Tuesday Morning, April 17, 1962

8:30 A.M. Scientific Session: THORACIC SURGERY FORUM

Khorassan Room

14. An Objective Comparative Evaluation of Vascular Clamps

JD Mortensen, and Grant A. Hickman

(by invitation), Salt Lake City, Utah

A comparative evaluation of the performance of various currently popular vascular clamps has been carried out in which three parameters of the clamps have been carefully assessed: 1) A method was devised for testing the occlusive ability of the clamps to determine how much intraatrial fluid pressure they could withstand without leaking. 2) The holding ability of the clamps was investigated to quantitate their reliability or resistance to slipping. 3) Finally, the trauma produced when the clamps were applied with measured force to arteries in living anesthetized animals was assessed by both gross and microscopic pathologic study. Fourteen different vascular clamps have been objectively evaluated as described above. The results are presented in tabular, comparative form. There is surprising difference in performance from clamp to clamp in all three parameters investigated. Certain of the clamps should be excluded from clinical use because of poor performance in the occlusive tests, others do not perform satisfactorily on the holding tests, hence are unreliable Several clamps cause significant trauma, and cannot be recommended for clinical use on this basis. Clamps that perform acceptably on all tests include the Senning, Muller-Markham, and Potts fine-toothed clamps, the atraugrip Bailey, Glover, and DeBakey clamps, and the Kapp-Beck serrated clamps. Most clamps will perform unsatisfactorily if not properly used. Suggestions and precautions to assure proper use of vascular clamps are made.

15. Neutron Activation Analysis in the Study of Pulmonary Disease: The Use of an Atomic Reactor as a Laboratory Instrument

John H. Kennedy (by invitation), and

W. F. Bethard (by invitation), San Diego, Calif.

Sponsored by Cifford F. Storey, San Diego, Calif.

The identification of specific elements by the analytic technique of neutron activation analysis was described by Hevesy in 1936. It is accomplished by bombarding samples and standards with neutrons in order to convert the elements to unstable radioactive forms so that identification and quantitation can be carried out by appropriate counting procedures. The significant advantages to this method are extreme sensitivity (e.g. arsenic (As 76) can be detected in concentrations of 0.005 micro-grams), freedom from reagent contamination, and in many cases nondestructive analysis of the sample. This method has been used during the past three years in the petroleum industry and in the quantitation of trace elements (e.g. manganese) in body fluids. The authors describe the use of an inherently safe nuclear reactor (TRIGA) for the analysis of normal and diseased pulmonary tissues obtained at surgery. At present analyses may be carried out in biologic tissues for many elements, including arsenic, iodine, aluminum, copper, silicon, vanadium, zinc, manganese and beryllium. Examples of gamma ray energy spectra obtained by neutron activation analysis from pulmonary biopsies are presented as well as a short color film illustrating the experimental method. The authors are at present using this method to study the arsenic content in normal and cancerous lung in smokers and nonsmokers. Arsenic, known to be carcinogenic, occurs in varying concentrations in tobacco leaf.

16. Left Heart Bypass: Experimental and Clinical Observations on its Regulation with Particular Reference to Maintenance of Maximal Renal Blood Flow

John E. Connolly, Samuel L. Kountz (by invitation), and

Robert J. Boyd (by invitation), Palo Alto, Calif.

Left heart bypass is now a well recognized technique to permit prolonged cross-clamping of the thoracic aorta. Also there are indications that it may prove to be advantageous in the mechanical support of acute heart failure. Various problems in the determination and regulation of proper proximal and distal pressures to assure left heart decompression and at the same time maximal renal blood flow have been encountered in clinical cases to be presented. Left heart bypass during aortic cross-clamping has been performed on dogs and measurements made of left atrial, aortic root and femoral artery pressures, as well as renal artery flow using a square-wave electromagnetic flowmeter. It was found that if the aortic root pressure is maintained at the pre-bypass level, the femoral pressure and renal blood flow remain near normal. However, if a rise as little as 10mm. Hg mean pressure is allowed in the aortic root, the distal aortic pressure drops significantly and the renal blood flow falls dramatically, even greater than can be explained by the decreased distal aortic pressure. Experiments were then performed to investigate the relationship of renal blood flow to left atrial pressure and confirmed that slight increases in left atrial pressure produced a striking diminution in renal blood flow suggesting a reflex regulation of renal blood flow mediated via stretch receptors in the left atrium. In the light of these findings, a simplified technique of bypass will be presented with recommendations as to its precise regulation and the length of time it can be safely carried out

