Development of a two-hit lethal liver injury model in swine.

PURPOSE: Noncompressible truncal hemorrhage remains a leading cause of preventable death in the prehospital setting. Standardized and reproducible large animal models are essential to test new therapeutic strategies. However, existing injury models vary significantly in consistency and clinical accuracy. This study aims to develop a lethal porcine model to test hemostatic agents targeting noncompressible abdominal hemorrhages. METHODS: We developed a two-hit injury model in Yorkshire swine, consisting of a grade IV liver injury combined with hemodilution. The hemodilution was induced by controlled exsanguination of 30% of the total blood volume and a 3:1 resuscitation with crystalloids. Subsequently, a grade IV liver injury was performed by sharp transection of both median lobes of the liver, resulting in major bleeding and severe hypotension. The abdominal incision was closed within 60 s from the injury. The endpoints included mortality, survival time, serum lab values, and blood loss within the abdomen. RESULTS: This model was lethal in all animals (5/5), with a mean survival time of 24.4 ± 3.8 min. The standardized liver resection was uniform at 14.4 ± 2.1% of the total liver weight. Following the injury, the MAP dropped by 27 ± 8mmHg within the first 10 min. The use of a mixed injury model (i.e., open injury, closed hemorrhage) was instrumental in creating a standardized injury while allowing for a clinically significant hemorrhage. CONCLUSION: This novel highly lethal, consistent, and clinically relevant translational model can be used to test and develop life-saving interventions for massive noncompressible abdominal hemorrhage.

Safety of the injectable expanding biopolymer foam for non-compressible truncal bleeding in swine.

BACKGROUND: A novel hydrophobically modified chitosan (hm-chitosan) polymer has been previously shown to improve survival in a non-compressible intra-abdominal bleeding model in swine. We performed a 28-day survival study to evaluate the safety of the hm-chitosan polymer in swine. METHODS: Female Yorkshire swine (40-50 kg) were used. A mild, non-compressible, closed-cavity bleeding model was created with splenic transection. The hm-chitosan polymer was applied intra-abdominally through an umbilical nozzle in the same composition and dose previously shown to improve survival. Animals were monitored intraoperatively and followed 28 days postoperatively for survival, signs of pain, and end-organ function. Gross pathological and microscopic evaluations were performed at the conclusion of the experiment. RESULTS: A total of 10 animals were included (hm-chitosan = 8; control = 2). The 2 control animals survived through 28 days, and 7 of the 8 animals from the hm-chitosan group survived without any adverse events. One animal from the hm-chitosan group required early termination of the study for signs of pain, and superficial colonic ulcers were found on autopsy. Laboratory tests showed no signs of end-organ dysfunction after exposure to hm-chitosan after 28 days. On gross pathological examination, small (<0.5 cm) peritoneal nodules were noticed in the hm-chitosan group, which were consistent with giant-cell foreign body reaction in microscopy, presumably related to polymer remnants. Microscopically, no signs of systemic polymer embolization or thrombosis were noticed. CONCLUSION: Prolonged intraperitoneal exposure to the hm-chitosan polymer was tolerated without any adverse event in the majority of animals. In the single animal that required early termination, the material did not appear to be associated with end-organ dysfunction in swine. Superficial colonic ulcers that would require surgical repair were identified in 1 out of 8 animals exposed to hm-chitosan.

SELF-EXPANDING FOAM VS PRE-PERITONEAL PACKING FOR EXSANGUINATING PELVIC HEMORRHAGE.

