Body Mass Index and Outcomes in Critically Injured Blunt Trauma Patients: Weighing the Impact

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.

Impact of obesity on outcomes of patients with acute respiratory distress syndrome: a retrospective analysis of a large clinical database

OBJECTIVE

To evaluate the link between obesity and mortality in patients with acute respiratory distress syndrome (ARDS).

METHODS

We performed a retrospective cohort study of a large clinical database. A Cox proportional hazards regression model was used to calculate the hazard ratio (HR) and 95% confidence interval (CI) for the relationship between body mass index (BMI) and mortality. The primary endpoint was 30-day death rate and the secondary endpoints were 90-day and 1‑year mortality.

RESULTS

Overall, 418 patients with ARDS were enrolled in the study, including 185 women and 233 men (age: 70.7 ± 44.1 years; BMI: 28.7 ± 8.1 kg/m2). Compared with patients with normal weight, obese patients were younger (60.1 ± 13.7, p = 0.003) and a higher percentage of these patients were women (51.3% vs. 49.0%, p = 0.001). The HRs (95% CI) of 30-day mortality in the underweight, overweight, and obese populations were 1.82 (0.85, 3.90), 0.59 (0.29, 1.20), and 3.85 (1.73, 8.57), respectively, after adjustment for other confounding factors. A similar pattern was also seen for death after 90 days and after 1 year. A U-shaped association between BMI and 30-day mortality was discovered by curve fitting.

CONCLUSION

Obesity had a significant impact on the short- and long-term mortality in patients with ARDS. There was a U-shaped relationship between BMI and mortality, while a higher BMI was associated with an increased risk of death in patients with ARDS.

Effect of magnesium sulfate on oxygenation and lung mechanics in morbidly obese patients undergoing bariatric surgery: a prospective double-blind randomized clinical trial

BACKGROUND

Respiratory mechanics are often significantly altered in morbidly obese patients and magnesium sulfate (MgSO4) is a promising agent for managing several respiratory disorders. This study aimed to examine the effects of MgSO4 infusions on arterial oxygenation and lung mechanics in patients with morbid obesity undergoing laparoscopic bariatric surgery.

METHODS

Forty patients with morbid obesity aged 21-60 years scheduled for laparoscopic bariatric surgery under general anesthesia were randomly allocated to either the control (normal saline infusion) or MgSO4 group (30 mg/kg lean body weight [LBW] of 10% MgSO4 in 100 ml normal saline intravenously over 30 min as a loading dose, followed by 10 mg/kg LBW/h for 90 min). The primary outcome was intraoperative arterial oxygenation (ΔPaO2/FiO2). Secondary outcomes included intraoperative static and dynamic compliance, dead space, and hemodynamic parameters.

RESULTS

At 90 min intraoperatively, the Δ PaO2/FiO2 ratio and the Δ dynamic lung compliance were statistically significantly higher in the MgSO4 group (mean ± SE: 16.1 ± 1.0, 95% CI [14.1, 18.1] and 8.4 ± 0.5 ml/cmH2O, 95% CI [7.4, 9.4]), respectively), and the Δ dead space (%) was statistically significantly lower in the MgSO4 group (mean ± SE: -8.0 ± 0.3%, 95% CI [-8.6, -7.4]) (P < 0.001). No significant differences in static compliance were observed.

CONCLUSIONS

Although MgSO4 significantly preserved arterial oxygenation and maintained dynamic lung compliance and dead space in patients with morbid obesity, the clinical relevance is minimal. This study failed to adequately reflect the clinical importance of these results.

Adiposity and Coagulation: Predicting Postinjury Coagulation With Advanced Imaging Analysis

INTRODUCTION

Anatomic distribution of adipose tissue has demonstrated variable associations with hypercoagulability. Utilizing a retrospective analysis of a previously enrolled prospective cohort, we assessed computed tomography (CT) scan-based anthropometric and volumetric measures of adiposity as predictors of postinjury hypercoagulability.

METHODS

Segmentation analysis of arrival CT scans in significantly injured patients at a single level-I trauma center enrolled from December 2017 to August 2021 were analyzed for anthropometric indices of waist circumference (WC) and sagittal abdominal diameter (SAD), and volumetric parameters of visceral adipose tissue, superficial/deep subcutaneous adipose tissue, psoas/paravertebral muscle volume, and abdominal wall muscle volume. Associations with thromboelastography (TEG) were explored.

RESULTS

Data from 91 patients showed strong correlations between body mass index and standard anthropometric measures of WC and SAD (P < 0.001); calculated volumes of subcutaneous adipose tissue and visceral adipose tissue (P < 0.001); and ratios of subcutaneous adipose:psoas muscle (SP ratio) and visceral adipose:psoas muscle ratio (both with P < 0.001, respectively). Correlation between TEG maximal amplitude (MA) and body mass index and SAD were not significant, with only weak correlation between TEG-MA and WC (r = 0.238, P = 0.041). Moderate but significant correlations existed between SP ratio and TEG-MA (r = 0.340, P = 0.005), but not visceral adipose:psoas muscle ratio (r = 0.159, P = 0.198). The relationship between TEG-MA and SP ratio remained significant when adjusted for injury severity score and lactate level (b = 0.302, P = 0.001).

CONCLUSIONS

SP ratio is more strongly correlated with TEG-MA than standard obesity measures, and independently predicts increasing clot strength/stability after injury. Coagulation-relevant measures of sarcopenic obesity can be measured on CT scan, and may be used to optimize thromboprophylaxis strategies for obese injured patients.

Preoperative Body Mass Index, Waist Circumference, and Mortality After Major Cancer Surgery: A Nationwide Cohort Study in Korea

BACKGROUND

Body mass index (BMI) and waist circumference (WC) were used to evaluate nutritional status and obesity. We aimed to examine whether preoperative BMI or WC was associated with mortality after cancer surgery.

METHODS

This population-based cohort study used data extracted from the National Health Insurance Service database of South Korea. We included adult patients who underwent major cancer surgery with curative intent between January 1, 2016, and December 31, 2020.

RESULTS

A total of 87,220 patients were included in the final analysis, and 1,374 (1.6%) died within 90 days after cancer surgery. In the multiple logistic regression model, the BMI < 18.5/kg/m² and > 35 kg/m² groups showed 1.98-fold (odds ratio [OR], 1.98; 95% confidence interval [CI], 1.58-2.49; P < 0.001) and 2.60-fold (OR, 2.60; 95% CI, 1.25-5.40; P < 0.001) higher 90-day mortality after cancer surgery than did the BMI 18.5-24.9 kg/m² group. The 25.0-29.9 kg/m² (P = 0.144) and 30.0-34.9 kg/m² (P = 0.105) BMI groups did not show significant differences compared to the BMI 18.5-24.9 kg/m² group. Compared with the normal WC group, the high (P = 0.052) and very high (P = 0.232) WC groups also did not show significant differences in terms of 90-day mortality.

CONCLUSIONS

Preoperative BMI < 18.5 kg/m² and > 35 kg/m² is associated with an elevated risk of 90-day mortality after major cancer surgery. However, preoperative WC was not significantly associated with 90-day mortality after cancer surgery.

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.

Observational, prospective, single-center study: Should body mass index be added to the scoring criteria of hepatic critically ill patients in the intensive care unit

BACKGROUND

Obesity has recently become more prevalent, and thus the coexistence of liver cirrhosis with obesity has become very pervasive. The purpose of this study is to investigate the correlation between abnormal body mass index (BMI) (overweight and obese) and clinical outcomes in critically ill cirrhotic patients.

METHODS

This is a single-center, prospective observational study of cirrhotic patients admitted to the intensive care unit for either medical or surgical indications in the period from February 2018 to December 2020. Patients were categorized based on their body mass index and the reason for admission to the intensive care unit (ICU).

RESULTS

The current study enrolled 517 patients; 39.3% were overweight, and 19.5% were obese (85% were class 1 and 2). Surgical subgroup analysis revealed that the hospital stay was shorter in the obese than average weight patients (p-value= 0.039), and ICU stay was shorter in overweight patients than patients with average weight (p-value= 0.022). The incidence of acute kidney injury was shorter in the obese group than in overweight and average-weight patients (p-value= 0.045). The medical subgroup analysis revealed that the need for noninvasive ventilation was lower in the obese and overweight groups than in the normal group (p-value= 0.040).

