Challenges in Pulmonary Risk Assessment and Perioperative Management in Bariatric Surgery Patients

Bariatric surgery has serious associated medical comorbidity and procedure-related risks and is, thus, considered an intermediate-to-high-risk non-cardiac surgery. Altered respiratory mechanics, obstructive sleep apnea (OSA), and less often, pulmonary hypertension and postoperative pulmonary embolism are the major contributors to poor pulmonary outcomes in obese patients. Attention to posture and positioning is critical in patients with OSA. Suspected OSA patients requiring intravenous narcotics should be kept in a monitored setting with frequent assessments and naloxone kept at the bedside. Use of reverse Tredelenburg position, preinduction, maintenance of positive end-expiratory pressure, and use of continuous positive airway pressure can help improve oxygenation in the perioperative period.     

Evidence Supporting Routine Polysomnography Before Bariatric Surgery

Background: Obstructive sleep apnea (OSA) is common in morbidly obese patients, with a reported prevalence from 12 to 40%. Preoperative diagnosis of OSA is important for both perioperative airway management and the prevention of postoperative pulmonary complications. BMI has been reported to be an independent risk factor, and has been used recently in scoring systems to help predict OSA. Our hypothesis was that OSA is highly prevalent in patients presenting for bariatric surgery, and that BMI alone is not a good predictor of the presence or absence of sleep apnea. Methods: A cross-sectional study was undertaken of the last 170 consecutive patients presenting for bariatric surgery in a single surgeon's practice. Clinical and demographic data were available from our prospective database, and polysomnography results were reviewed retrospectively. Sleep apnea was noted as present or absent, and graded from mild to severe. The patient population was stratified by BMI into severely obese (BMI 35-39.9), morbidly obese (BMI 40-49.9), super-obese (BMI 50-59.9), and super-super-obese (BMI ≥ 60). Results: OSA had been diagnosed before surgical consultation in 26 of the 170 patients (15.3%). Sleep studies were not available in 7 patients (4.1%). The remaining 137 patients (80.6%) had sleep data available, and 105 (76.6%) had sleep apnea (based on American Board of Sleep Medicine criteria).There was no correlation of sleep apnea with BMI. The overall prevalence of OSA in this cohort was 77% (131/170). Conclusions: In this large patient cohort, sleep apnea was prevalent (77%) independent of BMI, and most cases were not diagnosed before bariatric surgical consultation.These data support the use of routine screening polysomnography before bariatric surgery.     

Metabolic Syndrome after Laparoscopic Bariatric Surgery

Background  Metabolic syndrome (MS) is common among morbidly obese patients undergoing bariatric surgery. The aim of this study was to assess the impact and predictors of bariatric surgery on the resolution of MS. Methods  Subjects included 286 patients [age 44.0 ± 11.5, female 78.2%, BMI 48.7 ± 9.4, waist circumference 139 ± 20 cm, AST 23.5 ± 14.9, ALT 30.0 ± 20.1, type 2 diabetes mellitus (DM) 30.1% and MS 39.2%] who underwent bariatric surgery. Results  Of the entire cohort, 27.3% underwent malabsorptive surgery, 55.9% underwent restrictive surgery, and 16.8% had combination restrictive–malabsorptive surgery. Mean weight loss was 33.7 ± 20.1 kg after restrictive surgery (follow up period 298 ± 271 days), 39.4 ± 22.9 kg after malabsorptive surgery (follow-up period 306 ± 290 days), and 28.3 ± 14.1 kg after combination surgery (follow-up period 281 ± 239 days). Regardless of the type of bariatric surgery, significant improvements were noted in MS (p values from <0.0001–0.01) as well as its components such as DM (p values from <0.0001–0.0005), waist circumference (p values <0.0001), BMI (p values <0.0001), fasting serum triglycerides (p values <0.0001 to 0.001), and fasting serum glucose (p values <0.0001). Additionally, a significant improvement in AST/ALT ratio (p value = 0.0002) was noted in those undergoing restrictive surgery. Multivariate analysis showed that patients who underwent malabsorptive bariatric procedures experienced a significantly greater percent excess weight loss than patients who underwent restrictive procedures (p value = 0.0451). Percent excess weight loss increased with longer postoperative follow-up (p value <0.0001). Conclusions  Weight loss after bariatric surgery is associated with a significant improvement in MS and other metabolic factors.     

