Rates and Risk Factors for 30-Day Morbidity After One-Stage Vertical Banded Gastroplasty Conversions: A Retrospective Analysis.

Background: The vertical banded gastroplasty (VBG) is a historic restrictive bariatric operation often requiring further surgery. In this investigation utilizing the 2021 Metabolic and Bariatric Surgery Accreditation and Quality Improvement Program (MBSAQIP) national dataset, we aim to better define the outcomes of VBG conversions.Methods: We queried the 2021 MBSAQIP dataset for patients who underwent a conversion from a VBG to Roux-en-Y gastric bypass (RYGB) or sleeve gastrectomy (SG). Demographics, comorbidities, laboratory values, and additional patient factors were examined. Rates of key consequential outcome measures 30-day readmission, reoperation, reintervention, mortality, and a composite endpoint (at least 1 of the 4) were further calculated.Results: We identified 231 patients who underwent conversion from VBG to SG (n = 23), RYGB (n = 208), or other anatomy (n = 6), of which 93% of patients were female, and 22% of non-white race. The median age was 56 years and body-mass index (BMI) was 43 kg/m2. The most common surgical indications included weight considerations (48%), reflux (25%), anatomic causes (eg, stricture, fistula, and ulcer; 10%), and dysphagia (6.5%). Thirty-day morbidity rates included reoperation (7.8%), readmission (9.1%), reintervention (4.3%), mortality (.4%), and the composite endpoint (15%). Upon bivariate analysis, we did not identify any specific risk factor for the 30-day composite endpoint.Discussion: One-stage VBG conversions to traditional bariatric anatomy are beset with higher 30-day morbidity relative to primary procedures. Additional MBSAQIP data will be required for aggregation, to better characterize the risk factors inherent in these operations.

Prediction of 30-Day Morbidity and Mortality After Conversion of Sleeve Gastrectomy to Roux-en-Y Gastric Bypass: Use of an Artificial Neural Network.

BACKGROUND: Conversion of sleeve gastrectomy to Roux-en-Y gastric bypass is indicated primarily for unsatisfactory weight loss or gastroesophageal reflux disease (GERD). This study aimed to use a comprehensive database to define predictors of 30-day reoperation, readmission, reintervention, or mortality. An artificial neural network (ANN) was employed to optimize prediction of the composite endpoint (occurrence of 1+ morbid event). METHODS: Areview of 8895 patients who underwent conversion for weight-related or GERD-related indications was performed using the 2021 MBSAQIP national dataset. Demographics, comorbidities, laboratory values, and other factors were assessed for bivariate and subsequent multivariable associations with the composite endpoint (P ≤ .05). Factors considered in the multivariable model were imputed into a three-node ANN with 20% randomly withheld for internal validation, to optimize predictive accuracy. Models were compared using receiver operating characteristic (ROC) curve analysis. RESULTS: 39% underwent conversion for weight considerations and 61% for GERD. Rates of 30-day reoperation, readmission, reintervention, mortality, and the composite endpoint were 3.0%, 7.1%, 2.1%, .1%, and 9.1%, respectively. Of the nine factors associated with the composite endpoint on bivariate analysis, only non-white race (P < .001; odds ratio 1.4), lower body-mass index (P < .001; odds ratio .22), and therapeutic anticoagulation (P = .001; odds ratio 2.0) remained significant upon multivariable analysis. Areas under ROC curves for the multivariable regression, ANN training, and validation sets were .587, .601, and .604, respectively. DISCUSSION: Identification of risk factors for morbidity after conversion offers critical information to improve patient selection and manage postoperative expectations. ANN models, with appropriate clinical integration, may optimize prediction of morbidity.

The Effect of Fluid Pre-loading on Vital Signs and Hemodynamic Parameters in a Porcine Model of Lipopolysaccharide-Induced Endotoxemia.