BACKGROUND: Mortality for pelvic fracture patients presenting with hemorrhagic shock ranges from 21-57%. The objective of this study was to develop a lethal and clinically-relevant pelvic hemorrhage animal model with and without bony fracture for evaluating therapeutic interventions. ResQFoam is a self-expanding foam that has previously been described to significantly decrease mortality in large-animal models of abdominal exsanguination. We hypothesized that administration of ResQFoam into the pre-peritoneal space could decrease mortality in exsanguinating pelvic hemorrhage. METHODS: Two pelvic hemorrhage models were developed using non-coagulopathic swine. Pelvic hemorrhage model #1: bilateral, closed-cavity, major vascular retro-peritoneal hemorrhage without bony pelvic fracture. After injury, animals received no treatment (control, n = 10), underwent pre-peritoneal packing using laparotomy pads (n = 11), or received ResQFoam (n = 10) injected into the pre-peritoneal space. Pelvic hemorrhage model #2: unilateral, closed-cavity, retro-peritoneal hemorrhage injury (with intra-peritoneal communication) combined with complex pelvic fracture. After injury, animals received resuscitation (control, n = 12), resuscitation with pre-peritoneal packing (n = 10) or with ResQFoam injection (n = 10) into the pre-peritoneal space. RESULTS: For model #1, only ResQFoam provided a significant survival benefit. The median survival times were 50 and 67 minutes for pre-peritoneal packing and ResQFoam, compared to 6 minutes with controls (p = 0.002 and 0.057, respectively). Foam treatment facilitated hemodynamic stabilization and resulted in significantly less hemorrhage (21.5 ± 5.3 g/kg) relative to controls (31.6 ± 5.0 g/kg, p < 0.001) and pre-peritoneal packing (32.7 ± 5.4 g/kg, p < 0.001). For model #2, both ResQFoam and pre-peritoneal packing resulted in significant survival benefit compared to controls. The median survival times were 119 and 124 minutes for the pre-peritoneal packing and ResQFoam groups, compared to 4 minutes with controls (p = 0.004 and 0.013, respectively). CONCLUSIONS: Percutaneous injection of ResQFoam into the pre-peritoneal space improved survival relative to controls, and similar survival benefit was achieved compared to standard pre-peritoneal pelvic packing. The technology has potential to augment the armamentarium of tools to treat pelvic hemorrhage.Study Type: This is a Basic Science paper and, therefore, does not require level of evidence.

Open Abdomen in Elderly Patients With Surgical Sepsis: Predictors of Mortality.

INTRODUCTION: Elderly patients are frequently presenting with emergency surgical conditions. The open abdomen technique is widely used in abdominal emergencies needing rapid control of intrabdominal contamination. However, specific predictors of mortality identifying candidates for comfort care are understudied. METHODS: The 2013-2017 the American College of Surgeons-National Surgical Quality Improvement Program database was queried for emergent laparotomies performed in geriatric patients with sepsis or septic shock in whom fascial closure was delayed. Patients with acute mesenteric ischemia were excluded. The primary outcome was 30-d mortality. Univariable analysis, followed by multivariable logistic regression, was performed. Mortality was computed for combinations of the five predictors with the highest odds ratios (OR). RESULTS: A total of 1399 patients were identified. The median age was 73 (69-79) y, and 54.7% were female. 30-d mortality was 50.6%. In the multivariable analysis, the most important predictors were as follows: American Society of Anesthesiologists status 5 (OR = 4.80, 95% confidence interval [CI], 1.85-12.49 P = 0.002), dialysis dependence (OR = 2.65, 95% CI 1.54-4.57, P < 0.001), congestive hearth failure (OR = 2.53, 95% CI 1.52-4.21, P < 0.001), disseminated cancer (OR = 2.61, 95% CI 1.55-4.38, P < 0.001), and preoperative platelet count of <100,000 cells/µL (OR = 1.87, 95% CI 1.15-3.04, P = 0.011). The presence of two or more of these factors resulted in over 80% mortality. The absence of all these risk factors results in a survival rate of 62.1%. CONCLUSIONS: In elderly patients, surgical sepsis or septic shock requiring an open abdomen for surgical management is highly lethal. The presence of several combinations of preoperative comorbidities is associated with a poor prognosis and can identify patients who can benefit from timely initiation of palliative care.

Revisiting abdominal closure in mesenteric ischemia: is there an association with outcome?

PURPOSE: Current guidelines advocate liberal use of delayed abdominal closure in patients with acute mesenteric ischemia (AMI) undergoing laparotomy. Few studies have systematically examined this practice. The goal of this study was to evaluate the effect of delayed abdominal closure on postoperative morbidity and mortality in patients with AMI. METHODS: We performed a retrospective cohort study of the ACS-NSQIP 2013-2017 registry. We included patients with a diagnosis of AMI undergoing emergency laparotomy. Patients were divided into two groups based on the type of abdominal closure: (1) delayed fascial closure (DFC) when no layers of the abdominal wall were closed and (2) immediate fascial closure (IFC) if deep layers or all layers of the abdominal wall were closed. Propensity score matching was performed based on comorbidities, pre-operative, and operative characteristics. Univariable analysis was performed on the matched sample. RESULTS: The propensity-matched cohort consisted of 1520 patients equally divided into the DFC and IFC groups. The median (IQR) age was 68 (59-77), and 836 (55.0%) were female. Compared to IFC, the DFC group showed increased in-hospital mortality (38.9% vs. 31.6%, p = 0.002), 30-day mortality (42.4% vs. 36.3%, p = 0.012), and increased risk of respiratory failure (59.5% vs. 31.2%, p < 0.001). CONCLUSIONS: The delayed fascial closure technique was associated with increased mortality compared to immediate fascial closure. These findings do not support the blanket incorporation of delayed closure in mesenteric ischemia care or its previously advocated liberal use.

