank (2013-2021) for adults sustaining isolated, blunt abdominal trauma stratified by BMI. We performed a doubly robust, augmented inverse-propensity weighted multivariable logistic regression to estimate the average treatment effect (ATE) of BMI on mortality and the presence of abdominal organ injury.

RESULTS

36,350 patients met the inclusion criteria. In our study, 41.4 % of patients were normal-weight (BMI 18.5-24.9), 20.6 % were obese (BMI 30-39.9), and 4.7 % were severely obese (BMI≥40). In these cohorts, the abdominal abbreviated injury scale (AIS) was 2 (2 -3). Obese and severely obese patients had significantly reduced presence of pancreas, spleen, liver, kidney, and small bowel injuries. The predicted probability of abdominal AIS severity decreased significantly with increasing BMI. Crude mortality was significantly higher in obese (1.3 %) and severely obese patients (1.3 %) compared to normal-weight patients (0.7 %). Obese and severely obese patients demonstrated non-statistically significant changes in the mortality of +26.4 % (ATE 0.264, 95 %CI -0.108-0.637, p = 0.164) and +55.5 % (ATE 0.555, 95 %CI -0.284-1.394, p = 0.195) respectively, compared to normal weight patients.

CONCLUSION

BMI may protect against abdominal injury in adults with isolated, blunt abdominal trauma. Mortality did not decrease in association with increasing BMI, as this may be offset by the increase in co-morbidities in this population.

Obesity and Penetrating Trauma: Outcomes from a Level 1 Trauma Center in New York City

Background

Obesity is associated with increased morbidity and mortality in trauma scenarios; however, there has been conflicting evidence on outcomes of obesity and penetrating injuries, specifically gunshot wounds and stab wounds. We hypothesized that obesity may be protective due to a "cushioning effect" attributed to increased adiposity.

Methods

This was a retrospective cohort study of patients presenting to a Level 1 Trauma Center with a penetrating trauma (gunshot/stab) injury during 2008-2021. Patients with a BMI ≥ 30 were compared to those with a BMI < 30. The primary outcome was Injury Severity Score (ISS). Secondary outcomes included intensive care unit (ICU) length of stay, days on ventilation, length of hospital stay, service of admission (trauma surgery, general surgery, discharged home, general medical floor), the body region of injury(s), Abbreviated Injury Scale (AIS), OR requirement, type of surgery, and discharge status. Statistical analysis was performed using χ2-test or Fisher's exact tests for categorical data, and Student's t-test or Mann-Whitney U-test for continuous variables with p < 0.05 as statistically significant. Subgroup analysis was performed based on the mechanism of injury.

Results

There were 721 patients that met inclusion criteria, of which 540 were classified in the non-obese group and 181 (25.1%) in the obese group. The primary outcome, mean ISS score, in obese patients (9.0, SD = 13.0) and non-obese patients (9.4, SD = 13.8) was similar between groups respectively. Secondary outcomes, which included rates of severe abdominal injury (AIS ≥ 3), rates of intra-abdominal organ injury, and rates of gastro-intestinal resection, were also similar between non-obese and obese patients.

Conclusion

This study did not demonstrate the existence of a "cushioning effect" in the setting of penetrating traumatic injury. Patients with increased BMI had similar a ISS score and patterns of injury as their non-obese counterparts.

Seat belt injuries and external markings at autopsy in cases of lethal vehicle crashes

A study was undertaken to determine what injuries are associated with the wearing of seat belts and if the presence of cutaneous seat belt markings observed on victims of lethal vehicle crashes increased the likelihood of underlying injury. Autopsy reports from the files at Forensic Science South Australia were reviewed for all fatal motor vehicle crashes from January 2014 to December 2018. A total of 173 cases were included for analysis with 127 occupants wearing seat belts at the time of impact (73.4%) (age range = 18-93; mean = 45 M:F = 81:46). Of these, only 38 had external seat belt markings (29.9%) (age range = 19-83; mean = 49 M:F = 20:18). Logistic regression modelling showed that occupants who were wearing seat belts were more likely to experience closed head injury without skull fractures in addition to mesenteric and gastrointestinal injury. Increasing body mass index increased the incidence of seat belt markings (p < 0.01) and markings were more likely to be found in the presence of bilateral pelvic fractures. Thus, external seat belt markings were observed in only a minority of seatbelt wearers, and more often in individuals with higher BMIs and with bilateral pelvic fractures (possibly associated with greater momentum and impact force).

