THORACIC SURGERY FORUM

Ballroom

15. An Investigation of Induced Chronic Hyperthermia and In Vivo Heat Dissipation

W. F. Bernhard, R. Harvey*, J. C. Norman*, G. Lafarge*,

T. Robinson*, and L. Van Someren*, Boston, Mass.

Since development of an implantable energy source (for powering a total cardiac prosthesis) is an essential part of artificial heart research, the mechanism to achieve excess heat dissipation assumes importance. Regardless of the energy converter used, it is unlikely that a conversion efficiency greater than 10% can be attained. Studies indicate that a blood pump (for man) requires 2 to 5 watts of pumping power; therefore, 20 to 50 watts of thermal power must be continually rejected from the body. In this study, the circulating blood was selected as the heat transfer medium. Stainless steel tubes, with thermally insulated electrical heaters on their outer surfaces and a coating of graphite-benzalkonium-heparin on their inner surfaces, were implanted in the aortas of dogs. The heaters were energized to power levels ranging from 8 to 40 watts (continuously) for intervals up to six months. Serial determinations were made of rectal, esophageal and blood temperature, plasma hemoglobin, blood viscosity, red cell fragilities, plasma protein profile, and thyroid, hepatic, renal, and cardiovascular function. Analysis of these data indicate that heat (40 watts) generated by a power source can be dissipated with only a small (1°C) increase in core temperature.

16. An Evaluation of the Protective Effect of Hyperbaric Oxy-genation on the Central Nervous System During Circulatory Arrest

Gordon F. Moor*, Robert Fuson*, George Margolis*,

Ivan W. Brown, Jr., and Wirt W. Smith*, Durham, N.C.

One of the hopes of hyperbaric oxygenation has been the theoretical possibility of increasing the blood and tissue stores of physically dissolved oxygen to permit a significantly longer period of circulatory arrest without damage to the central nervous system. Using dogs and employing a critical neuropathologic study of the central nervous system as the determining end point, 179 separate experiments have been done. These have considered not only hyperbaric oxygenation, but the additional influence of hypothermia and added CO². Methods: Periods of total circulatory arrest of 5, 10 and 15 minutes at one (normal) and 3 atm. abs. were studied in normothermic and in modest hyperthermic (28-30° C.) animals using 100% oxygen or a mixture of oxygen and CO². EKG and arterial pressures were monitored and blood gas values and pH were determined at the ambient pressures of the experiments. The animals were allowed to recover and autopsy carried out 5-7 days later. Special emphasis was placed upon a detailed study of the CNS by neuropathologist. The clinical and neuropathologic findings will be discussed. Our results are not in agreement with previously published reports but are consistent with theoretical calculations based upon the increased levels of blood oxygen content.

17. An Anatomical Study of the Peripheral Pulmonary Lymphatics

Timothy C. Pennell*, Winston-Salem, N.C

Sponsored by H. H. Bradshaw

An anatomical study of the peripheral pulmonary lymphatic system of human lungs is presented. Post-mortem expanded fixation of human lungs was accomplished with formalin vapor and the peripheral pulmonary lymphatic channels were injected with radiographic contrast media. The details of this technique are discussed. Gross, microscopic and radiographic studies, including cine fluroscopy was carried out. As illustrated, these studies revealed the following: 1) Numerous lymphatic valves exist throughout the lungs. These valves display a fairly constant anatomical relationship, but allow an extremely variable direction of flow in the peripheral lymphatics. 2) The direction of flow in the interlobar septum, contrary to previous publications, is towards the hilum. 3) Numerous anastomotic sites exist between the perivascular and peribronchial channels in the system, apparently without a consistent anatomical relationship. 4) On the basis of present studies no definite segmental relationship of the peripheral pulmonary lymphatics can be established or delineated. These findings are contrary to previous published information concerning the subject, and these differences will be discussed.