17. A Study of the Peripheral (IVC and SVC) and Central (Splanchnic) Venous Flow Rates During Extracorporeal Bypass

Jay L. Ankeney, S. K. Murthy (by invitation), and

Frederick LaRochelle (by invitation), Cleveland, Ohio

A technique has been developed with appropriate catheterization of the venae cavae plus external pumping in which it is possible to measure continuously the central (splanchnic) and peripheral (IVC and SVC) venous flow rates Utilizing this method, central and peripheral venous flow rates have been measured before, during and following a 45 minute period of total cardiopulmonary bypass at a rate of 75 cc/kilo./min utilizing a rotating disc oxygenator with gravity drainage. With a constant arterial inflow, flow rates in these two areas remain relatively constant throughout perfusion. Progressively increasing the arterial perfusion rate results in a relatively greater increase in peripheral than splanchnic flow, without a proportional increase in arterial pressure. Therefore, total peripheral vascular resistance decreases and a straight line relationship between systemic pressure and flow rates does not exist during perfusion. Vasopressors result in a decrease in peripheral flow with a concomitant increase in the splanchnic blood flow and elevation of portal vein pressure. This report will also include a study of the effects of lowering body temperature (hypothermia) upon the relative flow rates in these two vascular beds during perfusion.

18. A Study of Prepulmonary Bypass in the Development of an Artificial Placenta for Prematurity and Respiratory Distress Syndrome of the Newborn

John C. Callaghan, Edmonton, Alberta, Canada

In the early portion of this study, 14 lambs taken by cesarian section were subjected to extracorporeal circulation and submerged in amniotic fluid in an artificial placenta. Ten of these animals were maintained for periods of ten to nineteen hours under conditions of artificial foetal circulation. Six mongrel dogs were subjected to periods of controlled suffocation during which time they were perfused with oxygenated blood into the right alriurn from a membrane oxygenator. Lower caval blood and peripheral arterial blood were returned to the oxygenator. Four newborn puppies weighing 500 to 700 grams were maintained with satisfactory cardiac output with approximately one-third of their cardiac output infused as oxygenated blood into the right atrium resulting in peripheral saturations of 75-85%. The pulmonary artery and its capillary bed acted as a conduit for the oxygenated blood It is felt that this means of circulation is feasible in the premature child and newborn baby with respiratory distress syndrome. Here venous cannulation alone with the infusion of oxygenated blood into the right atrium is used in a manner not too dissimilar to that of placental circulation.

19. Physiologic Principles of Coronary Perfusion

Robert F. Shaw (by invitation), New York, N.Y

Sponsored by George H. Humphreys II, New York, N.Y

The perfusion characteristics of the myocardium have been investigated with a view toward determining optimal coronary perfusion techniques The response of the myocardial vascular bed to perfusion by pressure-determined and flow-determined systems has been studied in open-chest anesthetized dogs at different levels of steady cardiac effort and during cardiopulmonary bypass. Coronary perfusion pressure and coronary flow were varied independent of aortic pressure. During pressure-determined perfusion, a characteristic vasomotor response to alterations in perfusion pressure was observed in each of over 700 observations in 22 dogs. Abrupt changes of perfusion pressure caused abrupt changes of flow; within 0.5 seconds, active coronary vasomotion intervened to return flow toward its original level in both the working and bypassed hearts. This mechanism is capable of regulating coronary flow independent of perfusion pressure over the range, 70-145 mm Hg. The level at which flow is regulated correlates with the level of cardiac effort. These studies demonstrate an intrinsic mechanism by which the heart regulates coronary flow in accordance with its needs, operative normally and in pressure-determined systems, but not in flow-determined systems. The effects of under-perfusion and over-perfusion on cardiac contractility will be presented. A pneumatic pressure-regulating reservoir which can convert any positive displacement pump from a flow-determined to a pressure-determined system will be described.