The SAGES Bariatric Surgery Outcome Initiative

Background The recent initiative for identifying centers of excellence in bariatric surgery calls for documentation of surgical outcomes. The SAGES Outcomes Initiative is a national database introduced in 1999 as a method for surgeons to accumulate and compare their data with summary national data. A bariatric-specific dataset was established later in 2001. The aim of this study was to compare the outcomes of bariatric surgery from the Society of American Gastrointestinal Endoscopic Surgeons’ (SAGES) bariatric database with data derived from a national administrative database of academic centers. Methods Between 2001 and 2004, 24 surgeons with 1,954 patients participated in the SAGES Bariatric Outcome Initiative, and 97 institutions with 42,847 patients participated in the University HealthSystem Consortium (UHC) database. Only 7 of the 24 surgeons participating in the SAGES Bariatric Outcome Initiative submitted more than 50 cases. The main outcome measures included demographics, comorbidities, type of bariatric procedure, operative time, length of hospital stay, short- and long-term complications, mortality, and weight loss. Results Both datasets were comparable for gender. Roux-en-Y gastric bypass had been performed for 88% of the patients in the SAGES database and 96% of the patients in the UHC database. Associated comorbidities were similar between the two groups except for a higher rate of hyperlipidemia for the patients in the SAGES database. The SAGES database contains more bariatric-specific information such as body mass index, operative time, blood loss, bariatric-specific complications, long-term complications, and weight loss data than the UHC database. According to the available data, no statistically significant differences exist between the two datasets in terms of perioperative complications and mortality. Conclusions The SAGES Bariatric Outcome Initiative provides valuable bariatric-specific data not currently available in an administrative database that may be useful for benchmarking purposes. However, this database is currently underutilized. Presented at the Annual 2005 Meeting of the Society of American Gastrointestinal Endoscopic Surgeons (SAGES), Hollywood, FL, USA, 14 April 2005     

Obesity and Obstructive Sleep Apnea-Hypopnea Syndrome: the Impact of Bariatric Surgery

Obstructive sleep apnea-hypopnea syndrome (OSAHS) is characterized by successive episodes of cessation or decrease in respiratory airflow, in which obesity is an important risk factor. The prevalence of the disease in morbidly obese patients is ∼70%. Treatment is based on the use of continuous positive airway pressure (CPAP) and weight loss in obese patients.Weight loss by dieting often produces unsatisfactory results, and the use of CPAP does not show good adherence because of being long-term and uncomfortable. Bariatric surgery has emerged as the treatment for morbid obesity and various associated co-morbidities. This article reviews the principal studies that evaluate the modifications in obstructive sleep apnea after bariatric surgery, showing that surgery is an effective treatment for the management of OSAHS in morbidly obese patients.     

Bariatric Surgery and Bariatric Psychology: Evolution of the Dutch Approach

Background Success of bariatric surgery is largely dependent on patients’ abilities to change their lifestyle and underlying psychosocial and behavioral factors; these factors should be carefully scrutinized. However, no consensus or guidelines exist for these evaluations. Materials and Methods To get a better understanding of the practice of bariatric surgery and bariatric psychology in The Netherlands and its evolution, a survey of bariatric surgery programs was conducted. Results Between 2000 and 2005, performance of bariatric surgery in The Netherlands has increased from 564 to more than 2,000 annually, mostly adjustable gastric banding. Most hospitals have a multidisciplinary selection process, and in 89% of the cases, a mental health specialist was involved. Conclusion Bariatric surgery in The Netherlands has increased tremendously; however, it is mostly limited to restrictive procedures, and there is no consensus regarding the psychological evaluation of patients.     

Preoperative Weight Gain in Bariatric Surgery

A significant weight gain with a mean of 4.4 kg was found between the date of acceptance for bariatric surgery and the date of admission to hospital for the operation.     

