Computed tomography-defined abdominal adiposity is associated with acute kidney injury in critically ill trauma patients*

Beyond body mass index: exploring the role of visceral adipose tissue in intensive care unit outcomes

Obesity is a worldwide health crisis and poses significant challenges in critical care. Many studies suggest an 'obesity paradox', in which obesity, defined by body mass index (BMI), is associated with better outcomes. However, the inability of BMI to discriminate between fat and muscle or between visceral adipose tissue and subcutaneous adipose tissue, limits its prediction of metabolic ill health. We suggest that the 'obesity paradox' may be more reflective of the limitations of BMI than the protective effect of obesity. We explore the biological processes leading to visceral fat accumulation, and the evidence linking it to outcomes in critical illness. In the 'spillover' hypothesis of adipose tissue expansion, caloric excess and impaired expansion of storage capacity in the subcutaneous adipose tissue lead to accumulation of visceral adipose tissue. This is associated with a chronic inflammatory state, which is integral to the link between visceral adiposity, type 2 diabetes mellitus, and ischaemic heart disease. We review the current evidence on visceral adiposity and critical illness outcomes. In COVID-19, increased visceral adipose tissue, irrespective of BMI, is associated with more severe disease. This is mirrored in acute pancreatitis, suggesting visceral adiposity is linked to poorer outcomes in some hyperinflammatory conditions. We suggest that visceral adiposity's chronic inflammatory state may potentiate acute inflammation in conditions such as COVID-19 and acute pancreatitis. Further work is required to investigate other critical illnesses, especially sepsis and acute respiratory distress syndrome, in which current evidence is scarce. This may give further insights into pathophysiology and inform tailored treatment and nutrition strategies based on body fat distribution.

Visceral adipose tissue area predicts major adverse kidney events in patients with acute necrotizing pancreatitis

BACKGROUND

Given the previously reported harmful effects of abdominal fat burden on kidney function, we aim to investigate the relationship between major adverse kidney events within 30 days (MAKE30) and abdominal obesity in acute necrotizing pancreatitis (ANP) patients and explore the underlying risk factors.

METHODS

A retrospective cohort study of all patients admitted within 72 h after the first episode of ANP to a tertiary center between June 2015 and June 2019 was conducted. Automatic image analysis software was used to calculate the area of subcutaneous adipose tissue (SAT), visceral adipose tissue (VAT) and skeletal muscle from computed tomography scans at the umbilical level. The potential risk factors of MAKE30 were analyzed by logistic regression.

RESULTS

A total of 208 eligible ANP patients were enrolled, with an incidence of 23% for MAKE30. VAT area was more closely associated with the development of MAKE30, with an area under the ROC curve of 0.69 (cutoff value 200 cm2, 63.8% sensitivity and 66.7% specificity). Multivariate logistic regression analysis demonstrated that VAT area [OR 1.01 (1.01-1.02); p < 0.001] was an independent risk factor in predicting MAKE30. Patients with a VAT area > 200 cm2 had more requirements of renal replacement therapy (32% vs. 12%, P < 0.001), and a significantly higher incidence of other poor clinical outcomes (all p < 0.05).

CONCLUSION

Early assessment of the VAT area may help identify ANP patients at high risk of MAKE30, suggesting that it could be a potential indicator for adverse kidney events.

Skeletal muscle density as a new predictor of abdominal infection in abdominal trauma patients

BACKGROUND AND AIMS

Skeletal muscle density (SMD) is a valuable prognostic indicator in various conditions such as cancer, liver cirrhosis. Yet, the connection between SMD and intra-abdominal infection in individuals who have suffered abdominal injuries is still unclear. The purpose of this research is to examine how well SMD can predict intra-abdominal infection in patients who have suffered abdominal trauma.

METHODS

Participants with abdominal injuries were included in this research from January 2015 to April 2023. Based on the sex-specific cut off values of SMD, the entire population was split into two categories. Prognostic factors were identified through logistic regression analysis. ROC was used to assess the predictive accuracy of SMD and its combinations with other biomarkers for clinical outcomes.

RESULTS

A total of 220 patients were ultimately included in the study. Patients in the group with low SMD exhibited a higher incidence of intra-abdominal infection, longer hospital stays, and increased hospital costs. In patients with abdominal trauma, low SMD was identified as a significant independent predictor of intra-abdominal infection (OR 2.397; 95 % CI 1.117-5.141, p = 0.025). Low SMD had a higher area under the curve (AUC) in ROC analysis compared to TRF, NRS2002 score, and APACHEII score for predicting intra-abdominal infection (AUC 0.70, 95 % CI 0.61-0.78, p = 0.002). Moreover, low SMD showed associations with clinical outcomes such as hospital stay length and costs (p < 0.01).

CONCLUSIONS

Low SMD is recognized as an independent risk factor for predicting intra-abdominal infections in this patient population. Notably, SMD is emerging as a novel predictor of abdominal infections in patients with abdominal trauma.

Association between albumin-corrected anion gap and in-hospital mortality of intensive care patients with trauma: A retrospective study based on MIMIC-Ⅲ and Ⅳ databases

BACKGROUND

To investigate the correlation between albumin-corrected anion gap(ACAG) within the first 24 hours of admission and in-hospital mortality in trauma patients in intensive care unit(ICU).

MATERIALS AND METHODS

We utilized the MIMIC-Ⅲ and MIMIC-Ⅳ databases to examine trauma patients admitted to the ICU. The relationship between ACAG and in-hospital mortality in trauma patients was analyzed using Receiver Operating Characteristic(ROC) curve, Kaplan-Meier (K-M) survival curve, and Cox regression model. Propensity score matching (PSM) and subgroup analysis were conducted to enhance stability and reliability of the findings. Mortality at 30-day and 90-day served as secondary outcomes.

