Hemodynamic dysfunction in obesity hypoventilation syndrome and the effects of treatment with surgically induced weight loss

Big breathing: the complex interaction of obesity, hypoventilation, weight loss, and respiratory function

Obesity places a significant load on the respiratory system, affecting lung volumes, respiratory muscle function, work of breathing, and ventilatory control. Despite this, most morbidly obese individuals maintain eucapnia. However, a subgroup of morbidly obese individuals will develop chronic daytime hypercapnia, described as the obesity hypoventilation syndrome (OHS). While obesity is obviously a crucial component of this syndrome, the relationship between excess fat accumulation and the development of awake hypercapnia is complex and extends beyond simply impairments of pulmonary mechanics and lung volumes as a consequence of obesity. Various compensatory mechanisms operate to maintain eucapnia even in the presence of extreme obesity. However, if compensation is impaired, hypoventilation will ensue. While obesity alone does not account for the development of hypoventilation, weight loss will produce significant improvements in lung function and awake gas exchange. Such improvements have the potential to substantially reduce morbidity and mortality in these individuals. Nevertheless, many individuals remain overweight despite substantial weight loss, with persistence of upper airway obstruction. Attention to this residual abnormality is important given the high incidence of cardiovascular abnormalities, including pulmonary hypertension, in individuals with OHS.

American Association of Clinical Endocrinologists, The Obesity Society, and American Society for Metabolic & Bariatric Surgery medical guidelines for clinical practice for the perioperative nutritional, metabolic, and nonsurgical support of the bariatric surgery patient

American Association of Clinical Endocrinologists, The Obesity Society, and American Society for Metabolic & Bariatric Surgery Medical Guidelines for Clinical Practice are systematically developed statements to assist health-care professionals in medical decision making for specific clinical conditions. Most of the content herein is based on literature reviews. In areas of uncertainty, professional judgment was applied. These guidelines are a working document that reflects the state of the field at the time of publication. Because rapid changes in this area are expected, periodic revisions are inevitable. We encourage medical professionals to use this information in conjunction with their best clinical judgment. The presented recommendations may not be appropriate in all situations. Any decision by practitioners to apply these guidelines must be made in light of local resources and individual patient circumstances. The American Society for Parenteral & Enteral Nutrition fully endorses sections of these guidelines that address the metabolic and nutritional management of the bariatric surgical patient.

American Association of Clinical Endocrinologists, The Obesity Society, and American Society for Metabolic & Bariatric Surgery Medical Guidelines for Clinical Practice for the perioperative nutritional, metabolic, and nonsurgical support of the bariatric surgery patient

American Association of Clinical Endocrinologists, The Obesity Society, and American Society for Metabolic & Bariatric Surgery Medical Guidelines for Clinical Practice are systematically developed statements to assist healthcare professionals in medical decision making for specific clinical conditions. Most of the content herein is based on literature reviews. In areas of uncertainty, professional judgment was applied. These guidelines are a working document that reflects the state of the field at the time of publication. Because rapid changes in this area are expected, periodic revisions are inevitable. We encourage medical professionals to use this information in conjunction with their best clinical judgment. The presented recommendations may not be appropriate in all situations. Any decision by practitioners to apply these guidelines must be made in light of local resources and individual patient circumstances. The American Society for Parenteral & Enteral Nutrition fully endorses sections of these guidelines that address the metabolic and nutritional management of the bariatric surgical patient.

The incidence of pulmonary embolism in open versus laparoscopic gastric bypass

Obesity independently increases the risk of pulmonary embolism (PE). We compare a superobese population (body mass index [BMI] > 55 kg/m(2)) undergoing open gastric bypasses (OGBs) with a similarly matched group of laparoscopic gastric bypasses (LGB) to see if the incidence of PE differs. We included all patients undergoing OGB (n = 193, average BMI = 51 kg/m(2)) at our institution by a single surgeon between July 1999 and April 2001. Thirty-one patients were superobese (BMI > 55 kg/m(2)). LGB was started at our institution in April 2001. Since that time 213 patients (average BMI = 52 kg/m(2)) have undergone the procedure. One hundred and nine patients were superobese. Pre- and postoperative prophylaxis included sequential compression stockings and subcutaneous heparin. Postoperatively, patients who developed signs of hypoxia, tachypnea, or tachycardia underwent a chest X-ray and spiral computed tomography. In addition, all patients who expired in the 30-day postoperative period underwent postmortem examination. Data were analyzed using the chi-squared test. In the OGB group, four patients (2.1%) developed PE. All occurred in superobese patients with a BMI > 55 kg/m(2). Three were fatal PEs and one was nonfatal. None of these patients had a prior history of deep vein thrombosis, PE, venous stasis disease, or pulmonary hypertension. In the LGB group, one patient (0.9%) had a nonfatal PE. This patient had a history of deep vein thrombosis. The incidence of PE was statistically higher in the superobese OGB group (P < 0.01). Despite the theoretical hindrance to venous return and vena caval compression observed with pneumoperitoneum, fewer PEs occurred in the laparoscopic group. Our data, however, suggest that patients with a BMI > 55 kg/m(2) might be at an increased risk for PE independent of operative approach.

Standard therapies for pulmonary arterial hypertension

After half a century of clinical experience and research, management of pulmonary arterial hypertension remains a challenge. Currently, data to support the use of standard therapies for pulmonary arterial hypertension (oxygen supplementation, diuretics, digoxin, anticoagulation, and calcium channel blockers) are mostly retrospective, uncontrolled prospective, or derived from other diseases with similar but not identical manifestations. In the absence of any further prospective, controlled studies, it is reasonable to use these therapies when they are tolerated. When these therapies are poorly tolerated, however, the threshold for discontinuation should be low.