Timing and choice of systemic anticoagulation in the setting of extremity arterial injury repair.

PURPOSE: The role of perioperative anticoagulation in the setting of peripheral arterial injury remains unclear. We hypothesized that early initiation of anticoagulation is associated with a reduced amputation rate without increasing bleeding complications. METHODS: Using the 2016-2019 ACS-TQIP database, adult patients with upper and lower extremity vascular injuries who underwent open arterial repair and received anticoagulation were included. Patients were divided into two groups: (1) early venous thromboembolism prophylaxis (≤ 24 h) and (2) late prophylaxis (> 24 h) following arterial repair. The primary outcomes were the rates of limb amputation and bleeding complications. Multivariable logistic regression was used to estimate the impact of timing and type of anticoagulation on the rates of limb amputation and bleeding complications. RESULTS: 4379 patients were included, and 83.9% were males. 68.1% of patients received early anticoagulation, whereas 31.9% received late thromboprophylaxis. Low-molecular-weight heparin (LMWH) was used in 62.0% of patients, and unfractionated heparin (UFH) was administered in 34.3% of patients. Multivariable analysis showed that late initiation of thromboprophylaxis (OR = 1.69 [1.16-2.45], p = 0.006) and use of UFH (OR = 2.61 [1.80-3.79], p < 0.001) were associated with increased rate of amputation. Early initiation of anticoagulation (OR = 2.16 [1.63-2.85], p < 0.001) was associated with increased risk of bleeding complications requiring blood transfusions. Similarly, the use of UFH was associated with a higher rate of bleeding events compared to LWMH (OR = 2.61, [1.80-3.79], p < 0.001). CONCLUSION: Patients with the operative repair of arterial injuries receiving early perioperative anticoagulation demonstrated an improved limb salvage outcome than those who received late thromboprophylaxis. Our data also suggest that early initiation of prophylaxis may be associated with increased bleeding risk, which may be attenuated using LMWH compared to UFH.

Complicated Abdominal Wall Hernias in the Elderly: Time Is Life and Comorbidities Matter.

BACKGROUND: Abdominal wall hernias represent a common problem that can present as surgical emergencies with increased morbidity and mortality. The data examining outcomes in elderly patients with hernia emergencies is scant. METHODS: The 2007-2017 ACS-NSQIP database was queried. Patients ≥65 years old with a diagnosis of acute complicated abdominal wall hernia were included. Univariable and multivariable analyses were used to identify independent predictors of 30-day mortality and surgical site infection (SSI). RESULTS: Main predictors of 30-day mortality were admission from nursing home or chronic care facility (OR = 1.62, 95% CI: 1.10-2.38, P = .014), transfer from outside ED (OR = 1.81, 95% CI: 1.31-2.51, P < .001), days from admission to operation (OR = 1.05, 95% CI: 1.02-1.08, P = .002), recent significant weight loss (OR = 1.95, 95% CI: 1.12-3.37, P = .018), pre-operative septic shock (OR = 4.13, 95% CI: 2.44-6.99, P < .001), ventilator dependence (OR = 2.50, 95% CI: 1.29-4.81, P = .006), and ASA status. When compared to open repair, laparoscopic repair emerged as protective against SSI (OR = .34, 95% CI: .17-.66, P = .001). Bowel resection (OR = 2.15, 95% CI: 1.63-2.84, P < .001) and increasing wound class were risk factors for SSI. CONCLUSION: In the elderly patient presenting with an acute complicated abdominal wall hernia, time to surgery is crucial for survival, and comorbidities influence outcome. Laparoscopy is an option in management due to its decreased risk of surgical site infection without increased mortality, whenever patient factors are favorable for this approach.

