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Biomedical subjects

Edward H Livingston

Publications and source records attributed to Edward H Livingston.

At least 19 recordsLinked to original sources
PubMed2006

Development of bariatric surgery-specific risk assessment tool.

BACKGROUND: Administrative databases have increasingly been used to assess bariatric surgery outcomes, resulting in policy recommendations about bariatric practice. However, surgical outcomes must be risk adjusted to compare patients of varying potential risk fairly with those to whom the policies will apply. To date, the risk adjustment tools used for database analysis of bariatric surgical outcomes have been those designed for other purposes, and their sensitivity for bariatric outcomes has not been established. METHODS: Bariatric surgical procedures contained in the National Hospital Discharge Summary for 1993-2003 were assembled into a database. The standard set of Elixhauser co-morbidity variables used by the Agency for Healthcare Research and Quality were entered into the database. Those variables that were significantly associated with adverse outcomes were entered into a stepwise-elimination logistic regression equation, yielding a set of variables related to adverse outcomes from bariatric surgery. These were then prospectively applied to another database (the National Inpatient Survey) to determine their sensitivity for predicting outcomes and were compared with the commonly used Charlson score. RESULTS: The variables significantly correlating with bariatric adverse events included chronic pulmonary disease, hypertension, diabetes with chronic complications, fluid and electrolyte disorders, deficiency anemias, and depression. Age and male gender were also signficantly related to adverse events. The c-index (a correlative index, with .5 showing no, and 1, a perfect, relationship) for bariatric surgery mortality with the Charlson index is .52. For the Elixhauser-based system we developed, it is .72. CONCLUSIONS: We have developed a new risk-adjustment tool for bariatric surgery outcomes studies that use administrative databases. Its performance was clearly better than that of the commonly used Charlson co-morbidity score. Bariatric studies that have used the Charlson index should not be considered adequately risk adjusted.

Adolescent↗
PubMed2006

National Surgical Quality Improvement Program analysis of bariatric operations: modifiable risk factors contribute to bariatric surgical adverse outcomes.

BACKGROUND: The increase in obesity coupled with greater acceptance of the field of bariatric surgery has resulted in a substantial rise in the number of weight-loss operations. Because obese individuals are at high risk for surgical complications, concern about the safety of bariatric procedures exists. Earlier investigations of the clinical features associated with surgical complications have produced conflicting results. We sought to identify risk factors for surgical complications in a large, nationally representative population of US veterans. STUDY DESIGN: We analyzed data on bariatric procedures performed at 12 Veterans' Affairs medical centers approved to perform weight-loss operations between 1998 and 2004. Detailed pre-, intra-, and postoperative information and longterm mortality data were prospectively collected using the National Surgical Quality Improvement Program methodology. We used multivariable logistic regression to identify clinical features associated with postoperative complications. RESULTS: Among 575 bariatric patients assessed between 1998 and 2004, 74% were men with a mean age of 51 years. Thirty-day mortality was 1.4%. Overall complication rate was 19.7%. Of those with complications, one-half were of considerable clinical importance, as they were associated with prolonged length of stay. Clinical features that were predictive of adverse events in our multivariable analyses were superobesity, weight>350 pounds, and smoking. A more than 20 pack-year history of smoking was also associated with difficulty in weaning from a ventilator postoperatively. CONCLUSIONS: We identified smoking and superobesity as preoperative risk factors associated with postoperative complications. Future studies should examine the effect of preoperative weight loss and smoking cessation on bariatric procedure outcomes.

Bariatric Surgery↗
PubMed2006

The impact of age and Medicare status on bariatric surgical outcomes.

HYPOTHESIS: Medicare status and increasing age are associated with poor outcomes from bariatric surgical procedures. DESIGN: Survey. SETTING: National sample of hospitalized patients in the United States. PATIENTS AND INTERVENTION: Adult patients undergoing bariatric surgery in 2001 and 2002. MAIN OUTCOME MEASURES: Mortality and adverse events. RESULTS: We assessed 25 428 bariatric procedures with logistic regression, finding that age (odds ratio, 1.04; 95% confidence interval, 1.02-1.07), male sex (odds ratio, 2.45; 95% confidence interval, 1.48-4.03), electrolyte disorders (odds ratio, 13.91; 95% confidence interval, 8.29-23.33), and congestive heart failure (odds ratio, 4.96; 95% confidence interval, 2.52-9.77) were independent risk factors for bariatric surgery mortality. Adverse outcomes increased as a function of age in a nearly linear fashion, with a steep increase after the age of 65 years. Most Medicare patients undergoing these operations were younger than 65 years and had a much greater disease burden than non-Medicare patients. CONCLUSIONS: Age, male sex, electrolyte disorders, and congestive heart failure were independent risk factors for bariatric surgical mortality. Limiting bariatric surgical procedures to those younger than 65 years is warranted because of the high morbidity and mortality associated with these operations in older patients.