Influence of operative timing on perioperative outcomes of patients with the seatbelt sign

Background

The seatbelt sign (SBS) is a pattern of bruising/contusions on the chest and abdominal wall following motor vehicle collisions. The aim of this analysis is to investigate the influence of time to surgery following identification of the SBS on perioperative outcomes.

Methods

A retrospective review of the Trauma Quality Improvement Program database from 2017 to 2019 was performed. Patients included in this retrospective analysis were involved in motor vehicle collisions, experienced blunt abdominal trauma, presented with skin abrasions/contusions in the SBS distribution, were hemodynamically stable, and underwent laparotomy. Demographics, vital signs, injury severity score, Glasgow coma scale, preoperative CT scans (P-CT), and time from presentation to surgery were recorded. Time from presentation to surgery was subdivided by data quartiles as immediate (<1.3 h), early (1.3-4 h), and delayed (>4 h). The influence of operative timing on postoperative mortality, hospital length of stay (LOS), intensive care unit (ICU) LOS, and ventilator days was assessed in multivariate analyses.

Results

A total of 1523 patients were included; 280 underwent immediate, 610 early, and 633 delayed surgery. Patients undergoing surgery in the early and delayed groups who received P-CT scans had shorter mean times to operation (4.52 h vs 5.24 h, p < 0.01). In multivariate analysis, patients who underwent delayed surgery stayed in the hospital 2.5 days longer (p < 0.001), spent 2.8 additional days in the ICU (p < 0.001), and spent 3.75 additional days on a ventilator (p < 0.001) than patients who received early surgery. Within the early and delayed surgical groups, P-CT was associated with lower mortality (OR 0.46 95 % CI 0.24-0.88, p < 0.01) in multivariate analysis.

Conclusions

Early surgical intervention was associated with improved patient outcomes by reducing hospital and ICU LOS and ventilator days. Conducting P-CT reduced the time to surgery and mortality. Utilization of P-CT for screening hemodynamically stable patients with the SBS upon admission may expedite identification of the potential need for surgical management of abdominal injury.

Obesity and outcomes in trauma - a systematic review and meta-analysis

BACKGROUND

The physiological abnormalities relating to obesity and metabolic syndrome can contribute to worse outcomes following trauma especially in class 2 and 3 obesity. The aim of this systematic review was to determine whether patients with a higher class of obesity who suffer traumatic injury have a higher risk of worse outcomes including in-hospital mortality than normal-weight patients.

METHODS

A systematic search of MEDLINE, EMBASE, CENTRAL, Web of Science and CINAHL was performed for studies that reported a comparison of in-hospital obesity-related outcomes against normal-weight individuals aged 15 years and older following trauma. Single or multiple injuries from either blunt and/or penetrating trauma were included. Burn-related injuries, isolated head injury and studies focusing on orthopaedic related perioperative complications were excluded.

RESULTS

The search yielded 7405 articles; 26 were included in this systematic review. 945,511 patients had a BMI>30. A random-effects meta-analysis was performed for analysis of all four outcomes. Patients with class 3 obesity (BMI>40) have significantly higher odds of in-hospital mortality than normal-BMI individuals following blunt and penetrating trauma (OR, 1.75; 95% CI, 1.39-2.19, p=<0.00001), significantly longer hospital LOS (SMD, 0.23; 95% CI, 0.21-0.25; p<0.00001) and significantly longer ICU LOS (SMD, 0.19; 95% CI, 0.12-0.26; p<0.0001). In contrast, studies that examined blunt and penetrating trauma and classified obesity with a threshold of BMI>30 found no significant difference in the odds of in-hospital mortality (OR, 0.94; 95% CI, 0.86-1.02, p=0.13).