Delayed fascial closure in nontrauma abdominal emergencies: A nationwide analysis.

BACKGROUND: Initially used in trauma management, delayed abdominal closure endeavors to decrease operative time during the index operation while still being lifesaving. Its use in emergency general surgery is increasing, but the data evaluating its outcome are sparse. We aimed to study the association between delayed abdominal closure, mortality, morbidity, and length of stay in an emergency surgery cohort. METHODS: The 2013 to 2017 American College of Surgeons National Surgical Quality Improvement Program database was examined for patients undergoing emergency laparotomy. The patients were classified by the timing of abdominal wall closure: delayed fascial closure versus immediate fascial closure. Propensity score matching was performed based on preoperative covariates, wound classification, and performance of bowel resection. The outcomes were then compared by univariable analysis. RESULTS: After matching, both the delayed fascial closure and immediate fascial closure groups consisted of 3,354 patients each. Median age was 65 years, and 52.6% were female. The delayed fascial closure group had a higher in-hospital mortality (35.3% vs 25.0%, P < .001), a higher 30-day mortality (38.6% vs 29.0%, P < .001), a higher proportion of acute kidney injury (9.5% vs 6.6%, P < .001), a lower proportion of postoperative sepsis (11.8% vs 15.6%, P < .001), and a lower proportion of surgical site infection (3.4% vs 7.0%, P < .001). CONCLUSION: Compared with immediate fascial closure, delayed fascial closure is associated with an increased mortality in the patients matched based on comorbidities and surgical site contamination. In emergency general surgery, delaying abdominal closure may not have the presumed overarching benefits, and its indications must be further defined in this population.

Bowel Ischemia in COVID-19 Infection: One-Year Surgical Experience.

BACKGROUND: COVID-19 is a deadly multisystemic disease, and bowel ischemia, the most consequential gastrointestinal manifestation, remains poorly described. Our goal is to describe our institution's surgical experience with management of bowel ischemia due to COVID-19 infection over a one-year period. METHODS: All patients admitted to our institution between March 2020 and March 2021 for treatment of COVID-19 infection and who underwent exploratory laparotomy with intra-operative confirmation of bowel ischemia were included. Data from the medical records were analyzed. RESULTS: Twenty patients were included. Eighty percent had a new or increasing vasopressor requirement, 70% had abdominal distension, and 50% had increased gastric residuals. Intra-operatively, ischemia affected the large bowel in 80% of cases, the small bowel in 60%, and both in 40%. Sixty five percent had an initial damage control laparotomy. Most of the resected bowel specimens had a characteristic appearance at the time of surgery, with a yellow discoloration, small areas of antimesenteric necrosis, and very sharp borders. Histologically, the bowel specimens frequently have fibrin thrombi in the small submucosal and mucosal blood vessels in areas of mucosal necrosis. Overall mortality in this cohort was 33%. Forty percent of patients had a thromboembolic complication overall with 88% of these developing a thromboembolic phenomenon despite being on prophylactic pre-operative anticoagulation. CONCLUSION: Bowel ischemia is a potentially lethal complication of COVID-19 infection with typical gross and histologic characteristics. Suspicious clinical features that should trigger surgical evaluation include a new or increasing vasopressor requirement, abdominal distension, and intolerance of gastric feeds.

Development of a field artificial intelligence triage tool: Confidence in the prediction of shock, transfusion, and definitive surgical therapy in patients with truncal gunshot wounds.