Background Animal models of distributive hypotension and resuscitation allow the assessment of hemodynamic monitoring modalities and resuscitation strategies. The fluid-first paradigm for resuscitation is currently being challenged with clinical trials. In this investigation, venous return and perfusion are assessed, and full hemodynamics are characterized, in a porcine model of endotoxemic hypotension with and without fluid pre-loading. Methods Two groups of six pigs had the induction of standardized endotoxemic hypotension ("critical hypotension"). Group 1 underwent four 10 cc/kg crystalloid boluses, and Group 2 was not fluid pre-resuscitated. Both groups underwent progressive norepinephrine (NE) up-titration to 0.25 mcg/kg/minute over 30 minutes. Vital signs, central parameters, and laboratory values were obtained at baseline, "critical hypotension," after each bolus and during NE administration. Results Endotoxemia decreased the systemic vascular resistance (SVR) in Group 1 (1031±106 dyn/s/cm-5 versus 738±258 dyn/s/cm-5; P=0.03) and Group 2 (1121±196 dyn/s/cm-5 versus 759±342 dyn/s/cm-5; P=0.003). In Group 1, the four fluid boluses decreased heart rate (HR), pulmonary capillary wedge pressure (PCWP), and central venous pressure (CVP) (P<0.05). No changes were observed in blood pressure, cardiac output (CO), or lactate. NE up-titration increased HR in Group 1 and decreased CVP in both groups. Higher final CVP (11 {3} versus 4 {4} mmHg; P=0.01) and PCWP (5 {1} versus 2 {2} mmHg; P=0.005) values were observed in Group 1 relative to Group 2, reflecting increased venous return. Conclusions Porcine endotoxemic hypotension and resuscitation were robustly characterized. In this model, fluid loading improved venous return with NE, though perfusion (CO) was preserved by increased NE-induced chronotropy.

Central Venous Waveform Analysis and Cardiac Output in a Porcine Model of Endotoxemic Hypotension and Resuscitation.

BACKGROUND: Cardiac output (CO) is a valuable proxy for perfusion, and governs volume responsiveness during resuscitation from distributive shock. The underappreciated venous system has nuanced physiology that confers valuable hemodynamic information. In this investigation, deconvolution of the central venous waveform by the fast Fourier transformation (FFT) algorithm is performed to assess its ability to constitute a CO surrogate in a porcine model of endotoxemia-induced distributive hypotension and resuscitation. STUDY DESIGN: Ten pigs were anesthetized, catheterized, and intubated. A lipopolysaccharides infusion protocol was used to precipitate low systemic vascular resistance hypotension. Four crystalloid boluses (10 cc/kg) were then given in succession, after which heart rate, mean arterial pressure, thermodilution-derived CO, central venous pressure (CVP), and the central venous waveform were collected, the last undergoing fast Fourier transformation analysis. The amplitude of the fundamental frequency of the central venous waveform's cardiac wave (f0-CVP) was obtained. Heart rate, mean arterial pressure, CVP, f0-CVP, and CO were plotted over the course of the boluses to determine whether f0-CVP tracked with CO better than the vital signs, or than CVP itself. RESULTS: Distributive hypotension to a 25% mean arterial pressure decrement was achieved, with decreased systemic vascular resistance (mean 918 ± 227 [SD] dyne/s/cm-5 vs 685 ± 180 dyne/s/cm-5; p = 0.038). Full hemodynamic parameters characterizing this model were reported. Slopes of linear regression lines of heart rate, mean arterial pressure, CVP, f0-CVP, and CO were -2.8, 1.7, 1.8, 0.40, and 0.35, respectively, demonstrating that f0-CVP values closely track with CO over the 4-bolus range. CONCLUSIONS: Fast Fourier transformation analysis of the central venous waveform may allow real-time assessment of CO during resuscitation from distributive hypotension, possibly offering a venous-based approach to clinical estimation of volume responsiveness.

Hemodynamic Parameters in the Assessment of Fluid Status in a Porcine Hemorrhage and Resuscitation Model.

