Date Published: December 28, 2011
Publisher: Hindawi Publishing Corporation
Author(s): Lebron Cooper.
Little has been recently published about specific postoperative complications following thoracic surgery in the morbidly obese patient. Greater numbers of patients who are obese, morbidly obese, or supermorbidly obese are undergoing surgical procedures. Postoperative complications after thoracic surgery in these patients that can lead to increased morbidity and mortality, prolonged hospital stay, and increased cost of care are considered. Complications include difficulties with mask ventilation and securing the airway, obstructive sleep apnea with risk of oversedation, pulmonary complications related to reduced total lung capacity, reduced functional residual capacity, and reduced vital capacity, risks of aspiration pneumonitis and ventilator-associated pneumonia, cardiomyopathies, and atrial fibrillation, inadequate diabetes management, positioning injuries, increased risk of venous thrombosis, and pulmonary embolism. The type of thoracic surgical procedure may also pose other problems to consider during the postoperative period. Obese patients undergoing thoracic surgery pose a challenge to those caring for them. Those working with these patients must understand how to recognize, prevent, and manage these postoperative complications.
Little has been recently published about specific postoperative complications following thoracic surgery in the morbidly obese patient. Anesthesia and postoperative management of morbidly obese patients in thoracic surgery are based on experience in these patients undergoing other types of procedures . While approximately 5% of patients undergoing surgical procedures are considered morbidly obese (BMI > 40 kg/m2), another 30% of patients in the US are considered obese (BMI > 30 kg/m2) . The exact number of these who require thoracic surgery is unknown. However, considering that postoperative complications are a major cause of morbidity, mortality, prolonged hospital stay, and increased cost of care, it is important that those working with these patients during the postoperative period understand how to recognize, prevent, and manage these complications .
Mask ventilation and intubation may be difficult in the morbidly obese patient secondary to excessive tissue in the posterior pharyngeal wall . A Mallampati score of III or IV and increased neck circumference have been found to be the best predictors of potential difficulty with tracheal intubation . These considerations should be kept in mind when planning extubation following thoracic surgery in the morbidly obese patient, whether using a double-lumen tube or a single-lumen endotracheal tube with a bronchial blocker. The extubation plan should consider the initial ease of mask ventilation, the difficulty of intubation (should reintubation become necessary), and the type of procedure performed. In a comparison between transmediastinal and transthoracic esophagectomy, Bartels et al. found that early extubation (within 6 hours) following transthoracic esophagectomy prolongs ICU length of stay and leads to an increase rate of mortality , although the recent trend to extubate immediately after resection in the operating room has been shown to be equally safe. When comparing early extubation in the operating room to late extubation in the ICU, Lanuti et al. found that operative approach did not influence the failure to extubate . Positioning morbidly obese patients in reverse Trendelenburg has been suggested to optimize ventilation and access to the airway should the need for reintubation occur .
Although most morbidly obese patients have probably not had previous sleep studies to prove the existence of obstructive sleep apnea, many may actually have this disease. The American Society of Anesthesiologists Task Force on Perioperative Management Practice Guidelines for the perioperative management of patients with obstructive sleep apnea warns that judicious use of sedatives and opiates in the perioperative period is indicated in patients with obstructive sleep apnea . It is probably wise to consider judicious use of sedatives and opiates in all morbidly obese patients to prevent oversedation and delayed airway obstruction. Nonsteroidal analgesics may reduce the need for opiates in the postoperative period .
Morbidly obese patients have reduced total lung capacity, reduced functional residual capacity, and reduced vital capacity . Alveolar arterial oxygenation gradient is increased, and atelectasis has been found to persist for at least 24 hours in morbidly obese patients, whereas it disappeared in the nonobese . Consideration should be given to the increased likelihood of pulmonary complications in these patients postoperatively. Complications related to residual atelectasis may result in desaturation. Pneumonia, bronchospasm, atelectasis, acute respiratory insufficiency, prolonged ventilation, and bronchial infections were found in 33.9% of patients with mild to moderate COPD undergoing general surgery. Risk factors for increased pulmonary complications were male gender, amount of smoking, duration of surgery over 270 minutes, low FEV1/FVC ratio, and chest or upper abdominal incision . A study of 147 lobectomies, comparing VATS versus open thoracotomy, found that VATS patients, in spite of having more comorbidities, had significantly less postoperative pneumonia, fewer chest tube days, and a shorter hospital length of stay .
Right ventricular dysfunction can be demonstrated by echocardiography in many obese patients, even if asymptomatic . A great risk of pulmonary and systemic hypertension, related to increased blood volume and higher cardiac output, may exist in morbidly obese patients. Obesity cardiomyopathy with left- and right-heart failure secondary to eccentric right and left ventricular hypertrophy may result if these are present for a long period of time. The risk may be increased in the presence of long-standing obstructive sleep apnea .
The risk of thromboembolism is thought to be greater in morbidly obese patients . Deep venous thrombosis and skin ulcerations are common in the morbidly obese patient. Varicose veins may occur, and lymphoedema may result . Pulmonary embolism is a real risk for these patients, especially those with decreased mobility . Morbidly obese patients have been shown to have a greater incidence of postoperative complications than normal-weight patients undergoing cardiac surgery . Meticulous venous thromboembolism prophylaxis is necessary to decrease the incidence of these complications.
Although little has been published specifically related to morbidly obese patients undergoing thoracic surgery, the risk of postoperative complications is high, which can result in increased morbidity and mortality, increased length of stay, and increased costs of care. Anesthesia providers must be aware of these complications to prevent and manage these patients in the postoperative period. Clinical outcome studies specifically related to the morbidly obese patients are still lacking.