RESULTS

The study enrolled a total of 1038 patients. The AUC for ACAG (0.701, 95%CI: 0.652-0.749) was notably higher than that for anion gap and albumin. The Log-rank test revealed that the optimal cut-off point of ACAG for predicting in-hospital mortality was determined to be 20.375mmol/L. The multivariate Cox regression analysis demonstrated an independent association between high ACAG level and a higher risk of in-hospital mortality (HR = 3.128, 95% CI: 1.615-6.059). After PSM analysis, a matched cohort consisting of 291 subjects was obtained. We found no signifcant interaction in most stratas. Finally, The in-hospital, 30-day, and 90-day survival rates in the high ACAG group exhibited a statistically decrease compared to those in the low ACAG group both pre- and post-matching.

CONCLUSION

The elevated level of ACAG was found to be independently associated with increased in-hospital mortality among trauma patients in the ICU.

High Fat-to-Muscle Ratio Was Associated with Increased Clinical Severity in Patients with Abdominal Trauma

Overweight and moderate obesity confer a survival benefit in chronic diseases such as coronary artery disease and chronic kidney disease, which has been termed the "obesity paradox". However, whether this phenomenon exists in trauma patients remains controversial. We performed a retrospective cohort study in abdominal trauma patients admitted to a Level I trauma center in Nanjing, China between 2010 and 2020. In addition to the traditional body mass index (BMI) based measures, we further examined the association between body composition-based indices with clinical severity in trauma populations. Body composition indices including skeletal muscle index (SMI), fat tissue index (FTI), and total fat-to-muscle ratio (FTI/SMI) were measured using computed tomography. Our study found that overweight was associated with a four-fold risk of mortality (OR, 4.47 [95% CI, 1.40-14.97], p = 0.012) and obesity was associated with a seven-fold risk of mortality (OR, 6.56 [95% CI, 1.07-36.57], p = 0.032) compared to normal weight. Patients with high FTI/SMI had a three-fold risk of mortality (OR, 3.06 [95% CI, 1.08-10.16], p = 0.046) and double the risk of an intensive care unit length of stay ≥ 5 d (OR, 1.75 [95% CI, 1.06-2.91], p = 0.031) compared to patients with low FTI/SMI. The obesity paradox was not observed in abdominal trauma patients, and high FTI/SMI ratio was independently associated with increased clinical severity.

The Impact of Myosteatosis Percentage on Short-Term Mortality in Patients with Septic Shock

The impact of myosteatosis on septic patients has not been fully revealed. The aim of the study was to evaluate the impact of the myosteatosis area and percentage on the 28-day mortality in patients with septic shock. We conducted a single center, retrospective study from a prospectively collected registry of adult patients with septic shock who presented to the emergency department and performed abdominal computed tomography (CT) from May 2016 to May 2020. The myosteatosis area defined as the sum of low attenuation muscle area and intramuscular adipose tissue at the level of the third lumbar vertebra was measured by CT. Myosteatosis percentages were calculated by dividing the myosteatosis area by the total abdominal muscle area. Of the 896 patients, 28-day mortality was 16.3%, and the abnormal myosteatosis area was commonly detected (81.7%). Among variables of body compositions, non-survivors had relatively lower normal attenuation muscle area, higher low attenuation muscle area, and higher myosteatosis area and percentage than that of survivors. Trends of myosteatosis according to age group were different between the male and female groups. In subgroup analysis with male patients, the multivariate model showed that the myosteatosis percentage (adjusted OR 1.02 [95% CI 1.01–1.03]) was an independent risk factor for 28-day mortality. However, this association was not evident in the female group. Myosteatosis was common and high myosteatosis percentage was associated with short-term mortality in patients with septic shock. Our results implied that abnormal fatty disposition in muscle could impact on increased mortality, and this effect was more prominent in male patients.

Incidence and Perioperative Risk Factors of Acute Kidney Injury Among Lung Transplant Recipients

BACKGROUND

Acute kidney injury (AKI) is a significant burden in an early postoperative period after lung transplantation (LT). The development of severe AKI, including a need for continuous renal replacement therapy (CRRT), is associated with increased mortality among lung transplant recipients. Evaluation of AKI incidence and predictive factors related to the development of severe AKI and with the use of CRRT in the early postoperative period after LT.

METHODS

Retrospective study of 73 consecutive patients after LT operated between 2015 and 2018 in our center. We noted the stage of AKI according to KDIGO guidelines in the 7 postoperative days.

RESULTS

We noted AKI among 62 lung transplant recipients (84.9%). We recognized the first and second stages of AKI in 21 patients (28.8%) and 19 patients 26%, respectively (group A). We identified severe AKI (group C) in 22 recipients (30.1%), 9 of whom needed CRRT postoperatively. There was a nonsignificant difference between groups in baseline serum creatinine (0.69 ± 0.22 mg/dL vs 0.84 ± 0.34; P = .073). Group C subjects statistically more often suffered from pulmonary hypertension (P < .001) and diabetes (P < .001). In both groups, the duration of the procedure was comparable, but, among patients with severe AKI, procedures were performed more often with the use of extracorporeal circulation (50% vs 68%; P = .194) CONCLUSIONS: Pulmonary hypertension and diabetes could be significant risk factors of high-grade AKI development after LT. Identification of factors modifying renal insufficiency development in lung transplant recipients needs further investigations.

Adipose tissue provides a cushioning effect in low-energy isolated blunt thoracic trauma: a prospective observational study

INTRODUCTION

This study aimed to investigate the specific effects of subcutaneous adipose tissue thickness (SATT) on trauma-related injury (TRI) development in patients with low-energy isolated blunt thoracic trauma.

