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.

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.

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.

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.

EDITOR’S PERSPECTIVE

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.

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.

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.

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.

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.

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.

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 λ_3, 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.

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.

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.

Acute Transverse Myelitis Associated with Salmonella Bacteremia: A Case Report

Patient: Female, 28

Final Diagnosis: Acute transverse myelitis

Symptoms: Ascending paralysis

Medication: —

Clinical Procedure: —

Specialty: Infectious Diseases

Independent Preoperative Predictors of Prolonged Length of Stay after Laparoscopic Appendectomy in Patients over 30 Years of Age: Experience from a Single Institution

Prompt discharge after laparoscopic appendectomy (LA) is a marker of quality of care, fiscally desirable and feasible in select patients. Patients over 30 comprise a more heterogeneous cohort known to experience worse outcomes after LA. We aimed to identify easily available preoperative risk factors portending a postoperative length of stay ≥2 days among patients above age 30. In this investigation, 296 included patients from a single institution who underwent LA for acute appendicitis from 2010 to 2014 were retrospectively reviewed for preoperative demographics, laboratory studies, comorbidities, presentation characteristics, radiographic finding, and other rationally selected factors for association with postoperative length of stay ≥2 days. Bivariate and multivariate analysis was conducted to determine independent risk factors, which were subsequently modeled via receiver-operating characteristic curve generation and Kaplan-Meier analysis. “Classic” presentation [odds ratio (OR) = 0.5, P = .02], elevated red cell distribution width (RDW; OR = 1.5/% increase, P = 0.004) as well as evidence of rupture on CT (OR = 6.9, P < 0.001) were independently associated with postoperative length of stay ≥ 2 days. Modeling length of stay using these factors generated an area under the curve of 0.713 ± 0.037. Kaplan-Meier analysis of “classic” presentation, elevated RDW, and evidence of rupture on CT through the fifth postoperative day generated log-rank P values of 0.02, 0.05, and ≤ 0.001, respectively. In summary, lack of “classic” presentation, elevated RDW, and CT evidence of rupture are novel risk factors for prolonged postoperative length of stay in LA patients over 30. These findings may help target patients most appropriate for prompt discharge.

Independent Preoperative Predictors of Prolonged Length of Stay after Laparoscopic Appendectomy in Patients Over 30 Years of Age: Experience from a Single Institution

Prompt discharge after laparoscopic appendectomy (LA) is a marker of quality of care, fiscally desirable and feasible in select patients. Patients over 30 comprise a more heterogeneous cohort known to experience worse outcomes after LA. We aimed to identify easily available preoperative risk factors portending a postoperative length of stay ≥2 days among patients above age 30. In this investigation, 296 included patients from a single institution who underwent LA for acute appendicitis from 2010 to 2014 were retrospectively reviewed for preoperative demographics, laboratory studies, comorbidities, presentation characteristics, radiographic finding, and other rationally selected factors for association with postoperative length of stay ≥2 days. Bivariate and multivariate analysis was conducted to determine independent risk factors, which were subsequently modeled via receiver-operating characteristic curve generation and Kaplan-Meier analysis. "Classic" presentation [odds ratio (OR) = 0.5, P = .02], elevated red cell distribution width (RDW; OR = 1.5/% increase, P = 0.004) as well as evidence of rupture on CT (OR = 6.9, P < 0.001) were independently associated with postoperative length of stay ≥ 2 days. Modeling length of stay using these factors generated an area under the curve of 0.713 ± 0.037. Kaplan-Meier analysis of "classic" presentation, elevated RDW, and evidence of rupture on CT through the fifth postoperative day generated log-rank P values of 0.02, 0.05, and ≤ 0.001, respectively. In summary, lack of "classic" presentation, elevated RDW, and CT evidence of rupture are novel risk factors for prolonged postoperative length of stay in LA patients over 30. These findings may help target patients most appropriate for prompt discharge.

