Hypoxemia after gastric bypass surgery for morbid obesity

Respiratory failure of two sp gastric bypass patients and subsequent rescue with extracorporeal membrane oxygenation

Severe obesity is a chronic condition that is difficult to treat through diet and exercise alone. Gastrointestinal surgery for obesity (bariatric surgery) alters the digestive process by either restrictive surgical alterations or malabsorptive operations. Some 10 - 20% of patients who have weight-loss surgery require follow-up operations to correct complications. Hypoxemia after gastric bypass surgery for morbid obesity, a reported complication, can occur as early as 24 h post surgery.

Two patients presented with severe hypoxia and were placed on veno-venous extracorporeal membrane oxygenation (ECMO). Patient No. 1 had an obstruction of the alimentary limb of the gastric bypass due to suture adhesions, and patient No. 2 had an incarcerated diaphragmatic hernia. While on ECMO, ventilation using a protective strategy (60% FiO2, pressure-controlled ventilation inspiratory pressure (PCV) IP 25-27, positive end-expiratory pressure (PEEP) 10-14, permissive hyper-capnia) was employed. An inflow cannula to the level of the right atrium served as arterial outflow from the circuit to the patient, while the femoral vein served as venous inflow to the ECMO circuit.

Although ECMO in adult respiratory failure is often used as the last resort due to serious associated adverse events, we report two patients with life-threatening complications from gastric bypass who were rescued, resuscitated to day 7, and uneventfully discharged from the hospital to home.

Non-invasive ventilation in the postoperative period: Is there a role?

Non-invasive positive pressure ventilation or non-invasive ventilation (NIV) has emerged as a simpler and safer alternative to invasive mechanical ventilation in patients developing acute postoperative respiratory failure. The benefits of NIV as compared to intubation and mechanical ventilation include lower complications, shorter duration of hospital stay, reduced morbidity, lesser cost of treatment and even reduced mortality rates. However, its use may not be uniformly applicable in all patient groups. This article reviews the indications, contraindications and evidence supporting the use of NIV in individual patient groups in the postoperative period. The anaesthesiologist needs to recognise the subset of patients most likely to benefit from NIV therapy so as to apply it most effectively. It is equally important to promptly identify signs of failure of NIV therapy and be prepared to initiate alternate ways of respiratory support. The author searched PubMed and Ovid MEDLINE, without date restrictions. Search terms included Non-invasive ventilation, postoperative and respiratory failure. Foreign literature was included, though only articles with English translation were used.

Airway management in the obese patient

Airway management is a major factor underlying morbidity and mortality in the obese population. The validity of anthropomorphic prediction model in assessing a difficult airway is less accurate compared with lean subjects. Preoperative evaluation and anticipation of potential complications are critical for safe and successful intubation. Application of noninvasive positive airway pressure can prevent atelectasis and improve oxygenation during the anesthetic induction as well during the postoperative period and after liberation from mechanical ventilation. When performed by trained operators, bedside percutaneous dilatation tracheostomy in obese patients has a safety profile comparable to surgical tracheostomy but provides advantages including ease of performance and lesser cost, and obviates transporting a critically ill patient outside the intensive care unit.

A review of adolescent obesity: prevalence, etiology, and treatment

Much of adult obesity has its roots in childhood. One of the tragedies of the current obesity epidemic is the significant and increasing prevalence of obesity in the young. One principal predictor of adult obesity is childhood obesity. We describe here the classification, epidemiology, causality, comorbidities, and treatment of adolescent obesity, both pharmacologic and surgical.

Assessment and management of the obese patient

BACKGROUND

The perioperative care of the clinically severe obese patient presents numerous unique challenges. As an increasing number of people in North America fall into the category of the clinically severe obese, the care of these patients will become increasingly more challenging and prevalent. These patients have unique issues with regards to cardiovascular, pulmonary, and thromboembolic complications. In addition, hospital equipment must be able to accommodate the body habitus of this population.

MATERIALS AND METHODS

A Medline search using "perioperative care," "morbid obesity," "thromboembolic complications," "preoperative screening," and "postoperative care" as key words was performed for English-language articles. Further references were obtained through cross-referencing the bibliography cited in each work.

DISCUSSION

The management of the clinically severe obese patient requires meticulous preoperative, perioperative, and postoperative care. Careful preoperative planning is essential before taking the patient to the operating room. To have excellent outcomes, a multidisciplinary approach, including the primary care physician, anesthesiologist, surgeon, nursing staff, and social work, is necessary.

Surgery for obesity

The medical risks of obesity increase exponentially as weight increases, and these risks are reduced by sustained weight loss. Behavior modification and dieting provide an approximately 6% loss of body weight at 1 year. Fenfluramine provides an approximately 8% weight loss at 1 year, which can be doubled to 16% when a drug such as phentermine, which works through a different biochemical mechanism, is added to it. This amount of weight loss is insufficient for many severely obese individuals. It was with these facts in mind that the National Institutes of Health Consensus Conference in 1992 recommended that obesity surgery is an appropriate treatment for patients with a body mass index greater than 40 kg/m2 who had failed in attempts at medical treatment and for patients with a body mass index greater than 35 kg/m2 with severe complications of obesity. Vertically banded gastroplasty and Roux-en-Y gastric bypass are the two operations presently recommended because of their relative safety and effectiveness. This article reviews previous procedures that have provided insight into the mechanisms by which these surgeries cause weight loss. The presently used surgeries and their results also are reviewed because until medical therapy improves substantially, surgery remains the most reasonable treatment option for most morbidly obese patients.

[Per- and post-operative gas exchange: isocapnic hyperventilation versus normoventilation]

The effects of isocapnic hyperventilation (A) and normoventilation (B) on PaCO2, PaO2 and A-aDO2 were compared in 102 patients undergoing elective surgery, randomized into two comparable groups A and B. Cases for thoracic, high abdominal and intracranial surgery were excluded, as well as patients with clinically evident pulmonary pathology. A volumetric ventilator was used in association with three different breathing systems (A: Bain system and circle system without CO2 absorption; B: circle system with CO2 absorption). The groups were comparable, except for percentage of overweight: 75% in group A and 56% in group B. Overweight was defined as weight above the mean ideal weight of 100%, and obesity as a weight above 120% the mean ideal weight. Blood gases were sampled 1) preoperatively, 2) 15 min and 3) 60 min after the beginning of mechanical ventilation, 4) postoperatively, 90 min after extubation, without supplemental oxygen. The preoperative mean PaO2 values were 79 +/- 11.4 mmHg (A) and 82.5 +/- 13.2 mmHg (B); the PaCO2 were 37.2 +/- 3.7 mmHg (A) and 37.2 +/- 3.8 mmHg (B). During surgery, PaO2 was distinctly higher (p less than 0.01) in group A than in group B (on average 15-20 mmHg higher), indicating the favourable effect of great tidal volumes on gas exchange. Correspondingly, the A-aDO2 was less increased in group A than in group B (p less than 0.01). At 15 min, 33% of the patients were hypocapnic (PaCO2 less than 35 mmHg): one case in group A and three in group B could be classed as severe hypocapnia (PaCO2 = 25-30 mmHg).(ABSTRACT TRUNCATED AT 250 WORDS)