Body Contouring Surgery Following Bariatric Surgery and Dietetically Induced Massive Weight Reduction: A Risk Analysis

Background  This study analyzed the impact of weight reduction method, preoperative, and intraoperative variables on the outcome of reconstructive body contouring surgery following massive weight reduction. Methods  All patients presenting with a maximal BMI ≥35 kg/m² before weight reduction who underwent body contouring surgery of the trunk following massive weight loss (excess body mass index loss (EBMIL) ≥ 30%) between January 2002 and June 2007 were retrospectively analyzed. Incomplete records or follow-up led to exclusion. Statistical analysis focused on weight reduction method and pre-, intra-, and postoperative risk factors. The outcome was compared to current literature results. Results  A total of 104 patients were included (87 female and 17 male; mean age 47.9 years). Massive weight reduction was achieved through bariatric surgery in 62 patients (59.6%) and dietetically in 42 patients (40.4%). Dietetically achieved excess body mass index loss (EBMIL) was 94.20% and in this cohort higher than surgically induced reduction EBMIL 80.80% (p < 0.01). Bariatric surgery did not present increased risks for complications for the secondary body contouring procedures. The observed complications (26.9%) were analyzed for risk factors. Total tissue resection weight was a significant risk factor (p < 0.05). Preoperative BMI had an impact on infections (p < 0.05). No impact on the postoperative outcome was detected in EBMIL, maximal BMI, smoking, hemoglobin, blood loss, body contouring technique or operation time. Corrective procedures were performed in 11 patients (10.6%). The results were compared to recent data. Conclusion  Bariatric surgery does not increase risks for complications in subsequent body contouring procedures when compared to massive dietetic weight reduction. None of the authors had a commercial interest in the subject of the study or financial benefit from the results.     

Anti-Xa Levels in Bariatric Surgery Patients Receiving Prophylactic Enoxaparin

Background Limited data exist regarding efficacy and dosing of low-molecular-weight heparins, including enoxaparin, for morbidly obese patients. Prophylactic doses of 30 to 60 mg every 12 h have been described in bariatric surgery patients with appropriate anti-Xa levels reported between 0.18 and 0.6 units/mL. Methods Fifty-two laparoscopic gastric bypass or banding patients were enrolled. Patients were divided into two groups by the dose of enoxaparin that was given: Group 1—enoxaparin 30 mg every 12 hours—and Group 2—enoxaparin 40 mg every 12 h. Anti-Xa levels were obtained 4 h after the first and third doses. Levels between 0.18–0.44 units/mL were considered appropriate. Results There were 19 patients (74% female, mean body mass index [BMI] 48.4 kg/m²) in Group 1 and 33 patients (82% female, mean BMI 48.5 kg/m²) in Group 2. In Group 1, anti-Xa levels were 0.06 and 0.08 units/mL after the first and third doses, respectively. In Group 2, anti-Xa levels were 0.14 and 0.15 units/mL after first and third doses, respectively (p = NS). There was a statistically significant difference in anti-Xa levels between Group 1 first dose and Group 2 first dose (p < 0.05) and between Group 1 third dose and Group 2 third dose (p < 0.05). Percentage of appropriate anti-Xa levels at first dose differed 0% vs. 30.8% (Group 1 vs. Group 2; p = 0.01) and at third dose 9.1% vs. 41.7% (Group 1 vs. Group 2; p = 0.155). Conclusion When prophylactic dose enoxaparin of 30 mg every 12 h was changed to 40 mg every 12 h in bariatric surgery patients, anti-Xa levels significantly increased with prophylactic dose enoxaparin in bariatric surgery patients. The percentage of appropriate levels also increased; however, more than half of the patients receiving 40 mg every 12 hours failed to reach therapeutic levels. No levels were supratherapeutic. Dosage of 40 mg every 12 h may not be sufficient for bariatric surgery patients. Presented at the Society of American Gastrointestinal Endoscopic Surgeons annual meeting; April 18–22, 2007; Las Vegas, NV.     