Traditional graft preparation decreases physiologic responses, diminishes viscoelasticity, and reduces cellular viability of the conduit: A porcine saphenous vein model

Traditional methods of intraoperative human saphenous vein preparation for use as bypass grafts can be deleterious to the conduit. The purpose of this study was to characterize acute graft preparation injury, and to mitigate this harm via an improved preparation technique. Porcine saphenous veins were surgically harvested (unprepared controls, UnP) and prepared using traditional (TraP) and improved preparations (ImP). The TraP used unregulated radial distension, marking with a surgical skin marker and preservation in heparinized normal saline. ImP used pressure-regulated distension, brilliant blue FCF-based pen marking and preservation in heparinized Plasma-Lyte A. Rings from each preparation were suspended in a muscle bath for characterization of physiologic responses to vasoactive agents and viscoelasticity. Cellular viability was assessed using the methyl thiazolyl tetrazolium (MTT) assay and the terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay for apoptosis. Contractile responses to potassium chloride (110 mM) and phenylephrine (10 µM), and endothelial-dependent and independent vasodilatory responses to carbachol (0.5 µM) and sodium nitroprusside (1 µM), respectively, were decreased in TraP tissues compared to both UnP and ImP tissues (p ⩽ 0.05). TraP tissues demonstrated diminished viscoelasticity relative to UnP and ImP tissues (p ⩽ 0.05), and reduced cellular viability relative to UnP control (p ⩽ 0.01) by the MTT assay. On the TUNEL assay, TraP tissues demonstrated a greater degree of apoptosis relative to UnP and ImP tissues (p ⩽ 0.01). In conclusion, an improved preparation technique prevents vascular graft smooth muscle and endothelial injury observed in tissues prepared using a traditional approach.

Papaverine Prevents Vasospasm by Regulation of Myosin Light Chain Phosphorylation and Actin Polymerization in Human Saphenous Vein

Objective

Papaverine is used to prevent vasospasm in human saphenous veins (HSV) during vein graft preparation prior to implantation as a bypass conduit. Papaverine is a nonspecific inhibitor of phosphodiesterases, leading to increases in both intracellular cGMP and cAMP. We hypothesized that papaverine reduces force by decreasing intracellular calcium concentrations ([Ca²⁺]_i) and myosin light chain phosphorylation, and increasing actin depolymerization via regulation of actin regulatory protein phosphorylation.

Approach and Results

HSV was equilibrated in a muscle bath, pre-treated with 1 mM papaverine followed by 5 μM norepinephrine, and force along with [Ca²⁺]_i levels were concurrently measured. Filamentous actin (F-actin) level was measured by an in vitro actin assay. Tissue was snap frozen to measure myosin light chain and actin regulatory protein phosphorylation. Pre-treatment with papaverine completely inhibited norepinephrine-induced force generation, blocked increases in [Ca²⁺]_i and led to a decrease in the phosphorylation of myosin light chain. Papaverine pre-treatment also led to increased phosphorylation of the heat shock-related protein 20 (HSPB6) and the vasodilator stimulated phosphoprotein (VASP), as well as decreased filamentous actin (F-actin) levels suggesting depolymerization of actin.

Conclusions

These results suggest that papaverine-induced force inhibition of HSV involves [Ca²⁺]_i-mediated inhibition of myosin light chain phosphorylation and actin regulatory protein phosphorylation-mediated actin depolymerization. Thus, papaverine induces sustained inhibition of contraction of HSV by the modulation of both myosin cross-bridge formation and actin cytoskeletal dynamics and is a pharmacological alternative to high pressure distention to prevent vasospasm.

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.

Impaired weight loss in laparoscopic adjustable gastric banding patients over 50 years of age: diabetes mellitus as an independent risk factor

INTRODUCTION

Laparoscopic adjustable gastric banding (LAGB) represents a safe and effective bariatric procedure, particularly for patients over 50. Preoperative risk factors for impaired post-LAGB excess weight loss are not well characterized for this population. This study aimed to identify demographics, characteristics or comorbidities associated with excess weight loss at 6 and 12 months postoperatively (EWL180 and EWL365, respectively) for these patients.

METHODS

One hundred and seventeen LAGB patients >50 years of age from 2005 to 2014 were retrospectively reviewed for factors potentially associated with EWL180 and EWL365. Rationally selected variables chosen for analysis included age, race, gender, initial body mass index and preoperative weight loss; comorbidities assessed included hypertension, psychiatric disorders and diabetes mellitus (DM). Variables correlated with EWL180 or EWL365 on bivariate linear regression analysis (P ≤ .05) were input into multivariate linear regression analysis to confirm independent association.