20. A New Method for Coronary Arteriography by Means of Acetylcholine Asystole with Controlled Return of Heart Rate Using a Cardiac Pacemaker

Aydin Bilgutay (by invitation), and

C. Walton Lillehei, Minneapolis, Minn.

Coronary arteriography with acetylcholine induced asystole has gained some acceptance within the last few years. Its wider clinical application has awaited further developments to make it safer and more reliable Analysis of the response of hearts to acetylcholine in 70 canine electrocardiograms and our experimental and clinical work with the development of pacemaking equipment for control of heart block suggested the combination of acetylcholine for asystole and pacemaker restoration of the heartbeat for obtaining coronary arteriograms more safely. A method has been developed where asystole is induced by acetylcholine, a coronary arteriogram is taken, and the controlled return of the heartbeat is assured by means of cardiac pacemaker stimulation via an internal electrode introduced to the right ventricle through the saphenous vein. With the cardiac rate maintained by the pacemaker after acetylcholine induced asystole, the blood pressure is immediately restored and the dangers of serious or fatal arrhythmias due to myocardial anoxia are obviated. The phase of recovery with its associated arrhythmias when acetylcholine arrest alone is utilized is replaced by a regular beat of the pacemaker and the time for return of the previously present heart rate is greatly shortened. This method was tested extensively before its first clinical application in a patient who had had a preoperative coronary angiogram and a myocardial revascularization procedure nine months before. The coronary arteriograms obtained with this new technique have provided visualization significantly superior to other methods previously utilized.

21. Cerebrospinal Fluid Pressure Changes Following Experimental Superior Vena Cava to Right Pulmonary Artery Shunt

Panagiotis Symbas, Leon Woods, and Harold A. Collins

(all by invitation), Nashville, Tenn

Sponsored by H. William Scott, Jr., Nashville, Tenn.

Occasional patients manifest evidence of transient cerebral disturbance following complete diversion of superior vena caval blood into the distal end of the right pulmonary artery. The transitory nature of the disturbance suggested cerebral edema as a possible cause. In order to clarify the changes in Cerebrospinal fluid pressure following superior vena cava to right pulmonary artery shunts, the following experimental study was undertaken. In a series of 21 adult mongrel dogs the superior vena cava was anastomosed to the right pulmonary artery in the manner described by Glenn. Gerebrospinal fluid pressures were determined by direct cisternal puncture preoperatively and at periodic intervals postoperatively. Autopsy examination was performed to determine the cause of death and patency of the anastomosis in those animals failing to survive the operative procedure. All animals demonstrated a fairly striking increase in the cerebrospinal fluid pressure following operation The increase in the cerebrospinal fluid pressure correlated reasonably well with the increase in external jugular venous pressure. In those animals failing to survive operation the manifestations were suggestive of cerebral impairment, and cerebral edema could be demonstrated at autopsy despite the presence of a patent anastomosis. The results of this study suggest that an increased cerebrospinal fluid pressure following superior vena cava to right pulmonary artery anastomosis can produce cerebral edema as an undesirable complication. Current studies are concerned with the most efficacious method for prevention of cerebral edema following this operation

22. Catechol Amine and Serotonin Response to Cardiopulmonary Bypass

Robert L. Replogle, Morris Levy, and

Richard C. Lillehei (all by invitation), Minneapolis, Minn.

Sponsored by Robert E. Gross, Boston, Mass

Demonstration of a similarity in the changes of epinephrine, norepinephrine, and serotonin during both prolonged cardiopulmonary bypass and hemorrhagic shock might be useful as evidence for consideration of a common denominator predisposing to their visceral complications. For this reason circulating plasma epinephrine, norepinephrine and serum serotonin were measured in 14 patients before, during and after extra-corporeal circulation of periods varying from 30 minutes to 35/a hours. There were 9 normothermic, moderate flow (60-75 ml/kg) and 5 hypothermic, low flow (25-30 ml/kg at 28-30°C) perfusions. While a marked increase in plasma epinephrine concentration occurred during moderate flow, normothermic perfusion, no change or only a slight increase in plasma epinephrine was seen during low flow, hypothermic perfusion. A decrease in serum serotonin was regularly observed during both types of perfusion, indicating release of platelet-bound serotonin. Renal function was depressed to varying degrees in all patients undergoing bypass; but in two patients who had a prolonged bypass (2 and 3½ hours) with moderate flow and normothermia, striking elevations in plasma epinephrine were associated with profound depressions in renal function, tubular necrosis and death. These studies show a catecholamine and serotonin response during normothermic, moderate flow perfusion similar to that previously described during hemorrhagic shock. The deleterious effects of increased catechol amine concentrations appear directly correlated with the length of the cardiopulmonary bypass. Hypothermia, however, blunts this stress response even when the perfusion flow is less than half that usually used in moderate flow perfusions. The clinical significance of these findings as well as the significance of the serotonin changes will be discussed.