Endoscopic Cervical Bariatric Surgery: Follow-up Study in a Porcine Model

BACKGROUND: The realisation of bariatric surgery has to date modified the digestive process solely through procedures within the abdominal cavity. However, endocrine surgeons have recently demonstrated the feasibility of a minimally invasive approach to the neck. In this study, we explored the feasibility, safety and weight progression of a bariatric procedure performed at the neck. METHODS: Eleven 40-50 kg Yorkshire pigs underwent endoscopic placement of an adjustable band to the cervical esophagus (ECB). Weight was monitored at postoperative days 15, 30, and after 7 weeks; weight progression was compared with an identical group of pigs who underwent a sham procedure. At autopsy, the surgical site was evaluated in a microscopic and macroscopic manner. RESULTS: Mean operating time was 66 +/- 5.76 min. All pigs tolerated the procedure well, except one subject that experienced food intolerance. The ECB group experienced significantly slower weight gain than the sham group (P = 0.005). Proper location of the band and absence of microscopic lesions at the esophageal wall were confirmed at autopsy and pathological examination. CONCLUSION: Bariatric surgery at the neck is feasible and produces effects on weight reduction. Further refinements and longer observation periods are required to propose this procedure as safe and effective alternative in humans.     

Patients Who are Delayed from Undergoing Bariatric Surgery Do Not have Improved Weight Loss

Background Many patients have a prolonged wait time between initial surgeon visit and actual surgery day. Whereas there are various reasons for this, few have examined if patient wait time for bariatric surgery has any affect on weight loss. This investigation studies the hypothesis that patients who wait longer for bariatric surgery do not have improved weight loss over those with shorter wait times. Methods All patients in a private academic practice who underwent laparoscopic gastric bypass over a 6-month period were included in this study. The time from initial office visit to actual surgery date was calculated to be wait time (WT). Reasons for short or long WT were not investigated. The relationship between WT and percentage excess body weight loss (%EBWL) was examined. In addition, patients whose WT was greater than 6 months (WT > 6) were compared to those less than 6 months (WT < 6). Pearson’s correlation coefficients and two-tailed Mann–Whitney tests were used as appropriate. Results There were 104 patients with 99 patients who had a >1 year follow-up. WT did not correlate with %EBWL (r = 0.09, p = 0.37). There was no difference in %EBWL in the WT > 6 group versus the WT < 6 group (73 vs. 70%; p = NS). Patients who had <50% EBWL waited an average of 281 versus 254 days for those who have >50% EBWL (p = NS). Conclusions Patients who wait longer before having bariatric surgery do not show improved weight loss. Weight loss success was not related to wait time. These results suggest that prolonged mandatory weight times are not an effective method for improving bariatric surgery weight loss outcomes. Mandatory delays for bariatric surgery should not be required, as they have no scientific merit. Presented at the World Congress of the International Federation for the Surgery of Obesity, Sydney, Australia, September 1, 2006.     

Revisional Bariatric Surgery

Background  Revisional surgery is required in a significant number of patients because of failure to lose weight, loss of quality of life, weight regain, or complications of the previous procedure. It has traditionally been associated with higher complication rates, and there appears to be no standardized surgical approach to revisional surgery. The aim of the study was to review the revisional procedures performed at St George Private Hospital and analyze the outcomes of the different types of revisional surgery. Methods   We performed a retrospective review of 75 patients who underwent revisional surgery between December 2003 and October 2007. Demographic, anthropometric, perioperative, and clinical follow-up data were collected, and statistical analyses were performed using SPSS version 14.0. Results  Sixty-six of the 75 patients were female. The mean age at the time of revision was 46.32 (22–68) years. Mean initial weight was 119.08 kg, and body mass index (BMI) was 43.42 kg/m². The lowest BMI and excess weight loss (EWL) recorded after primary surgery was 36.9% and 53.5%, respectively. At the time of revision, the mean EWL was 24.79. The EWL at 3 months and 6 months were 41.7% and 47.8%, respectively. Revision was performed laparoscopically in 51 patients and via laparotomy in 24 patients. There was no mortality in the cohort, but there were 17.3% minor and 4.0% major perioperative morbidities. Conclusion  Our study suggests that revision can be performed safely. Weight loss is satisfactory, and complications of the previous operations were all reversed. Furthermore, revisions may be done laparoscopically, including those who had previous open procedures.     