CONCLUSIONS

There is a higher risk of in-hospital mortality in patients living with class 3 obesity following trauma when compared with individuals with normal BMI. The management of patients with obesity is complex and trauma systems should develop specific weight related pathways to manage and anticipate the complications that arise in these patients. Systematic review registration number PROSPERO registration: CRD42021234482 Level of Evidence: Level 3.

Cushioning the blow: role of perirenal fat in renal trauma injury severity

OBJECTIVES

To explore the association between perirenal fat thickness (PFT) and renal trauma grade. We hypothesise this association is related to a shock-absorbing effect of adiposity around the kidney.

PATIENTS AND METHODS

We identified all patients with renal trauma who arrived at the emergency department of a single trauma centre between 2014 and 2020. Radiology images were reviewed to measure the PFT around the uninjured kidney due to disrupted PFT around the traumatised kidney. Patients with no available images or penetrating trauma mechanism were excluded. Logistic regression was used to assess the relation between PFT and high-grade renal trauma (HGRT; defined as American Association for the Surgery of Trauma Renal Grade IV-V), adjusting for age, sex, and Injury Severity Scale (ISS).

RESULTS

A total of 150 patients with renal trauma were included. The median (interquartile range) age was 38.5 (26-52) years and 106 (70.7%) were males. The PFT ranged between 2.1 and 50.1 mm, and 31 (20.7%) had HGRT. Interestingly, PFT only mildly correlated with body mass index (BMI; Pearson correlation coefficient 0.42, P < 0.001). Those with HGRT had significantly lower PFT compared to those without HGRT (median 9.5 vs 11.9 mm, P = 0.047). In the multivariable analysis adjusting for age, sex, and ISS, increasing PFT was associated with decreased odds (odds ratio 0.91, 95% confidence interval 0.84-0.98; P = 0.015) of HGRT.

CONCLUSION

Increasing PFT is associated with lower risk of HGRT following blunt injury. These results support a protective cushion role of adiposity in renal trauma. Notably, PFT was not strongly correlated with BMI, underscoring limitations of BMI in measuring adiposity.

Outcomes of the overweight and obese major trauma patient in the rural setting

PURPOSE

Overweight and obese patients are more prevalent in rural and remote areas and are of major public health concern in Australia. We aimed to evaluate the mortality and morbidity of overweight and obese trauma patients in the rural Australian context.

METHOD

This was a retrospective cohort study on 207 major trauma patients (injury severity score [ISS] > 12) treated at the Mackay Base Hospital between 2018 and 2021. Data was extracted from the Mackay Base Hospital trauma database and hospital records. Outcomes were compared between body mass index (BMI) groups.

RESULTS

There were 164 males (79%) and 43 females (21%). The average BMI was 27.09 (standard deviation 5.46). 7 patients (3%) were in the underweight category (BMI < 18.5 kg/m²), 70 (34%) were of normal weight (BMI 18.5-24.9 kg/m²), 79 (38%) were overweight (BMI 25-29.9 kg/m²), and 51 (25%) were obese (BMI > 30 kg/m²). The majority of trauma was blunt (n = 203, 98%). Compared to patients with normal BMI, obese patients were significantly more likely to require intubation, intensive care unit (ICU) admission, and have a longer ICU stay. There were no significant differences in requirement for surgery, duration of surgery, hospital length of stay, ventilator time, or mortality (P > 0.05). However, subgroup analysis of the obese patient group showed an increased rate of complications (sepsis, acute kidney injury, fluid overload and pneumonia), longer ventilation times, hospital and ICU length of stay with increasing BMI in these patients.