BACKGROUND: In-field triage tools for trauma patients are limited by availability of information, linear risk classification, and a lack of confidence reporting. We therefore set out to develop and test a machine learning algorithm that can overcome these limitations by accurately and confidently making predictions to support in-field triage in the first hours after traumatic injury. METHODS: Using an American College of Surgeons Trauma Quality Improvement Program-derived database of truncal and junctional gunshot wound (GSW) patients (aged 16-60 years), we trained an information-aware Dirichlet deep neural network (field artificial intelligence triage). Using supervised training, field artificial intelligence triage was trained to predict shock and the need for major hemorrhage control procedures or early massive transfusion (MT) using GSW anatomical locations, vital signs, and patient information available in the field. In parallel, a confidence model was developed to predict the true-class probability (scale of 0-1), indicating the likelihood that the prediction made was correct, based on the values and interconnectivity of input variables. RESULTS: A total of 29,816 patients met all the inclusion criteria. Shock, major surgery, and early MT were identified in 13.0%, 22.4%, and 6.3% of the included patients, respectively. Field artificial intelligence triage achieved mean areas under the receiver operating characteristic curve of 0.89, 0.86, and 0.82 for prediction of shock, early MT, and major surgery, respectively, for 80/20 train-test splits over 1,000 epochs. Mean predicted true-class probability for errors/correct predictions was 0.25/0.87 for shock, 0.30/0.81 for MT, and 0.24/0.69 for major surgery. CONCLUSION: Field artificial intelligence triage accurately identifies potential shock in truncal GSW patients and predicts their need for MT and major surgery, with a high degree of certainty. The presented model is an important proof of concept. Future iterations will use an expansion of databases to refine and validate the model, further adding to its potential to improve triage in the field, both in civilian and military settings. LEVEL OF EVIDENCE: Prognostic, Level III.

A Paradigm Shift in Critical Care Infrastructure in Complex Settings: Evaluating an Ultraportable Operating Room to Improve Field Surgical Safety.

INTRODUCTION: Scarcity of operating rooms and personal protective equipment in far-forward field settings make surgical infections a potential concern for combat mortality and morbidity. Surgical and transport personnel also face infectious risks from bodily fluid exposures. Our study aimed to describe the serial, proof-of-concept testing of the SurgiBox technology: an inflatable sterile environment that addresses the aforementioned problems, fits on gurneys and backpacks, and drapes over incisions. MATERIALS AND METHODS: The SurgiBox environmental control unit and inflatable enclosure were optimized over five generations based on iterative feedback from stakeholders experienced in surgery in austere settings. The airflow system was developed by analytic modeling, verified through in silico modeling in SOLIDWORKS, and confirmed with prototype smoke-trail checking. Particulate counts evaluated the enclosure's ability to control and mitigate users' exposures to potentially infectious contaminants from the surgical field in various settings. SurgiBox enclosures were setup over a mannequin's torso, in a configuration and position for either thoracic or abdominal surgery. A particle counter was serially positioned in sternotomy and laparotomy positions, as well as bilateral flank positions. This setup was repeated with open ports exposing the enclosure to the external environment. To simulate stress scenarios, sampling was repeated with enclosure measurements during an increase in external particulate concentration. RESULTS: The airflow technology effectively kept contaminants away from the incision and maintained a pressure differential to reduce particle entry. Benchtop testing demonstrated that even when ports were opened or the external environment had high contaminant burden, the enclosed surgical field consistently registered 0 particle count in all positions. Time from kit opening to incision averaged 54.5 seconds, with the rate-limiting step being connecting the environmental control unit to the enclosure. The portable kit weighted 5.9 lbs. CONCLUSIONS: Analytic, in silico, and mechanical airflow modeling and benchtop testing have helped to quantify the SurgiBox system's reliability in creating and maintaining an operating room-quality surgical field within the enclosure as well as protecting the surgical team outside the enclosure. More recent and ongoing work has focused on specifying optimal use settings in the casualty chain of care, expanding support for circumferential procedures, automating airflow control, and accelerating system setup. SurgiBox's ultimate goal is to take timely, safe surgery to patients in even the most austere of settings.

Isolated rib cage fractures in the elderly: Do all patients belong to the intensive care unit? A retrospective nationwide analysis.