BACKGROUND: Measuring fluid status during intraoperative hemorrhage is challenging, but detection and quantification of fluid overload is far more difficult. Using a porcine model of hemorrhage and over-resuscitation, it is hypothesized that centrally obtained hemodynamic parameters will predict volume status more accurately than peripherally obtained vital signs. METHODS: Eight anesthetized female pigs were hemorrhaged at 30 ml/min to a blood loss of 400 ml. After each 100 ml of hemorrhage, vital signs (heart rate, systolic blood pressure, mean arterial pressure, diastolic blood pressure, pulse pressure, pulse pressure variation) and centrally obtained hemodynamic parameters (mean pulmonary artery pressure, pulmonary capillary wedge pressure, central venous pressure, cardiac output) were obtained. Blood volume was restored, and the pigs were over-resuscitated with 2,500 ml of crystalloid, collecting parameters after each 500-ml bolus. Hemorrhage and resuscitation phases were analyzed separately to determine differences among parameters over the range of volume. Conformity of parameters during hemorrhage or over-resuscitation was assessed. RESULTS: During the course of hemorrhage, changes from baseline euvolemia were observed in vital signs (systolic blood pressure, diastolic blood pressure, and mean arterial pressure) after 100 ml of blood loss. Central hemodynamic parameters (mean pulmonary artery pressure and pulmonary capillary wedge pressure) were changed after 200 ml of blood loss, and central venous pressure after 300 ml of blood loss. During the course of resuscitative volume overload, changes were observed from baseline euvolemia in mean pulmonary artery pressure and central venous pressure after 500-ml resuscitation, in pulmonary capillary wedge pressure after 1,000-ml resuscitation, and cardiac output after 2,500-ml resuscitation. In contrast to hemorrhage, vital sign parameters did not change during over-resuscitation. The strongest linear correlation was observed with pulmonary capillary wedge pressure in both hemorrhage (r2 = 0.99) and volume overload (r2 = 0.98). CONCLUSIONS: Pulmonary capillary wedge pressure is the most accurate parameter to track both hemorrhage and over-resuscitation, demonstrating the unmet clinical need for a less invasive pulmonary capillary wedge pressure equivalent.

The Role of Preoperative Anemia in Predicting Short-Term Morbidity and Mortality After Roux-en-Y Gastric Bypass.

BACKGROUND: Preoperative anemia has been suggested as a contraindication to gastric bypass. Using the Metabolic and Bariatric Surgery Accreditation and Quality Improvement database, this study sought to determine the role of preoperative hematocrit on 30-day morbidity and mortality after laparoscopic Roux-en-Y gastric bypass for weight loss. METHODS: A cohort of 31 981 patients was reviewed for factors associated with a composite primary end point including 30-day reoperation, readmission, reintervention, or mortality, including degree of anemia. Analyzed separately by gender, factors significant on bivariate analysis were included in nominal logistic multivariate analysis to assess for independent significance of the hematocrit level as a risk factor for the primary end point. RESULTS: Upon multivariate analysis, the hematocrit level was significantly associated with the 30-day end point in the male cohort (P = .05), specifically, severe anemia (hematocrit <35%) conferred an increased risk relative to a normal hematocrit (odds ratio 1.5, P = .03). There was no association of hematocrit with the 30-day end point in the female cohort. CONCLUSION: Bariatricians should carefully consider the appropriateness of a gastric bypass over a less anemogenic procedure such as sleeve gastrectomy in patients, particularly men with preoperative anemia.

Prediction of thirty-day morbidity and mortality after laparoscopic sleeve gastrectomy: data from an artificial neural network.

