TUESDAY MORNING, MAY 2, 1972

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

Los Angeles Ballroom

17. Perfusion of the Brain with Venous Blood During Human Heart Lung Bypass

STANLEY GIANNELLI, JR.*, EDWARD F. CONKLIN*, STEPHEN

M. AYRES* and THOMAS F. NEALON, JR., New York, New York

Microemboli to the brain are considered to be the major source of postoperative electroencephalographic changes in open-heart patients. Pre- and postoperative EEG tracings were obtained in 150 consecutive patients perfused without microfilters and in 50 subsequent patients employing Swank filters in the arterial line. Each group had a 50% incidence of EEG slowing. In the filter group, however, the seventy was reduced from 1.5 to 0.5 cycles per second.

To improve filtration further, the brain was perfused with venous blood, ultrafiltered by the patient's own capillary bed. A double lumen catheter was employed, inserted into the aortic arch. The brain was perfused with one-third of total venous flow. The rest of the body was perfused with oxygenator blood. Hypothermia to 30° C was employed. The oxyhemoglobin saturation of the cerebral perfusate varied from 60 to 80%. The five patients so perfused to date have all survived without EEG alteration. A prospective, randomized study is being initiated to evaluate EEG and behavioral function. The results of this study and cerebral metabolic data from both groups will be presented.

*By Invitation

18. Subendocardial Ischemia Following Cardiopulmonary Bypass

GERALD D. BUCKBERG*, BERNARD TOWERS*, DONALD E. PAGLIA*.

DONALD G. MULDER and JAMES V. MALONEY, Los Angeles, California

Subendocardial necrosis in the absence of coronary artery obstruction is reported to cause half the patient deaths following cardiopulmonary bypass (Najafi, Taber). The cause of this necrosis is unknown. This study (56 dogs, 18 patients) demonstrates the etiology of the lesion and shows that its incidence is higher than suspected.

Blood flow to endocardial and epicardial muscle was measured with radio-nuclide microspheres in dogs during various states of cardiac work created by aortic stenosis, patent ductus, artificial pacing, arteriovenous fistula, and isoproterenol administration. Subendocardial damage occurred whenever blood flow to the endocardium was deficient, this deficiency could always be predicted from the interrelation between two easily monitored pressures.

The hearts of 18 consecutive patients (patent coronary arteries) who died after bypass were examined by a special histochemical technique which allows detection of damaged myocardium before it is visible grossly or microscopically. Subendocardial necrosis was identified grossly in five patients, microscopically in two patients, and histochemically in 9 of the remaining 11 (five control hearts were normal). The clinical records show that Subendocardial ischemia occurs with either high or low cardiac output.

Routine monitoring of aortic and left atrial pressure can, with special calculation, be used to warn of impeding subendocardial ischemia.

*By Invitation

19. Disseminated Intravascular Coagulation Following Ex-tracorporeal Circulation

ARTHUR D. BOYD*, RICHARD M. ENGELMAN*, REGENT L.

BEAUDET* and HENRIETTE LACKNER*, New York, New York

Sponsored by Frank C. Spencer

Disseminated intravascular coagulation (DIG) has been recognized with increasing frequency following sepsis and trauma, but has seldom been detected after extracorporeal circulation. A year ago a 45 year old woman developed gangrene of all four extremities from DIG complicating a low cardiac output after mitral valve replacement. She recovered but amputation of all four extremities was necessary.

Subsequently DIG has been recognized in seven other patients with a low cardiac output after prosthetic valve replacement. Four of the seven died. Recently developed hematologic tests for fibrin split products now permit an early and more accurate diagnosis of this syndrome. This is of great importance as prompt treatment with Heparin may prevent grave complications. Clinical features of DIG emphasizing early diagnosis and treatment will be presented.

*By Invitation

20. Magnesium and Open Heart Surgery

EDGARD TURNIER*, JOHN J. OSBORN*, FRANK GERBODE

and ROBERT POPPER*, San Francisco, California

The metabolism and clinical importance of magnesium was studied in 31 patients undergoing cardiopulmonary bypass. The following measurements were made: serum and urine magnesium, calcium, sodium, erythrocytes and muscle magnesium. The muscle magnesium determination showed a low level before surgery and a slight increase during cardiopulmonary bypass. Erythrocyte magnesium was at a normal level preoperatively and did not change after surgery. A significant drop in serum magnesium was found during the first one half hour of perfusion. The duration of bypass up to four hours did not increase the initial fall of the serum magnesium value. An increase in tubular reabsorption of magnesium was found in the postoperative period.