CONCLUSIONS

Despite having similar Child-Pugh (CP) and Sequential Organ Failure Assessment Score (SOFA) scores on admission, obese patients had better outcomes than non-obese patients, demonstrating the obesity paradox. Further research is required on BMI as a predictive score in a patient with critical cirrhosis as an indicator of obesity.

Operative management of acute abdomen after bariatric surgery in the emergency setting: the OBA guidelines

BACKGROUND

Patients presenting with acute abdominal pain that occurs after months or years following bariatric surgery may present for assessment and management in the local emergency units. Due to the large variety of surgical bariatric techniques, emergency surgeons have to be aware of the main functional outcomes and long-term surgical complications following the most performed bariatric surgical procedures. The purpose of these evidence-based guidelines is to present a consensus position from members of the WSES in collaboration with IFSO bariatric experienced surgeons, on the management of acute abdomen after bariatric surgery focusing on long-term complications in patients who have undergone laparoscopic sleeve gastrectomy and laparoscopic Roux-en-Y gastric bypass.

METHOD

A working group of experienced general, acute care, and bariatric surgeons was created to carry out a systematic review of the literature following the Preferred Reporting Items for Systematic Review and Meta-analysis Protocols (PRISMA-P) and to answer the PICO questions formulated after the Operative management in bariatric acute abdomen survey. The literature search was limited to late/long-term complications following laparoscopic sleeve gastrectomy and laparoscopic Roux-en-Y gastric bypass.

CONCLUSIONS

The acute abdomen after bariatric surgery is a common cause of admission in emergency departments. Knowledge of the most common late/long-term complications (&gt; 4 weeks after surgical procedure) following sleeve gastrectomy and Roux-en-Y gastric bypass and their anatomy leads to a focused management in the emergency setting with good outcomes and decreased morbidity and mortality rates. A close collaboration between emergency surgeons, radiologists, endoscopists, and anesthesiologists is mandatory in the management of this group of patients in the emergency setting.

Adipose tissue: a neglected organ in the response to severe trauma?

Despite the manifold recent efforts to improve patient outcomes, trauma still is a clinical and socioeconomical issue of major relevance especially in younger people. The systemic immune reaction after severe injury is characterized by a strong pro- and anti-inflammatory response. Besides its functions as energy storage depot and organ-protective cushion, adipose tissue regulates vital processes via its secretion products. However, there is little awareness of the important role of adipose tissue in regulating the posttraumatic inflammatory response. In this review, we delineate the local and systemic role of adipose tissue in trauma and outline different aspects of adipose tissue as an immunologically active modifier of inflammation and as an immune target of injured remote organs after severe trauma.

Volume-outcome relationships in laryngeal trauma processes of care: a retrospective cohort study

PURPOSE

The extent to which patients with laryngeal trauma undergo investigation and intervention is largely unknown. The objective of this study was to therefore determine the association between hospital volume and processes of care in patients sustaining laryngeal trauma.

METHODS

This retrospective cohort study used the American College of Surgeons Trauma Quality Improvement Program database. Adult patients (≥ 18) who sustained traumatic laryngeal injuries between 2012 and 2016 were eligible. The exposure of interest was average annual laryngeal trauma volume categorized into quartiles. The primary and secondary outcomes of interest were the performances of diagnostic and therapeutic laryngeal procedures respectively. Multivariable logistic regression under a generalized estimating equations approach was utilized.

RESULTS

In total, 1164 patients were included. The average number of laryngeal trauma cases per hospital ranged from 0.2 to 7.2 per year. Diagnostic procedures were performed in 31% of patients and therapeutic in 19%. In patients with severe laryngeal injuries, diagnostic procedures were performed on a higher proportion of patients at high volume centers than low volume centers (46% vs 25%). In adjusted analysis, volume was not associated with the performance of diagnostic procedures. Patients treated at centers in the second (OR 1.94 [95% CI 1.29-2.90]) and third (OR 1.67 [95% CI 1.08-2.57]) volume quartiles had higher odds of undergoing a therapeutic procedure compared to the lowest volume quartile.

CONCLUSION

Hospital volume may be associated with processes of care in laryngeal trauma. Additional research is required to investigate how these findings relate to patient and health system outcomes.

Utilization and in-hospital complications of catheter ablation for atrial fibrillation in patients with obesity and morbid obesity

Background

Real‐world data on atrial fibrillation (AF) ablation outcomes in obese populations have remained scarce, especially the relationship between obesity and in‐hospital AF ablation outcome.

Hypothesis

Obesity is associated with higher complication rates and higher admission trend for AF ablation.

Methods

We drew data from the US National Inpatient Sample to identify patients who underwent AF ablation between 2005 and 2018. Sociodemographic and patients' characteristics data were collected, and the trend, incidence of catheter ablation complications and mortality were analyzed, and further stratified by obesity classification.

Results

A total of 153 429 patients who were hospitalized for AF ablation were estimated. Among these, 11 876 obese patients (95% confidence interval [CI]: 11 422–12 330) and 10 635 morbid obese patients (95% CI: 10 200–11 069) were observed. There was a substantial uptrend admission, up to fivefold, for AF ablation in all obese patients from 2005 to 2018 (p < .001). Morbidly obese patients were statistically younger, while coexisting comorbidities were substantially higher than both obese and nonobese patients (p < .01) Both obesity and morbid obesity were significantly associated with an increased risk of total bleeding, and vascular complications (p < .05). Only morbid obesity was significantly associated with an increased risk of ablation‐related complications, total infection, and pulmonary complications (p < .01). No difference in‐hospital mortality was observed among obese, morbidly obese, and nonobese patients.

Conclusion

Our study observed an uptrend in the admission of obese patients undergoing AF ablation from 2005 through 2018. Obesity was associated with higher ablation‐related complications, particularly those who were morbidly obese.

Diet-induced obesity in mice impairs host defense against Klebsiella pneumonia in vivo and glucose transport and bactericidal functions in neutrophils in vitro

Obesity impairs host defense against Klebsiella pneumoniae, but responsible mechanisms are incompletely understood. To determine the impact of diet-induced obesity on pulmonary host defense against K. pneumoniae, we fed 6-wk-old male C57BL/6j mice a normal diet (ND) or high-fat diet (HFD) (13% vs. 60% fat, respectively) for 16 wk. Mice were intratracheally infected with Klebsiella, assayed at 24 or 48 h for bacterial colony-forming units, lung cytokines, and leukocytes from alveolar spaces, lung parenchyma, and gonadal adipose tissue were assessed using flow cytometry. Neutrophils from uninfected mice were cultured with and without 2-deoxy-d-glucose (2-DG) and assessed for phagocytosis, killing, reactive oxygen intermediates (ROI), transport of 2-DG, and glucose transporter (GLUT1-4) transcripts, and protein expression of GLUT1 and GLUT3. HFD mice had higher lung and splenic bacterial burdens. In HFD mice, baseline lung homogenate concentrations of IL-1β, IL-6, IL-17, IFN-γ, CXCL2, and TNF-α were reduced relative to ND mice, but following infection were greater for IL-6, CCL2, CXCL2, and IL-1β (24 h only). Despite equivalent lung homogenate leukocytes, HFD mice had fewer intraalveolar neutrophils. HFD neutrophils exhibited decreased Klebsiella phagocytosis and killing and reduced ROI to heat-killed Klebsiella in vitro. 2-DG transport was lower in HFD neutrophils, with reduced GLUT1 and GLUT3 transcripts and protein (GLUT3 only). Blocking glycolysis with 2-DG impaired bacterial killing and ROI production in neutrophils from mice fed ND but not HFD. Diet-induced obesity impairs pulmonary Klebsiella clearance and augments blood dissemination by reducing neutrophil killing and ROI due to impaired glucose transport.

Emergencies in obese patients: a narrative review

Obesity is associated to an increased risk of morbidity and mortality due to respiratory, cardiovascular, metabolic, and neoplastic diseases. The aim of this narrative review is to assess the physio-pathological characteristics of obese patients and how they influence the clinical approach during different emergency settings, including cardiopulmonary resuscitation. A literature search for published manuscripts regarding emergency and obesity across MEDLINE, EMBASE, and Cochrane Central was performed including records till January 1, 2021. Increasing incidence of obesity causes growth in emergency maneuvers dealing with airway management, vascular accesses, and drug treatment due to both pharmacokinetic and pharmacodynamic alterations. Furthermore, instrumental diagnostics and in/out-hospital transport may represent further pitfalls. Therefore, people with severe obesity may be seriously disadvantaged in emergency health care settings, and this condition is enhanced during the COVID-19 pandemic, when obesity was stated as one of the most frequent comorbidity. Emergency in critical obese patients turns out to be an intellectual, procedural, and technical challenge. Organization and anticipation based on the understanding of the physiopathology related to obesity are very important for the physician to be mentally and physically ready to face the associated issues.