PATIENTS AND METHODS

This prospective observational study was performed between March 2018-March 2019. Patients admitted to our hospital because of blunt thoracic trauma were enrolled. SATT in axial CT images of the thorax was measured using the four anatomically designated localizations. Patients were analyzed in terms of demographic data, BMI, comorbid diseases, causes of injury, vital parameters, visual analog scale, trauma score, injury type, treatment, and hospitalization. A poor clinical outcome was defined as the development of a TRI.

RESULTS

The study group consisted of 152 patients (43 female, 109 male). The mean age was 49 ± 19.1 years. There was a positive linear association between the BMI and SATT for all the patients in the study. TRI frequency was higher in the low-SATT subgroup than in the high-SATT group (p < 0.001). BMI and mean SATT values were related to a poor logistic regression analysis outcome (p < 0.01). Being in the low-BMI subgroup was a risk factor for TRI development (p < 0.01; OR:0.23;95% CI:0.08-0.61).

CONCLUSION

We found that a low SATT and BMI were related to a poor clinical outcome in our study group. It is essential to carefully examine these patients in detail, even in low-energy trauma. Subcutaneous tissue over the thorax serves as a protective shield for other thoracic structures in patients with LEBTT.

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.

Volumetric Markers of Body Composition May Improve Personalized Prediction of Major Arterial Bleeding After Pelvic Fracture: A Secondary Analysis of the Baltimore CT Prediction Model Cohort

METHODS

This work is a retrospective secondary analysis of a single institution cohort used in the development of the Baltimore CT prediction model. The cohort includes 115 consecutive patients that underwent admission contrast-enhanced CT of the abdomen and pelvis for blunt trauma with pelvic ring disruption followed by conventional angiography. Major arterial injury requiring angioembolization served as the outcome variable. Angioembolization was required in 73/115 patients (63% of the cohort). Average age was 46.9 years (±SD 20.4). Body composition measurements were determined as 2-dimensional (2D) or 3-dimensional (3D) parameters and included mid-L3 trabecular bone attenuation, abdominal visceral fat area or volume, and percent muscle fat fraction (as a marker of sarcopenia) measured using segmentation and histogram analysis.

RESULTS

Models incorporating 2D (Model B) or 3D markers (model C) of body composition showed improvement over the original Baltimore model (model A) in all parameters of performance, quality, and fit (area under the receiver-operating curve [AUC], Akaike information criterion, Brier score, Hosmer-Lemeshow test, and adjusted-R2). Area under the receiver-operating curve increased from 0.83 (A), to 0.86 (B), and 0.88 (C). The greatest improvement was seen with 3D parameters.

CONCLUSION

Once automated, quantitative visualization tools providing "free" 3D body composition information can be expected to improve personalized precision diagnostics, outcome prediction, and decision support in patients with bleeding pelvic fractures.

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.

Relationship of body mass index, serum creatine kinase, and acute kidney injury after severe trauma

OBJECTIVES

Body mass index (BMI) is associated with acute kidney injury (AKI) after trauma, but underlying mechanisms are unclear. Body mass index correlates with both excess adiposity and increased muscle mass. Since the latter could predispose to severe rhabdomyolysis after trauma, we hypothesized that the BMI-AKI association may be partially explained by a direct relationship of BMI with serum creatine kinase (CK).

METHODS

Prospective cohort study of 463 critically ill patients admitted to a level I trauma center from 2005 to 2015 with Injury Severity Score of >15 and serum CK measured in the first 7 days. We defined AKI by AKI Network creatinine criteria. We used simple linear regression to determine the association of BMI with peak CK and multivariable logistic regression to adjust the BMI-AKI association for peak CK and confounders.

RESULTS

Median age was 43 years, 350 (76%) were male, 366 (79%) had blunt mechanism, and median Injury Severity Score was 24. Body mass index was associated with peak CK (R = 0.05, p < 0.001). Acute kidney injury developed in 148 patients (32%), and median time to peak CK was 29 hours (interquartile range, 15-56 hours) after presentation. Body mass index was significantly associated with AKI in multivariable models adjusted for age, race, sex, diabetes, injury mechanism and severity, and red blood cell transfusions (odds ratio [OR], 1.31 per 5 kg/m; 95% confidence interval [CI], 1.09-1.58; p = 0.004). Adding peak CK to the model partially attenuated the association of BMI with AKI (OR, 1.26 per 5 kg/m; 95% CI, 1.04-1.52; p = 0.018), and peak CK was also associated with AKI (OR, 1.19 per natural log; 95% CI, 1.00-1.41; p = 0.049). Peak CK remained associated with AKI when restricted to patients with values of <5,000 U/L (OR, 1.31 per natural log; 95% CI, 1.01-1.69; p = 0.043).

CONCLUSION

Serum CK correlated with BMI and partially attenuated the association of BMI with AKI after major trauma, suggesting that excess muscle injury may contribute to the BMI-AKI association.

LEVEL OF EVIDENCE

Epidemiologic study, level III.

BRR-Net: A tandem architectural CNN-RNN for automatic body region localization in CT images

PURPOSE

Automatic identification of consistently defined body regions in medical images is vital in many applications. In this paper, we describe a method to automatically demarcate the superior and inferior boundaries for neck, thorax, abdomen, and pelvis body regions in computed tomography (CT) images.