BACKGROUND: Multiple patient factors may convey increased risk of 30-day morbidity and mortality after laparoscopic vertical sleeve gastrectomy (LVSG). Assessing the likelihood of short-term morbidity is useful for both the bariatric surgeon and patient. Artificial neural networks (ANN) are computational algorithms that use pattern recognition to predict outcomes, providing a potentially more accurate and dynamic model relative to traditional multiple regression. Using a comprehensive national database, this study aims to use an ANN to optimize the prediction of the composite endpoint of 30-day readmission, reoperation, reintervention, or mortality, after LVSG. METHODS: A cohort of 101,721 LVSG patients was considered for analysis from the 2016 Metabolic and Bariatric Surgery Accreditation and Quality Improvement Program national dataset. Select patient factors were chosen a priori as simple, pertinent and easily obtainable, and their association with the 30-day endpoint was assessed. Those factors with a significant association on both bivariate and multivariate nominal logistic regression analysis were incorporated into a back-propagation ANN with three nodes each assigned a training value of 0.333, with k-fold internal validation. Logistic regression and ANN models were compared using area under receiver-operating characteristic curves (AUROC). RESULTS: Upon bivariate analysis, factors associated with 30-day complications were older age (P = 0.03), non-white race, higher initial body mass index, severe hypertension, diabetes mellitus, non-independent functional status, and previous foregut/bariatric surgery (all P < 0.001). These factors remained significant upon nominal logistic regression analysis (n = 100,791, P < 0.001, r2= 0.008, AUROC = 0.572). Upon ANN analysis, the training set (80% of patients) was more accurate than logistic regression (n = 80,633, r2= 0.011, AUROC = 0.581), and it was confirmed by the validation set (n = 20,158, r2= 0.012, AUROC = 0.585). CONCLUSIONS: This study identifies a panel of simple and easily obtainable preoperative patient factors that may portend increased morbidity after LSG. Using an ANN model, prediction of these events can be optimized relative to standard logistic regression modeling.

Obesity in Liver Transplantation: A Risk Factor for Unplanned Reoperation and Prolonged Operative Time.

Selection of orthotopic liver transplantation (OLT) candidates is increasingly inclusive of patients with high BMI. We aim to characterize the influence of obesity on the surgical outcome measures of prolonged operative time and unplanned reoperation. We reviewed the records of obese and normal weight OLT recipients over a 10-year period from a single institution. Variables that trended (P < 0.1) with endpoints on univariate analysis were put into multivariate logistic regression models to determine independent association (P < 0.05). We included 195 obese and 171 normal weight OLT recipients in our study. On multivariate analysis, obesity was the only preoperative risk factor that trended with unplanned reoperation (odds ratio 2, P = 0.05). Similarly, only obesity remained independently associated with prolonged length of operation (defined as ≥275 minutes) on multivariate analysis (odds ratio 1.7, P = 0.04). In summary, obesity may make OLT more technically challenging and, thus, represents an independent risk factor for unplanned reoperations and prolonged operative time.

A Structured Remediation Program Results in Durable Improvement of American Board of Surgery In-Training Examination (ABSITE®) Performance.

The objective of this study was to assess the results of a structured remediation program for surgical residents scoring poorly on the American Board of Surgery In-Training Examination®. Residents scoring below the threshold (<20th percentile) were placed in a remediation program consisting of textbook-based review and mandatory weekly quizzes overseen by the program director. The effects of the program were assessed over a five-year period (2014-2018). Of 168 tests taken, 23 (13.7%) instances of scoring below the threshold occurred (average percentile 11, range 1-19). Postremediation scores in the subsequent year improved with a median (IQR) percentile increase of 29 [23.5, 46] (P < 0.001). Two residents scored below the threshold twice; all others continued to score above the threshold. Participation in a structured remediation program results in dramatic improvement in American Board of Surgery In-Training Examination® performance, and a single occurrence of poor performance does not necessarily lead to a permanent handicap in academic performance.

Laparoscopic Sleeve Gastrectomy has a Lower Risk of Postoperative Bleeding Than Laparoscopic Roux-en-Y Gastric Bypass.

Measures to reduce postoperative bleeding (POB) after bariatric surgery is skewed toward laparoscopic sleeve gastrectomy (LSG). We use 2015 Metabolic and Bariatric Surgery Accreditation and Quality Improvement Program (MBSAQIP) to characterize the differences in bleeding rates between LSG and laparoscopic Roux-en-Y gastric bypasses (LRYGB). Propensity score matching and multivariable logistic regressions tested for independent differences in POB rates. A total of 168,093 patients from 742 centers were identified in the data set. After selection 36,925 patients with LRYGB and 20,020 patients with LSG were included in the analysis. A total of 710 (1.25%) patient suffered a POB. The independent odds of POB were 38% lower for patients having LSG compared with those having LRYGB (odds ratio, 0.62; 95% confidence interval=0.51-0.76). This difference is more pronounced with intraoperative securing of the staple line. Appropriate measures to reduce POB after each type of bariatric procedure is warranted.