The impact of BMI on morbidity and mortality after femoral fractures

Purpose

Femur fractures are the result of high energy injury and are associated with life-threatening complications. Therefore, we studied how body mass index (BMI) contributes to complications after femoral fractures.

Methods

Using the 2016 American College of Surgeons Trauma Quality Improvement Program (ACS TQIP) database, we stratified 41,362 patients into groups based on their BMI: Normal Weight (NW), Overweight (OW), Obese (OB), Severely Obese (SO), and Morbidly Obese (MO). We compared each BMI group to the NW cohort for differences in demographic factors, comorbidities, complications, and mechanism of injury.

Results

OB, SO, and MO patients sustained higher rates of traumatic injury from high energy mechanisms, such as motor vehicle trauma, in comparison to NW patients, who sustained more injuries from falls (p < 0.05). Correspondingly, obese patients were more likely than NW patients to sustain shaft and distal end fractures (p < 0.05). At hospital admission, obese patients presented with more comorbidities, such as bleeding disorders, congestive heart failure, diabetes mellitus, and hypertension (p < 0.05). Despite these individual findings, patients with OB, SO, and MO BMI, as opposed to NW BMI, were independently associated with a higher probability of developing at least one post-trauma complication. More specifically, MO patients were associated with a 45% higher odds of developing a complication (p < 0.05).

Conclusion

Irrespective of presenting with more comorbidities and sustaining high energy injuries, OB, SO, and MO patients were independently associated with having a higher risk of developing complications following a femoral fracture. Overall, better clinical outcomes are observed among patients with no underlying conditions and normal BMI.

A trauma-related survival predictive model of acute respiratory distress syndrome

Purpose

The purpose of this study was to construct and validate a simple model for the prediction of survival in patients with trauma‐related ARDS.

Methods

This is a single‐center, retrospective cohort study using MIMIC‐III Clinical Database.

Results

842 patients were included in this study. 175 (20.8%) died in‐hospital, whereas 215 (25.5%) died within 90 days. The deceased group had higher Acute Physiology Score (APS III), Sequential Organ Failure Assessment (SOFA), and Simplified Acute Physiology Score II (SAPS II). In multivariate logistic regression model, independent risk factors for mortality in ARDS patients included age ([odds ratio] OR, 1.035; 95% confidence interval [CI], 1.020–1.049), body mass index (OR, 0.957; 95% CI, 0.926–0.989), red blood cell distribution width (OR, 1.283; 95% CI, 1.141–1.443), hematocrit (OR, 1.055; 95% CI, 1.017–1.095), lactate (OR, 1.226; 95% CI, 1.127–1.334), blood urea nitrogen (OR, 1.025; 95% CI, 1.007–1.044), acute kidney failure (OR, 1.875; 95% CI, 1.188–2.959), sepsis (OR, 1.917; 95% CI, 1.165–3.153), type of admission (emergency vs. elective [OR, 2.822; 95% CI, 1.647–4.837], and urgent vs. elective [OR, 5.156; 95% CI, 1.896–14.027]). The area under the curve (AUC) of the model was 0.826, which was superior than the SAPS II (0.776), APS III (0.718), and SOFA (0.692). In the cross‐validation model, the accuracy of the test set was 0.823, the precision was 0.643, and the AUC was 0.813.

Conclusions

We established a prediction model using data commonly used in the clinic, which has high accuracy and precision and is worthy of use in clinical practice.

"Obesity Paradox" in Acute Respiratory Distress Syndrome Among Patients Undergoing Cardiac Surgery: A Retrospective Study

Background

The “obesity paradox” exists in many diseases. It is unclear whether it also exists in acute respiratory distress syndrome (ARDS). The purpose of our study was to clarify the relationship between obesity and the development of and hospital mortality from ARDS among patients who underwent cardiac surgery.

Material/Methods

This retrospective case-control study included 202 patients with ARDS and 808 matching patients without ARDS. We clarified the relationship between obesity and the development of ARDS after adjusting for confounding factors by multiple logistic regression analysis. A total of 202 ARDS patients were divided into survival and mortality groups. After all confounding factors were adjusted by multiple logistic regression analysis, we demonstrated the relationship between obesity and mortality from ARDS.

Results

We found a significant association between body mass index (BMI) and the development of ARDS; the cutoff point of BMI was 24.78 kg/m² by adjusting for confounding factors for the development of ARDS. When the BMI was lower than 24.78 kg/m², the higher BMI was a protective factor (odds ratio [OR] 0.68, P=0.000, 95% confidence interval [CI] 0.55–0.84). When the BMI was higher than 24.78 kg/m², the higher BMI was a risk factor (OR 1.07, P=0.050, 95% CI 1.00–1.14). However, obesity was found to be associated with decreased ARDS mortality by adjusting for confounding factors (OR 0.91, P=0.039, 95% CI 0.83–1.00).

Conclusions

An “obesity paradox” may exist in ARDS among patients with obesity who undergo cardiac surgery.

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.

Impact of obesity on outcomes in patients with acute respiratory syndrome

Objectives

We assessed the relationship between obesity and all-cause mortality in patients with acute respiratory distress syndrome (ARDS).

Methods

In this retrospective cohort study, patient data were extracted from the eICU Collaborative Research Database and the Medical Information Mart for Intensive Care Database III. Body mass index (BMI) was grouped according to World Health Organization classifications: underweight, normal weight, overweight, obese. Cox regression models estimated hazard ratios (HRs) and 95% confidence intervals (CIs) of all-cause mortality related to obesity.

Results

Participants included 185 women and 233 men, mean age 70.7 ± 44.1 years and mean BMI 28.7 ± 8.1 kg/m². Compared with normal weight patients, obese patients tended to be younger (60.1 ± 13.7 years) and included more women (51.3% vs. 49.0%). In the unadjusted model, HRs (95% CIs) of 30-day mortality for underweight, overweight, and obesity were 1.57 (0.76, 3.27), 0.64 (0.39, 1.08), and 4.83 (2.25, 10.35), respectively, compared with those for normal weight. After adjustment, HRs (95% CIs) of 30-day mortality for underweight, overweight, and obesity were 1.82 (0.85, 3.90), 0.59 (0.29, 1.20), and 3.85 (1.73, 8.57), respectively, compared with the reference group; 90-day and 1-year all-cause mortalities showed similar trends.

Conclusions

Obesity was associated with increased all-cause mortality in patients with ARDS.

Morbidity and Mortality in the Obese Trauma Intensive Care Unit Patient

INTRODUCTION

Obesity is an epidemic in the United States, known to be associated with comorbidities. However, some data show that obesity may be a protective factor in some instances. The purpose of this study is to determine if there are differences in morbidity and mortality when comparing the obese and non-obese critically ill trauma patient populations.

MATERIALS AND METHODS

This was a retrospective study conducted at Prisma Health Upstate in Greenville, South Carolina, an Adult Level 1 Trauma Center. Patients over the age of 18 years admitted due to trauma from February 6, 2016 to February 28, 2019 were included in this study. Burn patients were excluded. An online trauma database was used to obtain age, sex, body mass index, Glasgow coma score (GCS), injury severity score (ISS), revised trauma score (RTS), days on mechanical ventilation, hospital length of stay (LOS), and intensive care unit (ICU) LOS.

RESULTS

There were 2365 critically ill trauma patients who met inclusion criteria for this study. 1570 patients were men (66.38%) and mean age was 53.2 ± 20.9. Of the patients, 2166 patients had blunt trauma (91.59%). Median GCS was 15 (interquartilerange [IQR]: 12, 15), median RTS was 12 (IQR: 11, 12), and median ISS was 17 (IQR: 9, 22). Obese critically ill trauma patients had significantly lower odds of mortality than nonobese (OR .686, CI 0.473-.977). Penetrating traumas (OR: 4.206, CI: 2.478, 6.990), increased ISS (OR: 1.095, CI: .473, 1.112), and increased age (OR: 1.036, CI: 1.038, 1.045) were associated with significantly increased odds of mortality.

DISCUSSION

The obesity paradox is observed in the obese critically ill trauma patient population.