Impact of obesity and bariatric surgery on cardiovascular disease

Morbid obesity is a growing public health concern with multiple associated cardiovascular comorbidities. Bariatric surgery has emerged as a safe and effective treatment for morbidly obese patients at risk for, or already suffering from, cardiovascular disease. Weight loss induced by the surgery has been shown to improve cardiovascular risk factors, cardiac structure and function, and the clinical course of established cardiovascular disease. The role of adipocyte-derived cytokines in mediating cardiovascular pathophysiology in obesity-and its modulation after weight loss-is under active investigation.

Pulmonary considerations in obesity and the bariatric surgical patient

Severe obesity can be associated with significant alterations in normal cardiopulmonary physiology. The pathophysiologic effects of obesity on a patient's pulmonary function are multiple and complex. The impact of obesity on morbidity and mortality are often underestimated. Bariatric surgery has been shown to be the most effective modality of reliable and durable treatment for severe obesity. Surgical weight loss improves and, in most cases, completely resolves the pulmonary health problems associated with obesity.

Follow-up of Roux-en-Y gastric bypass patients at 5 or more years postoperatively

BACKGROUND

Short-term results (24 to 36 months) after Roux-en-Y gastric bypass (RYGBP) have been extensively described. Little is reported on the patients operated > or = 5 years ago. We analyzed the results of weight loss, resolution of co-morbidities and nutritional complications of patients submitted to the silicone ring RYGBP, at least 5 years before.

METHODS

75 morbidly obese patients who underwent silicone ring RYGBP between Oct 1995 and Dec 1999, 18 men and 57 women, were studied. Demographic data, nutritional status and the presence of co-morbidities (type 2 diabetes, hypertension, sleep apnea, dyslipidemia) were accessed. Pre- and postoperative BMI were registered, along with excess weight loss (EWL). Nutritional deficiencies were accessed by laboratory assays.

RESULTS

Mean follow-up was 87 months. Initial BMI was 56.7 +/- 10 kg/m2. After 2 years, BMI had dropped to 29.3 +/- 6.8, and by the last interview BMI was 35.5 +/- 10. %EWL after 2 years was 80.2 +/- 17.3%, and at the end was 71.8 +/- 21.6%. After 2 years, only 1 of the 75 patients (1.33%) had not achieved an EWL of at least 50%. At the end, 23 patients (30.6%) could not maintain this EWL. Resolution of diabetes was 76.5%, arterial hypertension 37.3% and sleep apnea 93.5%. Iron, vitamin B12 and vitamin D were the most common nutritional deficiencies.

CONCLUSIONS

Long-term follow-up (5 to 9 years) after the RYGBP was associated with satisfactory mantainance of EWL, and resolution or improvement of the main co-morbidities was observed in the majority of the patients.

Clinical resolution of severely symptomatic pseudotumor cerebri after gastric bypass in an adolescent

Pseudotumor cerebri is a disease characterized by increased intracranial pressure, often manifested by headaches, and occasionally leading to severe visual impairment or even blindness. Most cases in adolescents, as in adults, are associated with obesity. We report a 16-year-old morbidly obese adolescent girl (body mass index 42.3 kg/m(2)) with severely symptomatic pseudotumor cerebri who had progressive visual field deficits and elevated intracranial pressure (opening pressure on lumbar puncture of 50 cm H(2)O) despite intensive medical management and placement of both ventriculoperitoneal and lumboperitoneal shunts. Six months after she underwent gastric bypass surgery, she had lost 43% of her excess body weight and had had near complete regression of her visual field deficits, along with normalization of her intracranial pressures. This case demonstrates the dramatic reversal of symptoms of pseudotumor cerebri with surgically induced weight loss. Gastric bypass should be considered as a treatment option for adolescents with severe and progressive pseudotumor cerebri.

Experience with inferior vena cava filter placement in patients undergoing open gastric bypass procedures

OBJECTIVE

Patients undergoing open gastric bypass (OGB) for morbid obesity are at significant risk for pulmonary embolism (PE) despite the use of subcutaneous heparin injections and sequential compression devices. Prophylactic preoperative inferior vena cava (IVC) filter placement may reduce this risk. We report our experience with simultaneous IVC filter placement and OGB in an operating room setting.

METHODS

From July 1999 to April 2001, 193 patients (group 1) underwent OGB. Eight patients had prophylactic intraoperative IVC filters placed for deep vein thrombosis, PE, or pulmonary hypertension. From May 2001 to January 2003, 181 patients (group 2) underwent OGB. There were 33 IVC filters placed for body mass index (BMI) greater than 55 kg/m2 in addition to the above-mentioned criteria. To confirm observations made in group 1 and 2 patients, from July 2003 to May 2005, 197 patients (group 3) underwent OGB, and patients with a BMI greater than 55 kg/m2 (n = 35) were offered IVC filter placement. Group 3A (n = 17) consented to IVC filter placement, and group 3B (n = 18) did not.

RESULTS

Fifty-eight IVC filters were placed (100% technical success rate) with an increase in operating room time of 20 +/- 5 minutes. In group 1, the eight patients with IVC filters had a BMI greater than 55 kg/m2. There were four PEs (3 fatal and 1 nonfatal) in the other 185 patients, all which occurred in patients with BMIs greater than 55 kg/m2. In group 2, there were no PEs. The perioperative PE rate in these patients was reduced from 13% (4/31; 95% confidence interval [CI], 1.1%-25.7%) to 0% (0/33; 95% CI, 0%-8.7%). Perioperative mortality was reduced from 10% (3/31; 95% CI, 0%-20.0%) to 0% (0/33; 95% CI, 0%-8.7%). There were no pulmonary emboli or deaths related to PE in group 3A patients. Group 3B patients had a 28% PE rate (two fatal and three nonfatal) and an 11% PE-related death rate. None of the remaining patients in group 3 had a PE.

