[Preoperative risk and perioperative management of obese patients]

The obese patient is at an increased risk of perioperative complications. Most importantly, these include difficult access to the airways (intubation, difficult or impossible ventilation), and post-extubation respiratory distress secondary to the development of atelectasis or obstruction of the airways, sometimes associated with the use of morphine derivatives. The association of obstructive sleep apnea syndrome (OSA) with obesity is very common, and induces a high risk of peri- and postoperative complications. Preoperative OSA screening is crucial in the obese patient, as well as its specific management: use of continuous positive pre, per and postoperative pressure. For any obese patient, the implementation of protocols for mask ventilation and/or difficult intubation and the use of protective ventilation, morphine-sparing strategies and a semi-seated positioning throughout the care, is recommended, combined with close monitoring postoperatively. The dosage of anesthetic drugs should be based on the theoretical ideal weight and then titrated, rather than dosed to the total weight. Monitoring of neuromuscular blocking should be used where appropriate, as well as monitoring of the depth of anesthesia. The occurrence of intraoperative recall is indeed more frequent in the obese patient than in the non-obese patient. Appropriate prophylaxis against venous thromboembolic disease and early mobilization are recommended, as thromboembolic disease is increased in the obese patient. The use of non-invasive ventilation to prevent the occurrence of acute post-operative respiratory failure and for its treatment is particularly effective in obese patients. In case of admission to ICU, an individualized ventilatory management based on pathophysiology and careful monitoring should be initiated.

Obesity and sleep-disordered breathing--when two 'bad guys' meet

Sleep-disordered breathing (SDB), in particular obstructive sleep apnoea (OSA) and obesity hypoventilation syndrome (OHS) are associated with significant morbidity and mortality. The prevalence of these conditions is rapidly rising mainly due to the worldwide increase in obesity. Obesity contributes to the pathogenesis of SDB in multiple ways including altering upper airway anatomy and collapsibility, ventilatory control and increasing respiratory work load. There is also increasing evidence that OSA itself contributes to the development of obesity. Moreover, both OSA and obesity promote the activation of inflammatory pathways, which is likely a key mechanism in cardiovascular and metabolic disease processes. Early recognition of SDB is important as effective treatments are available. Public health measures to reduce the prevalence of obesity are urgently required to halt the increasing burden of SDB.

A discussion of airway and respiratory complications along with general considerations in obese patients

Obesity is defined as the degree of excess weight associated with adverse health consequences. Within Great Britain, it is reported that a quarter of men and women are obese; these rates have trebled over the past 20 years. In 2001, it was estimated that obesity cost the National Health Service at least half a billion pounds, with a further two billion pounds lost on lower productivity and lost output. Obesity poses a significant risk factor for diseases, such as coronary heart disease, diabetes mellitus and certain forms of cancer, amongst others. Obese individuals pose significant problems to the clinician because of airway and respiratory complications. Sleep apnoea, obesity-hypoventilation syndrome, pulmonary atelectasis are associated with obesity and tracheostomy insertion is made all the more difficult in these patients. This article aims to discuss some of these issues relevant to the clinician and examine present strategies for dealing with them.

Pleiotropic role of IGF-I in obesity hypoventilation syndrome

CONTEXT

Obesity hypoventilation syndrome (OHS) is defined by the association between obesity and daytime arterial hypercapnia. The syndrome includes in variable proportion impaired diaphragmatic weakness, decreased central ventilatory drive and nearly systematically occurrence of sleep apnea. An increased cardio-vascular risk has been demonstrated compared to normocapnic obesity. IGF-I has a pleiotropic role in metabolism, ventilatory control, muscle function and cardiovascular protection.

OBJECTIVES AND DESIGN

We performed a case control study comparing somatotropic axis changes including IGF-I in obese with or without OHS.

METHODS

Patients underwent respiratory function tests, CO(2) ventilatory responses, polysomnography and somatotropic axis exploration (GH, IGF-I and IGFBP-3).