23. Myocardial Metabolism in the Hypothermia Bypassed Heart

Maurice G. Fuquay (by invitation), Charles A. Bucknam (by invitation),

and Howard D. Sirak, Columbus, Ohio

In 58 dogs, an investigation was undertaken to compare the effects on the bypassed heart of potassium and cold-induced cardiac arrest. An arrest_ interval of 30 minutes was induced at 37°, 30°, 20° and 10°C. The indices for evaluating myocardial metabolism at each temperature were the pH, CO₂ content, O₂ saturation, glucose, lactic acid and pyruvic acid levels, and a number of enzymes in postarrest samples of coronary sinus blood. Results showed less metabolic acidosis and better oxygenation at 20°C than in any of the other groups. Moderate levels of cooling (not below 20°C) reduced myocardial acidosis by decreasing the oxygen requirements of the tissues. However, with hypothermia at 10°C myocardial acidosis still developed even when the rest of the body was being perfused at high levels with well-oxygenated blood. Metabolic acidosis of the coronary arterial blood was most severe in the 37°C potassium-arrest and in the 10°C cold-arrest groups. From the standpoint of those enzymes which are highly concentrated in cardiac muscle, there was less production of enzymes at the lower temperatures. A close correlation was found between the enzyme concentration in coronary sinus blood and the level of hypothermia, the lowest values being obtained in the colder groups while the higher values consistently accompanied potassium arrest at 37°C or 30°C cold arrest. Serum glutamic-oxaloacetic transaminase and serum pyruvic-oxaloacetic transaminase were the most sensitive indices.

24. Tissue Oxygen Tension During Total Body Perfusion and Hypothermia

Earle B. Mahoney., James A. Deweese (by invitation),

Paul D. Harris (by invitation), Clay E. Phillips, Jr. (by invitation),

and Seymour I. Schwartz (by invitation),

Rochester, N. Y.

The efficacy of total body perfusion, as determined by the oxygen tension of vital organs, has been examined in the dog. Changes in tissue oxygen tension have been measured by means of a modified technique of stationary platinum electrode polarography. The studies have been performed during perfusion with varying flow rates and at various levels of body hypothermia. 1) Normothermia with Varying Flow Rates: The oxygen tension of brain, liver and kidney remain remarkably constant until perfusion rates are decreased to 40cc/Kg/min. but muscle oxygen tension is reduced with perfusion below 80cc/Kg/min. 2) Myocardial and Muscle Oxygen Tension with Low FJow Rates and Hypothermia- Flow rates of below 40cc/Kg/min. at normothermia resulted in a profound decrease in oxygen tension but at 15°-20°C oxygen tension was maintained with low flow rates. 3) Hypothermic Cardiac Arrest: Coronary artery perfusion with cold blood (5°C) was used to lower the myocardial temperature to lower than 10°C and this low temperature was maintained with saline ice with no further perfusion. The myocardial oxygen tension was maintained at essentially normal levels for periods of 30 minutes of arrest. 4) The relation of blood flow and oxygen tension of various organs at varying levels of hypothermia will be discussed.

25. Cardiac and Peripheral Vascular Responses to Hyperther-mia Induced by Blood Stream Heating

T. Cooper (by invitation), V. L. Willman (by invitation),

and G. R. Hanlon, St. Louis, Mo.

The re-establishment of thermal equilibrium following total body per-fusion is usually initiated by direct blood stream heating through a heat exchanger and is often accompanied by frank pyrexia in the early post-perfusion period. The ability of the circulatory system to foster heat loss under these circumstances is limited by the effects of the heat on the heart and regulatory mechanisms. These studies were designed to permit description of the cardiac effects of hyperthermia apart from the effects on peripheral resistance and blood volume. In 5 dogs in which cardiac rate was electronically controlled, myocardial contractility, as measured by ventricular function curves and by myocardial strain gauge arches, was unchanged or improved until the temperature exceeded 41°C after which it gradually deteriorated. In 6 other animals, cardiopulmonary effects were eliminated by extracorporeal perfusion. Systemic flow was held constant so that changes in mean arterial pressure reflected changes in total peripheral resistance and changes in the extracorporeal venous reservoir reflected changes in intracorporeal blood volume. As intravascular temperature was elevated to 40°C, arterial pressure rose an average of 26%. Intracorporeal blood volume decreased 50-250 ml. Heating after ganglionic blockade resulted in a decrease in arterial pressure and negligible changes in the proportion of blood in the intracorporeal and extracorporeal circuits. The data emphasize the importance of regulation of blood volume while rewarming on cardiopulmonary bypass and during the febrile phase in the early post-operative period and emphasize the importance of avoiding hyperpyrexia because of its deleterious effects on myocardial function.

