Surfactant Deficiency in Adults

Pulmonary surfactant is a complex mixture of lipids and protein, which works principally to lower the surface tension of the air liquid interface within the airways and reduce the work of breathing. Deficiency of surfactant in the premature newborn is a principal mechanism in the development of respiratory distress in that population. Over the past decade, surfactant replacement therapy in premature infants has significantly increased survival and decreased the likelihood of significant long-term pulmonary sequelae. Surfactant deficiency in adults with acute respiratory distress syndrome has long been recognized. Although clinical trials of surfactant therapy in adults have not achieved the level of success seen in neonates, multiple recent trials have suggested that success is possible. These results have fueled currently ongoing large clinical trials. The past decade has also revealed that surfactant’s roles are far more numerous than lowering alveolar surface tension. Surfactant also contributes to maintaining the patency of conducting airways, host defense, and mucociliary clearance. The importance of these newly identified roles has been supported by evidence of surfactant dysfunction in airway diseases other than adults respiratory distress syndrome, including asthma and chronic bronchitis. This report reviews the following: (1) surfactant synthesis and composition, (2) surfactant functions, (3) clinical states of surfactant deficiency, and (4) the status of surfactant replacement therapies. …

Preoperative Evaluation of Patients with Lung Cancer Undergoing Thoracic Surgery

Surgery is currently the only potentially curative treatment modality for patients with early-stage non–small-cell lung cancer. Because of a high prevalence of chronic obstructive pulmonary disease in patients with lung cancer, they represent a special subset of patients for whom preoperative evaluation of cardiopulmonary status is especially important. The goal of preoperative evaluation of patients with lung cancer is to assess whether the neoplasm is surgically resectable and to estimate the risk of perioperative morbidity and mortality. Screening spirometry should be obtained in all patients. If the preoperative FEV1 is less than 60% of the predicted normal, predicted postoperative FEV1 (PPO-FEV1) should be estimated based upon the preoperative value and the functional contribution of the lung to be resected. Patients with PPO-FEV1 of more than 40% of predicted normal can tolerate pneumonectomy. In patients who appear borderline candidates for surgery based on static lung function criteria, cardiopulmonary exercise testing with measurement of maximum oxygen consumption (JOURNAL/cpulm/04.02/00045413-200201000-00007/ENTITY_OV0312/v/2017-08-08T040534Z/r/image-pngO2max) can further help stratify patients in terms of their risk for perioperative mortality or complications of surgical resection. …

The Fibrinolytic Defect in Adult Respiratory Distress Syndrome: A New Therapeutic Opportunity?

Prominent alveolar fibrin deposition characterizes the adult respiratory distress syndrome (ARDS). Increased local expression of procoagulant activity and concurrently decreased fibrinolytic activity promote alveolar fibrin deposition in the lungs in ARDS. Thrombi in the lung vasculature and disseminated intravascular coagulation also occur in association with ARDS, further suggesting that disordered fibrin turnover may contribute to the pathogenesis of the syndrome. The fibrinolytic defect in ARDS potentiates alveolar fibrin deposition and organization of the fibrinous neomatrix, resulting in lung dysfunction and fibrotic repair. Similar disorders of pathways of fibrin turnover occur in systemic sepsis and these have recently been exploited to clinical advantage. Anticoagulant strategies have successfully been used in recent interventional trials in septic patients. The results of these trials suggest the possibility that this approach could be extrapolated to protect the lung in ARDS. Recent preclinical trials demonstrate that that similar anticoagulant strategies are feasible and effective in primates with evolving ARDS. Additional preclinical studies are now being performed to determine if fibrinolytic interventions likewise protect against lung injury in ARDS. Small clinical trials and case reports suggest that fibrinolysins can be of clinical benefit in selected patients with ARDS and support this approach. However, these agents increase the risk of bleeding. At this time, the use of fibrinolysins in ARDS patients is not routine and their place in the therapy of ARDS remains to be established. …

Acquired Methemoglobinemia: A Case Report of Benzocaine-Induced Methemoglobinemia and a Review of the Literature

Benzocaine is widely used as a topical anesthetic and is also present in a number of over-the-counter preparations. Methemoglobinemia is a rare, but potentially serious, complication of its use; a fact that is not well documented in the Physician’s Desk Reference or product inserts. Unfamiliarity with this complication may delay diagnosis and appropriate therapy. A case of methemoglobinemia occurring as a complication of using benzocaine during bronchoscopy is presented and is followed by a review of the literature and discussion of the pathophysiology, clinical presentation, diagnosis, and treatment of acquired methemoglobinemia. Methemoglobin is incapable of carrying oxygen and is formed when the ferrous iron in the heme molecule is oxidized to the ferric state. The normal mechanisms that convert methemoglobin back to hemoglobin can be overwhelmed by many oxidant drugs, resulting in toxic methemoglobinemia. The diagnosis should be entertained when cyanosis, unresponsive to 100% oxygen therapy, appears suddenly, especially when exposure to an oxidant drug is established. Diagnosis is confirmed by multiple-wavelength cooximetry. Most cases require only decontamination and supportive care. Methylene blue is the specific antidote, but should be reserved for more severe cases or if comorbid conditions make mild hypoxia unadvisable. Exchange transfusion or hemodialysis may be indicated in patients who fail to respond to methylene blue. …

Exercise Prescription for Patients With Chronic Lung Disease

Chronic lung disease (CLD) and any consequent disease-related muscle myopathy along with deconditioning can cause both dyspnea and/or leg discomfort during exertion. These unpleasant experiences frequently lead an individual to reduce or even eliminate daily tasks which adversely impacts quality of life for the individual. The primary goal of exercise training is to restore the individual patient to the highest possible level of independent function. Improvements in exertional breathlessness observed following an exercise training program may be due to a physiologic training effect, enhanced mechanical efficiency, and/or psychologic desensitization. Any symptomatic patient with CLD who is motivated to participate should be referred to a pulmonary rehabilitation program. Exercise prescription is based on the principle of “overload” training. Although there is no optimal or best training regimen established for patients with CLD, we provide general guidelines for the mode, frequency, intensity, and duration of exercise training. The recommended minimal intensity of exercise training is 50% of peak work rate, although exercise at “maximal limits tolerated by symptoms” may also be prescribed. The recommended minimal duration of training is 20 to 30 minutes of continuous exertion. Resistance training should be incorporated into a comprehensive exercise program. One approach for patients with CLD to monitor their training intensity is to use a “dyspnea target” as a guide for intensity of training effort. …