CONCLUSIONS

Intraoperative IVC filter placement for the prevention of PE in morbidly obese patients undergoing OGB is feasible. We observed a significant reduction in the perioperative PE rate when a BMI greater than 55 kg/m2 was used as an indication for IVC filter placement despite the use of subcutaneous heparin injections and sequential compression devices.

The effect of obesity surgery on obesity comorbidity

Obesity is epidemic in the modern world. It is becoming increasingly clear that obesity is a major cause of cardiovascular disease, diabetes, and renal disease, as well as a host of other comorbidities. There are at present no generally effective long-term medical therapies for obesity. Surgical therapy for morbid obesity is not only effective in producing long-term weight loss but is also effective in ameliorating or resolving several of the most significant complications of obesity, including diabetes, hypertension, dyslipidemia, sleep apnea, gastroesophageal reflux disease, degenerative joint disease, venous stasis, pseudotumor cerebri, nonalcoholic steatohepatitis, urinary incontinence, fertility problems, and others. The degree of benefit and the rates of morbidity and mortality of the various surgical procedures vary according to the procedure.

Abdominal Compartment Syndrome

BACKGROUND

Abdominal compartment syndrome (ACS) is a systemic syndrome involving derangement in cardiovascular haemodynamics, respiratory and renal functions as a result of sustained increase in intra-abdominal pressure (IAP) ending in multi-organ failure. It is a life threatening emergency and requires prompt action and treatment. For the last 20 years, there has been more awareness among surgeons and intensivists of ACS being a distinct disease entity but still widespread ignorance prevails. Presentation can be acute, chronic and acute on chronic. Initial diagnosis is clinical, confirmed by measurement of IAP. Treatment is abdominal decompression by laparostomy and delayed abdominal closure. Despite prompt treatment mortality remains high. Awareness among surgeons has increased because laparoscopy has resulted in determination of IAP as a readily measurable quantity and also they have been able to appreciate the benefit of abdominal decompression by performing repeated planned laparotomies for trauma.

METHODS

A medline, pubmed and Cochrane database search was performed and the articles found were cross referenced.

RESULTS AND CONCLUSION

Clinical diagnosis is not easy and serial urinary bladder pressure (UBP) monitoring leads to early diagnosis. Treatment is by laprostomy to decompress the abdomen followed by delayed abdominal closure.

Design and rationale of the Utah obesity study. A study to assess morbidity following gastric bypass surgery

PURPOSE

This paper details the design and baseline characteristics of a study on the morbidity associated with Roux-en-Y gastric bypass surgery (GBP) in severely obese adults. This study is designed to assess the effectiveness of GBP in reducing morbidity and maintaining weight loss. A wide array of clinical tests and psycho-behavioral questionnaires are included as part of the study.

METHODS

Three groups (n=1156 severely obese) have been recruited for this study: cases who were approved for and participated in surgery (n=415), a control group of GBP seeking individuals who were denied surgery (n=420) and a control group that was randomly chosen from a population of severely obese participants who were not seeking GBP (n=321). Clinical measures include: a physician interview and detailed medical history, resting electro- and echocardiograms, a submaximal exercise treadmill test and electrocardiogram, pulmonary function, limited polysomnography, resting metabolic rate, anthropometrics, resting and exercise blood pressure, comprehensive blood chemistry and urinalysis and dietary, quality of life and physical activity questionnaires. Most participants (76%) were tested following an overnight stay in a clinical research center. Remaining participants underwent less extensive testing in an outpatient clinic.

RESULTS

Baseline characteristics of the 1156 participants are available for selected measures. Mean+/-S.D. for BMI was 46+/-7.5 kg/m(2) (range=33 to 92) and for age was 44+/-11.4 years (range=18 to 72). The prevalence of diabetes and hypertension was 19% and 35%, respectively. Of the participants who had an echocardiogram or polysomnogram, 92% had left-ventricular hypertrophy and 85% had mild to severe sleep apnea. The two control groups were similar to the surgical group. At approximately 24 months, all participants will have a second clinical examination. Statistical comparisons of changes in morbidity variables will be made between the surgical and control groups.

CONCLUSIONS

This study design facilitates assessment of risks and benefits of GBP to perform recommendations on whether or not to perform surgery on the severely obese patient. Baseline and 2-year exams provide valuable data for comparison to future long-term follow-up data that can be collected at 5 and 10 years.

Obesity and cardiovascular disease: pathophysiology, evaluation, and effect of weight loss: an update of the 1997 American Heart Association Scientific Statement on Obesity and Heart Disease from the Obesity Committee of the Council on Nutrition, Physical Activity, and Metabolism

Obesity is becoming a global epidemic in both children and adults. It is associated with numerous comorbidities such as cardiovascular diseases (CVD), type 2 diabetes, hypertension, certain cancers, and sleep apnea/sleep-disordered breathing. In fact, obesity is an independent risk factor for CVD, and CVD risks have also been documented in obese children. Obesity is associated with an increased risk of morbidity and mortality as well as reduced life expectancy. Health service use and medical costs associated with obesity and related diseases have risen dramatically and are expected to continue to rise. Besides an altered metabolic profile, a variety of adaptations/alterations in cardiac structure and function occur in the individual as adipose tissue accumulates in excess amounts, even in the absence of comorbidities. Hence, obesity may affect the heart through its influence on known risk factors such as dyslipidemia, hypertension, glucose intolerance, inflammatory markers, obstructive sleep apnea/hypoventilation, and the prothrombotic state, in addition to as-yet-unrecognized mechanisms. On the whole, overweight and obesity predispose to or are associated with numerous cardiac complications such as coronary heart disease, heart failure, and sudden death because of their impact on the cardiovascular system. The pathophysiology of these entities that are linked to obesity will be discussed. However, the cardiovascular clinical evaluation of obese patients may be limited because of the morphology of the individual. In this statement, we review the available evidence of the impact of obesity on CVD with emphasis on the evaluation of cardiac structure and function in obese patients and the effect of weight loss on the cardiovascular system.