RESULTS

15 OHS (BMI: 41+/-5.6 kg/m(2), PaCO(2): 6.13+/-0.39 kPa, age: 55.6+/-5.9 years) and 15 matched obese without hypercapnia (BMI: 42+/-6.7 kg/m(2), PaCO(2): 5.13+/-0.27 kPa, age: 55.0+/-7.5 years) were compared. IGF-I and IGFBP-3 were significantly lowered in OHS, and negatively correlated with PaCO(2) (r=-0.615; P<0.001 and r=-0.452; P=0.016, respectively). Inspiratory capacity and forced vital capacity reflecting respiratory muscle strength decreased significantly with IGF-I (r=0.408; P=0.038). Triglycerides levels were higher in OHS (1.64+/-0.58 versus 1.13+/-0.56 g/L; P<0.01), and negatively associated with IGF-I (r=-0.418; P=0.027).

CONCLUSION

A low IGF-I level is associated with hypercapnia presumably by reducing ventilatory drive and favouring muscle weakness. The relationship between increased triglycerides and low IGF-I may represent one of mechanisms involved in the OHS increased cardio-vascular risk.

Upper airway mechanics

This review discusses the pathophysiological aspects of sleep-disordered breathing, with focus on upper airway mechanics in obstructive and central sleep apnoea, Cheyne-Stokes respiration and obesity hypoventilation syndrome. These disorders constitute the end points of a spectrum with distinct yet interrelated mechanisms that lead to substantial pathology, i.e. increased upper airway collapsibility, control of breathing instability, increased work of breathing, disturbed ventilatory system mechanics and neurohormonal changes. Concepts are changing. Although sleep apnoea is considered more and more to be an increased loop gain disorder, the central type of apnoea is now considered as an obstructive event, because it causes pharyngeal narrowing, associated with prolonged expiration. Although a unifying concept for the pathogenesis is lacking, it seems that these patients are in a vicious circle. Knowledge of common patterns of sleep-disordered breathing may help to identify these patients and guide therapy.

The obesity hypoventilation syndrome

We only need to look around us to see that we are in an epidemic of obesity and obesity-related medical problems. The obesity hypoventilation syndrome is a disorder in which an obese person with normal lungs chronically hypoventilates. Obesity impairs ventilatory mechanics, increases the work of breathing and carbon dioxide production, results in respiratory muscle dysfunction, and reduces ventilatory response to hypercapnia. Sleep-disordered breathing is present in most patients with the obesity hypoventilation syndrome. When noninvasive ventilation can be successfully introduced, hypoventilation can usually be corrected. Weight loss is the desirable long-term treatment for the obesity hypoventilation syndrome. This paper concisely overviews the physiologic factors that lead to the obesity hypoventilation syndrome and discusses therapies for it.

[Obesity and respiratory disorders]

The prevalence of obesity has considerably increased during the past thirty years. Possible consequences of obesity on respiratory physiology include a restrictive disorder, changes in ventilatory mechanics and an alteration of respiratory drive. Apart from the well established relation between obesity and obstructive sleep apnea-hypopnea syndrome, obesity is associated with two other respiratory disorders. On one hand, epidemiological and animal data suggest a causal relationship between obesity and asthma. On the other hand, morbid obesity is associated, through an alteration of the respiratory drive involving leptin, with a diurnal and nocturnal alveolar hypoventilation defining the obesity-hypoventilation syndrome. These data emphasize the necessity for the medical practitioner to investigate any respiratory symptomatology in obese patients.

Obesity and the lung: 3. Obesity, respiration and intensive care

Obesity is a major problem from a public health perspective and a difficult practical matter for intensivists. The obesity pandemic has required treating clinicians to develop an appreciation of the substantial pathophysiological effects of obesity on the various organ systems. The important physiological concepts are illustrated by focusing on obstructive sleep apnoea, obesity hypoventilation syndrome, abdominal compartment syndrome and ventilatory management of the obese patient with acute respiratory distress syndrome.