RESULTS

Preoperative DM (B = -9.1% EWL; 95% CI -13.6, -4.5%; P < .001) and African-American race (B = -8.8% EWL; 95% CI -17.3, -0.3%; P = .05) were independent risk factors for impaired EWL180. Only DM was a risk factor for impaired EWL365 (B = -9.7% EWL; 95% CI -17.7, -1.8%; P = .02).

CONCLUSIONS

LAGB is a successful operation in patients >50 years of age. Preoperative DM is an independent risk factor for impaired EWL in this cohort.

The influence of VKORC1 and CYP2C9 mutations on warfarin response after total hip and knee arthroplasty

AIMS

This study characterizes the influence of genotype at two loci on warfarin response after arthroplasty.

METHODS

121 postarthroplasty patients given warfarin thromboprophylaxis were reviewed for international normalized ratio (INR) values on the first three days postoperatively. Significant differences among genotypes in INR values on each of the first three postoperative days were assessed.

RESULTS

Wild-type patients at both loci (∼23% of patients) had yet to reach therapeutic INR (1.5-2.0) by postoperative day three more frequently than those with a mutation conferring hyper-responsiveness (61% vs. 30%; P ≤ .01).

CONCLUSIONS

Wild-type patients are not anticoagulated in a sufficiently prompt manner after arthroplasty.

Prediction of in-hospital mortality after ruptured abdominal aortic aneurysm repair using an artificial neural network

OBJECTIVE

Ruptured abdominal aortic aneurysm (rAAA) carries a high mortality rate, even with prompt transfer to a medical center. An artificial neural network (ANN) is a computational model that improves predictive ability through pattern recognition while continually adapting to new input data. The goal of this study was to effectively use ANN modeling to provide vascular surgeons a discriminant adjunct to assess the likelihood of in-hospital mortality on a pending rAAA admission using easily obtainable patient information from the field.

METHODS

Of 332 total patients from a single institution from 1998 to 2013 who had attempted rAAA repair, 125 were reviewed for preoperative factors associated with in-hospital mortality; 108 patients received an open operation, and 17 patients received endovascular repair. Five variables were found significant on multivariate analysis (P < .05), and four of these five (preoperative shock, loss of consciousness, cardiac arrest, and age) were modeled by multiple logistic regression and an ANN. These predictive models were compared against the Glasgow Aneurysm Score. All models were assessed by generation of receiver operating characteristic curves and actual vs predicted outcomes plots, with area under the curve and Pearson r(2) value as the primary measures of discriminant ability.

RESULTS

Of the 125 patients, 53 (42%) did not survive to discharge. Five preoperative factors were significant (P < .05) independent predictors of in-hospital mortality in multivariate analysis: advanced age, renal disease, loss of consciousness, cardiac arrest, and shock, although renal disease was excluded from the models. The sequential accumulation of zero to four of these risk factors progressively increased overall mortality rate, from 11% to 16% to 44% to 76% to 89% (age ≥ 70 years considered a risk factor). Algorithms derived from multiple logistic regression, ANN, and Glasgow Aneurysm Score models generated area under the curve values of 0.85 ± 0.04, 0.88 ± 0.04 (training set), and 0.77 ± 0.06 and Pearson r(2) values of .36, .52 and .17, respectively. The ANN model represented the most discriminant of the three.

CONCLUSIONS

An ANN-based predictive model may represent a simple, useful, and highly discriminant adjunct to the vascular surgeon in accurately identifying those patients who may carry a high mortality risk from attempted repair of rAAA, using only easily definable preoperative variables. Although still requiring external validation, our model is available for demonstration at https://redcap.vanderbilt.edu/surveys/?s=NN97NM7DTK.