18. Physiologic Studies of Lung Reimplantation and Homo-transplantation and the Effect of Dibenzyline on the Incidence of Vascular Thrombosis

Akhila N. Sharma*, Harry S. Soroff*, Andrew E. Bellas*,

Fabio Giron*, and Ralph A. Deterling, Jr., Boston, Mass.

The functional changes following homotransplantation of pulmonary tissue are a diminution of ventilation and CO₂ release in the presence of a normal oxygen uptake. The chief technical problem encountered in lung transplantation has been a high incidence of vascular thrombosis. The effects of Dibenzyline upon these physiologic changes and upon the incidence of vascular thrombosis were evaluated. Reimplantation of the left lower lobe of the lung was performed in 44 dogs. Thirty-one animals served as controls. Of this group seventeen developed vascular thrombosis. Thirteen animals were pre-treated with Dibenzyline. There was no instance of vascular thrombosis. The pulmonary blood flow, vascular resistance, gas exchange and diffusion capacity were unchanged in the five long-term survivors. Those animals which died had an increased pulmonary vascular resistance. Homotransplantation of the left lower lobe was performed in thirty-one animals. They received 4.0 mg/kg. Imuran daily. Twenty-one animals were controls. Sixteen of these animals, or 76%, died of vascular thrombosis. Three animals, 14%, were long-term survivors. Ten animals received Dibenzyline. Two, or 20%, were long-term survivors. Of the remaining eight animals, venous thrombosis occurred in only one animal. The long-term survivors showed a normal CO₂ uptake, but a decreased CO₂ release and diffusion capacity.

19. pH and Respiratory Work

Richard M. Peters, and E. McG. Hedgpeth, Jr.*, Chapel Hill, N.C.

Metabolic acidosis and respiratory acidosis are common complications of major cardiac and pulmonary surgery. Fall in blood pH is a stimulus for increased ventilation. Respiratory acidosis while indicative of respiratory insufficiency may be associated with increased ventilation in a subject with mechanical derangements of the lung. It has been shown that inhalation of CO₂ mixtures which lower pH increase airway resistance. To clarify whether changes in pH independent of change in pCO₂ alter respiratory mechanics, a series of ten dogs were ventilated at a constant rate and volume while metabolic acidosis was induced by infusion of HCl and respiratory acidosis by CO₂ inhalation. Changes in measured compliance resistance, elastic and resistive work were compared by multivariant analysis with the induced changes in pH, pCO₂ and [HCO₃]. Elastic properties were not significantly altered. Fall in pH led to a progressive rise in resistance and resistive work. Significant increases in airway resistance shown by these experiments leads to alterations in time constants of various lung units. This further adds to respiratory work and pH depression by disturbing coordination of ventilation and perfusion. These experiments further emphasize the importance of restoring pH to normal.

20. Electrophrenic Respiration by Radiofrequency Induction

Daniel W. Van Heeckeren*, and William W. L. Glenn,

New Haven, Conn.

Electrical stimulation of the phrenic nerve (electrophrenic respiration - EPR) will effectively control ventilation. EPR by radiofrequency (RF) induction as developed in this laboratory would appear to have several advantages over other techniques. To simulate normal diaphragmatic respiratory movement the wave-form envelope generated in the externally located RF transmitter may be varied in contour, amplitude or frequency by modulation of the carrier wave. The internally placed receiver unit delivers mono-phasic or bi-phasic impulses to the phrenic nerve by electrodes applied directly to the nerve or indirectly through the cava or pulmonary artery. RF-EPR has been carried out in animals for up to two years. Stimulation thresholds remained stable unless electrolysis occurred. Temporary paralysis of the ipsilateral diaphragm following chronic RF-EPR was observed. The suppression of spontaneous respiration by RF-EPR has been investigated. Tetanic unilateral phrenic nerve stimulation caused a period of apnea. This period was decreased slightly by ipsilateral phrenic sensory nerve root section, markedly by bilateral vagotomy and abolished by distal ipsilateral phrenicectomy. Efficiency of RF-EPR was demonstrated by arterial gas studies in nembutal-induced apnea and by differential bronchospirometry. A limited clinical experience with RF-EPR will be reported.