A similarity in the mode of excretion existed between magnesium, sodium, calcium and phosphorous preoperatively. Postoperatively, a significant inequality was found between sodium and magnesium. A difference of less significance was present between calcium and magnesium and no change was noted for phosphorous. Clinically, no instance of anythmia could be directly attributed to low serum magnesium value. A low incidence of mental aberrations was found to result in spontaneous recovery.

It is suggested that the intracellular level of magnesium is the most reliable way to diagnose a deficiency state.

*By Invitation

21. The Effect of Deep Hypothermia and Circulatory Arrest on the Distribution of Systemic Blood Flow in Rhesus Monkeys

L. W. RUDY*, J. K. BOUCHER* and

L. H. EDMUNDS, JR., San Francisco, California

We studied the distribution of systemic blood flow during deep hypothermia before and after 60 minutes of circulatory arrest (C.A.) at 15ºC (rectal temperature). Eleven rhesus monkeys weighing 3 to 4.5 kg were anesthetized with phencyclidine HC1 (I.M.) and morphine (I.V.). The bypass circuit from the right atrium to the ascending aorta included a membrane oxygenator and was pruned to produce a mixed venous hematocrit of 24%. Arterial and central venous pressures, ECG, and rectal temperature were continuously monitored. Arterial pO₂, pCO₂, pH, blood chemistries, and urine output were measured intermittently. We measured the distribution of systemic blood flow on 5 occasions in each monkey with batches of microspheres (15 m), each labeled with a different radionuclide. Total systemic blood flow was measured by microsphere reference samples and pump calibration. The monkey was then killed and all organs and tissues weighed and counted. Total systemic blood flow (200 ml/kg/mm) at the 5 microsphere injections did not differ within each experiment. Mean changes in systemic blood flow (percentage of total flow ± 1 standard deviation) were: flow to the heart decreased from 3.5 ± 1.2 (control) to 1.7 ± 0.7 during rewarming; flow to the kidneys decreased during hypothermia before (11.4 ± 3.8) and was greatly reduced after C.A. (4.5 ± 2.1), but returned to control levels during rewarming; cerebral blood flow decreased from control (9.2 ± 1.1) to 5.8 ± 1.8 at 15° C, and to 5.4 ±1.4 during rewarming; flow increased to the gastrointestinal tract during hypothermia before (17.9 ± 5.7) and after (17.2 ± 4.8) C.A. compared to the control level (8.2 ± 2.2); flow to skeletal muscle greatly increased after C.A. at 15° C from 6.2 ± 1.6 (control) to 13.1 ± 3.1. These changes observed during and after deep hypothermia and circulatory arrest will help to explain some of the clinical observations seen in patients treated similarly.

*By Invitation

22. Perfusion Without Donor Blood

ROBERT S. LITWAK, BENNETT A. MITCHELL*, MELVIN KAHN*,

SAMUEL BERGER*, LOUIS ALEDORT*. ROY A. JURADO*

and SALVADOR B. LUKBAN*, New York, New York

The high incidence of hepatitis (18.3%) following cardiopulmonary bypass at this institution has stimulated attempts to develop a technique in which donor blood is not used. The current protocol involves withdrawal of 500 ml of blood from the patient (a) 4 days prior to surgery and (b) after anesthetic induction (during (b) an equal volume of 5% pasteurized human serum albumin (PHSA) is administered). Perfusion (2.2 L/M² at 37.5 C) is conducted with a minimally pruned Bentley oxygenator (precautionary low level "pump off" switch installed). Priming perfusate is a NaHCO₃, buffered mixture of PHSA (49.5 g/L), electrolytes (Na 150, K 4.9 and Cl 107 mEq/L) and glucose (5.7 g/L). Osmolality is 340 mOsm/L. During perfusion a 5% solution of NaHCO₃ is administered at 2.5 ml/Kg/hr.

24 cases have been operated in which an attempt was made to avoid donor blood. Cardiac index (5 patients) fell 13% and systemic pressure 12% after blood withdrawal and replacement with PHSA. Perfusion hematocrit (hct) averaged 22 and was 24 two hours post-perfusion (PP). Residual perfusate and previously collected autologous blood was administered PP. Supplemental PHSA was given for volume loading. Acid-base stability was maintained. Hct averaged 27 two weeks PP and most patients had a marked reticulocytosis (8%) by the 6th PP day. Coagulation studies were normal by the 2nd PP day except for low platelets which became normal by day 6.