CONCLUSION

The majority of trauma presentations in our regional community are in overweight or obese patients. Overweight and obese patients are more likely to require intubation and have a longer intensive care unit admission than normal weight counterparts. Amongst obese patients, those with BMI > 40 (obesity class 3) are at significantly increased risk of complications.

The effect of obesity on inpatient outcomes in lower extremity trauma: A systematic review and meta-analysis

BACKGROUND

Obesity is a growing global health problem and a well-recognized risk factor for many medical conditions. This meta-analysis was conducted to assess the effect of obesity on overall complication occurrence, mortality, and hospital length of stay in patients with nonpathological lower limb trauma.

METHODS

The EMBASE, PUBMED, and MEDLINE electronic databases were searched from inception to April 1, 2020, for studies published in English. References cited by chosen studies were also checked manually for inclusion. Studies chosen for the analysis were prospective observational or retrospective cohort studies reporting on total complications of patients with acute traumatic, nonpathological, lower limb fractures that required internal fixation, with or without other underlying conditions. Two investigators independently reviewed the full text of eligible studies for inclusion and extracted data. Inconsistency was resolved through consultation with other authors.

RESULTS

Sixteen studies with 404,414 patients were investigated in this study. The data showed obesity was related with increased total complications (odds ratio [OR], 0.65; 95% confidence interval [CI], 0.51-0.83; p < 0.01), increased wound complications (OR, 0.41; 95% CI, 0.25-0.66; p < 0.01), and increased mortality rate (OR, 0.64; 95% CI, 0.45-0.91; p < 0.05). Six cohort studies also showed prolonged hospital length of stay in obese patients.

CONCLUSION

Our results suggest that obesity is associated with increased complication and mortality rates, as well as longer hospital length of stay in patients with lower-limb trauma who required surgical treatment. These findings may raise attention to optimize surgical technique and develop individualized treatment for obese patients.

LEVEL OF EVIDENCE

Systematic reviews, level IV.

The Impact of Obesity on Renal Trauma Outcome: An Analysis of the National Trauma Data Bank from 2013 to 2016

BACKGROUND

The obesity paradox has been recently demonstrated in trauma patients, where improved survival was associated with overweight and obese patients compared to patients with normal weight, despite increased morbidity. Little is known whether this effect is mediated by lower injury severity. We aim to explore the association between body mass index (BMI) and renal trauma injury grade, morbidity, and in-hospital mortality.

METHODS

A retrospective cohort of adults with renal trauma was conducted using 2013-2016 National Trauma Data Bank. Multiple regression analyses were used to assess outcomes of interest across BMI categories with normal weight as reference, while adjusting for relevant covariates including kidney injury grade.

RESULTS

We analyzed 15181 renal injuries. Increasing BMI above normal progressively decreased the risk of high-grade renal trauma (HGRT). Subgroup analysis showed that this relationship was maintained in blunt injury, but there was no association in penetrating injury. Overweight (OR 1.02, CI 0.83-1.25, p = 0.841), class I (OR 0.92, CI 0.71-1.19, p = 0.524), and class II (OR 1.38, CI 0.99-1.91, p = 0.053) obesity were not protective against mortality, whereas class III obesity (OR 1.46, CI 1.03-2.06, p = 0.034) increased mortality odds. Increasing BMI by category was associated with a stepwise increase in odds of acute kidney injury, cardiovascular events, total hospital length of stay (LOS), intensive care unit LOS, and ventilator days.

CONCLUSIONS

Increasing BMI was associated with decreased risk of HGRT in blunt trauma. Overweight and obesity were associated with increased morbidity but not with a protective effect on mortality. The obesity paradox does not exist in kidney trauma when injury grade is accounted for.