Fibrinogen level at hospital admission after multiple injury correlates with BMI and is negatively associated with the need for transfusion and early multiple organ failure

INTRODUCTION

Bleeding and coagulopathy are leading causes of morbidity and lethal outcome after multiple injuries. The pathophysiology of traumatic coagulopathy is under extensive investigations and recent results highlighted the central role of fibrinogen and the fibrin polymerisation process. Our goal was to investigate the factors influencing fibrinogen level and the consequences of hypofibrinogenaemia with clinical importance.

METHODS

We conducted a retrospective analysis enrolling adult patients admitted to the shock room of a tertiary trauma centre in Hungary. Beside coagulation values, demographic data, injury related, transfusion and outcome parameters were collected from the hospital electronic charts. Only patients with complete e-chart were involved into final analysis. Multivariate linear and proportional odds logistic regression models were used to model outcomes - admission fibrinogen and SOFA score - controlling for age, sex, BMI, ISS and lactic acidosis.

RESULTS

54 patients were enrolled in final analysis. Among the parameters analysed, BMI was positively associated with fibrinogen level at admission (+0.23 g/l for every 5 unit of increase in BMI, 95% CI: 0.09-0.37, p=0.0021). Increased risk of transfusion was observed, if fibrinogen at admission was about 1.8 g/l or lower. Beside age and ISS, fibrinogen concentration was also a determinant of early organ failures as it negatively correlated with SOFA scores within 24 hours or care (OR=2.42, 95% CI: 1.05-5.62, for 1 g/l decrease, p=0.0388).

CONCLUSIONS

In our trauma cohort BMI seems to significantly influence fibrinogen level at admission. This result draws our attention to the possible differences of haemostasis process, and consequently different diagnostic and therapeutic thresholds in the management of obese trauma patients. Moderate hypofibrinogenaemia increases transfusion risk and beside ISS might be a prognostic factor of early MOF after multiple injuries.

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

Prevalence and Predictive Factors for Nosocomial Infection in the Military Hospitals: A Systematic Review and Meta-Analysis

Background:

To assess prevalence and predictive factors for Nosocomial Infection (NI) in the military hospitals.

Methods:

PubMed, Scopus, Cochrane and PreQuest databases were systematically searched for studies published between Jan 1991 and Oct 2017 that reported the prevalence of NI and predictive factors among military hospitals. We performed the meta-analysis using a random effects model. Subgroup analysis was done for heterogeneity and the Egger test to funnel plots was used to assess publication bias.

Results:

Twenty-eight studies with 250,374 patients were evaluated in meta-analysis. The overall pooled estimate of the prevalence of NI was 8% (95% 6.0–9.0). The pooled prevalence was 2% (95% CI: 2.0–3.0) when we did sensitivity analysis and excluding a study. The prevalence was highest in burn unit (32%) and ICU (15%). Reported risk factors for NI included gender (male vs female, OR: 1.45), age (Age≥65, OR: 2.4), diabetes mellitus (OR: 2.32), inappropriate use of antibiotics (OR: 2.35), received mechanical support (OR: 2.81), co-morbidities (OR: 2.97), admitted into the ICU (OR: 2.26), smoking (OR: 1.36) and BMI (OR: 1.09).

Conclusion:

The review revealed a difference of prevalence in military hospitals with other hospitals and shows a high prevalence of NI in burn units. Therefore careful disinfection and strict procedures of infection control are necessary in places that serve immunosuppressed individuals such as burn patient. Moreover, a vision for the improvement of reports and studies in military hospitals to report the rate of these infections are necessary.

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.

The Crashing Obese Patient

The obesity pandemic now affects hundreds of millions of people worldwide. As obesity rates continue to increase, emergency physicians are called on with increasing frequency to resuscitate obese patients. This article discusses important anatomic, physiologic, and practical challenges imposed by obesity on resuscitative care. Impacts on hemodynamic monitoring, airway and ventilator management, and pharmacologic therapy are discussed. Finally, several important clinical scenarios (trauma, cardiac arrest, and sepsis), in which alterations to standard treatments may benefit obese patients, are highlighted.

Blunt Versus Penetrating Neck Trauma: A Retrospective Cohort Study

OBJECTIVES/HYPOTHESIS

Despite being common, neck injuries have received relatively little attention for important quality of care metrics. This study sought to determine the association between blunt and penetrating neck injuries on mortality and length of stay, and to identify additional patient and hospital-level characteristics that impact these outcomes.

STUDY DESIGN

Retrospective cohort study utilizing the American College of Surgeons Trauma Quality Improvement Program database.

METHODS

Adult patients (≥18) who sustained traumatic injuries involving the soft tissues of the neck between 2012 and 2016 were eligible. Multiple imputation was used to account for missing data. Logistic regression and negative binomial models were used to analyze 1) in-hospital mortality and 2) length of stay respectively while adjusting for potential confounders and accounting for clustering at the hospital level.

RESULTS

In a cohort of 20,285 patients, the crude mortality rate was lower in those sustaining blunt neck injuries compared to penetrating injuries (4.9% vs. 6.0%, P < .01), while length of hospital stay was similar (median 9.9 vs. 10.2, P = 0.06). In adjusted analysis, blunt neck injuries were associated with a reduced odds of mortality during hospital admission (odds ratio: 0.66, 95% confidence intervals [0.564, 0.788]), as well as significant reductions in length of stay (rate ratio: 0.92, 95% confidence intervals [0.880, 0.954]).

CONCLUSIONS

Blunt neck injuries are associated with lower mortality and length of stay compared to penetrating injuries. Areas of future study have been identified, including elucidation of processes of care in specific organs of injury.

LEVEL OF EVIDENCE

Level 3 Laryngoscope, 131:E1109-E1116, 2021.

The effect of body mass index on outcomes following severe blunt chest trauma

INTRODUCTION

Obesity has been described as a significant risk factor for adverse outcomes in hospitalized patients. However, recent literature reports an "obesity paradox", suggesting that obesity may have a protective effect in a subset of surgical and critically ill patients. The present study assesses the effect of body mass index (BMI) on outcomes following severe isolated blunt chest trauma.

METHODS

This was a TQIP database study including patients with severe isolated blunt chest injury (chest AIS 3-5, extrathoracic AIS <3). Patients were excluded for age <20 or >89, death on arrival, facility transfer, or BMI <10 or >55. Patients were divided into five groups according to BMI: underweight (BMI <18.5), normal weight (18.5-24.9), overweight (25.0-29.9), obesity class 1 (30.0-34.9), obesity class 2 (35.0-39.9) and obesity class 3 (≥40.0). Logistic regression models were constructed to evaluate the effect of BMI on outcomes.

RESULTS

28,820 patients met criteria for inclusion in the analysis. After multivariable analysis, underweight patients as well as obesity class 2 and 3 patients had a significantly higher mortality (OR 1.86 [95% CI, 1.12-3.10], OR 1.48 [95% CI, 1.02-2.16], and OR 1.60 [95% CI, 1.03-2.50]), respectively. Underweight patients had significantly higher risk of overall complications as compared to normal weight patients (OR 1.58 [95% CI, 1.34-1.88]). Obesity class 2 and 3 were independently associated with increased respiratory complications (OR 1.60 [95% CI, 1.27-2.01] and OR 1.58 [95% CI, 1.20-2.09], respectively) and all classes of overweight and obese patients were associated with increased risk of VTE complications (OR 1.68 [95% CI, 1.23-2.27], OR 1.98 [95% CI, 1.42-2.77], OR 2.32 [95% CI, 1.55-3.48], OR 2.02 [95% CI, 1.23-3.33], respectively for overweight and obesity class 1, 2, 3).

CONCLUSIONS

The obesity paradox does not extend to severe blunt chest trauma. Underweight and obesity class 2 and 3 patients have worse mortality than normal weight patients. Obesity was independently associated with an increased risk of pulmonary and VTE complications.

Obesity is not associated with increased difficulty placing peripheral IVs in trauma activation patients

INTRODUCTION

Previous studies have identified obesity as a risk factor for difficult IV access, but this has not been studied in the acute trauma setting. The primary objective was to determine if obesity is associated with increased difficulty placing peripheral IVs in trauma patients. Secondary analysis evaluated IV difficulty and associations with nursing self-competence ratings, trauma experience, and patient demographics.

METHODS

Prospective, observational study at academic level I trauma center with 58,000 annual visits. Trauma activation patients between January and October of 2016 were included. Each nurse who attempted IV placement, completed anonymous 7 question survey, including trauma experience (years), self-competence and IV difficulty (Likert scales 1-5), and attempts. Demographic and clinical information was retrospectively collected from the EMR and nursing surveys. Descriptive statistics, chi-square tests, and spearman correlations were used.