Postoperative bleeding after laparoscopic Roux en Y gastric bypass: predictors and consequences.

BACKGROUND: Laparoscopic Roux-en-Y gastric bypass (LRYGB) is a common, safe and effective bariatric procedure. Bleeding is a significant source of postoperative morbidity. We aimed to determine the incidence, outcomes, and predictors of postoperative bleeding after LRYGB. METHODS: LRYGB patients included in the Metabolic and Bariatric Surgery Accreditation and Quality Improvement Program (MBSAQIP) 2015 dataset were identified. Preoperative and intraoperative factors were tested for associations with bleeding using univariable and multivariable logistic regression analysis. Outcomes of length of stay, in-hospital mortality, 30-day mortality, discharge disposition, and 30-day complications among patients with and without clinically significant postoperative bleeding were compared using multivariable regression. RESULTS: In the 43,280 LRYGB patients included in this analysis, postoperative bleeding occurred in 652 (1.51%) patients. Of these, 165 (25.3%) underwent a re-operation and 97 (14.9%) underwent an unplanned endoscopy for 'bleeding'. Postoperative bleeding was associated with a longer median postoperative length of stay (4 vs. 2 days), higher in-hospital mortality (1.23 vs. 0.04%), higher 30-day mortality (1.38 vs. 0.15%), discharge to an extended-care facility (3.88 vs. 0.6%), and higher rates of major complications (all P < 0.05). Independent predictors of postoperative bleeding included; a history of renal insufficiency (OR 2.55, 95% CI 1.43-4.52), preoperative therapeutic anticoagulation (OR 2.44, 95% CI 1.69-3.53), and revisional surgery (OR 1.45, 95% CI 1.06-1.97). Intraoperative associated factors included conversions (OR 3.37, 95% CI 1.42-7.97), and drain placement (OR 1.40, 95% CI 1.18-1.67). Robotic approaches resulted in independently lower postoperative bleeding rates (OR 0.50, 95% CI 0.32-0.77). CONCLUSIONS: Postoperative bleeding occurs in 1.5% of patients undergoing a LRYGB and is associated with significantly increased morbidity and mortality. We have identified patient and operative factors that are independently associated with postoperative bleeding.

A Novel Risk Score Predicts Operative Mortality After Acute Type A Aortic Dissection Repair.

BACKGROUND: Current stratification systems for patients presenting with acute type A aortic dissection rely on signs of malperfusion to predict mortality. The authors sought to develop an algorithm to readily risk stratify these patients using admission characteristics. METHODS: Two hundred sixty-nine consecutive patients who underwent type A repair between 2002 and 2015 were reviewed for easily obtainable preoperative demographics and laboratory values deemed a priori as potential predictors of operative mortality. Multiple logistic regression analysis was performed to determine independent significance, and linear regression was performed to generate the concomitant regression expression of the variables significant on bivariate analysis. RESULTS: Operative mortality was 16% (43/269) and was 29% (34/119) among patients who presented with malperfusion. Upon multivariate analysis, creatinine (p = 0.008), liver malperfusion (p = 0.006), and lactic acid level (p = 0.0007) remained independent significant predictors. Regression coefficients allowed the generation of a risk score as 5.5 × (lactic acid [mmol/L]) + 8 × (creatinine [mg/dL]) ± 8 (+ if liver malperfusion presents, - if no liver malperfusion). Upon receiver-operating characteristic curve analysis this model generated a c-statistic of 0.75. Operative mortality among patients within the lowest tertile (risk score < 7) was 4%, whereas patients in the middle (7 to 20) and highest (≥20) tertiles had mortality rates of 14% 37%, respectively. CONCLUSIONS: Although still requiring external validation, the innovative risk score presented necessitates knowledge of lactic acid, serum creatinine, and liver function tests. The algorithm predicts operative mortality with high accuracy and offers clinicians a novel tool to improve preoperative guidance and prognosis.