Endosomolytic Nano-Polyplex Platform Technology for Cytosolic Peptide Delivery To Inhibit Pathological Vasoconstriction

A platform technology has been developed and tested for delivery of intracellular-acting peptides through electrostatically complexed nanoparticles, or nano-polyplexes, formulated from an anionic endosomolytic polymer and cationic therapeutic peptides. This delivery platform has been initially tested and optimized for delivery of two unique vasoactive peptides, a phosphomimetic of heat shock protein 20 and an inhibitor of MAPKAP kinase II, to prevent pathological vasoconstriction (i.e., vasospasm) in human vascular tissue. These peptides inhibit vasoconstriction and promote vasorelaxation by modulating actin dynamics in vascular smooth muscle cells. Formulating these peptides into nano-polyplexes significantly enhances peptide uptake and retention, facilitates cytosolic delivery through a pH-dependent endosomal escape mechanism, and enhances peptide bioactivity in vitro as measured by inhibition of F-actin stress fiber formation. In comparison to treatment with the free peptides, which were endowed with cell-penetrating sequences, the nano-polyplexes significantly increased vasorelaxation, inhibited vasoconstriction, and decreased F-actin formation in the human saphenous vein ex vivo. These results suggest that these formulations have significant potential for treatment of conditions such as cerebral vasospasm following subarachnoid hemorrhage. Furthermore, because many therapeutic peptides include cationic cell-penetrating segments, this simple and modular platform technology may have broad applicability as a cost-effective approach for enhancing the efficacy of cytosolically active peptides.

Prediction of excess weight loss after laparoscopic Roux-en-Y gastric bypass: data from an artificial neural network

INTRODUCTION

Laparoscopic Roux-en-Y gastric bypass (LRYGB) has become the gold standard for surgical weight loss. The success of LRYGB may be measured by excess body mass index loss (%EBMIL) over 25 kg/m(2), which is partially determined by multiple patient factors. In this study, artificial neural network (ANN) modeling was used to derive a reasonable estimate of expected postoperative weight loss using only known preoperative patient variables. Additionally, ANN modeling allowed for the discriminant prediction of achievement of benchmark 50% EBMIL at 1 year postoperatively.

METHODS

Six hundred and forty-seven LRYGB included patients were retrospectively reviewed for preoperative factors independently associated with EBMIL at 180 and 365 days postoperatively (EBMIL180 and EBMIL365, respectively). Previously validated factors were selectively analyzed, including age; race; gender; preoperative BMI (BMI0); hemoglobin; and diagnoses of hypertension (HTN), diabetes mellitus (DM), and depression or anxiety disorder. Variables significant upon multivariate analysis (P < .05) were modeled by "traditional" multiple linear regression and an ANN, to predict %EBMIL180 and %EBMIL365.

RESULTS

The mean EBMIL180 and EBMIL365 were 56.4 ± 16.5 % and 73.5 ± 21.5%, corresponding to total body weight losses of 25.7 ± 5.9% and 33.6 ± 8.0%, respectively. Upon multivariate analysis, independent factors associated with EBMIL180 included black race (B = -6.3%, P < .001), BMI0 (B = -1.1%/unit BMI, P < .001), and DM (B = -3.2%, P < .004). For EBMIL365, independently associated factors were female gender (B = 6.4%, P < .001), black race (B = -6.7%, P < .001), BMI0 (B = -1.2%/unit BMI, P < .001), HTN (B = -3.7%, P = .03), and DM (B = -6.0%, P < .001). Pearson r(2) values for the multiple linear regression and ANN models were 0.38 (EBMIL180) and 0.35 (EBMIL365), and 0.42 (EBMIL180) and 0.38 (EBMIL365), respectively. ANN prediction of benchmark 50% EBMIL at 365 days generated an area under the curve of 0.78 ± 0.03 in the training set (n = 518) and 0.83 ± 0.04 (n = 129) in the validation set.

CONCLUSIONS

Available at https://redcap.vanderbilt.edu/surveys/?s=3HCR43AKXR, this or other ANN models may be used to provide an optimized estimate of postoperative EBMIL following LRYGB.

Preservation solution impacts physiologic function and cellular viability of human saphenous vein graft

INTRODUCTION

Recent clinical data suggest intraoperative preservation of human saphenous vein (HSV) in normal saline is associated with vein graft failure. We evaluated the influence of several preservation media on acute physiologic function and cellular viability of HSV conduit.