The obesity hypoventilation syndrome

The obesity hypoventilation syndrome, which is defined as a combination of obesity and chronic hypoventilation, utimately results in pulmonary hypertension, cor pulmonale, and probable early mortality. Since the classical description of this syndrome nearly fifty years ago, research has led to a better understanding of the pathophysiologic mechanisms involved in this disease process, and to the development of effective treatment options. However, recent data indicate the obesity hypoventilation syndrome is under-recognized, and under-treated. Because obesity has become a national epidemic, it is critical that physicians are able to recognize and treat obesity-associated diseases. This article reviews current definitions of the obesity hypoventilation syndrome, clinical presentation and diagnosis, present understanding of the pathophysiology, and treatment options.

Evidence-based medicine reports on obesity surgery: a critique

OBJECTIVE

To evaluate evidence in recent authoritative 'Evidence-Based Medicine' (EBM) reports on surgery for severe obesity.

METHODS

Focused review of Index Medicus citations and authors' own databases of publications on surgery for obesity, 1978-2004.

RESULTS

EBM criteria for assessment of strength of evidence requiring randomized controlled studies (RCTs) in these reports are inappropriate for evaluating invasive treatments such as surgery, which have robust physiological effects, are difficult to reverse and may have more serious side effects than the drug studies for which the criteria were promulgated. Flaws in these reports include omissions of important studies demonstrating improvements in comorbidity, factual errors in descriptions of operations and faulty analyses of outcomes of laparoscopic approaches. There are misinterpretations of cited papers, and inclusion of obsolete operations as well as a study generated during the 'learning curve' of an avowed complex procedure.

CONCLUSION

EBM analyses of surgical modalities affecting access to care require relevant evaluation criteria, true peer review and expert consultation. Authors' claims of objectivity by invoking use of evidence-based criteria applicable to drug treatment and other easily reversible forms of therapy are questionable. Decisions based on flawed EBM reports may adversely affect access to care for millions of severely obese patients.

Surgical management of obesity: a review of the evidence relating to the health benefits and risks

Obesity continues to plague our society in epidemic proportions. Surgery for morbid obesity is considered by many as the most effective therapy for this complex disorder. Today, multiple surgical procedures for the treatment of obesity are available. As with most procedures, there are benefits and risks associated with open and laparoscopic gastric bypass surgery, as well as with laparoscopic adjustable gastric banding and partial biliopancreatic bypass with a duodenal switch. The risks and complications associated with bariatric surgery may be serious and in some cases life threatening. However, surgery for obesity has shown remarkable results in helping patients to achieve significant long-term weight control. In addition, it is associated with improvement and often resolution of co-morbid conditions, including type 2 diabetes mellitus, systemic hypertension, obesity hypoventilation, sleep apnea, venous stasis disease, pseudotumor cerebri, polycystic ovary syndrome, complications of pregnancy and delivery, gastroesophageal reflux disease, stress urinary incontinence, degenerative joint disease, and non-alcoholic steatohepatitis.

Perioperative management of the post-gastric-bypass patient presenting for body contour surgery

Bariatric surgery has evolved as an effective and relatively safe treatment for morbid obesity. With nearly every region of the body as a potential operative site and an unprecedented number of surgical procedures available, we must give attention to thoughtful perioperative management. Bariatric surgery is a life-changing event for the morbidly obese patient, and the body contouring that follows weight loss often has an equally profound effect. Plastic surgeons must strive to maintain the highest level of safety in this pursuit. The authors address issues surrounding preoperative evaluation and measures to minimize the risk of complications.

Effects of bariatric surgery in older patients

OBJECTIVE

Evaluate the safety and efficacy of bariatric surgery in older patients.

BACKGROUND

Because of an increased morbidity in older patients who may not be as active as younger individuals, there remain concerns that they may not tolerate the operation well or lose adequate amounts of weight.

METHODS

The database of patients who had undergone bariatric surgery since 1980 and National Death Index were queried for patients <60 and >/= 60 years of age. GBP was the procedure of choice after 1985. Data evaluated at 1 and 5 years included weight lost, % weight lost (%WL), % excess weight loss (%EWL), % ideal body weight (%IBW), mortality, complications, and obesity comorbidity.

RESULTS

Eighty patients underwent bariatric surgery: age 63 +/- 3 years, 78% women, 68 white, 132 +/- 22 kg, BMI 49 +/- 7 kg/m, 217 +/- 32%IBW. Preoperative comorbidity, was greater (P < 0.001) in patients >/= 60 years. There were no operative deaths but 11 late deaths.