[Prader-Willi syndrome associated with obesity hypoventilation syndrome]

Prader-Willi syndrome (PWS) is a genetic disorder, characterized by shorter height, severe obesity and muscular hypotonicity. In particular, sleep disordered breathing (SDB) is a well-known complication in PWS. We encountered one case of PWS, complicated by typical obesity hypoventilation syndrome. A 23-year-old woman had been given a diagnosis of PWS as age 1, therefore she was treated with growth hormone replacement therapy, and with uvulopalatopharyngoplasty (UPPP) for her narrow throat. Her weight increased greatly to 96kg, body mass index (BMI) 51 kg/m2, resulting in hypersomnolence, cyanosis, heavy snoring, and nocturnal awakening. Eventually, she was admitted because of urinary incontinuence and loss of consciousness. On admission, she had severe hypoxia plus substantial hypercapnia, and her chest X-ray film showed severe cardiomegaly with massive pleural and pericardial effusion. On polysomnography (PSG) one week later, her apnea hypopnea index (AHI) was 16 with a mean nocturnal arterial saturation of 74%, mean percutaneous PCO2 59 Torr, which rose to 73 Torr during REM sleep. Non-invasive positive pressure ventilation (NPPV) was initiated, and improved her condition greatly. She was discharged, but continued to recieve NPPV, and her condition has stayed improved.

Impact of laparoscopic adjustable gastric banding on obesity co-morbidities in the medium- and long-term

BACKGROUND

The authors evaluated the impact of laparoscopic adjustable gastric banding (LAGB) on obesity-associated diseases in a series at 3 to 8 years postoperatively, namely diabetes, pulmonary disease, hypertension and knee joint pain.

METHODS

145 morbidly obese patients underwent LAGB with mean age 38 years and preoperative BMI 48.5 kg/m2 (range 34-77). Changes in BMI and excess BMI loss (EBL) were evaluated.

RESULTS

138 of the 145 patients (95%) were available for full follow-up. At last follow-up, BMI had dropped to 34.0 +/- 6.4 SD kg/m2, and mean EBL was 61.9 +/- 26.1%. Prevalence of obesity-associated disease was significantly reduced: diabetes decreased from 10% to 4%, treatment-requiring pulmonary disease from 15% to 5%, hypertension from 43% to 27%, and knee pain from 47% to 38%.

CONCLUSION

Following gastric banding, >75% of patients suffering from obesity-related disease had significant decrease or resolution of their co-morbidities.

[Obesity and respiratory tract disorders]

INTRODUCTION

Although in the shade of metabolic and cardiovascular complications, respiratory tract disorders are very frequent and are predominant in extremely obese subjects with body mass index (BMI > 4O kg/m2), most often of gynoid type.

CLASSIFICATION OF DISORDERS

These disorders can be classified into four groups: 1. Respiratory function disorders without alveolar hypovenitilation, 2. Pickwickian syndrome, 3. Sleep apnea syndrome and 4. Risks during surgical interventions.

CONCLUSION

This study includes detailed discussion of mechanisms of origin, pathophysiologic characteristics and clinical signs of each of these disorders and at the end a review of their treatment.

Pickwickian syndrome: the challenge of severe sleep apnea

Pickwickian syndrome is a severe form of sleep apnea in obese persons which involves mechanical impairment of ventilation resulting in greatly compromised gas exchange. Manifestations of the syndrome are associated with deposits of adipose tissue around the abdomen and diaphragm and are completely reversible with weight loss. Since sleep apnea is now recognized as a significant chronic health problem, nurses in intensive care, medical-surgical, and home care settings are increasingly challenged to provide competent assessment, care, and rehabilitation of affected individuals.

[The Pickwick syndrome. From literary speculations to sleep research]

The "wonderfully fat boy" Joe described in The Pickwick Papers, by Charles Dickens, is remarkable for his glorious appetite and many attacks of sleep during the day. His medical condition was introduced as the Pickwick syndrome by Burwell et al. in 1956. For some 20 years this was an important stimulus for sleep research. Some literary and historical aspects of The Pickwick Papers are presented. The many diagnoses given to poor Joe are discussed. This diagnostic survey may still be of interest, even if the syndrome has virtually disappeared from medical literature. How does the Pickwick syndrome, as doctors today see it, fit Dickens' original description? Did Joe really suffer from the Pickwick syndrome?

