Lewis Wetstein

Assessment of exercise oxygen consumption as preoperative criterion for lung resection

Determination of preoperative pulmonary function is crucial in avoiding complications from pulmonary resection. Many have employed static pulmonary function testing in an attempt to decrease morbidity and mortality from lung resections. The purpose of the present study was to correlate preoperative static pulmonary function, one-second forced expiratory volume (FEV1), and exercise O2 consumption (MVO2) with postoperative morbidity and mortality. Fifty consecutive patients underwent preoperative FEV1 and MVO2 determinations. A criterion for surgical resection included an FEV1 greater than 1.7 liters for pneumonectomy, greater than 1.2 liters for lobectomy, and greater than 0.9 liters for wedge resection. The surgeon was blinded as to the results of MVO2 studies. Mean age was 63.8 years (range, 47 to 76 years). There were 10 pneumonectomies, 28 lobectomies, and 12 wedge resections. Among the 50 surgical candidates selected solely on the standard FEV1 values, mortality was 4% (2/50) and morbidity, 12% (6/50). Stratification on the basis of exercise performance showed a 29% mortality (2/7) and a 43% morbidity (3/7) in patients with an MVO2 less than 10 ml/kg/min. Patients with an MVO2 less than 20 but greater than 10 ml/kg/min had a 10.7% morbidity (3/28), and there were no deaths. No patients with an MVO2 greater than 20 ml/kg/min sustained any morbidity or died (p less than 0.001). We conclude that exercise is an important criterion in the preoperative evaluation of patients for pulmonary surgery. An MVO2 less than 10 ml/kg/min is associated with significant morbidity and mortality.

Effect of transmural versus nontransmural myocardial infarction on inducibility of ventricular arrhythmias during sympathetic stimulation in dogs

Transmural myocardial infarction interrupts sympathetic nerves and denervates viable muscle distal to myocardial infarction. The effect of sympathetic stimulation on responses to programmed ventricular stimulation was studied in dogs without myocardial infarction (Group I: n = 5), with transmural anterior wall myocardial infarction (Group II: n = 6) and with nontransmural anterior wall myocardial infarction (Group III: n = 9). Ventricular effective refractory period during sympathetic stimulation decreased by 16 +/- 18, 1 +/- 2 and 12 +/- 8 ms (mean +/- SD) in viable muscle of the inferoapical left ventricle in Groups I, II and III, respectively, suggesting efferent sympathetic denervation by transmural myocardial infarction only. Sustained ventricular tachycardia or fibrillation was induced more easily during sympathetic stimulation in six of the six dogs with transmural infarction, but in only two of the nine dogs with nontransmural infarction (p less than 0.01). It is concluded that the partial sympathetic denervation produced by transmural myocardial infarction enhances the ease of induction of ventricular tachycardia and fibrillation during sympathetic stimulation. A similar mechanism may lead to increased risk for lethal arrhythmias during periods of high sympathetic tone in patients with transmural myocardial infarction.

Cyclosporine in Cardiac Transplantation

Cyclosporine is a new immunosuppressive drug that acts early in the exposure of a host to allogeneic stimulation. It is a peptide of fungal origin. It has selective action on T cells, leaving the other cells of the immune system intact. It acts by preventing the function of the early activation signals of T cells, such as the acquisition of receptors for Il 2 and Il 1. It is lipophilic, moderately well absorbed by the gut, and metabolized by the liver. Factors affecting absorption or hepatic metabolism alter the amount of cyclosporine available in the circulation. Circulating levels can be measured by radioimmunoassay or HPLC. Doses should be tailored to trough levels taken approximately 12 hours after an oral or intravenous dose or to individual pharmacokinetic curves. The drug is nephrotoxic, hepatotoxic, and neurotoxic. In addition, cyclosporine has been associated with hypertension, hemolytic-uremic syndrome, increased incidence of intravascular thrombotic events, hypertrichosis, gum hyperplasia, pericardial effusion, and lymphoproliferative disorders. Despite these complications, cyclosporine usage seems to have improved short-term cardiac allograft survival and to have reduced the complications associated with side effects of steroids. As a result, cyclosporine has spawned a resurgence of interest in cardiac transplantation, which will be of great benefit in prolonging the lives of patients with end-stage cardiac disease.