METHODS

For any three-dimensional (3D) CT image I, following precise anatomic definitions, we denote the superior and inferior axial boundary slices of the neck, thorax, abdomen, and pelvis body regions by NS(I), NI(I), TS(I), TI(I), AS(I), AI(I), PS(I), and PI(I), respectively. Of these, by definition, AI(I) = PS(I), and so the problem reduces to demarcating seven body region boundaries. Our method consists of a two-step approach. In the first step, a convolutional neural network (CNN) is trained to classify each axial slice in I into one of nine categories: the seven body region boundaries, plus legs (defined as all axial slices inferior to PI(I)), and the none-of-the-above category. This CNN uses a multichannel approach to exploit the interslice contrast, providing the neural network with additional visual context at the body region boundaries. In the second step, to improve the predictions for body region boundaries that are very subtle and that exhibit low contrast, a recurrent neural network (RNN) is trained on features extracted by CNN, limited to a flexible window about the predictions from the CNN.

RESULTS

The method is evaluated on low-dose CT images from 442 patient scans, divided into training and testing sets with a ratio of 70:30. Using only the CNN, overall absolute localization error for NS(I), NI(I), TS(I), TI(I), AS(I), AI(I), and PI(I) expressed in terms of number of slices (nS) is (mean ± SD): 0.61 ± 0.58, 1.05 ± 1.13, 0.31 ± 0.46, 1.85 ± 1.96, 0.57 ± 2.44, 3.42 ± 3.16, and 0.50 ± 0.50, respectively. Using the RNN to refine the CNN's predictions for select classes improved the accuracy of TI(I) and AI(I) to: 1.35 ± 1.71 and 2.83 ± 2.75, respectively. This model outperforms the results achieved in our previous work by 2.4, 1.7, 3.1, 1.1, and 2 slices, respectively for TS(I), TI(I), AS(I), AI(I) = PS(I), and PI(I) classes with statistical significance. The model trained on low-dose CT images was also tested on diagnostic CT images for NS(I), NI(I), and TS(I) classes; the resulting errors were: 1.48 ± 1.33, 2.56 ± 2.05, and 0.58 ± 0.71, respectively.

CONCLUSIONS

Standardized body region definitions are a prerequisite for effective implementation of quantitative radiology, but the literature is severely lacking in the precise identification of body regions. The method presented in this paper significantly outperforms earlier works by a large margin, and the deviations of our results from ground truth are comparable to variations observed in manual labeling by experts. The solution presented in this work is critical to the adoption and employment of the idea of standardized body regions, and clears the path for development of applications requiring accurate demarcations of body regions. The work is indispensable for automatic anatomy recognition, delineation, and contouring for radiation therapy planning, as it not only automates an essential part of the process, but also removes the dependency on experts for accurately demarcating body regions in a study.

Abdominal adiposity assessed using CT angiography associates with acute kidney injury after trans-catheter aortic valve replacement

AIM

To determine if there is an association between area-based visceral abdominal adipose tissue (VAT), subcutaneous abdominal adipose tissue (SAT), and abdominal circumference measured on computed tomography (CT) angiography before trans-catheter aortic valve replacement (TAVR) and post-TAVR acute kidney injury (AKI).

MATERIALS AND METHODS

In this retrospective cohort study of 106 TAVR patients, SAT and VAT areas and abdominal circumference was measured on a single CT section at L4 vertebral level. Univariate comparisons between patients who did and did not develop AKI were undertaken for radiological measurements. Multivariable logistic regression was used to assess association between CT measurements and the development of post-TAVR AKI.

RESULTS

Post-TAVR AKI occurred in 20 of 106 patients (19%). In univariate comparisons, body mass index (BMI) did not differ significantly between patients who did and did not develop AKI (p=0.14); however, VAT+SAT (443.2±163.7 versus 351±168.7 cm²; p=0.03), VAT (213.9±110.6 versus 153.9±96.1 cm²; p=0.03), and outer abdominal circumference (100.2±14.4 cm versus 91.8±13.3 cm; p=0.02) were significantly higher in the patients who did not develop post-TAVR AKI. These three measures on pre-TAVR CT angiogram remained significantly associated with reduced post-TAVR AKI with a lower incidence of post-TAVR AKI after multivariable adjustment for pre-TAVR estimated glomerular filtration rate and patient height (p<0.05).

CONCLUSION

This study found that increased abdominal obesity as assessed by measures on pre-TAVR CT angiogram is associated with a significantly lower incidence of AKI.

The Year in Cardiothoracic Transplantation Anesthesia: Selected Highlights from 2019

The highlights in cardiothoracic transplantation focus on the recent research pertaining to heart and lung transplantation, including expansion of the donor pool, the optimization of donors and recipients, the use of mechanical support, the perioperative and long-term outcomes in these patient populations, and the use of transthoracic echocardiography to diagnose rejection.

Rhabdomyolysis-induced acute kidney injury requiring hemodialysis after a prolonged immobilization at home in 2 morbidly obese women: case reports with literature review

Background

Rhabdomyolysis may develop into acute kidney injury (AKI), a life-threatening complication. Obese people are at risk for rhabdomyolysis due to prolonged immobilization. However, there are only a few reports of rhabdomyolysis-induced AKI due to prolonged immobilization after falls in morbidly obese people. Myoglobin is a causative compound for rhabdomyolysis-induced AKI, but the lack of treatments targeting its mechanism is a problem.

Case presentation

Two morbidly obese women (body mass index > 40.0 kg/m2) who fell on the floor at home and remained in the same posture for more than 12 h developed rhabdomyolysis-induced AKI. Both patients received aggressive fluid resuscitation but required hemodialysis because of persistent oliguria. They underwent 11 and 2 intermittent hemodialysis (HD) sessions with a conventional polymethylmethacrylate (PMMA) high-flux dialyzer, respectively, and their renal functions returned to baseline after withdrawal of HD.