BACKGROUND: Western Trauma Association guidelines recommend admitting patients 65 years or older with two or more rib fractures diagnosed by chest radiograph to the intensive care unit (ICU). Increased use of computed tomography has led to identification of less severe, "occult" rib fractures. We aimed to evaluate current national trends in disposition of older patients with isolated rib cage fractures and to identify characteristics of patients initially admitted to the ward who failed ward management. METHODS: A retrospective cohort study of patients 65 years or older with isolated two or more blunt rib cage fractures using the 2010 to 2016 American College of Surgeons Trauma Quality Improvement Program database was performed. Ward failure was defined as patients initially admitted to the ward with subsequent need for unplanned ICU admission or intubation. Multivariable analyses were derived to study the independent predictors of failure of ward management. Propensity score matching sub-analysis was used to assess outcomes in patients admitted to the ward versus ICU. RESULTS: There were 5,021 patients included in the analysis. Of these patients, 1,406 (28.0%) were admitted to the ICU. On multivariable analysis, age was an independent predictor of ICU admission. Of the 3,577 patients admitted directly to the ward, 38 (1.1%) patients required unplanned intubation or ICU admission. Independent predictors of failure of ward management included chronic renal failure (odds ratio [OR], 7.20; p ≤ 0.001; 95% confidence interval [CI], 2.50-20.76), traumatic pneumothorax (OR, 8.70; p = 0.008; 95% CI, 1.76-42.93), concurrent sternal fracture (OR, 6.52; p ≤ 0.001; 95% CI, 2.53-16.80), drug use disorder (OR, 6.58; p = 0.032; 95% CI, 1.17-36.96), and emergency department oxygen requirement or oxygen saturation less than 95% (OR, 2.38; p = 0.018; 95% CI, 1.16-4.86). Mortality was higher in patients with delayed ICU care versus patients with successful ward disposition (21.1% vs. 0.8%; p < 0.001). CONCLUSION: Our results suggest that the majority of isolated rib cage fractures in older patients are safely managed on the ward with exceedingly low ward failure rates (1.1%). Patients with failure of ward management have significantly higher mortality, and we have identified predictors of failing the ward. LEVEL OF EVIDENCE: Therapeutic/Care Management, level IV; Prognostic III.

Pre-peritoneal pelvic packing for early hemorrhage control reduces mortality compared to resuscitative endovascular balloon occlusion of the aorta in severe blunt pelvic trauma patients: A nationwide analysis.

BACKGROUND: Early hemorrhage control after severe blunt pelvic trauma is life-saving. The aim of this study is to compare the efficacy and outcomes of pre-peritoneal packing (PPP) and Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) with a subsequent hemorrhage control procedure to control life-threatening pelvic hemorrhage in trauma patients. METHODS: A 3-year (2015-2017) retrospective analysis of the Trauma Quality Improvement Program (TQIP) was performed. All blunt trauma patients (aged ≥15 years) who underwent PPP or Zone 3 REBOA placement were included while deaths on arrival and transfers were excluded. Patients were matched on clinical characteristics using propensity score matching (PSM). Univariate analysis was performed to compare mortality, time to procedure, time in ED, transfusion requirements, complications rates, and ICU and hospital length of stay (LOS) amongst patient groups. RESULTS: Of 420 trauma patients, 307 underwent PPP and 113 REBOA. Patients had similar hemodynamics and ISS upon presentation, but PPP patients had a higher GCS (P = 0.037) and more blunt kidney injuries (P = 0.015). After PSM, 206 trauma patients were included in the analysis. There were no significant differences in blood transfusion, LOS, or major complications. Time to REBOA was shorter than time to PPP (52 vs 77.5 min; P<0.001) with longer time in ED (65 vs 51 min; p = 0.023). The 24-hour (32.4 vs 17.7%; P = 0.23) and in-hospital mortality (52.0 vs 37.3%; P = 0.048) were higher after REBOA. CONCLUSION: PPP is associated with improved survival compared to REBOA placement. Delay in definitive hemorrhage control may provide a potential explanation, but causation remains unresolved. This data suggests that early PPP may offer a benefit over REBOA in the setting of hemorrhage after blunt pelvic trauma. Further, large, multi-institutional studies are warranted to support these findings. LEVEL OF EVIDENCE: Prognostic study, level III.

Smoking and risk of surgical bleeding: nationwide analysis of 5,452,411 surgical cases.

BACKGROUND: Although smoking is associated with several postoperative complications, a possible association with surgical bleeding remains unclear. We examined if smoking is associated with a higher risk of surgical bleeding. STUDY DESIGN AND METHODS: We included patients from the American College of Surgeons National Surgical Quality Improvement Program 2007-2016 from 680 hospitals across the United States. Patients with information on age, sex, surgical specialty, and smoking status were included. Surgical bleeding was defined as 1 or more red blood cell (RBC) units transfused intraoperatively to 72 hours postoperatively. The association between smoking and surgical bleeding was examined using logistic regressions adjusted for age, sex, body mass index, ethnicity, comorbidities, laboratory values, American Society of Anesthesiologists score, type of anesthesia, duration of surgery, work relative value unit (surrogate for operative complexity), surgical specialty, and procedure year. RESULTS: A total of 5,452,411 cases were recorded, of whom 19% smoked and 6% received transfusion. Odds ratios for transfusion were 1.06 (95% confidence interval [CI], 1.05-1.07) for smokers versus nonsmokers and 1.06 (95% CI, 1.04-1.09) for current smokers versus never-smokers. Odds ratios for cumulative smoking were 0.97 (95% CI, 0.95-1.00) for greater than 0 to 20 versus 0 pack-years, 1.04 (95% CI, 1.01-1.07) for greater than 20 to 40, and 1.12 (95% CI, 1.09-1.15) for greater than 40 (p for trend < 0.001). Hazard ratios for reoperations due to any cause and to bleeding were 1.28 (95% CI, 1.27-1.31) and 0.99 (95% CI, 0.93-1.04). CONCLUSION: Smoking was associated with a higher risk of RBC transfusion as a proxy for surgical bleeding across all surgical specialties combined.

