Monday Afternoon, May 7, 1956

2:00 P.M. Scientific Session: REGULAR PROGRAM.

Symposium on Anesthesia and Related Problems

(Papers 7-11, inclusive)

7. Contrast of Two Systems of Anesthesia for Thoracic Surgery.

Henry Beecher, Boston, Mass.

There is widespread agreement that anesthesia is a problem of crucial importance in the completion of successful thoracic surgery. Opinions differ widely as to what basic elements are essential in the field of anesthesia. An attempt will be made to review briefly what seem to the author to be the fundamental requirements for success in this area and then to pit recent developments against these matters. Particular emphasis will be given to contrasting the advantages and disadvantages of two prominent systems of anesthesia: ether vs. pentothal with a muscle relaxant.

8. A Consideration of Proper Methods in Thoracic Anesthesia.

E. M. Papper, New York, N. Y.

Consideration will be given to harmful influences upon the circulation which may result from anesthetic manipulations that are commonplace during thoracic surgery. The circulatory effects, during general anesthesia, of laryngospasm, endotracheal intubation and suction, assisted and controlled respiration, and insufficient alveolar ventilation will be discussed. A conclusion which may be drawn is that these maneuvers must be executed properly to avoid cardiocirculatory changes. Some comment on what is proper and what is poor in the management of anesthesia will also be offered.

9. The Cardio-Respiratory Dynamics of Controlled Respiration in the Open and Closed Chest.

Archer S. Gordon (by invitation) and Charles W. Fyre (by invitation),

Chicago, Ill.

The physiologic evaluation of controlled respiration has important practical applications in open or closed chest surgery. Careful analysis of the underlying cardio-respiratory dynamics provides criteria for optimal manual (bag) or mechanical (machine) control of respiration.

Detailed studies of circulatory and respiratory mechanisms have been carried out under controlled conditions on a series of open chest and closed chest human cases. Ventilatory effects were measured by determination of arterial oxygen saturation and pCO₂. Circulatory effects were monitored by means of continuously recording central arterial blood pressure as well as beat-to-beat analysis with a bristle flow meter.

In the closed chest, positive-negative controlled respiration proves most physiologic. However, there is no advantage to the use of a negative phase in the open chest. The ideal pressure breathing curve should show a fairly steep rise to a short inspiratory plateau followed by a precipitous drop to a prolonged expiratory plateau; the ratio of inspiration: expiration should be 30:70. Pressure-volume diagrams of the lungs and thorax indicate that about 12 mm. Hg positive pressure is required to provide adequate alveolar ventilation during intermittent positive pressure breathing. More positive pressure is required for positive-negative breathing but the negative pressure need not exceed -6 mm. Hg.

The inspiratory plateau provides optimal oxygenation and CO₂ elimination; the short duration of the positive phase exerts a minimal effect on beat-to-beat circulatory dynamics; and the prolonged expiratory plateau aids circulation by lowering the mean airway pressure.

10. The Significance of the Lung-Thorax Compliance in Ventilation During Thoracic Surgery.

William E. Brownlee (by invitation) and Frank F. Allbritten, Jr.,

Kansas City, Kansas

The measurement of pO₂, pCO₂ and pH of arterial blood during thoracic surgical operations has previously shown that pulmonary ventilation provided is frequently inadequate to maintain the normal partial pressure of carbon dioxide in arterial blood. It has been shown that a significant decrease in the efficiency of ventilation occurs and adequate ventilation can be obtained only by increasing the total volume of pulmonary ventilation.

The change of the volume of gas in the respiratory system per unit increase of the intratracheal pressure is a measure of the ease of the distensibility of the lung and the restriction to expansion imposed by surrounding structures. This relationship of airway pressure to the volume of gas within the respiratory system is termed lung-thorax compliance, a factor directly related to the total volume of pulmonary ventilation during anesthesia requiring pulmonary inflation. Compliance measurements have been accomplished in anesthetized and unanesthetized patients with normal and diseased cardiac and respiratory systems.

Many factors produce significant changes in the lung-thorax compliance. The findings suggest the intratracheal pressure required for the inflation phase of ventilation during anesthesia will vary considerably. The changes demonstrated in lung compliance indicate the intratracheal pressure required to produce an adequate total volume of ventilation with an inflation phase alone may be sufficient to decrease significantly cardiac output. These changes in lung-thorax compliance may compromise pulmonary ventilation during intrathoracic operations.

11. Inefficient Carbon Dioxide Absorption Requiring Increased Pulmonary Ventilation During Operations with an Open Thoracotomy.

Thomas F. Nealon (by invitation), George J. Haupt (by invitation),

Harold Chase (by invitation) and John H. Gibbon Jr., Philadelphia, Pa.

Two or three times the resting rate of ventilation has proved necessary to avoid respiratory acidosis during surgical operations. We have found that one of the chief causes of the increased ventilatory requirement results from the incomplete removal of carbon dioxide by the currently available anesthetic circuits and soda-lime canisters.