Conclusions

We should be aware that morbidly obese people are at risk for rhabdomyolysis-induced AKI due to prolonged immobilization, such as after falls. At present, prophylactic renal replacement therapy (RRT) is not recommended for rhabdomyolysis. We need to reevaluate whether RRT using the appropriate membranes to effectively remove myoglobin including the PMMA membrane can improve the renal outcome in patients with rhabdomyolysis-induced AKI.

ABCNet: A new efficient 3D dense-structure network for segmentation and analysis of body tissue composition on body-torso-wide CT images

PURPOSE

Quantification of body tissue composition is important for research and clinical purposes, given the association between the presence and severity of several disease conditions, such as the incidence of cardiovascular and metabolic disorders, survival after chemotherapy, etc., with the quantity and quality of body tissue composition. In this work, we aim to automatically segment four key body tissues of interest, namely subcutaneous adipose tissue, visceral adipose tissue, skeletal muscle, and skeletal structures from body-torso-wide low-dose computed tomography (CT) images.

METHOD

Based on the idea of residual Encoder-Decoder architecture, a novel neural network design named ABCNet is proposed. The proposed system makes full use of multiscale features from four resolution levels to improve the segmentation accuracy. This network is built on a uniform convolutional unit and its derived units, which makes the ABCNet easy to implement. Several parameter compression methods, including Bottleneck, linear increasing feature maps in Dense Blocks, and memory-efficient techniques, are employed to lighten the network while making it deeper. The strategy of dynamic soft Dice loss is introduced to optimize the network in coarse-to-fine tuning. The proposed segmentation algorithm is accurate, robust, and very efficient in terms of both time and memory.

RESULTS

A dataset composed of 38 low-dose unenhanced CT images, with 25 male and 13 female subjects in the age range 31-83 yr and ranging from normal to overweight to obese, is utilized to evaluate ABCNet. We compare four state-of-the-art methods including DeepMedic, 3D U-Net, V-Net, Dense V-Net, against ABCNet on this dataset. We employ a shuffle-split fivefold cross-validation strategy: In each experimental group, 18, 5, and 15 CT images are randomly selected out of 38 CT image sets for training, validation, and testing, respectively. The commonly used evaluation metrics - precision, recall, and F1-score (or Dice) - are employed to measure the segmentation quality. The results show that ABCNet achieves superior performance in accuracy of segmenting body tissues from body-torso-wide low-dose CT images compared to other state-of-the-art methods, reaching 92-98% in common accuracy metrics such as F1-score. ABCNet is also time-efficient and memory-efficient. It costs about 18 h to train and an average of 12 sec to segment four tissue components from a body-torso-wide CT image, on an ordinary desktop with a single ordinary GPU.

CONCLUSIONS

Motivated by applications in body tissue composition quantification on large population groups, our goal in this paper was to create an efficient and accurate body tissue segmentation method for use on body-torso-wide CT images. The proposed ABCNet achieves peak performance in both accuracy and efficiency that seems hard to improve any more. The experiments performed demonstrate that ABCNet can be run on an ordinary desktop with a single ordinary GPU, with practical times for both training and testing, and achieves superior accuracy compared to other state-of-the-art segmentation methods for the task of body tissue composition analysis from low-dose CT images.

Complications and Failure to Rescue After Abdominal Surgery for Trauma in Obese Patients

BACKGROUND

Although obesity is considered an epidemic in the United States, there is mixed evidence regarding the impact of obesity on outcomes after traumatic injury and major surgery. We hypothesized that obese patients undergoing trauma laparotomy would be at increased risk of failure to rescue (FTR), defined as death after a complication.

METHODS

We analyzed trauma registry data for adult patients who underwent abdominal exploration for trauma at all 30 level I and II Pennsylvania trauma centers, 2011-2014. We used competing risks regression to identify significant risk factors for complications. We used multivariable logistic regression to identify significant risk factors for FTR.

RESULTS

Of 95,806 admitted patients, 15,253 (15.9%) were categorized as obese. Overall, 3228 (3.4%) underwent laparotomy, including 2681 (83.1%) nonobese and 547 (17.0%) obese patients. Among obese patients, 47.2% had at least one complication and 28.7% had two or more complications, compared with 33.5% and 18.7% of nonobese patients, respectively. The most common complication was pneumonia (15.0% of obese and 10.5% of nonobese patients; P = 0.003), followed by sepsis (8.8% versus 4.2%; P < 0.001) and deep vein thrombosis (8.4% versus 5.9%; P < 0.001). Obesity was independently associated with complications (hazard ratio, 1.4; 95% confidence interval, 1.2-1.6). In multivariable analysis, obesity was not associated with FTR (odds ratio, 1.3; 95% confidence interval, 0.9-2.0).

CONCLUSIONS

Obesity is a risk factor for complications after traumatic injury but not for FTR. The increased risk of complications may reflect processes of care that are not attuned to the needs of this population, offering opportunities for improvement in care.

Obesity is associated with a reduced odds for blunt intra-abdominal injuries in children

OBJECTIVES

Children with obesity may possess unique injury characteristics that may affect their emergency care. To better understand this relationship, we investigated the association of obesity in pediatric trauma patients and intra-abdominal injuries (IAIs) and routinely utilized emergency department (ED) diagnostic procedures (computed tomography (CT) scans and ultrasound (US) examinations).

METHODS

This secondary data analysis utilized Pediatric Emergency Care Applied Research Network (PECARN) data from 2007 to 2010. Since height data were not available, children (2-17 years) with obesity were defined using weight-for-age percentiles. Non-parametric testing determined potential confounders. Adjusted odds ratios (aOR) were calculated using binary logistic regression for weight status and IAIs and diagnostic procedures.