Unilateral High-Frequency Jet Ventilation during One-Lung Ventilation for Thoracotomy

One-lung ventilation is indicated during thoracic operations for bronchopleural fistula, pulmonary abscess, and pulmonary hemorrhage in spite of the possibility of the development of severe hypoxemia. To evaluate methods for improving oxygen transport during one-lung ventilation, we applied high-frequency jet ventilation (HFJV) and continuous positive airway pressure (CPAP) to the nondependent lung following deflation to atmospheric pressure in each procedure, and measured the effects on cardiac output and arterial oxygenation. In each case, the dependent lung was ventilated with conventional intermittent positive pressure ventilation (IPPV). Eight patients were studied during posterolateral thoracotomy using double-lumen endobronchial tubes. HFJV or CPAP to the nondependent lung improved arterial oxygenation significantly during both closed and open stages of the surgical procedures (p less than 0.008). When the chest was open, HFJV maintained satisfactory cardiac output, whereas CPAP usually decreased cardiac output (p less than 0.008). There were no significant differences in mean partial pressure of arterial carbon dioxide between HFJV, CPAP, and deflation to atmospheric pressure. In conclusion, HFJV to the nondependent lung provides not only satisfactory oxygenation but also good cardiac output, thereby maintaining better oxygen transport than CPAP or deflation to atmospheric pressure, while the dependent lung is ventilated with IPPV during one-lung ventilation for thoracotomy.

Current Status of Surgery for Ventricular Tachyarrhythmias

This article outlines the accepted histopathologic and electrophysiologic theories underlying the etiology of medically refractory ventricular tachyarrhythmias. It delineates the indications and techniques for the electrophysiologic study of the ventricle. Finally, the surgical procedures available as well as their indications and results are elucidated.

Technique for Implantation of Phrenic Nerve Electrodes

Permanent ventilatory support is necessary in patients with upper motor neuron respiratory muscle paralysis and central alveolar hypoventilation. Weaning these patients from chronic ventilation is extremely advantageous. Diaphragm pacing accomplishes this goal. In the past implantation of phrenic nerve electrodes has been undesirable either because the procedure is too extensive or because of the high failure rates. This report describes a simple, expeditious, and uniformly successful technique for bilateral phrenic nerve electrode placement.

Current Status of Coronary Artery Bypass Grafting for Coronary Artery Atherosclerosis

Coronary artery bypass grafting has now undergone 18 years of proven benefit in the treatment of myocardial ischemic disease. The technique of CABG has been further extended to other situations in which myocardial blood supply is threatened, such as cardiac trauma, aneurysms of coronary arteries, and congenital lesions. The emphasis in choosing CABG over medical therapy in 1985 should be preservation of myocardium at jeopardy of infarction as well as relief of angina. Proximal stenoses in vessels subserving viable muscle that is ischemic at rest or with minimal exercise should be treated with reperfusion by angioplasty or CABG to prevent further injury. After infarction occurs and ventricular function is impaired, CABG is also necessary to preserve remaining myocardium at jeopardy. Such an aggressive approach seems warranted with todays excellent surgical results. Long-term results have also improved, as more attention has been paid to saphenous vein graft preparation, use of mammary artery grafts, complete revascularization, use of antiplatelet agents, control of spasm, and identification of hypercoagulable states that may require sodium warfarin (Coumadin). Angioplasty of vein grafts and distal anastomoses also appears promising to help extend the results of initial CABG. Figure 1 is our recommended approach for the treatment of coronary atherosclerosis.