Bariatric Surgery Can Correct Iron Depletion in Morbidly Obese Women: A Link with Chronic Inflammation

Background Obesity is associated with a chronic and low-grade inflammation which may cause hypoferremia as seen in patients with chronic inflammatory diseases. The aim of the present study was to investigate the relationship between iron status and markers of inflammation in morbidly obese women and the effect of bariatric surgery. Methods Our cohort of patients consisted of 178 morbidly obese females selected for bariatric surgery. Clinical and biochemical data were recorded before surgery, and histopathological studies were carried out on preoperative liver biopsy samples. Fifty-five patients have been followed up after bariatric surgery. Results A high prevalence of iron depletion was present in this cohort, with 53% having a transferrin saturation ratio below 0.20. Iron depletion was significantly correlated with raised levels of indices of inflammation, C-reactive protein (CRP), orosomucoid and haptoglobin), and with the white blood cell count. In multivariate analysis, orosomucoid and CRP were independently associated with iron depletion. Moreover, 6 months after bariatric surgery, inflammation level decreased, which was inversely correlated with the increase in transferrin saturation. Conclusions Iron depletion is common in morbidly obese women. Low-grade chronic inflammation associated with obesity could be a modulator of iron uptake and utilization. Bariatric surgery may reduce chronic inflammation and improve iron status.     

Challenges in Cardiac Risk Assessment in Bariatric Surgery Patients

Bariatric surgery has serious associated medical comorbidity and procedure-related risks and is thus considered an intermediate- to high-risk noncardiac surgery. Most patients referred for bariatric surgery have a low or very low functional capacity, making cardiac risk assessment imperative. Stress echocardiography has a high negative predictive value and can avoid some of the table weight and torso diameter problems associated with myocardial perfusion imaging. Echocardiograph contrast agents improve the ability to identify endocardial borders and assess ventricular wall motion and may be used with stress and nonstress imaging protocols. Single photon emission computer tomography (SPECT) imaging with attenuation correction, combined supine and prone imaging, use of technetium isotope, and positron emission tomography (PET) imaging may all provide some advantage for myocardial perfusion imaging for the obese patient.     

Characterizing Bariatric Surgery Utilization and Complication Rates in the Adolescent Population

Introduction

Bariatric surgery is an increasingly common treatment of morbid obesity in the United States and has demonstrated effective weight loss and improvement of comorbidities. We used the National Surgical Quality Improvement Program (NSQIP) data to characterize bariatric surgery utilization and complication rates in the adolescent population.

Increase of Osteopontin Plasma Concentrations After Bariatric Surgery Independent from Inflammation and Insulin Resistance

Background  Osteopontin (OPN) is a multifunctional matrix glycoprotein associated with bone metabolism and has been linked to chronic inflammation, insulin resistance, and atherosclerosis. Diet-induced weight loss decreases elevated OPN concentrations in obese patients. The aim of the current study was to investigate the role of OPN after bariatric surgery, where not only improvements of chronic inflammation, insulin resistance and comorbidities, but also malabsorption and altered bone metabolism have been reported. Methods  OPN plasma concentrations were determined in 31 morbidly obese patients (5 men, 26 women, BMI 46.2 ± 7.1 kg/m², age 41 ± 11 years; mean ± SD) before and 18 months after bariatric surgery, together with parameters of bone metabolism and inflammation. Results  OPN concentrations increased by +20.3 ± 26.6 ng/ml (mean ± SD, p < 0.01), concomitant to a weight loss of −38 ± 22 kg, and a decrease in BMI by −13.1 ± 7.7 kg/m² (both p < 0.01). HOMA-index improved from 5.2 ± 3.4 to 1.5 ± 1.0 (p < 0.01). Calcium concentrations slightly decreased, and phosphate increased (−0.06 ± 0.13 mmol/l and +0.08 ± 0.16 mmol/l, respectively; both p < 0.05), while 25-OH-VitaminD₃ remained unchanged and PTH tended to increase (+5.1 ± 14.0 pg/ml, p = 0.054). Monocyte chemoattractant protein 1 and interleukin 18 were significantly decreased and associated with HOMA both before and after bariatric surgery. ΔOPN was correlated with ΔPTH, but not with other parameters. Conclusions  OPN plasma concentrations increased concomitant to weight loss after bariatric surgery, which was independent from an improvement of insulin sensitivity and a decrease of inflammatory markers. Further studies are needed to differentiate whether these changes in bone metabolism after bariatric surgery are secondary to calcium deficiency or an adaptation to weight loss. This work has been submitted in abstract form and will be in part presented at the American Diabetes Association 68th Scientific Sessions 2008, June 6th–10th, San Francisco, CA, USA.     