Age Factors↗
PubMed2006

Colon cancer and apoptosis.

BACKGROUND: The implementation of new therapeutic options for the management of metastatic colon cancer mandates a revisit to apoptosis and its role in colon cancer tumorigenesis with an emphasis on the mechanisms leading to chemotherapeutic resistance and immune system evasion of colon cancer cells. DATA SOURCES: Literature regarding molecular apoptosis mechanisms and the role of apoptosis in colon cancer progression are reviewed by this article. CONCLUSION: Programmed cell death has rapidly emerged as a potential target for cancer treatment at various stages of tumor progression. Chemoprevention, immuno-regulation, and metastasis are prospective targets by which apoptotic mechanisms could be utilized in the prevention and management of tumorigenesis. Understanding how defects in the death receptor pathway of apoptosis permit colon cancer cells to escape the immune system would allow for treatment options whereby the body's immune system could again recognize and eliminate unwanted cells.

Antineoplastic Agents↗
PubMed2006

Outcome of portal injuries following bariatric operations.

BACKGROUND: Portal vein thrombosis is rare following Roux-en-Y gastric bypass (RYGBP). Its natural history is dependent on the etiology of the thrombosis. Iatrogenic injuries at bariatric operations resulting in portal vein thrombosis are lethal complications typically necessitating a liver transplant, whereas postoperative portal vein thrombosis without an injury to the portal vein has a benign course. There are currently no data on management or prognostic factors of portal vein thrombosis after bariatric operations. METHODS: 3 patients referred for liver transplantation secondary to portal vein injury following bariatric surgery between 2000 and 2003 are presented. RESULTS: 2 super-obese (BMI>or=50 kg/m2) and 1 morbidly obese (BMI 44 kg/m2) patients sustained portal vein injuries during bariatric surgery (RYGBP 2, VBG 1) by experienced bariatric surgeons. In each case, the portal injury was identified and repaired. Thrombosis followed reconstruction in all 3 patients. All 3 underwent emergency liver transplantation, but died of sepsis and multi-organ failure following transplantation. Review of the literature found no cases of traumatic portal vein injuries following bariatric operations and 2 cases of postoperative portal vein thrombosis: 1 following LRYGBP (BMI 46) and one after a Lap-Band (BMI 41). CONCLUSION: Injury to the portal vein resulting from difficulty in discerning the anatomy of the intra-abdominal structures in the morbidly obese, is a lethal complication of bariatric surgery. Super-obese patients submitting to bariatric surgery should lose weight, undergo a two-stage bariatric procedure, or undergo laparoscopic RYGBP to minimize the risk of portal injury. Postoperative portal vein thrombosis has a benign course and can be managed conservatively.

Adult↗
PubMed2005

Statistical power and estimation of the number of required subjects for a study based on the t-test: a surgeon's primer.

The underlying concepts for calculating the power of a statistical test elude most investigators. Understanding them helps to know how the various factors contributing to statistical power factor into study design when calculating the required number of subjects to enter into a study. Most journals and funding agencies now require a justification for the number of subjects enrolled into a study and investigators must present the principals of powers calculations used to justify these numbers. For these reasons, knowing how statistical power is determined is essential for researchers in the modern era. The number of subjects required for study entry, depends on the following four concepts: 1) The magnitude of the hypothesized effect (i.e., how far apart the two sample means are expected to differ by); 2) the underlying variability of the outcomes measured (standard deviation); 3) the level of significance desired (e.g., alpha = 0.05); 4) the amount of power desired (typically 0.8). If the sample standard deviations are small or the means are expected to be very different then smaller numbers of subjects are required to ensure avoidance of type 1 and 2 errors. This review provides the derivation of the sample size equation for continuous variables when the statistical analysis will be the Student's t-test. We also provide graphical illustrations of how and why these equations are derived.

Data Interpretation, Statistical↗
PubMed2005

Meta-analysis: surgical treatment of obesity.