METHODS

Unprepared (UP) HSV obtained from coronary artery bypass graft patients was characterized on a muscle bath after 2-hour storage in 6 solutions: Plasma-Lyte A, 0.9% NaCl (normal saline), University of Wisconsin solution, Celsior solution, autologous whole blood, or glutathione-ascorbic acid L-arginine (GALA) solution. Vascular smooth muscle contractility was assessed after exposure to depolarizing KCl and phenylephrine. The relaxation of phenylephrine-precontracted HSV to sodium nitroprusside and carbachol (endothelial-independent and -dependent relaxation, respectively) was also assessed. Cellular viability was determined via the methyl thiazolyl tetrazolium (MTT) assay. Rat aortae were used to assess the effect of pH during graft preservation on endothelial-dependent relaxation.

RESULTS

Preservation of HSV in normal saline and autologous whole blood impaired contractile responses to KCl relative to UP tissues, whereas preservation in University of Wisconsin solution and Celsior solution enhanced contractile responses (P < .05). Relative to UP tissues, responses to phenylephrine were decreased with preservation in normal saline, whereas preservation in University of Wisconsin solution, Celsior solution, and GALA all potentiated these responses (P < .05). Only preservation in normal saline impaired endothelial-independent relaxation (P = .005). Preservation in Plasma-Lyte A (P = .02), normal saline (P = .002), and University of Wisconsin solution (P = .02) impaired endothelial-dependent relaxation. Normal saline preservation decreased MTT viability index relative to UP tissues (0.02 ± 0.002 mg(-1)0.5 mL(-1) vs 0.033 ± 0.005 mg(-1)0.5 mL(-1); P = .03). Endothelial function was impaired by acidic pH in rat aorta.

CONCLUSION

Preservation of HSV in normal saline causes graft injury leading to impaired physiologic function and decreased viability of the HSV. This harm is mitigated by the use of buffered salt solutions as preservation media.

Abstract 293: Clinical Predictors of Endothelial Function in Human Saphenous Vein

BACKGROUND: Human saphenous vein (HSV) remains the most widely utilized conduit for vascular bypass procedures. Outcomes remain limited by vein graft failure and intimal hyperplasia. Endothelial function is considered an important determinant of vein graft failure. We have observed significant variability in endothelial function in freshly isolated HSV samples. We therefore evaluated clinical predictors of endothelial function in HSV.

Methods: We obtained freshly isolated HSV samples from the operating room immediately following harvest from patients undergoing coronary artery bypass procedures from Vanderbilt University Hospital and the Nashville VA Hospital. We obtained HSV samples prior to any intraoperative manipulations. HSV viability, smooth muscle function, and endothelial-dependent relaxation (EDR) were measured in a muscle bath. We collected the following clinical and demographic information: age, height, weight, gender, ethnicity, medical comorbidities, laboratory values (creatinine, HbA1c, lipids), ejection fraction, preoperative medication regimen, and method of vein graft harvest. We performed a univariate and multivariate analysis of predictors of endothelial function in HSV.

Results: HSV samples were obtained from 149 patients. HSV EDR varied from -11% to 63%. Open harvest was employed for 39 HSV samples, compared with endoscopic harvest in 110 HSV samples. On univariate analysis, only open harvest was a statistically significant predictor of endothelial function (p=0.02): mean HSV EDR was 21.5% in HSV samples harvested open, compared with 15.4% in HSV harvested with an endoscopic technique. HSV EDR was also improved with preoperative aspirin use: mean HSV EDR was 18% in patients with preoperative aspirin use compared with 11.6% in patients who were not administered preoperative aspirin in a multivariate model when controlling for method of vein graft harvest (p=0.05).

Conclusions: Endoscopic vein graft harvest is associated with endothelial dysfunction in HSV, while preoperative aspirin use is associated with improved endothelial function. Further work will be necessary to determine whether these factors are associated with development of intimal hyperplasia and vein graft failure.

Brilliant blue FCF as an alternative dye for saphenous vein graft marking: effect on conduit function

IMPORTANCE

Surgical skin markers are used off-label to mark human saphenous veins (HSVs) to maintain orientation before implantation as aortocoronary or peripheral arterial bypass grafts. These surgical skin markers impair functional responses of the HSV tissue.

OBJECTIVES

To investigate the effect of brilliant blue dye 1 (brilliant blue FCF [for food coloring]; hereinafter, FCF) as a nontoxic alternative marking dye and to determine whether FCF has pharmacological properties.