Potential Applications of Global Protein Expression Analysis (Proteomics) in Morbid Obesity and Bariatric Surgery

Global protein expression analysis, known as proteomics, has emerged as a novel scientific technology currently successfully applied to several fields of medicine including cancer and transplantation. Thereby, a thorough exploration of the pathogenic mechanisms and a better understanding of the pathophysiology of diseases as well as identification of diagnostic biomarkers have been achieved. In this paper, we outline the basic principles and potential applications of this promising tool in bariatric surgery where proteomics might hold great potential for new insights into diagnostic and therapeutic decision making based on improved knowledge of metabolic regulations pre- and postsurgical interventions in morbidly obese patients.     

Serum Phenylalanine Concentration as a Marker of Liver Function in Obese Patients Before and After Bariatric Surgery

Background  Human obesity is associated with increased serum phenylalanine concentration, which is probably caused by liver dysfunction related to liver steatosis. This study examines whether improvements of liver function after bariatric surgery is associated with a decrease of serum phenylalanine concentration caused by an increase of phenylalanine metabolism. Method  Serum phenylalanine and alanine aminotransferase (an independent predictor of liver steatosis) concentrations as well as several parameters related to obesity were measured in 16 obese patients (seven men and nine women) before and 6 months after vertical banded gastroplasty. Ten (six men and four women) lean, healthy subjects served as controls. Results  Obese patients before surgery had approximately twofold higher serum phenylalanine concentration than control subjects. The serum phenylalanine concentration decreased 6 months after bariatric surgery. Serum alanine aminotransferase (ALT) concentration was higher in obese patients before surgery, and decreased 6 months after bariatric surgery. Changes in serum phenylalanine concentration correlated positively with changes of ALT concentration (r = 0.75; p < 0.001). The body weight, BMI, HOMA-IR, serum triacylglycerol, LDL-cholesterol/HLD-cholesterol ratio, leptin, insulin, and glucose concentrations were higher in obese patients, and decreased 6 months after bariatric surgery. Serum HDL-cholesterol concentration was lower in obese patients before surgery than in control subjects and increased 6 months after surgery. Conclusion  Results obtained indicate that bariatric surgery-induced weight loss had beneficial effects on several laboratory parameters including serum phenylalanine, ALT, lipid concentrations and insulin resistance. A strong positive correlation between serum phenylalanine and serum ALT concentrations suggests that deterioration of liver function in obese patients is contributing to a decrease in phenylalanine metabolism and consequently to the increase of serum phenylalanine concentration. One can suppose that serum phenylalanine concentration could be noninvasive marker of liver dysfunction associated with liver steatosis in obese patients.     

Bariatric surgery trends: an 18-year report from the International Bariatric Surgery Registry

BACKGROUND: The epidemic of morbid obesity has increased bariatric procedures performed. Trend analyses provide important information that may impact individual practices. METHODS: Patient data from 137 surgeons were examined from 1987 to 2004 (41,860 patients) using Cochran-Armitage Trend test and Generalized Linear Model. RESULTS: Over an 18-year period, surgeon preference for combined restrictive-malabsorptive procedures increased from 33% to 94%, while simple gastric restriction decreased correspondingly (P < .0001). Surgeons per worksite doubled and cases per surgeon increased 71%. Laparoscopic procedures increased to 24%. The percentage of males, mean operative age, and initial body mass index (BMI) increased significantly (P < .0001). Postoperative hospital stay decreased from 5.0 to 3.9 days (P < .0001). The most common procedure in 2004 was Roux-en-Y gastric bypass (RYGB) (59%). CONCLUSION: Bariatric surgery patients are now older and heavier, length of stay is shorter, and the laparoscopic approach is more frequent. From 1987 to 2004, the general trend shows a clear preference for combined restrictive-malabsorptive operations.