RESULTS

200 patients included in the study with 185 BMI calculations. 110 overweight (BMI > 25) and 48 obese (BMI > 30). 70 (35%) female, 149 (75%) white, average age 48. Increased BMI and IV difficulty displayed spearman correlation (ρ) of 0.026 (P = 0.72) suggesting against significant association. Increased trauma experience and self-competence ratings significantly correlated with decreased IV difficulty, ρ = -0.173 and -0.162 (P = 0.010 and 0.014). There was no statistically significant association with IV difficulty in regards to patient race, age, sex, or location of IV placement.

CONCLUSION

Obesity was not associated with increased difficulty in placing peripheral IVs in trauma activation patients. Nurses with greater trauma experience and higher self-competence ratings, had less difficulty inserting IVs.

Isolated severe blunt traumatic brain injury: effect of obesity on outcomes

OBJECTIVE

Obesity has been widely reported to confer significant morbidity and mortality in both medical and surgical patients. However, contemporary data indicate that obesity may confer protection after both critical illness and certain types of major surgery. The authors hypothesized that this "obesity paradox" may apply to patients with isolated severe blunt traumatic brain injuries (TBIs).

METHODS

The Trauma Quality Improvement Program (TQIP) database was queried for patients with isolated severe blunt TBI (head Abbreviated Injury Scale [AIS] score 3-5, all other body areas AIS < 3). Patient data were divided based on WHO classification levels for BMI: underweight (< 18.5 kg/m2), normal weight (18.5-24.9 kg/m2), overweight (25.0-29.9 kg/m2), obesity class 1 (30.0-34.9 kg/m2), obesity class 2 (35.0-39.9 kg/m2), and obesity class 3 (≥ 40.0 kg/m2). The role of BMI in patient outcomes was assessed using regression models.

RESULTS

In total, 103,280 patients were identified with isolated severe blunt TBI. Data were excluded for patients aged < 20 or > 89 years or with BMI < 10 or > 55 kg/m2 and for patients who were transferred from another treatment center or who showed no signs of life upon presentation, leaving data from 38,446 patients for analysis. Obesity was not found to confer a survival advantage on univariate analysis. On multivariate analysis, underweight patients as well as obesity class 1 and 3 patients had a higher rate of mortality (OR 1.86, 95% CI 1.48-2.34; OR 1.18, 95% CI 1.01-1.37; and OR 1.41, 95% CI 1.03-1.93, respectively). Increased obesity class was associated with an increased risk of respiratory complications (obesity class 1: OR 1.19, 95% CI 1.03-1.37; obesity class 2: OR 1.30, 95% CI 1.05-1.62; obesity class 3: OR 1.55, 95% CI 1.18-2.05) and thromboembolic complications (overweight: OR 1.43, 95% CI 1.16-1.76; obesity class 1: OR 1.45, 95% CI 1.11-1.88; obesity class 2: OR 1.55, 95% CI 1.05-2.29) despite a decreased risk of overall complications (obesity class 2: OR 0.82, 95% CI 0.73-0.92; obesity class 3: OR 0.83, 95% CI 0.72-0.97). Underweight patients had a significantly increased risk of overall complications (OR 1.39, 95% CI 1.24-1.57).

CONCLUSIONS

Although there was an obesity-associated decrease in overall complications, the study data did not demonstrate a paradoxical protective effect of obesity on mortality after isolated severe blunt TBI. Obese patients with isolated severe blunt TBI are at increased risk of respiratory and venous thromboembolic complications. However, underweight patients appear to be at highest risk after severe blunt TBI, with significantly increased risks of morbidity and mortality.

Obesity associated with increased postoperative pulmonary complications and mortality after trauma laparotomy

Background

Patient-related risk factors for the development of postoperative pulmonary complications (PPCs) include age ≥ 60-years, congestive heart failure, hypoalbuminemia and smoking. The effect of obesity is unclear and has not been shown to independently increase the likelihood of PPCs in trauma patients undergoing trauma laparotomy. We hypothesized the likelihood of mortality and PPCs would increase as body mass index (BMI) increases in trauma patients undergoing trauma laparotomy.

Methods

The Trauma Quality Improvement Program (2010–2016) was queried to identify trauma patients ≥ 18-years-old undergoing trauma laparotomy within 6-h of presentation. A multivariable logistic regression analysis was used to determine the likelihood of PPCs and mortality when stratified by BMI.

Results

From 8,330 patients, 2,810 (33.7%) were overweight (25–29.9 kg/m²), 1444 (17.3%) obese (30–34.9 kg/m²), 580 (7.0%) severely obese (35–39.9 kg/m²), and 401 (4.8%) morbidly obese (≥ 40 kg/m²). After adjusting for covariates including age, injury severity score, chronic obstructive pulmonary disease, smoking, and rib/lung injury, the likelihood of PPCs increased with increasing BMI: overweight (OR = 1.37, CI 1.07–1.74, p = 0.012), obese (OR = 1.44, CI 1.08–1.92, p = 0.014), severely obese (OR = 2.20, CI 1.55–3.14, p < 0.001), morbidly obese (OR = 2.42, CI 1.67–3.51, p < 0.001), compared to those with normal BMI. In addition, the adjusted likelihood of mortality increased for the morbidly obese (OR = 2.60, CI 1.78–3.80, p < 0.001) compared to those with normal BMI.

Conclusion

Obese trauma patients undergoing emergent trauma laparotomy have a high likelihood for both PPCs and mortality, with morbidly obese trauma patients having the highest likelihood for both. This suggests obesity should be accounted for in risk prediction models of trauma patients undergoing laparotomy.

Electronic supplementary material

The online version of this article (10.1007/s00068-020-01329-w) contains supplementary material, which is available to authorized users.

Risk factors of nosocomial infection after cardiac surgery in children with congenital heart disease

Background

The aim of our study was to analyze the risk factors of nosocomial infection after cardiac surgery in children with congenital heart disease (CHD).

Methods

We performed a retrospective cohort study, and children with CHD who underwent open-heart surgeries at Shanghai Children’s Medical Center from January 1, 2012 to December 31, 2018 were included. The baseline characteristics of these patients of different ages, including neonates (0–1 months old), infants (1–12 months old) and children (1–10 years old), were analyzed, and the association of risk factors with postoperative nosocomial infection were assessed.

Results

A total of 11,651 subjects were included in the study. The overall nosocomial infection rate was 10.8%. Nosocomial infection rates in neonates, infants, and children with congenital heart disease were 32.9, 15.4, and 5.2%, respectively. Multivariate logistic regression analysis found age (OR 0798, 95%CI: 0.769–0.829; P < 0.001), STS risk grade (OR 1.267, 95%CI: 1.159–1.385; P < 0.001), body mass index (BMI) <5th percentile (OR 1.295, 95%CI: 1.023–1.639; P = 0.032), BMI >95th percentile (OR 0.792, 95%CI: 0.647–0.969; P = 0.023), cardiopulmonary bypass (CPB) time (OR 1.008, 95%CI: 1.003–1.012; P < 0.001) and aortic clamping time (OR 1.009, 1.002–1.015; P = 0.008) were significantly associated with nosocomial infection in CHD infants. After adjusted for confounding factors, we found STS risk grade (OR 1.38, 95%CI: 1.167–1.633; P < 0.001), BMI < 5th percentile (OR 1.934, 95%CI: 1.377–2.715; P < 0.001), CPB time (OR 1.018, 95%CI: 1.015–1.022; P < 0.001), lymphocyte/WBC ratio<cut off value (OR 3.818, 95%CI: 1.529–9.533; P = 0.004) and AST>cut off value (OR 1.546, 95%CI: 1.119–2.136; P = 0.008) were significantly associated with nosocomial infection in CHD children.

Conclusion

Our study suggested STS risk grade, BMI, CPB duration, low lymphocyte/WBC or high neutrophil/WBC ratio were independently associated with nosocomial infection in CHD infant and children after cardiac surgery.

Obesity May Not be Protective in Abdominal Stab Wounds

Context:

Current protocols for the management of abdominal stab wounds were established based on retrospective data from prior decades. Few have investigated whether higher body mass index (BMI) affects outcomes after these injuries.

Aim:

The aim was to determine the effects of obesity on outcomes in abdominal stab wound patients.

Setting and Design:

This was a retrospective cohort study at a Level I university-associated trauma center in the United States.