BACKGROUND: Controversy exists regarding the effectiveness of surgery for weight loss and the resulting improvement in health-related outcomes. PURPOSE: To perform a meta-analysis of effectiveness and adverse events associated with surgical treatment of obesity. DATA SOURCES: MEDLINE, EMBASE, Cochrane Controlled Trials Register, and systematic reviews. STUDY SELECTION: Randomized, controlled trials; observational studies; and case series reporting on surgical treatment of obesity. DATA EXTRACTION: Information about study design, procedure, population, comorbid conditions, and adverse events. DATA SYNTHESIS: The authors assessed 147 studies. Of these, 89 contributed to the weight loss analysis, 134 contributed to the mortality analysis, and 128 contributed to the complications analysis. The authors identified 1 large, matched cohort analysis that reported greater weight loss with surgery than with medical treatment in individuals with an average body mass index (BMI) of 40 kg/m2 or greater. Surgery resulted in a weight loss of 20 to 30 kg, which was maintained for up to 10 years and was accompanied by improvements in some comorbid conditions. For BMIs of 35 to 39 kg/m2, data from case series strongly support superiority of surgery but cannot be considered conclusive. Gastric bypass procedures result in more weight loss than gastroplasty. Bariatric procedures in current use (gastric bypass, laparoscopic adjustable gastric band, vertical banded gastroplasty, and biliopancreatic diversion and switch) have been performed with an overall mortality rate of less than 1%. Adverse events occur in about 20% of cases. A laparoscopic approach results in fewer wound complications than an open approach. LIMITATIONS: Only a few controlled trials were available for analysis. Heterogeneity was seen among studies, and publication bias is possible. CONCLUSIONS: Surgery is more effective than nonsurgical treatment for weight loss and control of some comorbid conditions in patients with a BMI of 40 kg/m2 or greater. More data are needed to determine the efficacy of surgery relative to nonsurgical therapy for less severely obese people. Procedures differ in efficacy and incidence of complications.

Adolescent↗
PubMed2005

Hospital costs associated with bariatric procedures in the United States.

BACKGROUND: Weight loss operations are being performed at an exponentially increasing rate. Although highly effective for controlling obesity and its complications, the operations are expensive. The operations are thought to be cost-effective, but there has not been an analysis of the costs associated with these procedures at a national level precluding definitive cost-effectiveness studies useful for policy determination. METHODS: The 2001 and 2002 National Inpatient Survey (NIS) was used to establish costs attributable to bariatric surgery. This survey contains discharge information for approximately 20% of all US hospital admissions in any given year. Bariatric procedures were identified by ICD-9-CM procedures codes and diagnostic related group (DRG) 288 (operating room [OR] procedures for obesity). RESULTS: Of the commonly performed operations, laparoscopic gastric bypass had the lowest hospital charges (19,794 dollars/case) relative to open gastric bypass (22,313 dollars/case) and laparoscopic banding procedures (25,355 dollars/case). Laparoscopic gastric bypass resulted in fewer charges because of a 1-day shorter median length of stay. DISCUSSION: These data provide benchmarks for the costs associated with the weight loss procedures commonly performed in the United States. Although laparoscopic gastric bypass is the lease costly approach to bariatric surgery, the fact that costs are lower because of decreased length of stay can be disadvantageous for hospitals reimbursed on a per diem basis.

Cost of Illness↗
PubMed2005

Indications for selective intraoperative cholangiography.

The indications for selective intraoperative cholangiography (IOC) include a clinical history of jaundice, pancreatitis, elevated bilirubin level, abnormal liver function test results, increased amylase levels, a high lipase level, or dilated common bile duct on preoperative ultrasonography. Although these clinical features are widely accepted as indications for IOC, they have not been tested for their ability to predict choledocholithiasis. Charts were reviewed for a 6-month time period in 2003 at Parkland Memorial Hospital for all patients undergoing cholecystectomy. Univariate analysis and logistic regression were used to determine which factors predicted choledocholithiasis. Of the 572 patients undergoing cholecystectomies during the study period, 189 underwent IOC and common bile duct stones were found in 57. Only preoperative hyperbilirubinemia or ultrasonograph identification of common bile duct dilation reliably predicted choledocholithiasis. There were 13 cases of choledocholithiasis that would not have been identified by preoperative hyperbilirubinemia or an enlarged common bile duct. However, common bile duct stones were clinically significant in only 2 of the 13 cases. One of these was treated with postoperative endoscopic retrograde cholangiopancreatography, and the other was treated with laparoscopic common bile duct exploration. Preoperative identification of a dilated common bile duct or elevated bilirubin levels can be the sole criteria for performing IOC on a selective basis in patients without malignancy. Reliance on a history of remote jaundice, pancreatitis, elevated liver function test values, or pancreatic enzymes results in unnecessary IOCs.

Adult↗
PubMed2005

Technical complications are rising as common duct exploration is becoming rare.