It has been necessary to break the protocol in 4 of the 24 cases (3 required additional volume loading in the O.R., 1 had a HCT drop to 16 three days pp). 20 of the 24 patients survived and none have developed hepatitis from the PHSA. One patient died of ventricular arrhythmias despite K supplementation. The other 3 deaths were believed to be unrelated to the perfusion technique.

A practical method of perfusion in which only autologous blood would be employed has obvious advantages. Although not uniformly successful, the approach described appears to be promising.

*By Invitation

23. Early Complications of Long-Term Respiratory Support

WILLIAM H. FLEMING*, Decatur, Georgia,

JOHN C. BO WEN*, Cleveland, Ohio

Sponsored by Charles R. Hatcher

A prospective study of 128 consecutive patients receiving mechanical ventilatory support for an average of nine days each showed that central nervous system injury and pulmonary sepsis each accounted for 36% of the 59 deaths. Stress ulcer (10%) was next in frequency as a cause of death. The necrotizing organisms Pseudomonas Aeroginosa and Staphylococcus accounted for the rather surprising 15% incidence of non-traumatic pneumothorax which occurred in these patients, as well as causing all the 21 deaths due to pulmonary sepsis. Wet lung syndrome occurred in 16 patients, but was not a cause of death. Bronchoscopy consistently improved both the arterial oxygenation and effective king compliance in 35 patients with atelectasis. There were no hemorrhages from major arteries associated with the 128 tracheostomies, and only one tracheoesophageal fistula in nearly 1200 patient-days of respirator use.

*By Invitation

24. The Management of Interstitial Pulmonary Edema - Significance of Hypoproteinemia

JOSEPH M. GIORDANO*, HERMAN KLINGENMAIER*, WILLIAM L. JOSEPH*

and PAUL C. ADKINS, Washington, D.C.

Pulmonary insufficiency secondary to nonthoracic trauma has become an important clinical problem and is being recognized more frequently as a major complication following stress. In the past delayed recognition has often led to eventual respiratory failure and death.

Nine patients are presented with the findings of interstitial pulmonary edema. The diagnosis was made on the basis of the characteristic radiographic changes, a low pO₂ despite a high FIO₂, decreased lung compliance and the absence of other pulmonary problems to account for a decreased oxygen saturation. In addition, all of the patients demonstrated a serum albumin less than 50 per cent of normal. Treatment consisted of restriction of intravenous saline and water, massive amounts of intravenous albumin to elevate oncotic pressure, Lasix to remove mobilized fluid and continuous positive pressure ventilation to maintain alveolar patency during exploration. All of the individuals responded to this regimen with improvement in respiratory function providing physicians with valuable time to treat their primary problem.

The pathophysiology of this disease and results of an experimental model emphasizing the significance of hypoalbuminemia in the etiology of this lesion will be discussed.

*By Invitation

25. The Clinical and Experimental Evaluation of a Controlled Pressure Intratracheal Cuff

GEORGE J. MAGOVERN, JOHN G. SHIVELY* and

DAVID C. FECHT*, Pittsburgh, Pennsylvania

The complications of prolonged tracheal intubation with cuffed tracheostomy tubes are well known. This paper presents a biomedical engineering analysis of the physical factors at the cuff-trachea interface and confirms the dangerously high interface pressures that can be expected when even relatively soft extensible cuffs are used.

As a result, a simple and practical cuff system has been developed for automatic pressure regulations not exceeding 20 mm. of mercury in the endotracheal balloon cuff which still effectively controls sealing pressure. The system employs a specially designed extra tracheal balloon whose physical factors determine the internal pressure in the spherical shaped endotracheal balloon cuff. This control pressure balloon permits conventional and safe installation procedures in that too much air cannot be injected, since the excess volume will be retained in the control balloon as a reservoir of inflating gas at the correct pressure for continuous inflation of the endotracheal cuff. The system may accept as much as 100 centimeters of gas without significant effect on the tracheal cuff interface. This system has undergone extensive laboratory testing as well as routine clinical application for the past eight months in fifty patients. These results will be presented with endoscopic pictures of the tracheal cuff interface of patients on prolonged ventilation.