Materials and Methods:

We reviewed medical records of 100 adult patients admitted to our trauma center with abdominal stab wounds. Demographics, types of internal organ injury, gastrointestinal (GI) resection and repair, mortality, length of hospital stay (LOS), units of blood transfused within 24 h of admission, need and indications for exploratory laparotomy, surgical site infections (SSI), and need for re-operation were compared between obese and nonobese patients.

Statistical Analysis:

Categorical and continuous outcome variables were compared between the two groups using Chi-squared and independent-samples t-tests, respectively. BMI was evaluated as a predictor of outcomes using univariate and multivariate logistic regression.

Results:

Records of 100 adult abdominal stab wound patients were reviewed. Twenty-five patients were obese. The obese group was older (38.76 vs. 31.23, P = 0.018). Rates of therapeutic laparotomy were similar between obese and nonobese patients (20 [80.00%] vs. 64 [85.33%]). Obesity was associated with longer LOS (9.6 vs. 6.5, P = 0.026). In the multivariate analysis, increasing BMI was an independent predictor of need for GI resection (odds ratio: 1.10 [1.02–1.18], P = 0.018). One patient from the obese group died.

Conclusions:

Obese patients with abdominal stab wounds have longer LOS than nonobese patients. Increasing BMI was an independent predictor of need for GI resection.

The impact of obesity on severity of solid organ injury in the adult population at a Level I trauma center

Background

The obese (body mass index, BMI > 30) have been identified as a subgroup of patients in regards to traumatic injuries. A recent study found that high-grade hepatic injuries were more common in obese than non-obese pediatric patients. This study seeks to evaluate whether similar differences exist in the adult population and examine differences in operative versus non-operative management between the obese and non-obese in blunt abdominal trauma.

Methods

Patient with trauma evaluated at an American College of Surgeons verified Level I trauma center from February 2013 to November 2016 were retrospectively reviewed. All patients aged >18 years with blunt mechanism of injury and a BMI listed in the trauma registry were included. Patients were excluded for incomplete data, including BMI or inability to grade hepatic or splenic injury. Data collected included age, gender, BMI, injury severity score, hospital length of stay, procedures on liver or spleen, and mortality. Organ injuries were scored using the American Association for the Surgery of Trauma grading scales, and were determined by either imaging or intraoperative findings. Obesity was classified as BMI > 30 compared with non-obese with BMI < 30.

Results

During the study period, 9481 patients were included. There were 322 spleen injuries and 237 liver injuries, with 64 patients sustaining both liver and splenic injuries. No differences existed in the percentage of high-grade hepatic or splenic injuries between the obese and non-obese. Obese patients with liver injuries were more likely to have procedural intervention than non-obese liver injuries and had higher rates of mortality. No differences were found in intervention for splenic injury between obese and non-obese.

Conclusions

Contrary to prior studies on adult and pediatric patients with trauma, this study found no difference between obese and non-obese patients in severity of solid organ injury after blunt abdominal trauma in the adult population. However, there was an increased rate of procedural intervention and mortality for obese patients with liver injuries.

Level of Evidence

3.

Surgical Site Infection Prevention Bundle in Cardiac Surgery

Background

Surgical site infections (SSI) are among the most prevalent infections in healthcare institutions, attributing a risk of death which varies from 33% to 77% and a 2- to 11-fold increase in risk of death. Patients submitted to cardiac surgery are more susceptible to SSI, accounting for 3.5% to 21% of SSI. The mortality rate attributable to these causes is as high as 25%. Prevention of SSI in cardiac surgery is based on a bundle of preventive measures, which focus on modifiable risks.

Objective

The objective of this study was to identify SSI risk factors in clean cardiac surgery.

Methods

A retrospective cohort study analyzed 1,846 medical records from patients who underwent clean cardiac surgery. Fisher’s exact test was used for bivariate comparison, and Poisson regression was used for independent analysis of SSI risk, considering a significance level of p < 0.05.

Results

The results of the study comprised a multivariate analysis. The variables that were associated with the diagnosis of SSI were: surgical risk index (OR: 2.575; CI: 1.224-5.416), obesity (OR: 2.068; CI: 1.457-2.936), diabetes mellitus (OR: 1,678; CI: 1.168-2.409), and blood glucose level (OR: 1.004; CI: 1.001-1.007).

Conclusions

This study evidenced that complete adherence to the bundle was not associated with a reduction in the risk of surgical infections. Diabetes mellitus, obesity, and surgical risk index assessment were, however, identified to increase association and consequently risk of SSI in cardiac surgery.

The effects of cryopreserved red blood cell transfusion on tissue oxygenation in obese trauma patients

BACKGROUND

Low tissue oxygenation (StO2) is associated with poor outcomes in obese trauma patients. A novel treatment could be the transfusion of cryopreserved packed red blood cells (CPRBCs), which the in vitro biochemical profile favors red blood cell (RBC) function. We hypothesized that CPRBC transfusion improves StO2 in obese trauma patients.

METHODS

Two hundred forty-three trauma patients at five Level I trauma centers who required RBC transfusion were randomized to receive one to two units of liquid packed RBCs (LPRBCs) or CPRBCs. Demographics, injury severity, StO2, outcomes, and biomarkers of RBC function were compared in nonobese (body mass index [BMI] < 30) and obese (BMI ≥ 30) patients. StO2 was also compared between obese patients with BMI of 30 to 34.9 and BMI ≥ 35. StO2 was normalized and expressed as % change after RBC transfusion. A p value less than 0.05 indicated significance.

RESULTS

Patients with BMI less than 30 (n = 141) and BMI of 30 or greater (n = 102) had similar Injury Severity Score, Glasgow Coma Scale, and baseline StO2. Plasma levels of free hemoglobin, an index of RBC lysis, were lower in obese patients after CPRBC (125 [72-259] μg/mL) versus LPRBC transfusion (230 [178-388] μg/mL; p < 0.05). StO2 was similar in nonobese patients regardless of transfusion type, but improved in obese patients who received CPRBCs (104 ± 1%) versus LPRPCs (99 ± 1%, p < 0.05; 8 hours after transfusion). Subanalysis showed improved StO2 after CPRBC transfusion was specific to BMI of 35 or greater, starting 5 hours after transfusion (p < 0.05 vs. LPRBCs). CPRBCs did not improve clinical outcomes in either group.

CONCLUSION

CPRBC transfusion is associated with increased StO2 and lower free hemoglobin levels in obese trauma patients, but did not improve clinical outcomes. Future studies are needed to determine if CPRBC transfusion in obese patients attenuates hemolysis to improve StO2.

LEVEL OF EVIDENCE

Therapeutic, level IV.

Impact of body mass index on outcomes after thoracic trauma-A matched-triplet analysis of the TraumaRegister DGU®

INTRODUCTION

Chest trauma and obesity are both associated with increased risks for respiratory complications (e.g. hypoxia, hypercarbia, pneumonia), which are frequent causes of posttraumatic morbidity and mortality. However, as there is only limited and inconsistent evidence, the aim of our study was to analyse the effect of body mass index (BMI) on patient outcomes after thoracic trauma.

PATIENTS AND METHODS

We screened 50.519 patients entered in TraumaRegister DGU^®, between 2004-2009, when the BMI was part of the standardized dataset. After matching for injury patterns and severity of trauma we performed a matched tripled analysis with regard to the BMI (group 1: <25.0 kg/m²; group 2: 25.0-29.9 kg/m²; group 3: >30.0 kg/m²). Data are shown as percentages and mean values with standard deviation.

RESULTS

The matching process yielded a cohort of 828 patients with serious blunt thoracic trauma, evenly distributed over the 3 BMI groups (276 triplets). BMI did not have an impact on the need for prehospital or emergency department interventions. There was a trend towards more liberal use of whole-body-CT scanning with increasing BMI (group 1: 68.8%; group 2: 73.2%; group 3: 75.0%). Additional abdominal injuries were more common in normal weight patients (Group 1: 28.3%; Group 2: 14.9%; Group 3: 17.8%). Obesity (BMI > 30.0 kg/m²) had a significant impact on the duration of mechanical ventilation (in days; group 1: 6.5 (9.4); group 2: 6.4 (8.9); group 3: 9.1 (14.4); p = 0.002), ICU days (in days; group 1: 11.5 (11.5); group 2: 10.9 (9.6); group 3: 14.1 (16.7); p = 0.005) and hospital length of stay (in days; group 1: 27.8 (19.3); group 2: 27.4 (19.2); group 3: 32.2 (25.9); p = 0.009). There were no significant differences regarding overall mortality (group 1: 3.6%; group 2: 1.8%; group 3: 4.0%; p = 0.26).