COMPLICATIONS

4 major wound infections, 2 anastomotic leaks, 10 symptomatic marginal ulcers, 5 stomal stenoses, 3 bowel obstructions, 26 incisional hernias (nonlaparoscopic), and 1 pulmonary embolism. At 1 year after surgery (94% follow-up), patients lost 38 +/- 11 kg, 57%EWL, 30%WL, BMI 34.5 +/- 7 kg/m, %IBW 153 +/- 31. Comorbidities decreased (P < 0.001); however, %WL and %EWL and improvement in hypertension and orthopedic problems, although significant, were greater in younger patients. At 5 years after surgery (58% follow-up), they had lost 31 +/- 18 kg, 50%EWL, 26%WL, BMI 35 +/- 8 kg/m, and %IBW 156 +/- 36.

CONCLUSIONS

Bariatric surgery was effective for older patients with a low morbidity and mortality. Older patients had more pre- and post-operative comorbidities and lost less weight than younger patients. However the weight loss and improvement in comorbidities in older patients were clinically significant.

Sleep problems in children with common medical disorders

Sleep problems are common in many pediatric medical disorders and complicate management and patient outcomes. A wide range of conditions, including asthma, cystic fibrosis, sickle cell disease, gastroesophageal reflux, neuromuscular diseases, scoliosis, craniofacial abnormalities, obesity, and chromosomal disorders, have various sleep disturbances, including sleep-disordered breathing, ventilatory dysfunction, sleep-onset and sleep maintenance problems, and circadian rhythm disturbances. Given the adverse neurocognitive and physiologic outcomes associated with a deranged night's sleep, it is important for pediatricians to be able to anticipate, recognize, and appropriately manage these problems. This article reviews the known sleep-related problems of a few relatively common pediatric disorders.

Diabetes and hypertension in severe obesity and effects of gastric bypass-induced weight loss

OBJECTIVE

To evaluate the preoperative relationships of hypertension and diabetes mellitus in severe obesity and the effects of gastric bypass (GBP)-induced weight loss.

SUMMARY BACKGROUND DATA

Severe obesity is associated with multiple comorbidities, particularly hypertension and type 2 diabetes mellitus, that may affect life expectancy.

METHODS

The database of patients who had undergone GBP by one general surgeon at a university hospital between September 1981 and January 2000 was queried as to weight, body mass index (BMI), pre- and postoperative diabetes, hypertension, and other comorbidities, including sleep apnea, hypoventilation, gastroesophageal reflux, degenerative joint disease, urinary incontinence, venous stasis, and pseudotumor cerebri.

RESULTS

Of 1,025 patients treated, 15% had type 2 diabetes mellitus and 51% had hypertension. Of those with diabetes, 75% also had hypertension. There was a progressive increase in age between patients who had neither diabetes nor hypertension, either diabetes or hypertension, or both diabetes and hypertension. At 1 year after GBP (91% follow-up), patients lost 66 +/- 18% excess weight (%EWL) or 35 +/- 9% of their initial weight (%WL). Hypertension resolved in 69% and diabetes in 83%. Patients who resolved their hypertension or diabetes had greater %EWL and %WL than those who did not. African-American patients had a higher risk of hypertension than whites before GBP and were less likely to correct their hypertension after GBP. There was significant resolution of other obesity comorbidity problems. At 5 to 7 years after GBP (50% follow-up), %EWL was 59 +/- 24 and %WL was 31 +/- 13; resolution of hypertension was 66% and diabetes 86%.

CONCLUSIONS

These data suggest that type 2 diabetes mellitus and hypertension may be indirectly related to each other through the effects of obesity, but not directly as to cause and effect. The longer a person remains severely obese, the more likely he or she is to develop diabetes, hypertension, or both. GBP-induced weight loss is effective in correcting diabetes, hypertension, and other comorbidities but is related to the %EWL achieved. Severely obese African-Americans were more likely to have hypertension and respond less well to GBP surgery than whites. These data suggest that GBP surgery for severe obesity should be provided earlier to patients to prevent the development of diabetes and hypertension and their complications.

Obesity and its surgical management

Obesity is increasing in epidemic proportions world-wide. Even mild degrees of obesity have adverse health effects and are associated with diminished longevity. For this reason aggressive dietary intervention is recommended. Patients with body mass indices exceeding 40 have medically significant obesity in which the risk of serious health consequences is substantial, with concomitant significant reductions in life expectancy. For these patients, sustained weight loss rarely occurs with dietary intervention. For the appropriately selected patients, surgery is beneficial. Various operations have been proposed for the treatment of obesity, many of which proved to have serious complications precluding their efficacy. A National Institutes of Health Consensus Panel reviewed the indications and types of operations, concluding that the banded gastroplasty and gastric bypass were acceptable operations for treating seriously obese patients. Surgical treatment is associated with sustained weight loss for seriously obese patients who uniformly fail nonsurgical treatment. Following weight loss there is a high cure rate for diabetes and sleep apnea, with significant improvement in other complications of obesity such as hypertension and osteoarthritis.

Assessing the relative contribution of individual risk factors on surgical outcome for gastric bypass surgery: a baseline probability analysis

BACKGROUND

Multiple regression is the best technique for the simultaneous analysis of the contributions of multiple risk factors to a surgical outcome. A probability analysis is used to determine the relative contribution of individual factors to the overall outcome being assessed. We used these techniques to determine which of the potential risk factors had the greatest impact on adverse outcomes following gastric bypass surgery.

METHODS

Records from 1067 consecutive patients undergoing Roux-Y gastric bypass at the UCLA Medical Center from December 1993 until June 2000 were reviewed. Major complications were used as the dependent variable in a multivariate logistic regression analysis, and 10 risk factors served as the independent variables. Based on the analysis, an average (i.e., baseline) patient was defined. Variations in the preoperative risk factors were then analyzed individually and in various combinations and their effect on the predicted probability for complication development was assessed.