Obesity and the heart

Obesity can result in alterations in cardiac structure and function even in the absence of systemic hypertension and underlying organic heart disease. Increased total blood volume creates a high cardiac output state that may cause ventricular dilatation and ultimately eccentric hypertrophy of the left (and possibly the right) ventricle. Eccentric left ventricular (LV) hypertrophy produces diastolic dysfunction. Systolic dysfunction may ensue due to excessive wall stress if wall thickening fails to keep pace with dilatation. This disorder is referred to as obesity cardiomyopathy. The presence of systemic hypertension in obese individuals facilitates development of LV dilatation and hypertrophy. Congestive heart failure may occur in such individuals, and may be attributable to LV diastolic dysfunction or to combined LV diastolic and systolic dysfunction. The sleep apnea/obesity hypoventilation syndrome occurs in 5% of morbidly obese individuals and is potentially life-threatening. Treatment of obesity cardiomyopathy consists of weight loss, salt restriction, and diuretics. Digitalis and vasodilators may be useful in selected cases. Central obesity is probably a risk factor for the development of coronary heart disease. Alterations in lipid and insulin metabolism may facilitate development of coronary heart disease in obese patients.

Head posture in obstructive sleep apnoea

In growing subjects, obstruction of the upper airway may lead to excessive vertical facial development. According to the soft-tissue stretching hypothesis (Solow and Kreiborg, 1977) this could be due to an increased cranio-cervical angulation triggered by the airway obstruction. The present study aimed to examine the effect of airway obstruction on cranio-cervical posture in a sample of adult patients with severe obstructive sleep apnoea (OSA). Lateral cephalometric radiographs taken in the natural head position (mirror position) were obtained from 50 male patients aged 28-70 with polysomnographic diagnosis of obstructive sleep apnoea. The Apnoea Index ranged from 21 to 98 episodes per hour with a mean of 54.6. Control samples were available from previous cephalometric studies of head posture in five samples of healthy subjects and one sample of congenitally blind subjects. The average cranio-cervical angle, NSL/OPT, was found to be extremely large (mean 104.1, SD 9.1) exceeding the average values in the control samples by 1-2 standard deviations (P < 0.001). It is suggested that the large cranio-cervical angle in OSA patients is a physiological adaptation aiming to maintain airway adequacy while the head, and thus the visual axis, is kept in its natural relationship to the true vertical. The findings thus provide evidence for the hypothesis that upper airway obstruction may trigger an increase in the cranio-cervical angulation.

[Late results of the treatment of patients with the extreme degree of alimentary-constitutional obesity by the method of formation of a small stomach]

The work analyses the results of treatment of 311 patients with extreme degrees of alimentary-constitutional obesity by formation of a small stomach. Fatal outcomes (1.9%) were encountered in the period of operative technique mastering. The late-term results were studied in 167 patients in follow-up periods of up to 3 years. The patients' average body weight was 149.4 kg, average height 166.2 cm, average body weight excess as compared to the ideal weight was 125.6%. Study of the late-term results of the operation showed that the postoperative weight loss depends on the initial weight excess and the diameter of the anastomosis formed between the proximal and distal parts of the stomach. The more the initial excess of weight as compared to the ideal value, the more the loss of body weight is. The diameter of the formed anastomosis should be no larger than 15 mm. Besides loss of weight, the activity of vital organs and systems is normalized after the operation, and arterial hypertension, diabetes mellitus, the Pickwickian syndrome, and metabolic polyarthritis take a milder course. The operation for formation of a small stomach made it possible for the patients to resume their customary occupation, freed them of the threat of invalidation, and reduced the duration of the disability period by 4.3 times. After surgical treatment the nature of the patients' life significantly improved; 95.8% of patients appraised the effect of the treatment as excellent and good.

[Clinical characteristics and morphology of Pickwickian syndrome]

Clinical and morphological evidence obtained for 23 patients with Pickwickian syndrome has been analysed. 18 patients had no other symptoms, 12 patients died of the disease. Standard signs of the syndrome (drowsiness, respiratory distress, diffuse cyanosis, etc.) were not universal, whereas mixed-type respiratory disorders occurred in all the patients as well as right heart hypertrophy, sclerosis and hyalinosis of the lesser circulatory bed found morphologically and histologically.