21. Tracheobronchial Reconstruction with Autologous Periosteum

Eric W. Fonkalsrud*, and William G. Plested*, Los Angeles, Calif.

Sponsored by Donald G. Mulder

Tracheal reconstruction with prosthetic materials or tissue grafts has generally been unsuccessful. The present study was undertaken to evaluate autologous costal periosteum as a pedicle flap or free graft for tracheal reconstruction. Both immediate and delayed rigid periosteal grafts were studied. Five groups of dogs were studied: 1) Costal periosteum was transplanted as a free graft to a defect in the cervical trachea. 2) Costal periosteum was placed over a large defect in the thoracic trachea as a pedicle flap. 3) A staged rib resection was performed with construction of a pedicle tube of periosteum over a solid plastic rod. Two and one-half weeks later a free circumferential graft of rigid periosteum was used to reconstruct a defect in the cervical trachea. 4) A staged rib resection was performed with molding of the periosteum into a sheet. At the second operation a free graft of rigid periosteum was placed over a large defect in the cervical trachea. 5) A staged periosteal flap was used to reconstruct a defect in the thoracic trachea. These studies indicated that autologous periosteum may serve as a suitable tissue for tracheobronchial reconstruction. Delayed rigid periosteal grafts function better than soft grafts transplanted immediately. Free periosteal grafts appear to take almost as well as pedicle flaps.

22. The Effect of Intraluminal Splinting in Preventing Caustic Stricture of the Esophagus

Stanley C. Fell*, August Denize*, Norwin Becker*, and

Elliott S. Hurwitt, New York, N.Y.

Despite the administration of steroids and antibiotics, there is a significant incidence of esophageal stricture following the ingestion of caustics. The effect of intraluminal esophageal splinting was studied in cats, using the method of Haller and Bachman to produce lye stricture. Antibiotics but no steroids were administered. Surviving control animals all developed esophageal strictures, confirming the reliability of the method. In 20 cats the effect of an endoesophageal polyvinyl prosthesis implanted in the normal esophagus was studied. Thirteen animals survived between 15 and 40 days. Postmortem examination revealed aspiration pneumonia in all, with varying degrees of esophagitis. In the experimental group esophageal splinting was performed one hour after lye burning. In 10 cats the prosthesis was removed in less than 15 days; 7 developed esophageal stricture within 3 weeks, following removal of the splint. In 20 cats intraluminal esophageal splinting was maintained from 15 to 40 days. Esophageal stricture did not occur, nor has it developed in surviving animals followed thus far for 6 months. The means by which splinting protects the esophagus from caustic stricture, and the clinical applicability of the method will be discussed.

23. Experimental Esophageal Stenosis and Its Treatment

Masaru Tsukamoto*, Floyd H. Lippa*, and Alan P. Thal,

Detroit, Mich.

The purpose of this experiment was to produce a model of esophageal stricture in dogs and to investigate the value of a gastric fundic patch in its correction. Thirty mongrel dogs were used. In one group of 15 dogs, 10% phenol was injected submucosally all around the esophagus above the esophagogastric junction, and then a skin graft was placed over the area of injection. In the other group of 15 dogs, a piece of fascia was put submucosally around the esophagus above the cardiac junction. Care was taken to prevent the stenosis of esophagus by fascia itself. Three weeks later, all the dogs in both groups had lost weight, and x-rays and esopha-goscopy showed severe stenosis of the distal esophagus and dilatation of the proximal esophagus. These dogs were operated upon again and the esophagus was incised longitudinally through the stenosed area and triangulated. A generous portion of gastric fundus was sutured over this area after biopsies were taken. The triangular defect in the esophagus protected by the overlying fundus was completely epithelialized four weeks after operation. The dogs gained weight, and x-rays and esophagoscopy demonstrated no reflux or stenosis of the esophagus.