RESULTS

The overall major complication rate in this series was 5.8%. The average patient was defined as a 334-pound woman who was 42.3 years of age. For this patient, the predicted complication rate by probability analysis was 3.9%. The greatest increase in the anticipated complication rate was attributable to revisional procedures that increased the rate to 6.5%. Many patients have a combination of risk factors; to this end, a 62-year-old, male patient with a 2SD increase in weight (i.e., 464 pounds) who was undergoing a revision operation and had a history of smoking, hypertension, diabetes, and sleep apnea had a predicted complication rate of 33.7%.

CONCLUSION

Probability analysis is a useful tool for determining the relative contribution of individual and combinations of risk factors for predicting the outcomes for surgical procedures. The four most influential factors for predicting a complication after gastric bypass surgery were; (1) male gender, (2) revisional surgery, (3) increasing age, and (4) increasing weight. These factors increased the predicted complication rate by 56, 67, 28 and 28%, respectively.

A Management Guideline for Obesity-Hypoventilation Syndromes

A survey of our pulmonary service revealed little consensus as to the definition, work-up, and management of hypoventilation, more often encountered in the presence of obesity. If hypoventilation is defined by an arterial carbon dioxide level above 45mmHg, 22% of artrial blood gas samples over a 5-month period met this criterium, suggesting a high Oany-causeO prevalence. This article presents the rationale and explanation for a management protocol for obesity-hypoventilation that is currently being assessed in the VA Medical Center and Case Western Reserve University training program in Pulmonary and Critical Care Medicine.

Could prolonged air travel be casually associated with subclavian vein thrombosis

BACKGROUND

Air travel associated with venous thromboembolism has recently achieved public awareness due to intense media coverage. The interest has focused on deep vein thrombosis (DVT) of the lower limbs with pulmonary embolism. The World Health Organization (WHO) is planning several international multicenter trials to study the problem and, if it exists, try to find a means for prevention.

METHODS

This is a case presentation of acute venous thromboembolism of the upper limbs associated with long-haul flights. Five patients were admitted to Straub Hospital in Honolulu after 5 to 10 hours flight.

RESULTS

Patient 1 had a previous shoulder injury with DVT; patient 2 had chronic atrial fibrillation; patients 3 and 5 had clavicular fractures; and patient 4 had a subclavian vein compression.

CONCLUSION

It is not possible to draw any conclusions about the association between air flights and subclavian vein thrombosis from this small retrospective case study. Our objective was to indicate the possibility of such a relationship.

Biexponential model for predicting weight loss after gastric surgery for obesity

BACKGROUND

Following gastric restrictive surgery, morbidly obese patients rarely achieve their ideal body weight defined by Metropolitan Life tables. The final body weight will depend on the initial body composition because there will be greater weight loss from fat than lean body mass. The purpose of this study was to develop a mathematical model that accurately estimates the rate and extent of weight loss following gastric bypass surgery.

METHODS

Patients underwent gastric bypass followed by intensive medical therapy and serial bioelectrical impedance analysis (BIA) body composition measurements. Differential equations were derived to model weight loss.

RESULTS

Weight loss in the fat and lean body compartments followed monoexponential decay kinetics with differing rate constants. Total body weight loss (W(T)) at time t was W(T) = k(f)(k(f) - k(l)) (W(f(o))e(-k(f)t) + W(l(o))e(-k(l)t)), where W(fo) and W(lo) are the initial fat and lean body masses determined by BIA and k(f) and k(l) are the rate constants for the fat and lean compartments, respectively. Following surgically induced weight loss, k(f) = 7.61 +/- 1.27 x 10(-2), and k(l) = -0.93 +/- 0.13 x 10(-2), with the ratio of residual sum of the squares to the total sum of the squares of 98.8%.

CONCLUSION

Accurate prediction of weight loss depends on the initial fat and lean compartment mass since each of these loses weight at a different rate and to a different extent. When these effects are accounted for, the total body weight loss can be accurately predicted for any given time following surgery.

Outcome success in obesity

Intentional weight loss improves many of the medical complications associated with obesity. Moreover, many of these beneficial effects have a dose-dependent relationship with the amount of weight lost and begin after only modest weight losses of 5% to 10% of initial body weight. There is no conclusive evidence that weight loss decreases mortality in obese people. The therapeutic effect of weight loss on risk factors for cardiovascular disease (insulin resistance and diabetes, dyslipidemia, and hypertension) has received the most attention in clinical trials. The hazard of developing coronary heart disease is directly related to the concomitant burden of risk factors. Modest weight loss can affect the entire cluster of risk factors simultaneously. Both negative energy balance and weight loss improve insulin sensitivity and glycemic control in obese patients with type 2 diabetes. Most studies have found that weight loss decreases serum triglyceride, total cholesterol, and low-density lipoprotein cholesterol concentrations and increases serum high-density lipoprotein cholesterol concentration. Regain of weight leads to relapse in triglyceride and cholesterol concentrations. Weight loss, independent of sodium restriction, decreases systolic and diastolic blood pressure. Dietary intervention is the cornerstone of weight-loss therapy. Most diets proposed for losing weight vary in two principal dimensions: energy content and macronutrient composition. Manipulation of food macronutrient content, energy density, and portion size can help decrease energy intake and facilitate weight loss.