Does a "Cushion Effect" Really Exist? A Morphomic Analysis of Vulnerable Road Users with Serious Blunt Abdominal Injury

Introduction: The severity of injury from motor vehicle crashes (MVCs) depends on complex biomechanical factors, and the bodily features of the injured person account for some of these factors. By assuming that vulnerable road users (VRUs) have limited protection resulting from vehicles and safety equipment, the current study analyzed the characteristics of fat distribution measured by computed tomography (CT) imaging and investigated the existence of a "cushion effect" in VRUs. Materials and Methods: This retrospective study enrolled 592 VRUs involved in MVCs who underwent CT scans. Visceral fat area and subcutaneous fat cross-sectional area were measured and adjusted according to total body area (TBA) and are presented as the visceral fat ratio and the subQ fat ratio (subcutaneous fat ratio). Risk factors for serious abdominal injury (maximum abbreviated injury scale (MAIS_abd ≥ 3)) resulting from MVCs were determined by univariate and multivariate analysis. Results: MAIS_abd ≥ 3 was observed in 104 (17.6%) of the patients. The subQ fat ratio at the L4 vertebral level was significantly lower in the MAIS_abd ≥ 3 group than in the MAIS_abd < 3 group (24.9 ± 12.0 vs. 28.1 ± 11.9%; p = 0.015). A decreased L4 subQ fat ratio was associated with a higher risk for MAIS_abd ≥ 3 in multivariate analysis (odds ratio 0.063; 95% CI 0.008-0.509; p = 0.009). Conclusion: The current study supported the "cushion effect" theory, and protection was apparently provided by subcutaneous fat tissue. This concept may further improve vehicle and safety designation in the future.

Low body mass index is associated with increased mortality in patients with pelvic and acetabular fractures

AIMS

Fractures of the pelvis and acetabulum are often the consequence of high energy trauma in young individuals or fragility fractures in osteoporotic bone. They can be life-threatening or life changing injuries. No published data exists comparing body mass index (BMI) and mortality for this patient group. The aim of this study was to identify if low BMI (<18.5) was a predictor of morbidity and mortality for patients with these injuries.

PATIENTS AND METHODS

Of the 1033 patients with pelvic or acetabular fractures referred to a single level 1 major trauma centre (MTC) over a 4.5-year period (August 2015 - January 2020); we retrospectively analysed data for all admitted patients. Data was collected on demographics, injury pattern, operative intervention and complications. Comparison was made between patients that were underweight (BMI<18.5) and patients that were not. Both in-hospital and post discharge complications were recorded including pulmonary embolus (PE), deep venous thrombosis (DVT), ileus, infection, loss of reduction and mortality at 6 months.

RESULTS

569 patients admitted to the MTC with a pelvic or acetabular fracture were included in our analysis. Underweight patients had a statistically significant increase in mortality both in-hospital (p = 0.019) and at 6 months post injury (p = 0.039) when compared to other BMI groups. No statistical significance was found between these BMI groups comparing morbidity: DVT (p = 0.712), PE (p = 0.736) nor ileus (p = 0.149). Covariate analysis showed that a low BMI was associated with triple the in-hospital mortality after correction for age and energy of injury (adjusted OR 3.028, 95% CI 1.059-8.659).

CONCLUSION

This is the first published study that demonstrates a statistically significant increase in mortality in patients with pelvic or acetabular fractures who are underweight. Surgeons should carefully consider appropriate peri-operative optimisation for these patients. Further investigation into the effects of low BMI and response to trauma is required.

Impact of Obesity on Mortality in Adult Trauma Patients

Introduction

Trauma is a major cause of morbidity and mortality amongst all populations in the United States. With the widespread increase of obesity in the United States, studies have been conducted to compare different body mass index (BMI) groups and their clinical outcomes for traumatic injuries. The goal of this study was to retrospectively compare mortality between adult trauma patients with a high BMI to those with a lower BMI as well as investigate whether the mechanism of trauma had an effect on the outcome.