24. Hemodilution in Extracorporeal Circulation: Large or Small Non-Blood Prime?

Anatolio B. Cruz, Jr.*, and J. C. Callaohan,

Edmonton, Alberta

Non-blood solutions, unmixed or in combination with homologous blood, and other ingredients have been used in small and large prime systems, with the respective proponents achieving good results. Thirty mongrel dogs of both sexes, weighing from 12 to 37 kg., divided into three groups, were placed on complete cardiopulmonary bypass for sixty minutes at normothermia, using disposable plastic bag oxygenators. The priming volumes were: Group I - 20cc/kg, Group II - 40cc/kg, and Group III - 80cc/kg, of Ringers Solution. No Alkali, THAM, or other diluents were added to the perfusate. Blood gases, pH, bicarbonate, buffer base, base excess, hemoglobin, hematocrit, lactic and pyruvic acids, electrolytes, blood sugar and plasma hemoglobin were determined before, during, and after perfusion, including the 8 hour post-bypass period. Acid base balance and metabolic derangements were minimal in Group I, and became worse in Groups II and III, although flow rates in the latter groups were the same as, or slightly better than, those in Group I. Animals in Groups II and III bled more in the post-bypass period, and remained unconscious longer. Survival rates were: Group I--100%, Group II - 60%, and Group III - 40%.

25. Body Fluid Compartment Changes After Open Intracardiac Operations

John Cleland*, James R. Pluth*, W. Newlon Tauxe*, and

John W. Kirklin, Rochester, Minn.

Our previous work demonstrated that increased blood volume (BV) and total body water (TBW) of patients with mitral stenosis returned to pre-dieted normal values two weeks after closed commissurotomy and extraplas-matic extracellular fluid failed to do so. 30 patients subjected to open intracardiac operations have now been studied pre-operatively, immediately postoperatively and two to thirty-five days later. Plasma volume was reduced immediately postoperatively (mean - 8%).There was greater reduction of red cell mass (ROM) following mitral valve replacement (mean - 31%) than aortic valve replacement (mean - 21%) or repair of congenital malformations (mean - 15%). Blood volumes late postoperatively were reduced compared to pre-operatively and similar to those immediately postoperatively. This is probably a result of improved cardiac performance after operation. Extracellular fluid (ECF - ⁸²Br) was increased immediately postoperatively (mean +13%) but especially in patients with recent congestive failure (mean +27%). Late postoperatively ECF in most patients returned to pre-operative values but were still above predicted normal. Abnormalities of renal function may be etiologic. TBW was unchanged immediately after surgery. Intracellular water appeared to be markedly decreased at that time.

26. The Importance of Micro-Embolism in the Pathogenesis of Organ Damage Caused by Prolonged Use of the Pump Oxygenator

P. G. Ashmore, D. B. Allardyce*, and S. H. Yoshtda*,

Vancouver, British Columbia

There is considerable evidence that blood exposed to oxygen in an extra-corporeal circulation for prolonged periods accumulates large numbers of microscopic aggregates. These aggregates are removed during passage through the circulation, and are an important source of organ damage. We have attempted to define the nature and etiology of these aggregates, their effects during perfusion, and methods of eliminating them from extracorporeal circulation systems. Fresh, unmatched blood was circulated and oxygenated in a disc oxygenator, for ten hour periods. Partial cardiopulmonary bypass was then instituted in dogs, using veno-arterial, and veno-venous perfusion in different groups. The effect on renal, cerebral and cardiovascular function was evaluated by clinical and histological studies. Pulmonary function was studied with measurement of blood gases, and by post-mortem studies of surface tension of lung extracts, pressure-volume characteristics of excised lungs and routine and electron microscopic examination of lung sections. Screen filtration pressures were measured in the circulating blood, as an index of its content of embolic material. These studies indicate the importance of particulate obstruction of the micro-circulation during extracorporeal circulation, and relate to the clinical use of prolonged assisted circulation.

27. Must Heparin Be Neutralized Following Open Heart Operations?

Aldo R. Castaneda*, Minneapolis, Minn.