Morbidity of severe obesity

Although obesity is an easy diagnosis to make, its etiologies, pathophysiology, and symptomatology are extraordinarily complex. Progress in surgical technique and anesthesiological management has substantially improved the safety of performing operations on the severely obese in the last 20 years. These improvements have occurred more or less empirically, without a full understanding of etiology or pathophysiology, although this has advanced concomitantly with improvements in practice. This review has attempted to provide a framework to facilitate progress in the neglected areas of patient selection and choice of operation, in an effort to improve long-term outcome. Despite the disparate etiologies of obesity and its diverse comorbidities and complications, there are unifying interdependent pathogenetic mechanisms of great relevance to the practice of antiobesity surgery. The rate of eating, whether driven by HPA dysfunction, ambient stress, or related hereditary susceptibility factors including the increased energy demands of an expanded body fat mass, participates in a cycle that results in disordered satiety (see Fig. 3). This leads to substrate overload, causing extensive metabolic abnormalities such as atherogenesis, insulin resistance, thrombogenesis, and carcinogenesis. This interpretation of the pathophysiology of obesity ironically accords with the original meaning of the word obesity: "to overeat." The ultimate solution to the problem of obesity--preventing it--will not be forthcoming until the food industry is forced to lower production and change its marketing strategies, as the liquor and tobacco industries in the United States were compelled to do. This cannot occur until the large and fast-growing populations of industrialized nations become educated in the personal implications of the energy principle. Regardless of whether school curricula are modified to prioritize health education, the larger problems of cultural and economic change remain for the groups most susceptible to obesity. In this context, antiobesity surgery will continue to thrive, especially in the absence of effective alternatives.

Complications of surgery for obesity

Morbidly obese patients are already considered high-risk because of their comorbidities. Surgical procedures for obesity are, for the most part, completely elective. Careful counseling of the patient before and after the surgery is extremely important. This article reviews the general complications of bariatric surgery and specific complications of restrictive procedures.

Effects of increased intra-abdominal pressure in severe obesity

This article gives an overview, citing animal and clinical studies, of the effects of increased intra-abdominal pressure (IAP) in severe obesity. Animal studies demonstrate that increased IAP increases pleural pressure, cardiac filling pressures, femoral venous pressure, renal venous pressure, systemic blood pressure, and vascular resistance, renin and aldosterone levels, and intracranial pressure. Thus, the comorbidities presumed secondary to increased IAP in obese patients include congestive heart failure, hypoventilation, venous stasis ulcers, gastroesophageal reflux, urinary stress incontinence, incisional hernia, pseudotumor cerebri, proteinuria, and systemic hypertension.

Echocardiographic features of the right heart in sleep-disordered breathing: the Framingham Heart Study

The effect of sleep-disordered breathing (SDB) on right heart structure and function is controversial. Studies of patients referred for evaluation of possible sleep apnea have yielded conflicting results, and the impact of SDB on the right heart has not been investigated in the general population. We examined the echocardiographic features of subjects with SDB at the Framingham Heart Study site of the Sleep Heart Health Study. Of 1,001 polysomnography subjects, 90 with SDB defined as a respiratory disturbance index (RDI) score > 90th percentile (mean RDI = 42) were compared with 90 low-RDI subjects (mean RDI = 5) matched for age, sex, and body mass index. Right heart measurements, made without knowledge of clinical status, were compared between groups. The majority of the subjects were male (74%). After multivariable adjustment, right ventricle (RV) wall thickness was significantly greater (p = 0.005) in subjects with SDB (0.78 +/- 0.02 cm) than in the low-RDI subjects (0.68 +/- 0.02 cm). Right atrial dimensions, RV dimensions, and RV systolic function were not found to be significantly different between subjects with SDB and the low-RDI subjects. We conclude that in this community-based study of SDB and right heart echocardiographic features, RV wall thickness was increased in subjects with SDB. Whether the RV hypertrophy observed in persons with SDB is associated with increased morbidity and mortality remains unknown.

The use of health-care resources in obesity-hypoventilation syndrome

OBJECTIVE

To document health-care utilization (ie, physician claims and hospitalizations) in patients with obesity-hypoventilation syndrome (OHS), for 5 years prior to the diagnosis and for 2 years after the diagnosis and initiation of treatment.

DESIGN

Retrospective observational cohort study.

SETTING

University-based sleep disorders center in Manitoba, Canada.

PATIENTS AND CONTROL SUBJECTS

Twenty OHS patients (mean [+/- SD] age, 52.7 +/- 9.5 years; body mass index [BMI], 47.3 +/- 11.0 kg/m(2); PaCO(2), 59.7 +/- 13.8 mm Hg; PaO(2), 51.6 +/- 12.4 mm Hg) were matched to two sets of control subjects. First, each case was matched to 15 general population control subjects (GPCs) by age, gender, and geographic location, and, second, each case was matched to a single obese control subject (OBC) who was matched using the same criteria as for the GPCs, plus the measurement of BMI.

MEASUREMENTS AND RESULTS

In the 5 years before diagnosis, the 20 OHS patients had (mean +/- SE) 11.2 +/- 1.8 physician visits per patient per year vs 5.7 +/- 0.8 (p < 0.01) visits for OBCs and 4.5 +/- 0.4 (p < 0.001) visits for GPCs. OHS patients generated higher fees, $623 +/- 96 per patient per year for the 5 years prior to diagnosis compared to $252 +/- 34 (p < 0.001) for OBCs and $236 +/- 25 (p < 0.001) for GPCs. OHS patients were much more likely to be hospitalized than were subjects in either control group in the 5 years prior to diagnosis (odds ratio [OR] vs GPCs, 8.6) (95% confidence interval [CI], 5.9 to 12.7); OR vs OBCs, 4.9 (95% CI, 2.3 to 10.1). In the 2 years after diagnosis and the initiation of treatment (usually continuous positive airway pressure or bilevel positive airway pressure), there was a significant linear reduction in physician fees. In the 2 years after the initiation of treatment, there was a 68.4% decrease in days hospitalized per year (5 years before treatment, 7.9 days per patient per year; after 2 years of treatment, 2.5 days per patient per year [p = 0.01]).