CONCLUSIONS

Obesity has a negative impact on outcomes after blunt chest trauma, as it is associated with prolonged duration of mechanical ventilation, ICU and hospital length of stay. Mortality did not seem to be affected, yet, further research is required to confirm these results in a larger cohort.

The Weighty Issue: The Impact of Body Mass Index (BMI) in Asian Trauma Patients

Background

The controversy surrounding the impact of Body Mass Index (BMI) on the outcome of trauma patients has been widely studied in the West. However, no such studies have looked at an Asian trauma population. The aim of our study was to investigate the impact of BMI on mortality, morbidity, severity and pattern of injury in trauma patients of multicultural Singapore.

Methods

In this prospective study, we recruited all trauma patients admitted to Tan Tock Seng Hospital over a 13 month period. Both the international World Health Organization (WHO) and Asian modified classifications of BMI were used for the purpose of our study. Patient demographics, co-morbidities, mechanism of injury, injury severity score (ISS), body regions injured, morbidity and mortality were collected using inpatient medical records.

Results

964 patients with a mean age of 50.5 years were recruited. Majority of injuries sustained were due to falls. There was no association between Asian BMI and ISS. Head, neck and cervical injuries occurred less commonly in the overweight and obese group, but BMI does not confer protection from truncal injury. BMI was not a significant risk factor for morbidity or mortality.

Conclusion

Being overweight does not appear to increase severity of injury in Asian trauma patients. BMI as an independent risk factor does not contribute to trauma mortality or morbidity. We conclude that BMI is not a significant contributing factor to adverse trauma outcomes in Asians.

Prevalence of cardiovascular and respiratory complications following trauma in patients with obesity

BACKGROUND

It is generally accepted that obesity puts patients at an increased risk for cardiovascular and respiratory complications after surgical procedures. However, in the setting of trauma, there have been mixed findings in regards to whether obesity increases the risk for additional complications.

OBJECTIVE

The aim of this study was to identify whether obese patients suffer an increased risk of cardiac and respiratory complications following traumatic injury.

METHODS

A retrospective analysis of 275,393 patients was conducted using the 2012 National Trauma Data Bank. Hierarchical regression modeling was performed to determine the probability of experiencing a cardiac or respiratory complication.

RESULTS

Patients with obesity were at a significantly higher risk of cardiac and respiratory complications compared to patients without obesity [OR: 1.81; CI: 1.72-1.91]. Prevalence of cardiovascular and respiratory complications for patients with obesity was 12.6% compared to 5.2% for non-obese patients.

CONCLUSIONS

Obesity is predictive of an increased risk for cardiovascular and respiratory complications following trauma.

Body Mass Index >35 as Independent Predictor of Mortality in Severe Traumatic Brain Injury

OBJECTIVE

Severe traumatic brain injury (TBI) has a major influence on polytrauma outcome. The aim of this study was to evaluate the impact of body mass index (BMI) on mortality and early neurologic outcome in patients suffering from severe TBI with a special focus on obesity classes II and III (BMI ≥35).

METHODS

A retrospective cohort analysis of patients suffering from a leading, at least severe TBI and registered in the TraumaRegister DGU was conducted. Patients alive on admission with full status documentation on Glasgow Coma Scale, height, and weight were classified into 4 BMI subgroups. Early neurologic outcome was classified using the Glasgow Outcome Scale.

RESULTS

A total of 1634 patients met the inclusion criteria. Lowest mortality was documented for BMI group 1 (15.2%, BMI 25.0-29.9918.5). Highest mortality was found in BMI group 5 (25.6%, BMI ≥35). BMI ≥35 was an independent predictor of mortality with an odds ratio of 3.15 (95% confidence interval [1.06-9.36], P = 0.039). Further independent mortality predictors were >65 years of age, a Glasgow Coma Scale of ≤13, an Abbreviated Injury Scale_head ≥5, prehospital cardiopulmonary resuscitation, and a prehospital blood pressure of <90 mm Hg. In terms of good early neurologic outcomes, no differences were recorded between the BMI groups (range 59.0%-62.6%, P = 0.087).

CONCLUSIONS

In this study a BMI ≥35 is an independent predictor of mortality and is associated with an inferior early functional neurologic outcome.

Adipose tissue location and contribution to postinjury hypercoagulability

OBJECTIVES

Obesity is associated with a hypercoagulable state at baseline and following injury. The anatomic location of adipose deposition may influence the type of thrombotic event, with visceral adipose tissue (VAT) associated with arterial thrombosis and subcutaneous adipose tissue (SAT) predisposing to venous thrombosis. We sought to determine whether adipose tissue amount and location correlated with measures of coagulation.

METHODS

All adult Level I trauma activations at our institution between January 2013 and August 2014 who underwent admission abdominal computed tomography scan and had admission rotational thromboelastometry measurements were included. Patients were excluded for history of anticoagulant use and known coagulopathy/hypercoagulable state. Admission computed tomography was used to obtain cross-sectional VAT and SAT areas at the umbilicus utilizing a novel software system; VAT and SAT measurements were associated with markers of coagulation utilizing Spearman correlation and stepwise linear regression with significance set at p < 0.05.

RESULTS

Two hundred forty-two patients met inclusion and exclusion criteria. Sixty-nine percent of patients sustained blunt injury, 79% were male, mean age was 40 years, 25% were obese or morbidly obese, and mean Injury Severity Scale score was 17. Seventeen percent of patients had acute deep venous thrombosis or pulmonary embolism during hospitalization. Neither SAT nor VAT correlated with prothrombin time, international normalized ratio, or partial thromboplastin time. Subcutaneous adipose tissue correlated positively with platelet count. Visceral adipose tissue and SAT correlated negatively with clot formation time and positively with TEM fibrinogen, α angle, maximum clot firmness, and lysis at 30 minutes; stronger correlations and greater significance were seen between SAT and these measures except for lysis at 30 minutes. Stepwise linear regression confirmed significant relationships between SAT and clot formation time, AA, and maximum clot firmness; VAT showed a significant relationship with TEM fibrinogen.

CONCLUSIONS

Increased adipose tissue correlates with relative hypercoagulability following trauma. Subcutaneous adipose tissue shows a stronger relationship with functional measures of coagulation, suggesting that SAT may be associated with hemorrhage resistance and hypercoagulability after injury.

LEVEL OF EVIDENCE

Prognostic study, level IV.

Evaluation of external pressure to the sacral region in the lithotomy position using the noninvasive pressure distribution measurement system

BACKGROUND

Pressure ulcers (PUs) in the sacral region can be a complication of surgical procedures performed in the lithotomy position. Previous reports have noted a difference between men and women in PU development related to the supine position, and body weight and body mass index (BMI) have been also described as known risk factors in supine position-related PU development. The BIG-MAT^® system is a noninvasive pressure distribution measurement device used to measure external pressure (EP). We used this system to investigate the relationship between EP to the sacral region in the lithotomy position and selected physical characteristics.

METHODS

We recruited 21 young, healthy volunteers (11 men and 10 women, aged 21.4±0.5 years). Using the BIG-MAT system, we measured four types of EP to the sacral region: box pressure, peak box pressure, contact pressure, and peak contact pressure. We analyzed the relationships between these dynamic parameters and physical characteristics of the participants.

RESULTS

There were no differences between men and women in the four types of EP, and no significant differences related to the participants' height, weight, or BMI.

CONCLUSION

An individual's height, weight, and BMI may not contribute to the risk of inducing lithotomy position-related PUs in the sacral region. The noninvasive pressure distribution measurement system BIG-MAT for patients in the lithotomy position during surgery could become a significant device when estimating EP at the sacral region.