Pulmonary function in morbid obesity

Morbid obesity is not infrequently associated with severe respiratory impairment. In our experience approximately 10 per cent of morbidly obese patients who underwent gastric surgery had severe respiratory impairment. Respiratory insufficiency of obesity can be divided into two primary breathing disorders: the obstructive sleep apnea syndrome (SAS) and the obesity hypoventilation syndrome (OHS). In its most severe form, when both SAS and OHS are present, it is called the Pickwickian syndrome. In our series 59 morbidly obese patients with respiratory insufficiency secondary to obesity underwent gastric surgery for weight reduction. Fourteen had OHS, 19 had SAS and 26 had both. Of these, two patients died of postoperative complications and one died at five weeks with an inconclusive autopsy, totalling an operative mortality rate of 3.4 per cent and a total mortality of 5.1 per cent. In our overall experience morbidly obese patients lost 67 per cent of excess weight after gastric procedures. In conclusion, surgically induced weight loss will markedly improve or correct respiratory insufficiency secondary to obesity. It will improve arterial oxygenation, minimize CO2 retention, expand lung volumes, correct polycythemia, and reduce apnea frequency. The magnitude of changes in these variables is clinically significant. Therefore, respiratory insufficiency of obesity should be considered a major indication for an aggressive approach to weight reduction. The jejunoileal bypass and unbanded gastroplasty operations have an unacceptable incidence of complications or failure, respectively. There is a high degree of recidivism following dietary programs. Sweets eaters will not do well with a gastroplasty procedure. Gastric bypass for individuals addicted to sweets or the vertical banded gastroplasty for "gorgers" are currently our procedures of choice and are associated with the average loss of two thirds of excess weight and correction of breathing problems associated with morbid obesity.

Gastric surgery for respiratory insufficiency of obesity

Morbid obesity is often associated with severe respiratory insufficiency, commonly known as the pickwickian syndrome. This can be divided into the following two primary breathing disorders which can affect patients alone or in combination: the obstructive sleep apnea syndrome (SAS); and the obesity-hypoventilation syndrome (OHS). Thirty-eight (14 percent) of 263 morbidly obese patients with respiratory insufficiency of obesity underwent gastric surgery for weight reduction. Ten had OHS, nine has SAS, and 19 had both. Of these patients, one died of postoperative complications, one died at five weeks with an inconclusive autopsy, one was lost to follow-up, and the time since surgery was too short (less than three months) in three. A total of 30 patients lost 45 +/- 25 percent (p less than 0.0001) of excess body weight within 3 to 12 months following surgery, when repeat pulmonary studies were done. Most patients continued to lose additional weight until two years, when they had lost 62 +/- 26 percent of excess weight. Nine patients failed initial surgery (gastroplasty); seven of these were successfully converted to gastric bypass. Weight loss was associated with a significant decrease in the percentage of sleep apnea from 44 +/- 15 to 8 +/- 11 (p less than 0.0001). In patients with OHS, the arterial oxygen pressure (PaO2) increased from 53 +/- 9 to 68 +/- 11 mm Hg (p less than 0.0001), and the arterial carbon dioxide tension decreased from 51 +/- 7 to 41 +/- 4 mm Hg (p less than 0.0001). Pulmonary function tests in the patients with OHS revealed significant increases, as a percentage of predicted normal, in the forced vital capacity, forced expiratory volume in one second, expiratory reserve volume, functional residual capacity, and total lung capacity. Secondary polycythemia, defined as a hemoglobin level greater than 16 g/dl associated with a PaO2 less than 60 mm Hg, was noted in 13 of 29 patients with OHS. This fell from 16.9 +/- 1.1 to 14.9 +/- 1.7 g/dl (p less than 0.001) after weight loss and improved pulmonary function.

The Pickwickian syndrome with hypertrophy of tonsils: a re-appraisal

Pronounced tonsilar hypertrophy was found in two obese patients suffering from hypersomnolence, periodic attacks of apnea and disturbing snoring at night. Both patients underwent tonsillectomy. Immediately after the operation the hypersomnolence disappeared, the breathing became normal, and the disturbing snoring at night ceased. Follow-up over a period of three years did not reveal any recurrence of these symptoms, even though the patients had not lost any weight during this period.