26. Viscosity Studies of Blood, Plasma and Plasma Substitutes in Extracorporeal Circulation

Keith Reemtsma (by invitation), and

Oscar Creech, Jr., New Orleans, La.

Various physiologic responses in extracorporeal circulation have been studied extensively, but scant attention has been directed toward physical changes in perfusing media. The measurement of viscosity has assumed increasing importance with the widespread use of hypothermia and, more recently, the introduction of diluents to extracorporeal circuits. Viscosity studies were performed with a recently developed ultrasonic viscosimeter Approximately 800 determinations were made, at temperatures form 0° to 50°G, on blood with different hematocnts and on plasma, dextran and dextrose solutions. Results were as follows: 1) At 37°C hematocrits up to 40% showed slight effect on viscosity; above 40% hematocnt, viscosity increased progressively with increasing hematocrit. 2) As temperature was lowered, vicosity increased much more steeply in blood with high hematocrits than in blood with low hematocrits. 3) At 37°C low-molecular-weight dextran (6% solution) was approximately twice as viscous as plasma, and high-molecular-weight dextran (6% solution) was four times as viscous as plasma. 4) With hypothermia, greater increases in viscosity were observed with dextran solutions than with whole blood, plasma or dextrose solutions These studies suggest that viscosity is especially important in the presence of high hematocrits and/or low temperatures. Low-molecular-weight dextran showed a two-fold effect on viscosity; it increased the viscosity of plasma but decreased the apparent viscosity of whole blood by lowering the hematocrit. The final effect on viscosity depended upon the diluent, hematocrit and temperature.

27. Pedicle Grafting of the Sino-Auricular Node to the Right Ventricle for the Treatment of Complete Atrio-Ventricular Block

Richard W. Ernst (by invitation), Dallas, Tex.

Sponsored by Donald L. Paulson, Dallas, Tex.

Sino-auricular pacing of the ventricles should be superior to electrical pacemaker stimulation in complete A-V block. An attempt to achieve this is presented. The area of the S-A node between the appendage and superior vena cava is identified with its nutrient artery. A horizontal mattress suture is started at the tip of the S-A node and continued along the path of the nutrient artery, thus excluding the S-A node with the artery from the right atrial wall. The excluded area is then resected leaving it attached near the A-V groove. A subepicardial tunnel over the right ventricle nearest to the graft from the A-V groove for a distance of 2 cm. is made through which the graft is passed. The free tip of the graft is anchored to the right ventricle with a loose suture. Two months later through a right atriotomy conduction through the atrio-ventricular bundle is blocked with sutures. Following this the pedicle graft in its new location is completely removed. Typical complete A-V block is noted only after the transplanted S-A node is removed. This indicates that the transplanted S-A node has taken the place of a new pacemaker with supraventricular qualities.

28. Hypoxia as the Cause of Hemorrhage Into The Cardiac Conduction System, Arrhythmia and Sudden Death

W. M. Thompson, Jr. (by invitation), Nalda Thung (by invitation),

J. F.Dammann, Jr., Rodriquez Perez (by invitation),

Miquel Sanmarco (by invitation), and

Charles Meheoan (by invitation), Charlottesville, Va.

A histologic study of the hearts of 60 newborn infants who died with symptoms of respiratory distress revealed a 30% incidence of hemorrhage isolated to the cardiac conduction system. A review of routine pathologic specimens did not show a single instance of isolated hemorrhage in this area Seventy-five hearts obtained from cardiac patients with or without surgery, revealed a better than 50% incidence of hemorrhage in the conduction system and this hemorrhage could be correlated with an episode of hypoxia. The findings in the newborn infants and in the latter group of patients signify that hypoxia plays an important role in the production of hemorrhage and subsequent death. On this basis, it was decided to subject animals to an atmosphere of normal carbon dioxide and reduced oxygen tension. A large series of rats, when subjected to an atmosphere of 6% oxygen, with a few exceptions, developed electrocardiographic evidence of arrhythmia and hemorrhage throughout the myocardium predominately in the area of the conduction system. Except for small areas of hemorrhage and congestion in the lungs, there was no further hemorrhage. These findings indicate that adequate oxygenation is of great importance in preventing arrhythmia and sudden death.