BACKGROUND: Both hospital and surgeon volume influence outcomes. With introduction of new technologies, some procedures are now performed less frequently. ERCP has replaced the need for common duct exploration (CDE) in most cases of choledocholithiasis. We explored the secular trends and outcomes of CDE and how they have changed relative to introduction of ERCP. STUDY DESIGN: The National Hospital Discharge Survey database was analyzed for the years 1979 to 2001. Procedural frequency of ERCP and CDE was determined. Charlson and Elixhauser comorbidity indices were used to characterize patients' disease burden for the years 1993 to 2001. Length of stay, mortality, and complication rates for each procedure were determined. RESULTS: At the beginning of the study period, an estimated 47,000 CDEs were performed annually. These declined to 7,700 per year as ERCP increased to 42,500 procedures per year at the end of the study period. CDE complication rates increased from 3.4% to 17.4% over the same period. Comorbidity analysis for the years 1993 to 2001 revealed that ERCP and CDE patients had equivalent disease burdens. Technical complication rates rose in parallel to the increased overall CDE complication rate. CONCLUSIONS: ERCP has replaced the need for most but not all CDE. With diminished CDE experience at a national level, the complication rate has markedly increased, at least in part from technical complications. Both choledocholithiasis treatment algorithms and clinical training paradigms need to account for the rarity of CDE and high complication rates associated with it, by incorporation of training modules in surgical residencies and advocating referral to centers having expertise in biliary tract operations from surgeons with little CDE experience.

Age Factors↗
PubMed2005

Complications of bariatric surgery.

The rise in bariatric operations has been exponential because of the greater acceptance for these procedures. Although complication rates are relatively low, they can result in formidable disability. Adverse outcomes also result in medical malpractice claims that are particularly problematic for bariatric surgery practices. For these reasons, surgeons performing these operations must be knowledgeable and must possess the technical skills required for managing complications when they occur. The purpose of this article is to review the major complications that occur following anti-obesity procedures and to provide recommendations regarding their management.

Anastomosis, Surgical↗
PubMed2005

Effect of diabetes and hypertension on obesity-related mortality.

BACKGROUND: Obesity is increasing and, along with it, greater mortality resulting from the overweight condition. Weight-reduction surgery is recommended for many obese patients based on a perceived risk of greater obesity-related mortality. However, many of the studies cited to justify this have aggregated patient groups together, making it difficult to apply their findings to individual patients. METHODS: The combined National Health Interview Survey database from the years 1986-1994 that has been linked to the National Death Index was analyzed. Patients were stratified for their body mass index (BMI) category, the presence or absence of diabetes and hypertension, gender, and race. The contribution of hypertension and diabetes to mortality was determined by Cox proportional hazards modeling. The absolute magnitude that the effect gender, race, BMI, hypertension, and diabetes had on mortality was determined by examination of stratified age-adjusted death rates. RESULTS: We analyzed 662,443 records from individuals interviewed between 1986 and 1994. Of these, 49,391 had died in the follow-up period (mean follow-up, 7.2 years; range, 1-14 years). Cox proportional hazards modeling-adjusting for age, race, and gender-revealed that hypertension (hazard ratio = 1.35 [95% CI 1.34-1.35], P < .0001) and diabetes (hazard ratio = 2.29 [95% CI 2.28-2.29], P < .0001) increased mortality independent of body weight. Serious obesity was associated with an increased mortality by Cox modeling (hazard ratio = 1.72 [95% CI 1.71-1.73], P < .0001); however, when assessed by stratified age-adjusted mortality rates, this increase was numerically small because of the relatively low mortality rate for those without hypertension or diabetes. The presence of hypertension or diabetes substantially increased age-adjusted mortality rates. Much of the increased mortality observed in diabetic patients was attributable to complications of diabetes and not necessarily from atherosclerosis. CONCLUSION: Because weight-loss surgery successfully cures hypertension or diabetes in most obese patients, it should be considered for obese patients having these diseases. Based on the greatly elevated mortality associated with diabetes, surgery may be justified for obese diabetic patients with BMIs lower than the currently accepted criteria. In contrast, for the morbidly obese without diabetes or hypertension, mortality is only slightly increased from obesity alone. In terms of mortality, the benefits of weight reduction resulting from weight-loss surgery are less clear if there is no coexistent diabetes or hypertension.

Adolescent↗
PubMed2005

Simplified resting metabolic rate-predicting formulas for normal-sized and obese individuals.