An infrared gas analyzer was used to measure the inspired and expired carbon dioxide concentration by the technique of Collier. These gases were sampled continuously through a small polyethylene tube connected to the endotracheal tube. A negative pressure was used to draw gas through the plastic tube and the micro-analyzer at a metered rate of 500 ml. per minute. Total ventilation was measured with a dry-test gas meter. The carbon dioxide tension of arterial blood was calculated from appropriate blood-gas analyses.

The results obtained indicate that with the commercially available anesthetic machines and carbon dioxide canisters studied, there was an appreciable concentration of carbon dioxide in the gas mixture inspired by the patient from the closed rebreathing circle-system circuit. These concentrations in some instances reached the amazing figure of 2.0 per cent. In every instance in which the patient rebreathed significant concentrations of carbon dioxide, pulmonary ventilation had to be markedly increased in order to prevent development of respiratory acidosis. The increase in pulmonary ventilation required was found to be roughly proportionate to the concentration of CO₂ in the inspired gas.

Employing a specially designed, very large soda-lime canister (designed by Brown) in place of those in the conventional anesthetic apparatus resulted in the complete elimination of CO₂ from the inspired gas and a marked diminution in the pulmonary ventilation necessary to prevent acidosis.

12. Aortic Valvulotomy Under Direct Vision During Hypothermia.

F. John Lewis, Norman E. Shumway (by invitation), Suad A. Niazi (by invitation)

and Robert B. Benjamin (by invitation), Minneapolis, Minn.

Since blind technics for the correction of aortic stenosis either through the left ventricle or the aorta have not been altogether satisfactory, efforts to develop a direct vision operation are justified. Hypothermia provides a logical technic for it has already proved to be satisfactory for open operations on the atrial septum and the pulmonary valves.

After experiments on dogs showed that it was possible to operate on the aortic valves under direct vision, the technic has been applied successfully in human patients with aortic stenosis. To do the operation the chest is entered bilaterally from the front after the patient has been cooled. Following inflow occlusion of the cavae and the pulmonary veins the aorta is opened just above the valves. All three commissures are cut under direct vision. To avoid air embolism, blood flow through the heart is restarted and fluid is injected into the left atrium before the aortic wound is finally closed. A distal aortic clamp is released just as the aortic wound is closed.

Though the valves cannot be restored to normal, a more accurate and complete division of the fused commissures can be obtained with this open method than is possible with blind technics. All three commissures can be opened without tearing the valve cusps.

Our clinical experience with the method will be reported.

13. The Indications for Lobectomy in the Treatment of the Lung.

Joseph L. Robinson and John C. Jones, Los Angeles, Calif.

The increasing proportion of patients with peripheral pulmonary lesions which X-ray survey and screening techniques are bringing to the thoracic surgeon, justifies another appraisal of the place lobectomy is playing in the surgical treatment of carcinoma of the lung.

In our own practice we have found ourselves electing to perform lobectomy on more and more patients. The conditions which have produced this change and the indications which we have adopted for the selection of patients for lobectomy are discussed. Followup statistics of our pulmonary resections (lobectomy and pneu-monectomy) of three or more years will be presented.

Finally, in order to gather information concerning the extent of the present day use by thoracic surgeons of lobectomy in treating pulmonary carcinoma, we have conducted a survey among the members of this Association and have summarized the results of that questionnaire.

14. Common Factors in Lung Cancer Survivors.

Richard H. Overholt and James A. Bougas (by invitation), Boston, Mass.

An appraisal has been made of 55 five-year survivals of patients treated for primary cancer of the lung. Common denominators in the studies of these fortunate individuals were these: 1. All had an abnormal shadow by X-ray; 2. In all, the extent and character of the lesion was settled by thoracotomy; 3. All had been treated by surgical excision.

Other factors were not constant. Bronchoscopic and cytologic examinations were helpful in some but in many, results were negative. No significant difference in these factors could be found when this group was compared with the other cases who succumbed to the disease within a five-year period. No verified case, untreated, or treated by other methods, such as, radiation or chemotherapy or combinations, survived five years.

An analysis of patients treated in the years 1950, 1951 and 1952 has been made in order to compare a more recent three-year salvage with the three-year results of those treated prior to 1950. From 1938 through 1952, 50 cases of bronchial adenoma were treated surgically and salvage figures will be presented.

Most thoracic surgeons have elected to employ radical pneumonectomy with extensive mediastinal lymph node dissection in the treatment of pulmonary carcinoma. There has been general agreement for limiting the resection to a lobe in the patient with low pulmonary reserve. Salvage studies indicate that other situations call for a more limited resection: 1. "Coin" or peripheral lesions without evidence of node involvement; 2. Bronchiolar carcinoma limited to lobes; 3. In palliative surgery, when gross tumor must be left behind in vertebra, great vessels, heart or contra-lateral mediastinum.

6:30 P.M.-8:30 P.M. COCKTAIL PARTY. Informal.

Hotel Fontainebleau.