RESULTS

There were 3846 patients with actual weight recorded: 3301 (85.8%) children without obesity and 545 (14.2%) with obesity. Children with obesity had decreased odds for IAI after adjusting for race, mechanical force injury (MFI) type, vomiting, and abdominal wall trauma (adjusted odds ratio (aOR)=0.58 (95% CI 0.35-0.97); p-value=0.04). Patients with obesity had reduced odds for a CT examination. No association was found between obesity status and US utilization. African-American patients had decreased odds for IAIs, CT scans and US examinations after adjustment which could be related to MFI type.

CONCLUSIONS

Obesity appears to reduce the odds for pediatric IAIs and CT scans, but not for US examinations. Selection bias is possible due to injury severity and missing or excluded weight data. Further research is needed in other pediatric populations with obesity and blunt injuries.

Adipose tissue quantification and primary graft dysfunction after lung transplantation: The Lung Transplant Body Composition study

BACKGROUND

Obesity is associated with an increased risk of primary graft dysfunction (PGD) after lung transplantation. The contribution of specific adipose tissue depots is unknown.

METHODS

We performed a prospective cohort study of adult lung transplant recipients at 4 U.S. transplant centers. We measured cross-sectional areas of subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) on chest and abdominal computed tomography (CT) scans and indexed each measurement to height.2 We used logistic regression to examine the associations of adipose indices and adipose classes with grade 3 PGD at 48 or 72 hours, and Cox proportional hazards models to examine survival. We used latent class analyses to identify the patterns of adipose distribution. We examined the associations of adipose indices with plasma biomarkers of obesity and PGD.

RESULTS

A total of 262 and 117 subjects had available chest CT scans and underwent protocol abdominal CT scans, respectively. In the adjusted models, a greater abdominal SAT index was associated with an increased risk of PGD (odds ratio 1.9, 95% CI 1.02-3.4, p = 0.04) but not with survival time. VAT indices were not associated with PGD risk or survival time. A greater abdominal SAT index correlated with greater pre- and post-transplant leptin (r = 0.61, p < 0.001, and r = 0.44, p < 0.001), pre-transplant IL-1RA (r = 0.25, p = 0.04), and post-transplant ICAM-1 (r = 0.25, p = 0.04). We identified 3 latent patterns of adiposity. The class defined by high thoracic and abdominal SAT had the greatest risk of PGD.

CONCLUSIONS

Subcutaneous, but not visceral, adiposity is associated with an increased risk of PGD after lung transplantation.

The association of post-lung transplant acute kidney injury with mortality is independent of primary graft dysfunction: A cohort study

BACKGROUND

Prior studies of post-lung transplant acute kidney injury (AKI) have not accounted for confounding effects of primary graft dysfunction (PGD). We sought to test the impact of PGD on AKI risk factors and on the association of AKI with mortality.

METHODS

We included patients transplanted at the University of Pennsylvania from 2005-12, defined AKI using consensus criteria during transplant hospitalization, and defined PGD as grade 3 at 48-72 hours. We used multivariable logistic regression to test the impact of PGD on AKI risk factors and Cox models to test association of AKI with one-year mortality adjusting for PGD and other confounders.

RESULTS

Of 299 patients, 188 (62.9%) developed AKI with 142 (75%) cases occurring by postoperative day 4. In multivariable models, PGD was strongly associated with AKI (OR 3.76, 95% CI 1.72-8.19, P = .001) but minimally changed associations of other risk factors with AKI. Both AKI (HR 3.64, 95% CI 1.68-7.88, P = .001) and PGD (HR 2.55, 95% CI 1.40-4.64, P = .002) were independently associated with one-year mortality.

CONCLUSIONS

Post-lung transplant AKI risk factors and association of AKI with mortality were independent of PGD. AKI may therefore be a target for improving lung transplant mortality rather than simply an epiphenomenon of PGD.

Plasma receptor interacting protein kinase-3 levels are associated with acute respiratory distress syndrome in sepsis and trauma: a cohort study

Background

Necroptosis, a form of programmed cell death mediated by receptor interacting serine/threonine-protein kinase-3 (RIPK3), is implicated in murine models of acute respiratory distress syndrome (ARDS). We hypothesized that plasma RIPK3 concentrations in sepsis and trauma would be associated with ARDS development and that plasma RIPK3 would reflect changes in lung tissue RIPK3 in a murine model of systemic inflammation.

Methods

We utilized prospective cohort studies of critically ill sepsis (n = 120) and trauma (n = 180) patients and measured plasma RIPK3 at presentation and 48 h. Patients were followed for 6 days for ARDS by the Berlin definition. We used multivariable logistic regression to determine the association of plasma RIPK3 with ARDS in each cohort, adjusting for confounders. In mice, we determined whether plasma and lung tissue RIPK3 levels rise concomitantly 4 h after injection with lipopolysaccharide and ZVAD-FMK, an apoptosis inhibitor.

Results

The change in plasma RIPK3 from presentation to 48 h (ΔRIPK3) was associated with ARDS in sepsis (OR 1.30, 95% CI 1.03–1.63, per ½ standard deviation) and trauma (OR 1.79, 95% CI 1.33–2.40). This association was not evident for presentation RIPK3 levels. Secondary analyses showed similar findings for the association of ΔRIPK3 with acute kidney injury and 30-day mortality. Mice injected with lipopolysaccharide and ZVAD-FMK had significantly higher plasma (p < 0.001) and lung (p = 0.005) RIPK3 than control mice.