Staple Line Treatment and Bleeding After Laparoscopic Sleeve Gastrectomy.

BACKGROUND AND OBJECTIVES: Staple line treatment during laparoscopic sleeve gastrectomy (LSG) remains a controversial issue among bariatric surgeons. The objective of this study was to compare rates of postoperative bleeding (POB) among various methods of staple line reinforcement. METHODS: The Metabolic and Bariatric Surgery Accreditation and Quality Improvement Program 2015 dataset was queried for patients undergoing an LSG. Patients were stratified by staple line treatment groups-no treatment (NT), suture oversewing (OVERSEW), buttressing by a commercial product (BUTTRESS), and both buttress and oversew (COMBINATION). The primary outcome was POB. Multivariable logistic regression was used to compare POB rates among the treatment groups. RESULTS: In the 98,142 LSG patients meeting selection criteria, 623 (0.63%) patients had POB and 181 (0.18%) required reoperation. POB occurred in 0.80% for the NT group, 0.68% for the OVERSEW group, 0.57% for the BUTTRESS group, and 0.55% for the COMBINATION group. On multivariable analyses, all treatment groups were less likely to have POB compared with the NT group-OVERSEW (odds ratio [OR] 0.73, 95% confidence interval [CI] 0.54-0.98), BUTTRESS (OR 0.70, 95% CI 0.57-0.84), and COMBINATION (OR 0.66, 95% CI 0.50-0.89) (all P < .01). Subset analysis revealed no difference between BUTTRESS and OVERSEW (OR 0.95, 95% CI 0.71-1.26, P = .71). CONCLUSIONS: Relative to an NT staple line, the use of OVERSEW or BUTTRESS can decrease the rates of POB by up to 30%. The use of these techniques should be strongly considered by the bariatric surgeon.

The Right Way to Teach Left-Handed Residents: Strategies for Training by Right Handers.

PURPOSE: Left-handed (LH) residents remain underrepresented among surgical trainees, and there are few available data on how best to train them. The challenge is amplified when pairing a LH resident with a right-handed (RH) mentor. This report provides recommendations on how to improve the training of LH surgeons in a safe and effective manner. METHODS: A comprehensive literature review was performed using different databases and search engines to identify all articles relevant to the training of LH residents. RESULTS: A total of 40 articles highlighted the challenges for LH surgical residents and RH mentors. Our recommendations are based on the following 4 themes: identifying inherent differences in left vs. RH residents, providing guidance to RH mentors training LH residents, adapting the RH environment to the LH surgeon, and maximizing safety during training. CONCLUSION: An organized approach needs to be taken in training the LH resident. Changes should be instituted at program-wide and national levels to ensure that the training experience of the sinistral surgical resident is optimized.

Exponential decay modeling can define parameters of weight loss trajectory after laparoscopic Roux-en-Y gastric bypass.

BACKGROUND: Laparoscopic Roux-en-Y gastric bypass (LRYGB) produces durable and clinically significant weight loss. We aim to characterize the trajectory of weight loss, and demonstrate the predictive ability of three-month performance on final weight loss. METHODS: Retrospective analysis of 1097 consecutive LRYGB patients allowed for assessment of conformity of various weight loss trajectory models. Establishing exponential decay as the optimal fit, initial, three-month and final BMI values were used to determine empiric rate constants (λ3). Empirically derived weight loss curves and associated rate constants (λ) were generated. RESULTS: Exponential decay optimally characterizes post-LRYGB weight loss trajectory. Final weight loss can be characterized by λ3, as well as by the demographics black race (P = 0.008) and initial BMI (P < 0.001). Stratification by three-month weight loss allowed derivation of weight loss trajectory curves to predict weight at any point until and including plateau. CONCLUSIONS: Weight loss after LRYGB conforms well to exponential decay, and postoperative trajectory can thus be predicted early. This allows the clinician early identification and intervention upon patients at risk of poor performance.