Trauma injury in adult underweight patients: A cross-sectional study based on the trauma registry system of a level I trauma center

The aim of this study was to investigate and compare the injury characteristics, severity, and outcome between underweight and normal-weight patients hospitalized for the treatment of all kinds of trauma injury.This study was based on a level I trauma center Taiwan.The detailed data of 640 underweight adult trauma patients with a body mass index (BMI) of <18.5 kg/m and 6497 normal-weight adult patients (25 > BMI ≥ 18.5 kg/m) were retrieved from the Trauma Registry System between January 1, 2009, and December 31, 2014. Pearson's chi-square test, Fisher's exact test, and independent Student's t-test were performed to compare the differences. Propensity score matching with logistic regression was used to evaluate the effect of underweight on mortality.Underweight patients presented a different bodily injury pattern and a significantly higher rate of admittance to the intensive care unit (ICU) than did normal-weight patients; however, no significant differences in the Glasgow Coma Scale (GCS) score, injury severity score (ISS), in-hospital mortality, and hospital length of stay were found between the two groups. However, further analysis of the patients stratified by two major injury mechanisms (motorcycle accident and fall injury) revealed that underweight patients had significantly lower GCS scores (13.8 ± 3.0 vs 14.5 ± 2.0, P = 0.020), but higher ISS (10.1 ± 6.9 vs 8.4 ± 5.9, P = 0.005), in-hospital mortality (odds ratio, 4.4; 95% confidence interval, 1.69-11.35; P = 0.006), and ICU admittance rate (24.1% vs 14.3%, P = 0.007) than normal-weight patients in the fall accident group, but not in the motorcycle accident group. However, after propensity score matching, logistic regression analysis of well-matched pairs of patients with either all trauma, motorcycle accident, or fall injury did not show a significant influence of underweight on mortality.Exploratory data analysis revealed that underweight patients presented a different bodily injury pattern from that of normal-weight patients, specifically a higher incidence of pneumothorax in those with penetrating injuries and of femoral fracture in those with struck on/against injuries; however, the injury severity and outcome of underweight patients varied depending on the injury mechanism.

Hyperglycemia-Mediated Oxidative Stress Increases Pulmonary Vascular Permeability

OBJECTIVE

Hyperglycemia in diabetes mellitus is associated with endothelial dysfunction as evidenced by increased oxidative stress and vascular permeability. Whether impaired glucose control in metabolic syndrome impacts pulmonary vascular permeability is unknown. We hypothesized that in metabolic syndrome, hyperglycemia increases lung vascular permeability through superoxide.

METHODS

Lung capillary Kf and vascular superoxide were measured in the isolated lungs of LZ and OZ rats. OZ were subjected to 4 weeks of metformin treatment (300 mg/kg/day orally) to improve insulin sensitivity. In a separate experiment, lung vascular permeability and vascular superoxide were measured in LZ exposed to acute hyperglycemia (30 mM).

RESULTS

As compared to LZ, OZ had impaired glucose and insulin tolerance and elevated vascular superoxide which was associated with an elevated lung Kf. Chronic metformin treatment in OZ improved glucose control and insulin sensitivity which was associated with decreased vascular oxidative stress and lung Kf. Acute hyperglycemia in isolated lungs from LZ increased lung Kf, which was blocked with the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor, apocynin (3 mM). Apocynin also decreased baseline Kf in OZ.

CONCLUSIONS

These data suggest that hyperglycemia in metabolic syndrome exacerbates lung vascular permeability through increases in vascular superoxide, possibly through NADPH oxidase.

Impact of Weight Extremes on Clinical Outcomes in Pediatric Acute Respiratory Distress Syndrome

OBJECTIVES

To determine whether weight extremes impact clinical outcomes in pediatric acute respiratory distress syndrome.

DESIGN

Post hoc analysis of a cohort created by combining five multicenter pediatric acute respiratory distress syndrome studies.

SETTING

Forty-three academic PICUs worldwide.

PATIENTS

A total of 711 subjects prospectively diagnosed with pediatric acute respiratory distress syndrome.

INTERVENTION

Subjects more than 2 years were included and categorized by Center for Disease Control and Prevention body mass index z score criteria: underweight (< -1.89), normal weight (-1.89 to +1.04), overweight (+1.05 to +1.64), and obese (≥ +1.65). Subjects were stratified by direct versus indirect lung injury leading to pediatric acute respiratory distress syndrome. The primary outcome was in-hospital mortality. In survivors, secondary analyses included duration of mechanical ventilation and ICU length of stay.

MEASUREMENTS AND MAIN RESULTS

A total of 331 patients met inclusion criteria; 12% were underweight, 50% normal weight, 11% overweight, and 27% obese. Overall mortality was 20%. By multivariate analysis, body mass index category was independently associated with mortality (p = 0.004). When stratified by lung injury type, there was no mortality difference between body mass index groups with direct lung injury; however, in the indirect lung injury group, the odds of mortality in the obese were significantly lower than normal weight subjects (odds ratio, 0.11; 95% CI, 0.02-0.84). Survivors with direct lung injury had no difference in the duration of mechanical ventilation or ICU length of stay; however, those with indirect lung injury, the overweight required longer duration of mechanical ventilation than other groups (p < 0.001).

CONCLUSIONS

These data support the obesity paradox in pediatric acute respiratory distress syndrome. Obese children with indirect lung injury pediatric acute respiratory distress syndrome have a lower risk of mortality. Importantly, among survivors, the overweight with indirect lung injury requires longer duration of mechanical ventilation. Our data require prospective validation to further elucidate the pathobiology of this phenomenon.

"Obesity Paradox" in Acute Respiratory Distress Syndrome: Asystematic Review and Meta-Analysis

Background

It is unclear whether an “obesity paradox” exists in the respiratory system, especially in acute respiratory distress syndrome (ARDS) and acute lung injury (ALI). Previous studies have postulated a causal relation between obesity and ARDS/ALI but have lacked power to form a definitive conclusion.

Objective

To investigate the relationships between obesity, ARDS/ALIrisk, and mortality.

Methods

A systematic search current to April 2016 was performed in Pubmed, EMBASE, Medline, Cochrane databases to find relevant studies. All studies that estimate the effect of obesity in the morbidity and mortality of ARDS/ALI were included.

Results

A total of 24 studies including 9,187,248 subjects were analyzed. The combined results from 16 studies that examined the effect of obesity in morbidity of ARDS/ALI showed an89% increase in odds ratio(pooled odds ratios (OR) 1.89, 95% confidence intervals (CI) 1.45 to 2.47). In subgroup analysis, compared to normal weight, obesity was associated with an increased risk of ARDS/ALI (OR1.57, 95% CI 1.30–1.90 for obese (BMI30-39.9kg/m²); OR1.75, 95% CI 1.42–2.15 for obese(BMI≥30kg/m²); OR1.67, 95% CI 1.04–2.68 for morbid obese(BMI≥40kg/m²)). The combined results from 9 studies that examined the effect of obesity in mortality of ARDS/ALI had a pooled odds ratio(pooled OR 0.63, 95% CI 0.41 to 0.98). Inversely, obesity was significantly associated with reduced risk of ARDS/ALI mortality(OR0.88, 95% CI 0.78–1.00 for overweight(BMI≤18.5m²); OR0.74, 95% CI 0.64–0.84 for obese (BMI30-39.9kg/m²);OR0.84, 95% CI 0.75–0.94 for 60days mortality; OR0.38, 95% CI 0.22–0.66 for 90days mortality).

Conclusions

Our data identify obesity as an important risk factor for the development of ARDS/ALI; however, ARDS/ALI outcomes are improved in this population when compared to individuals with a normal body mass index. This meta-analysis results supported ‘‘obesity paradox” in ARDS/ALI.

Association of Injury Factors, Not Body Mass Index, With Hospital Resource Usage in Trauma Patients

BACKGROUND

Allocating resources appropriately requires knowing whether obese patients use more resources during a hospital stay than nonobese patients.

OBJECTIVES

To determine if trauma patients with different body mass indexes differed in use of resources measured as a multifaceted outcome variable.

METHODS

A trauma registry was used for a retrospective study of adult patients admitted to a midwestern level I trauma center. Patients were stratified into 3 groups: nonobese (normal weight, overweight), obese, and morbidly obese. Three canonical correlation analyses were used to determine the relationship between patient/injury characteristics and hospital resource usage.

RESULTS

In a sample of 9771 patients, 71.2% were non-obese, 23.8% obese, and 5.0% morbidly obese. For patient/injury characteristics, Injury Severity Score and physiological complications were significant variables for all 3 groups. Scores on the Glasgow Coma Scale were significant for nonobese patients only. For resource usage, intensive care unit length of stay and procedures were significant variables for all 3 groups.

CONCLUSIONS

Associations between body mass index and outcomes have been noted when assessed as independent variables. However, when resource usage was assessed as a multifaceted outcome variable, injury factors (higher Injury Severity Score, lower scores on the Glasgow Coma Scale, more physiological complications) were associated with resource usage (increased length of stay in the intensive care unit and increased number of procedures). These findings provide clinicians a new perspective for evaluating the complex relationship between patient/injury characteristics and hospital resource usage.