Methods

This study was a retrospective review of all adult trauma patients presented to the emergency department at Arrowhead Regional Medical Center (ARMC) between January 2014 and October 2019. The outcome was all-cause mortality. Patients were grouped according to BMI and mechanisms of injury, including blunt trauma, low velocity penetrating trauma, and high velocity penetrating trauma. Patients were also stratified by injury severity scores (ISS).

Results

Among the 9642 patients assessed in this study, majority (88%) of patients sustained blunt trauma. The number of patients among the three different BMI groups was appropriately equal with 34.4% of normal BMI, 34.6% overweight, and 31.1% obese. The overall mortality of all patients studied was 2.6% (n=248). There was no statistically significant difference in mortality among the three different BMI groups for blunt trauma, penetrating trauma, and subgroup analyses stratified by ISS score (ISS<16 or ISS ≥ 16).

Conclusion

Our study found no statistically significant differences in mortality among the three BMI groups in regard to mortality, even when stratified by ISS, or mechanism of injury, and traumatic velocities.

The Obesity Paradox in the Trauma Patient: Normal May not Be Better

Objective

The obesity paradox is the association of increased survival for overweight and obese patients compared to normal and underweight patients, despite an increased risk of morbidity. The obesity paradox has been demonstrated in many disease states but has yet to be studied in trauma. The objective of this study is to elucidate the presence of the obesity paradox in trauma patients by evaluating the association between BMI and outcomes.

Methods

Using the 2014–2015 National Trauma Database (NTDB), adults were categorized by WHO BMI category. Logistic regression was used to assess the odds of mortality associated with each category, adjusting for statistically significant covariables. Length of stay (LOS), ICU LOS and ventilator days were also analyzed, adjusting for statistically significant covariables.

Results

A total of 415,807 patients were identified. Underweight patients had increased odds of mortality (OR 1.378, p < 0.001 95% CI 1.252–1.514), while being overweight had a protective effect (OR 0.916, p = 0.002 95% CI 0.867–0.968). Class I obesity was not associated with increased mortality compared to normal weight (OR 1.013, p = 0.707 95% CI 0.946–1.085). Class II and Class III obesity were associated with increased mortality risk (Class II OR 1.178, p = 0.001 95% CI 1.069–1.299; Class III OR 1.515, p < 0.001 95% CI 1.368–1.677). Hospital and ICU LOS increased with each successive increase in BMI category above normal weight. Obesity was associated with increased ventilator days; Class I obese patients had a 22% increase in ventilator days (IRR 1.217 95% CI 1.171–1.263), and Class III obese patients had a 54% increase (IRR 1.536 95% CI 1.450–1.627).

Conclusion

The obesity paradox exists in trauma patients. Further investigation is needed to elucidate what specific phenotypic aspects confer this benefit and how these can enhance patient care.

Level of evidence

Level III, prognostic study

Body Mass Index and Mortality in Blunt Trauma: The Right BMI can be Protective

BACKGROUND

There are limited studies examining the role of BMI on mortality in the trauma population. The aim of this study was to analyze whether the "obesity paradox" exists in non-elderly patients with blunt trauma.

METHODS

A retrospective study was performed on the Trauma Quality Improvement Program (TQIP) database for 2016. All non-elderly patients aged 18-64, with blunt traumatic injuries were identified. A generalized additive model (GAM) was built to assess the association of mortality and BMI adjusted for age, gender, race, and injury severity score (ISS).

RESULTS

28,475 patients (mean age = 42.5, SD = 14.3) were identified. 20,328 (71.4%) were male. Age (p < 0.0001), gender (p < 0.0001), and ISS (p < 0.0001) had significant associations with mortality. After GAM, BMI showed a significant U-shaped association with mortality (EDF = 3.2, p = 0.003). A BMI range of 31.5 ± 0.9 kg/m² was associated with the lowest mortality.

CONCLUSION

High BMI can be a protective factor in mortality within non-elderly patients with blunt trauma. However, underweight or morbid obesity suggest a higher risk of mortality.