Limiting Injury During Saphenous Vein Graft Preparation For Coronary Arterial Bypass Prevents Metabolic Decompensation.

Standard harvest and preparation of human saphenous vein (HSV) for autologous coronary and peripheral arterial bypass procedures is associated with injury and increased oxidative stress that negatively affect graft performance. In this study we investigated the global metabolomic profiles of HSV before (unprepared; UP) and after standard vein graft preparation (AP). AP-HSV showed impaired vasomotor function that was associated with increased oxidative stress, phospholipid hydrolysis and energy depletion that are characteristic of mechanical and chemical injury. A porcine model (PSV) was utilized to validate these metabolomic changes in HSV and to determine the efficacy of an improved preparation technique (OP) using pressure-regulated distension, a non-toxic vein marker, and graft storage in buffered PlasmaLyte solution in limiting metabolic decompensation due to graft preparation. Deficits in vasomotor function and metabolic signature observed in AP-PSV could be largely mitigated with the OP procedure. These findings suggest that simple strategies aimed at reducing injury during graft harvest and preparation represents a straightforward and viable strategy to preserve conduit function and possibly improve graft patency.

Unregulated saphenous vein graft distension decreases tissue viscoelasticity.

OBJECTIVES: Unregulated intraoperative distension of human saphenous vein (SV) graft leads to supraphysiologic luminal pressures and causes acute physiologic and cellular injury to the conduit. The effect of distension on tissue viscoelasticity, a biophysical property critical to a successful graft, is not well described. In this investigation, we quantify the loss of viscoelasticity in SV deformed by distension and compare the results to tissue distended in a pressure-controlled fashion. MATERIALS AND METHODS: Unmanipulated porcine SV was used as a control or distended without regulation and distended with an in-line pressure release valve (PRV). Rings were cut from these tissues and suspended on a muscle bath. Force versus time tracings of tissue constricted with KCl (110 mM) and relaxed with sodium nitroprusside (SNP) were fit to the Hill model of viscoelasticity, using mean absolute error (MAE) and r2-goodness of fit as measures of conformity. RESULTS: One-way ANOVA analysis demonstrated that, in tissue distended manually, the MAE was significantly greater and the r2-goodness of fit was significantly lower than both undistended tissues and tissues distended with a PRV (p<0.05) in KCl-induced vasoconstriction and SNP-induced vasodilation. CONCLUSIONS: Unregulated manual distension of SV graft causes loss of viscoelasticity and such loss may be mitigated with the use of an in-line PRV.

Upper Extremity Pulse Pressure Predicts Amputation-Free Survival after Lower Extremity Bypass.

Increased pulse pressure reflects pathologic arterial stiffening and predicts cardiovascular events and mortality. The effect of pulse pressure on outcomes in lower extremity bypass patients remains unknown. We thus investigated whether preoperative pulse pressure could predict amputation-free survival in patients undergoing lower extremity bypass for atherosclerotic occlusive disease. An institutional database identified 240 included patients undergoing lower extremity bypass from 2005 to 2014. Preoperative demographics, cardiovascular risk factors, operative factors, and systolic and diastolic blood pressures were recorded, and compared between patients with pulse pressures above and below 80 mm Hg. Factors were analyzed in bi- and multivariable models to assess independent predictors of amputation-free survival. Kaplan-Meier analysis was performed to evaluate the temporal effect of pulse pressure ≥80 mm Hg on amputation-free survival. Patients with a pulse pressure ≥80 mm Hg were older, male, and had higher systolic and lower diastolic pressures. Patients with pulse pressure <80 mm Hg demonstrated a survival advantage on Kaplan-Meier analysis at six months (log-rank P = 0.003) and one year (P = 0.005) postoperatively. In multivariable analysis, independent risk factors for decreased amputation-free survival at six months included nonwhite race, tissue loss, infrapopliteal target, and preoperative pulse pressure ≥80 mm Hg (hazard ratio 2.60; P = 0.02), while only tissue loss and pulse pressure ≥80 mm Hg (hazard ratio 2.30, P = 0.02) remained predictive at one year. Increased pulse pressure is independently associated with decreased amputation-free survival in patients undergoing lower extremity bypass. Further efforts to understand the relationship between increased arterial stiffness and poor outcomes in these patients are needed.