Conclusions

The change in plasma RIPK3 from presentation to 48 h in both sepsis and trauma patients is independently associated with ARDS, and plasma RIPK3 may reflect RIPK3 activity in lung tissue.

Electronic supplementary material

The online version of this article (10.1186/s13054-019-2482-x) contains supplementary material, which is available to authorized users.

Obese trauma patients have increased need for dialysis

PURPOSE

Obesity is a risk factor for the development of acute kidney injury but its effect on the need for dialysis in trauma has not been elucidated. Additionally, the contribution that obesity has towards risk of mortality in trauma is unclear. We hypothesized that patients with a higher body mass index (BMI) will have a higher risk for need of dialysis and mortality after trauma.

METHODS

This is a retrospective analysis using the National Trauma Data Bank. All patients ≥ 8 years old were grouped based on BMI: normal (18.5-24.99 kg/m²), obese (30-34.99 kg/m²), severely obese (35-39.99 kg/m²) and morbidly obese (≥ 40 kg/m²). The primary outcome was hemodialysis initiation. The secondary outcome was mortality during the index hospitalization.

RESULTS

From 988,988 trauma patients, 571,507 (57.8%) had a normal BMI, 233,340 (23.6%) were obese, 94,708 (9.6%) were severely obese, and 89,433 (9.0%) were morbidly obese. The overall rate of hemodialysis was 0.3%. After adjusting for covariates, we found that obese (OR 1.36, CI 1.22-1.52, p < 0.001), severely obese (OR 1.89, CI 1.66-2.15, p < 0.001) and morbidly obese (OR 2.04, CI 1.82-2.29, p < 0.001) patients had a stepwise increased need for hemodialysis after trauma. Obese patients had decreased (OR 0.92, CI 0.88-0.95, p < 0.001), severely obese had similar (OR 1.02, CI 0.97-1.08, p = 0.50) and morbidly obese patients had increased (OR 1.06, CI 1.01-1.12, p = 0.011) risk of mortality after trauma.

CONCLUSIONS

Obesity was associated with an increased risk for dialysis after trauma. Mortality risk was reduced in obese, similar in severely obese, and increased in morbidly obese trauma patients suggesting an inflection threshold BMI for risk of mortality in trauma.

Low to Moderate Air Pollutant Exposure and Acute Respiratory Distress Syndrome after Severe Trauma

RATIONALE

Exposure to air pollution has molecular and physiologic effects on the lung that may increase the risk of acute respiratory distress syndrome (ARDS) after injury.

OBJECTIVES

To determine the association of short- and long-term air pollutant exposures and ARDS risk after severe trauma.

METHODS

We analyzed data from a prospective cohort of 996 critically ill patients presenting with acute trauma and an injury severity score greater than 15. Exposures to ozone, nitrogen dioxide, sulfur dioxide, carbon monoxide, and particulate matter less than 2.5 μm were assessed by weighted averages of daily levels from all monitors within 50 km of the geocoded location of a patient's residence. Patients were followed for 6 days for the development of ARDS according to Berlin Criteria. The association between each exposure and ARDS was determined via multivariable logistic regression adjusting for potential confounders.

MEASUREMENTS AND MAIN RESULTS

ARDS developed in 243 (24%) patients. None of the short-term exposures averaged over the 3 days before presentation was associated with ARDS, except sulfur dioxide, which demonstrated a nonlinear association. Nitrogen dioxide, sulfur dioxide, and particulate matter less than or equal to 2.5 μm in aerodynamic diameter exposure over the 6 weeks before presentation was significantly associated with ARDS (P < 0.05). All long-term exposures (3 yr) were associated with ARDS (P < 0.01) in adjusted models, despite exposure levels largely below U.S. and European Union air quality standards.

CONCLUSIONS

Long-term low- to moderate-level air pollutant exposure is associated with a greater risk of developing ARDS after severe trauma and represents a novel and potentially modifiable environmental risk factor for ARDS.

Update on perioperative acute kidney injury

PURPOSE OF REVIEW

In this review, we discuss the latest updates on perioperative acute kidney injury (AKI) and the specific considerations that are relevant to different surgeries and patient populations.

RECENT FINDINGS

AKI diagnosis is constantly evolving. New biomarkers detect AKI early and shed a light on the possible cause of AKI. Hypotension, even for a short duration, is associated with perioperative AKI. The debate on the deleterious effects of chloride-rich solutions is still far from conclusion. Remote ischemic preconditioning is showing promising results in the possible prevention of perioperative AKI. No definite data show a beneficiary effect of statins, fenoldepam, or sodium bicarbonate in preventing AKI.

SUMMARY

Perioperative AKI is prevalent and associated with significant morbidity and mortality. Considering the lack of effective preventive or therapeutic interventions, this review focuses on perioperative AKI: measures for early diagnosis, defining risks and possible mechanisms, and summarizing current knowledge for intraoperative fluid and hemodynamic management to reduce risk of AKI.

Impact of sarcopenic obesity on 30-day mortality in critically ill patients with intra-abdominal sepsis

PURPOSE

This study aimed to investigate the association between sarcopenic obesity and 30-day mortality in critically ill patients with intra-abdominal sepsis.

MATERIAL AND METHODS

We analyzed 236 surgical ICU patients with sepsis due to intra-abdominal infection who underwent urgent surgical intervention. Sarcopenia, visceral obesity and sarcopenic obesity were analyzed by computed tomography scans using the third lumbar vertebrae skeletal muscle index and visceral adipose tissue area, using previously reported cutoff values.