OBJECTIVE: Resting metabolic rate (RMR) is known to be proportional to body weight and to follow allometric scaling principles. We hypothesized that RMR can be predicted from an allometric formula with weight alone as an independent variable. RESEARCH METHODS AND PROCEDURES: An allometric, power-law scaling model was fit to RMR measurements obtained from a cohort of patients being treated for weight loss. This, as well as many of the commonly used RMR-predicting formulas, was tested for RMR prediction ability against a large publicly available RMR database. Bland-Altman analysis was used to determine the efficacy of the various RMR-predicting formulas in obese and non-obese subjects. RESULTS: Power law modeling of the RMR-body weight relationship yielded the following RMR-predicting equations: RMR(Women) = 248 x Weight(0.4356) - (5.09 x Age) and RMR(Men) = 293 x Weight(0.4330) - (5.92 x Age). Partial correlation analysis revealed that age significantly contributed to RMR variance and was necessary to include in RMR prediction formulas. The James, allometric, and Harris-Benedict formulas all yielded reasonable RMR predictions for normal sized and obese subjects. DISCUSSION: A simple power formula relating RMR to body weight can be a reasonable RMR estimator for normal-sized and obese individuals but still requires an age term and separate formulas for men and women for the best possible RMR estimates. The apparent performance of RMR-predicting formulas is highly dependent on the methodology employed to compare the various formulas.

Adult↗
PubMed2004

Who was student and why do we care so much about his t-test?

Statistics is the study of populations, how they relate to one another and what effect sampling has in terms of representing the original population. Use of statistical tools has been facilitated by modern computer technology; however, given the ease in which results are obtained, it is easy to overlook potentially incorrect use of the various statistical tests. Statistical tools are invaluable for investigators because they make it possible to determine if scientific results are important. When a test is used, it is important to know that the result of any statistical test is valid to avoid erroneous conclusions. To do so, the investigator must have a basic understanding of the test's assumptions and limitations. Modern statistical packages often include a variety of results relating to the test's applicability to the data analyzed. Not uncommonly, biologists are unfamiliar with these analyses. This review intends to improve the reader's understanding of t-tests by providing a history of Student's t-test, and its assumptions, applications, and limitations. Part 1 of the series ("The Mean and Standard Deviation: What Does It All Mean?") reviewed basic aspects of distributions, measures of central tendency, and dispersion assessment. Small sample size effects on accurate estimation of a population mean and group comparisons for continuous data are presented in this review.

Data Interpretation, Statistical↗
PubMed2004

Do young colon cancer patients have worse outcomes?

Previous studies on colon cancer have noted rising incidence rates among young individuals and suggest that they may have more aggressive disease and worse 5-year survivals than their older counterparts. Our study uses a nationwide population-based cancer registry to analyze colon cancer presentations and outcomes in a young versus an older population. The records of patients with colon carcinoma were obtained from the Surveillance, Epidemiology, and End Results (SEER) national cancer database (1991-1999). Two cohorts based on age at diagnosis (20-40 years, n = 1334 vs. 60-80 years, n = 46,457) were compared for patient and tumor characteristics, treatment, and 5-year cancer-specific survival. A multivariate Cox regression was performed to identify predictors of survival. The young group had a higher proportion of black and Hispanic patients than did the older group (p < 0.001). Young patients had less stage I or II disease, more stage III or IV disease (p < 0.001), and worse-grade (poorly differentiated or anaplastic) tumors (p < 0.001). The 5-year stage-specific survival was similar for stage I and III disease (p = NS) but was significantly better for young patients with stage II and IV disease (p < 0.01). Using a nationally representative cancer registry, we found that young colon cancer patients tend to have later-stage and higher-grade tumors. However, they have equivalent or better 5-year cancer-specific survival compared to older patients. This population-based finding contradicts prior single-institution reports.

Adenocarcinoma↗
PubMed2004

Colorectal cancer in the young.

BACKGROUND: Colorectal cancer (CRC) is generally thought of as a disease of older persons; however a significant proportion of patients <40 years present with this disease. Many investigators have published single-institution series on CRC in the young, yet the data vary markedly. We performed a structured review of the current literature aiming to (1) characterize CRC in the young population and (2) determine how CRC in this population should be further addressed regarding detection and treatment. DATA SOURCES: A Medline literature search was completed. Articles were chosen to include those studies that examined patients <40 years old. A total of 55 articles were chosen from the search and review of the bibliographies. CONCLUSIONS: We found that CRC in the young population appears to be more aggressive, to present with later stage, and to have poorer pathologic findings. However, if detected early, young patients with Dukes' stage A or B lesions have better overall 5-year survival rates. These findings emphasize the need for health care providers to have a heightened awareness when caring for this young population, particularly because excellent modalities exist to diagnose and treat colorectal cancer.

Adult↗