Open and Endovascular Management of Inferior Mesenteric Artery Aneurysms: A Report of Two Cases.

Inferior mesenteric artery (IMA) aneurysms are a rare entity, attributing to 1% of Splanchnic aneurysms (Edogawa S, Shibuya T, Kurose K et al. Inferior mesenteric artery aneurysm: case report and literature review. Ann Vasc Dis 2013;6:98-101), often found incidentally on evaluation for other intra-abdominal pathologies. Similar to other visceral arterial aneurysms, there is an estimated 20-50% risk of potentially fatal rupture and repair is generally recommended. We report 2 patients with IMA aneurysms, using them as cases to illustrate feasibility of both open and endovascular management options. Patient 1 is a 69-year-old male with bilateral claudication found to have an asymptomatic 20-mm IMA aneurysm. This patient underwent aortobifemoral bypass with branch polytetrafluoroethylene graft to distal IMA after excision of IMA aneurysm. Patient 2 is a 32-year-old male who underwent an ex vivo renal artery aneurysm repair and was noted on routine follow-up to have an incidental saccular 1.5-cm IMA aneurysm for which he underwent endovascular coil embolization. Both patients had an unremarkable postoperative course with a notable absence of stigmata of bowel ischemia.

Hyperlactemia Predicts Surgical Mortality in Patients Presenting With Acute Stanford Type-A Aortic Dissection.

OBJECTIVE: Inspired by the limited facility of the Penn classification, the authors aimed to determine a rapid and optimal preoperative assessment tool to predict surgical mortality after acute Stanford type-A aortic dissection (AAAD) repair. DESIGN: Patients who underwent an attempted surgical repair of AAAD were determined using a de-identified single institution database. The charts of 144 patients were reviewed retrospectively for preoperative demographics and surrogates for disease severity and malperfusion. Bivariate analysis was used to determine significant (p≤0.05) predictors of in-hospital and 1-year mortality, the primary endpoints. Receiver operating characteristic curve generation was used to define optimal cut-off values for continuous predictors. SETTING: Single center, level 1 trauma, university teaching hospital. PARTICIPANTS: The study included 144 cardiac surgical patients with acute type-A aortic dissection presenting for surgical correction. INTERVENTIONS: Surgical repair of aortic dissection with preoperative laboratory samples drawn before patient transfer to the operating room or immediately after arterial catheter placement intraoperatively. MEASUREMENTS AND MAIN RESULTS: The study cohort comprised 144 patients. In-hospital mortality was 9%, and the 1-year mortality rate was 17%. Variables that demonstrated a correlation with in-hospital mortality included an elevated serum lactic acid level (odds ratio [OR] 1.5 [1.3-1.9], p<0.001), a depressed ejection fraction (OR 0.91 [0.86-0.96], p = .001), effusion (OR 4.8 [1.02-22.5], p = 0.04), neurologic change (OR 5.3 [1.6-17.4], p = 0.006), severe aortic regurgitation (OR 8.2 [2.0-33.9], p = 0.006), and cardiopulmonary resuscitation (OR 6.8 [1.7-26.9], p = 0.01). Only an increased serum lactic acid level demonstrated a trend with 1-year mortality using univariate Cox regression (hazard ratio 1.1 [1.0-1.1], p = 0.006). Receiver operating characteristic analysis revealed optimal cut-off lactic acid levels of 6.0 mmol/L and 6.9 mmol/L for in-hospital and 1-year mortality, respectively. CONCLUSION: Lactic acidosis, ostensibly as a surrogate for systemic malperfusion, represents a novel, accurate, and easily obtainable preoperative predictor of short-term mortality after attempted AAAD repair. These data may improve identification of patients who would not benefit from surgery.