The dose-dependent relationship between blood transfusions and infections after trauma: A population-based study.

OBJECTIVE: The relationship between total transfusion volume and infection in the trauma patient remains unclear, especially at lower volumes of transfusion. We sought to quantify the cumulative, independent impact of transfusion within 24 hours of admission on the risk of infection in trauma patients. METHODS: Using the Trauma Quality Improvement Program 2013 to 2016 database, we included all patients who received blood transfusions in the first 4 hours. Patients who were transferred or had incomplete/wrongly coded information on transfusion volume were excluded. Patients were divided into 20 cohorts based on the total blood product volume transfused in the first 24 hours. A composite infection variable (INF) was created, including surgical site infection, ventilator-associated pneumonia, urinary tract infection, central line associated blood stream infection, and sepsis. Univariate and stepwise multivariable logistic regression analyses were performed to study the relationship between blood transfusion and INF, controlling for demographics (e.g., age, sex), comorbidities (e.g., cirrhosis, diabetes, steroid use), severity of injury (e.g., vital signs on arrival, mechanism, Injury Severity Score), and operative and angiographic interventions. RESULTS: Of 1,002,595 patients, 37,568 were included. The mean age was 42 ± 18.6 years, 74.6% were males, 68% had blunt trauma, and median Injury Severity Score was 25 [17-34]. Adjusting for all available confounders, odds of INF increased incrementally from 1.00 (reference, 0-2 units) to 1.23 (95% confidence interval, 1.11-1.37) for 4 units transfused to 4.89 (95% confidence interval, 2.72-8.80) for 40 units transfused. Each additional unit increased the odds of INF by 7.6%. CONCLUSION: Transfusion of the bleeding trauma patient was associated with a dose-dependent increased risk of infectious complications. Trauma surgeons and anesthesiologists should resuscitate the trauma patient until prompt hemorrhage control while avoiding overtransfusion. LEVEL OF EVIDENCE: Retrospective cohort study, Therapeutic IV.

Cervical Spine Clearance in Trauma Patients with an Unreliable Physical Examination.

BACKGROUND: The objective of this study was to describe and compare the timing of cervical spine clearance in trauma patients with an unreliable physical examination. METHODS: We prospectively included adult trauma patients admitted with a cervical collar and an unreliable clinical examination (as defined by the NEXUS criteria) at two level 1 trauma centers: one in the USA (US) and one in Denmark (DK). We excluded patients with cervical spine injuries requiring a collar or surgery as treatment and patients with a collar placed after hospital arrival. The primary outcome was time from emergency department (ED) arrival to collar removal. Secondary outcomes included time to CT of the cervical spine (CTCS). At the US trauma center, an institutional protocol allowing cervical spine clearance exclusively by CTCS was in place. At the Danish trauma center, cervical spine clearance was based on a clinical evaluation by an orthopedic surgeon, usually after CTCS. RESULTS: A total of 113 patients were included (US: n = 56; DK: n = 57). The median age was 47 years, and 68% were males. The main reasons for an unreliable physical examination were a Glasgow Coma Scale score below 14 (35%), distracting injuries (26%), cervical spine tenderness (13%) and intoxication (13%). The injury severity score at the US trauma center was higher than at the DK trauma center (median: 17 vs. 11, p = 0.03). Both time to CTCS (median: 41 vs. 18 min, p < 0.0001) and time to collar removal (median: 1042 vs. 49 min, p < 0.0001) were significantly greater at the US trauma center. CONCLUSIONS: Time to collar removal was significantly greater in a trauma center utilizing a cervical spine clearance protocol based on CTCS. As patients may develop complications related to the collar, future studies should clarify how early removal can be implemented without increasing the risk of morbidity.