CONCLUSIONS

OHS patients are heavy users of health care for several years prior to evaluation and treatment of their sleep breathing disorder; there is a substantial reduction in days hospitalized once the diagnosis is made and treatment is instituted.

Acute renal failure due to abdominal compartment syndrome: report on four cases and literature review

We report on 4 cases of abdominal compartment syndrome complicated by acute renal failure that were promptly reversed by different abdominal decompression methods. Case 1: A 57-year-old obese woman in the post-operative period after giant incisional hernia correction with an intra-abdominal pressure of 24 mm Hg. She was sedated and curarized, and the intra-abdominal pressure fell to 15 mm Hg. Case 2: A 73-year-old woman with acute inflammatory abdomen was undergoing exploratory laparotomy when a hypertensive pneumoperitoneum was noticed. During the surgery, enhancement of urinary output was observed. Case 3: An 18-year-old man who underwent hepatectomy and developed coagulopathy and hepatic bleeding that required abdominal packing, developed oliguria with a transvesical intra-abdominal pressure of 22 mm Hg. During reoperation, the compresses were removed with a prompt improvement in urinary flow. Case 4: A 46-year-old man with hepatic cirrhosis was admitted after incisional hernia repair with intra-abdominal pressure of 16 mm Hg. After paracentesis, the intra-abdominal pressure fell to 11 mm Hg.

Continuous negative abdominal pressure device to treat pseudotumor cerebri

OBJECTIVE

To study the effects of an externally applied negative abdominal pressure device designed to lower the effects of intra-abdominal pressure (IAP) on headaches and pulsatile tinnitus in severely obese women with pseudotumor cerebri (PTC).

DESIGN

Short-term clinical intervention trial in the Clinical Research Center. Days 1 and 3 were 'control' days; on days 2 and 4-6 patients were in the device from 8:00 am to noon and from 1:00 to 5:00 pm, and on nights 7-11 they were in the device from 10:00 pm to 8:00 am. The last four patients were treated in a device with a counter-traction mechanism.

SUBJECTS

Seven centrally obese women with PTC.

MEASUREMENTS

Headache and pulsatile tinnitus severity were graded by the patient using visual analog scale (1-10) and averaged for the time that the device was in use or not in use. IAP was estimated from urinary bladder pressure (UBP) before and during device use. The internal jugular vein (IJV) elliptical cross-sectional area was measured with B-mode ultrasonography; the timed average velocity was measured by Doppler.

RESULTS

There was a decrease in both headache (6.8+/-0.8 to 4.2+/-0.8, P<0.05) and pulsatile tinnitus (4.2+/-0.5 to 1.8+/-0.5, P<0.02) within 5 min, and in headache (to 2.2+/-0.8, P<0.01) and tinnitus (to 1.7+/-0.5, P<0.01) within 1 h of device activation. UBP decreased (P<0.001) from 19.1+/-3 to 12.5+/-2.8 cmH2O. Headache remained improved throughout time that the device was used. During the second week, five of seven patients slept in the device without difficulty and four awoke without headache. There was a progressive decrease (P<0.01) in headache during the day after sleeping in the device at night as compared with days 1 and 3 when it was not used (6.5+/-0.5, day 1; 4.1+/-0.7, day 3; 3.1+/-0.8, day 8; 2.3+/-0.8, day 10). Headaches returned late in the afternoon in two patients; the device was reactivated and headache again improved. Five patients underwent IJV sonography; the IJV area decreased (129+/-53 to 100+/-44 mm2, P=0.06) without a change in IJV flow (1004+/-802 to 1000+/-589 ml/min) with the device. When activated, the device was pulled into the patient, creating discomfort that was alleviated with the counter-traction mechanism in the last four patients. One patient developed a 5 cm area of blisters that resolved when the device was worn over a hospital gown.

CONCLUSIONS

Decreasing IAP relieved headaches and pulsatile tinnitus in PTC. When patients slept in the device, they awoke without headache or tinnitus, which remained markedly improved throughout most of the following day. This study supports the hypothesis that PTC in obese women is secondary to an increased IAP.

Current status of medical and surgical therapy for obesity

The incidence of obesity (especially childhood obesity) and its associated health-related problems have reached epidemic proportions in the United States. Recent investigations suggest that the causes of obesity involve a complex interplay of genetic, environmental, psychobehavioral, endocrine, metabolic, cultural, and socioeconomic factors. Several genes and their protein products, such as leptin, may be particularly important in appetite and metabolic control, although the genetics of human obesity appear to involve multiple genes and metabolic pathways that require further elucidation. Severe obesity is frequently associated with significant comorbid medical conditions, including coronary artery disease, hypertension, type II diabetes mellitus, gallstones, nonalcoholic steatohepatitis, pulmonary hypertension, and sleep apnea. Long-term reduction of significant excess weight in these patients may improve or resolve many of these obesity-related health problems, although convincing evidence of long-term benefit is lacking. Available treatments of obesity range from diet, exercise, behavioral modification, and pharmacotherapy to surgery, with varying risks and efficacy. Nonsurgical modalities, although less invasive, achieve only relatively short-term and limited weight loss in most patients. Currently, surgical therapy is the most effective modality in terms of extent and duration of weight reduction in selected patients with acceptable operative risks. The most widely performed surgical procedure, Roux-en-Y gastric bypass, achieves permanent (followed up for more than 14 years) and significant weight loss (more than 50% of excess body weight) in more than 90% of patients.