DESIGN, SETTING, AND PARTICIPANTS

Segments of HSVs were collected in university hospitals from patients undergoing coronary artery bypass grafting procedures immediately after harvest (unmanipulated) or after typical intraoperative surgical graft preparation (after manipulation). Rat inferior venae cavae were used to determine the pharmacological properties and cellular targets of FCF. Endothelial and smooth muscle functional responses were determined in a muscle bath, and intimal thickening in HSVs was determined after 14 days in organ culture.

MAIN OUTCOMES AND MEASURES

Contractile responses were measured in force and converted to stress. Smooth muscle function was expressed as maximal responses to potassium chloride depolarization contractions. Endothelial function was defined as the percentage of relaxation of maximal agonist-induced contraction. Neointimal thickness was measured by histomorphometric analysis.

RESULTS

Human saphenous veins stored in the presence of FCF had no loss of endothelial or smooth muscle function. Unmanipulated HSVs preserved in the presence of FCF demonstrated a significant increase in endothelial-dependent relaxation (mean [SEM], 25.2% [6.4%] vs 30.2% [6.7%]; P = .02). Application of FCF to functionally nonviable tissue significantly enhanced the smooth muscle responses (mean [SEM], 0.018 [0.004] × 10⁵ N/m² vs 0.057 [0.016] × 10⁵ N/m²; P = .05). Treatment with FCF reduced intimal thickness in organ culture (mean [SEM], -17.5% [2.1%] for unmanipulated HSVs vs -27.9% [3.7%] for HSVs after manipulation; P < .001). In rat inferior venae cavae, FCF inhibited the contraction induced by the P2X7 receptor agonist 2'(3')-O-(4-benzoyl)benzoyl-adenosine-5'-triphosphate (mean [SEM], 14.8% [2.2%] vs 6.5% [1.8%]; P = .02) to an extent similar to the P2X7 receptor antagonist oxidized adenosine triphosphate (mean [SEM], 5.0% [0.9%]; P < .02 vs control) or the pannexin hemichannel inhibitor probenecid (mean [SEM], 7.3% [1.6%] and 4.7% [0.9%] for 0.5mM and 2mM, respectively; P < .05).

CONCLUSIONS AND RELEVANCE

Treatment with FCF did not impair endothelial or smooth muscle function in HSVs. Brilliant blue FCF enhanced endothelial-dependent relaxation, restored smooth muscle function, and prevented intimal hyperplasia in HSVs in organ culture. These pharmacological properties of FCF may be due to P2X7 receptor or pannexin channel inhibition. Brilliant blue FCF is an alternative, nontoxic marking dye that may improve HSV conduit function and decrease intimal hyperplasia.

Abstract 322: Balanced, pH-Buffered Preservation Solutions Improved Physiologic Response in Human Saphenous Vein Graft

Introduction: Human saphenous vein (HSV) autografting into the coronary or peripheral arterial system is a widely practiced surgical approach. The primary mechanism of early graft failure is neointimal hyperplasia. Unfortunately, standard practice entails vein preservation in harmful solutions, notably, normal saline (NS). We hypothesized a balanced, euosmolar, pH-buffered solution would promote enhanced vasoreactivity, cellular viability and ultimately, improved patency.

Methods: Unmanipulated samples of HSV tissue were obtained from patients undergoing CABG. Rings were cut and placed into University of Wisconsin (UW) solution, low-potassium UW, Celsior, PlasmaLyte (HP) and NS (all heparinized) for one hour, and hung on a muscle bath with unmanipulated control (UM). KCl-dependent contractility, as well as endothelial dependent (EDR) and independent (EIR) relaxation were assessed.

Results: One-way ANOVA demonstrated KCl-induced contractility was reduced in NS-preserved HSV; significantly so relative to UW (n=9, p<0.05, Graph A). UW, low-potassium UW and Celsior produced a phenylephrine (PE)-induced contraction significantly greater than that seen in NS (n=9, p<0.05, Graph B), while UM, UW and HP vein show enhanced EDR relative to NS (n=11, p<0.05, Graph C). No EIDR differences were observed (n=7, Graph D).

Conclusions: Using physiologic function to reflect graft viability, NS is toxic to HSV. KCl and PE-induced contractility, and EDR were all impaired. Thus, a buffered, balanced solution such as HP or UW is advocated for graft preservation.