Obesity as protective against, rather than a risk factor for, postoperative Clostridium difficile infection: A nationwide retrospective analysis of 1,426,807 surgical patients.

BACKGROUND: Recent studies suggest that obesity is a risk factor for Clostridium difficile infection, possibly due to disruptions in the intestinal microbiome composition. We hypothesized that body mass index (BMI) is associated with increased incidence of C. difficile infection in surgical patients. METHODS: In this nationwide retrospective cohort study in 680 American College of Surgeons National Surgical Quality Improvement Program participating sites across the United States, the occurrence of C. difficile infection within 30 days postoperatively between different BMI groups was compared. All American College of Surgeons National Surgical Quality Improvement Program patients between 2015 and 2016 were classified as underweight, normal-weight, overweight, or obese class I-III if their BMI was less than 18.5, 18.5 to 25, 25 to 30, 30 to 35, 35 to 40 or greater than 40, respectively. RESULTS: A total of 1,426,807 patients were included; median age was 58 years, 43.4% were male, and 82.9% were white. The postoperative incidence of C. difficile infection was 0.42% overall: 1.11%, 0.56%, 0.39%, 0.35%, 0.33% and 0.36% from the lowest to the highest BMI group, respectively (p < 0.001 for trend). In univariate then multivariable logistic regression analyses, adjusting for patient demographics (e.g., age, sex), comorbidities (e.g., diabetes, systemic sepsis, immunosuppression), preoperative laboratory values (e.g., albumin, white blood cell count), procedure complexity (work relative unit as a proxy) and procedure characteristics (e.g., emergency, type of surgery [general, vascular, other]), compared with patients with normal BMI, high BMI was inversely and incrementally correlated with the postoperative occurrence of C. difficile infection. The underweight were at increased risk (odds ratio, 1.15 [1.00-1.32]) while the class III obese were at the lowest risk (odds ratio, 0.73 [0.65-0.81]). CONCLUSION: In this nationwide retrospective cohort study, obesity is independently and in a stepwise fashion associated with a decreased risk of postoperative C. difficile infection. Further studies are warranted to explore the potential and unexpected association. LEVEL OF EVIDENCE: Prognostic/Epidemiologic, Level IV.

Spontaneous Retroperitoneal and Rectus Sheath Hemorrhage-Management, Risk Factors and Outcomes.

BACKGROUND: Spontaneous retroperitoneal and rectus sheath hemorrhage (SRRSH) is associated with high mortality in the literature, but studies on the subject are lacking. The objective of this study was to identify early predictors of the need for angiographic or surgical intervention (ASI) in patients with SRRSH and define risk factors for mortality. METHODS: We conducted a retrospective cohort study at a tertiary academic hospital. All patients with computed tomography-identified SRRSH between 2012 to 2017 were included. Exclusion criteria were age below 18 years, possible mechanical cause of SRRSH, aortic aneurysm rupture or dissection, and traumatic or iatrogenic sources of SRRSH. The primary outcome was the incidence of ASI and/or mortality. RESULTS: Of 100 patients included (median age 70 years, 52% males), 33% were transferred from another hospital, 82% patients were on therapeutic anticoagulation, and 90% had serious comorbidities. Overall mortality was 22%, but SRRSH-related mortality was only 6%. Sixteen patients underwent angiographic intervention (n = 10), surgical intervention (n = 5), or both (n = 1). Flank pain (OR 4.15, 95% CI 1.21-14.16, p = 0.023) and intravenous contrast extravasation (OR 3.89, 95% CI 1.23-12.27, p = 0.020) were independent predictors of ASI. Transfer from another hospital (OR 3.72, 95% CI 1.30-10.70, p = 0.015), age above 70 years (OR 4.24, 95% CI 1.25-14.32, p = 0.020), and systolic blood pressure below 110 mmHg at the time of diagnosis (OR 4.59, 95% CI 1.19-17.68, p = 0.027) were independent predictors of mortality. CONCLUSIONS: SRRSH is associated with high mortality but is typically not the direct cause. Most SRRSHs are self-limited and require no intervention. Pattern identification of ASI is hard.