RESULTS

The cohort was divided into 4 groups: 52 were diagnosed with sarcopenic obesity, 62 with sarcopenia only, 58 with visceral obesity only, and 64 with no sarcopenia or visceral obesity. 57 (24.2%) patients died within 30days. The frequency of 30-day mortality differed significantly among the groups. Multivariate analysis showed that only sarcopenic obesity was associated with increased risk for 30-day mortality. Sarcopenic patients were older than non-sarcopenic patients. To address this limitation, subgroup analyses stratified by age showed that the risk of 30-day mortality increased significantly in sarcopenic patients, both in patients with age≤70years and in those with age >70years.

CONCLUSION

Sarcopenic obesity is an independent risk factor for 30-day mortality in critically ill patients with intra-abdominal sepsis.

Postoperative acute kidney injury

Acute kidney injury (AKI) after cardiac surgery is a common and serious complication. Several definitions of AKI have been proposed recently, and include both increases in serum creatinine levels and decreases in urine output as diagnostic criteria. The pathophysiology of postoperative AKI is complex and involves both ischemic injury and systemic inflammation. Identifying risk factors, such as old age, underlying diabetes, heart failure, and obesity, may aid in the application of preventative methods for postoperative AKI. Additionally, recognizing different risks after different types of surgical procedures would be valuable. Novel biomarkers that could detect AKI more precisely at an earlier time point are being investigated. Several new biomarkers have been assessed in large multi-center studies and are believed to accommodate conventional clinical findings in diagnosing postoperative AKI. In high-risk patients, preventative measures, such as the maintenance of adequate hemodynamics and sufficient fluid resuscitation, could lower the incidence of postoperative AKI. Avoiding nephrotoxic agents and optimizing preoperative hemoglobin levels to avoid excessive transfusions would also be beneficial. In situations in which medical management fails to maintain sufficient urine output and acid-base and electrolyte homeostasis, early initiation of renal replacement therapy should be considered.

Increased Ratio of Visceral to Subcutaneous Adipose Tissue in Septic Patients Is Associated With Adverse Outcome

OBJECTIVES

Visceral and subcutaneous adipose tissue may contribute differentially to the septic inflammatory response. Accordingly, we tested the hypothesis that the ratio of visceral to subcutaneous adipose tissue is associated with altered sepsis outcome.

DESIGN

A retrospective analysis from a cohort of sepsis patients admitted between 2004 and 2009.

SETTING

A mixed medical-surgical ICU at St. Paul's Hospital in Vancouver, Canada.

PATIENTS

Patients older than 16 years old who had sepsis and underwent abdominal CT scan (n = 257) for clinical reasons.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We measured the visceral adipose tissue and subcutaneous adipose tissue areas and calculated the visceral adipose tissue-to-subcutaneous adipose tissue ratio. Visceral adipose tissue/subcutaneous adipose tissue was not correlated with body mass index (r = -0.015, p = NS) and therefore provides additional unique information independent of body mass index. Sepsis patients with higher visceral adipose tissue/subcutaneous adipose tissue had greater 90-day mortality than patients with lower visceral adipose tissue/subcutaneous adipose tissue (log-rank test, linear-by linear association p < 0.005). After adjustment for significant covariates using Cox regression, increased visceral adipose tissue/subcutaneous adipose tissue quartile was significantly associated with increased 90-day mortality with hazard ratios of 2.01 (95% CI, 1.01-3.99) for the third visceral adipose tissue/subcutaneous adipose tissue quartile compared with the first quartile and 2.32 (95% CI, 1.15-4.69) for the highest visceral adipose tissue/subcutaneous adipose tissue quartile when compared with the first quartile. Increased mortality for patients with higher visceral adipose tissue/subcutaneous adipose tissue was found for both patients with body mass index less than 25 kg/m (p = 0.004) and for body mass index greater than or equal to 25 kg/m (p = 0.023). Furthermore, we found significantly greater need for mechanical ventilation, renal replacement therapy, and ICU stay in patients in the highest visceral adipose tissue/subcutaneous adipose tissue quartile. The ratio of proinflammatory (interleukin-8) to anti-inflammatory (interleukin-10) plasma cytokine levels was greater in patients with higher visceral adipose tissue/subcutaneous adipose tissue than in those with lower visceral adipose tissue/subcutaneous adipose tissue (p = 0.043).

CONCLUSIONS

Visceral obesity, defined by a high visceral adipose tissue-to-subcutaneous adipose tissue ratio, contributes to adverse outcome in sepsis patients perhaps because of a greater pro- versus anti-inflammatory response.

[Above and beyond BMI : Alternative methods of measuring body fat and muscle mass in critically ill patients and their clinical significance]

Obesity leads to better survival in critically ill patients. Although there are several studies confirming this thesis, the "obesity paradox" is still surprising from the clinician's perspective. One explanation for the "obesity paradox" is the fact that the body mass index (BMI), which is used in almost all clinical evaluations to determine weight categories, is not an appropriate measure of fat and skeletal muscle mass and its distribution in critically ill patients. In addition, height and weight are frequently estimated rather than measured. Central obesity has been identified in many disorders as an independent risk factor for an unfavourable outcome. The first clues are to be found in intensive care. Along with obesity, an individual's entire muscle mass is a variable that has an influence on outcome. Central obesity can be measured relatively easily with an abdominal calliper, but the calculation of muscle mass is more complex. A valid and detailed measurement of this can be obtained using computed tomography (CT) images, acquired during routine care. For future clinical observation or interventional studies, single cross-sectional CT is a more sophisticated tool for measuring patients' anthropometry than a measuring tape and callipers. Patients with sarcopenic obesity, for example, who may be at a particular risk, can only be identified using imaging procedures such as single cross-sectional CT. Thus, BMI should take a back seat as an anthropometric tool, both in the clinic and in research.