*By Invitation

26. The Effect of Transpulmonary Pressure on Airway Smooth Muscle Tone

WALTER G. WOLFE*, J. A. NADEL*, PAUL GRAFT*

and DAVID C. SABISTON, JR., Durham, North Carolina

Airway smooth muscle tone during mechanical ventilation may have an effect on the distribution of ventilation and gas exchange. To determine if smooth muscle tone contributed to a change in airflow resistance with varying lung volume, measured transpulmonary pressure (Ptp), and airflow resistance (R_L) were determined and correlated with measured differences in airway diameter on bronchograms.

Twenty dogs were anesthetized with chloralose (50 mg./kg.) and urethane (500 mg./kg.), tracheostomy performed, and the lungs ventilated following induced paralysis with succinylcholine. Following bilateral cervical vagotomy, inflation of the lungs had an insignificant effect on R_L, but electrical stimulation of the peripheral ends of the vagi increased R_L, to 10 times above control levels at FRC. Increasing Ptp decreased the effect ofvagal stimulation and at 30 cm. of water it was not possible to increase the resistance. Tantalum bronchograms were obtained at various levels of Ptp during vagal stimulation and airway dimensions were compared at each Ptp with the control non-stimulated state. Bronchograms demonstrated uniform constriction of airways from the trachea, bronchi, and down to 2 mm. airways with vagal stimulation at FRC while at elevated Ptp's the airway diameter did not change.

From these studies the following conclusions may be drawn: (1) changes in airflow resistance which occur during ventilation at different lung volumes are due primarily to smooth muscle tone, a factor which has a profound effect upon the physical properties of the airways, and (2) contraction of smooth muscle in the airways is progressively inhibited with increasing Ftp.

*By Invitation

27. Pathophysiology and New Problems in Total Artificial Heart

TETSUZO AKUTSU*, HISATERU TAKANO*, HIROYUKITAKAGI*,

MANSON D. TURNER*, EDMOND C. HENSON* and

JACK W. CROWELL*, Jackson, Mississippi

Sponsored by James D. Hardy

Thirty hours of average survival time in our laboratory in the previous year has been prolonged to one week this year. Air-driven total artificial hearts (TAH) were implanted in 12 calves weighing around 160 lbs. One calf survived a little longer than 10 days. Cardiac output was maintained between 75 to 135 ml/kg/min. The initial pulse rate was set at 70, and was increased later with the increase of venous return. Mean pulmonary artery pressure ranged between 15 and 35 mmHg. Pulmonary function was not affected being indicated by 98% of O₂ saturation in arterial blood. Plasma free hemoglobin concentration decreased to 10-20 mg% following transient increase resulted from extracorporeal circulation. Postoperative animals were quite alive and behaved normally. No calf died by thromboembolism, and no calf showed specific syndrome related to TAH. Blood culture was positive in three out of four longest survivals. Since the TAH model has about a dozen of tubes and wires coming out through the chest wall for driving, monitoring and blood sampling, infection has now become a serious problem as the survival time became long. Durability of the device is another problem in prolonged pumping.

*By Invitation

28. Our Experience in Making Heart Prosthetics

B. V. PETROVSKY* and V. I. SHOUMAKOV*, Moscow, U.S.S.R.

Sponsored by John H. Kennedy

For several years we studied the problem of heart prosthesis. We developed several different models of an artificial heart implanted in thorax or paracorporally. These were pumps of diaphragm or sack type, and were equipped with various valves of ball or disk type to ensure blood flow in one direction. In a number of models the pump surfaces contracting with blood were coated (graphite-benzalkomum-heparme complex, synthetic velours) to prevent thrombosis. The models were driven pneumatically, hydraulically, electrohydraulically and electropneumatically. All prostheses were checked on stands imitating hydrodynamics of greater and lesser circulation. Thereafter, they were implanted in dogs and calves in conditions of artificial blood circulation in more than 100 experiments. During these experiments we mastered the surgical technique of prosthesis implantation, systems of control, and chose parameters of prosthesis operation. We studied hemodynamics, acid-alkali state, blood trauma and other data to make a conclusion about adequacy of operation of some prostheses. Survival time was several hours. The experience accumulated made it possible to develop a prosthesis construction and an automatic control system which we feel is suitable for short time use in clinical practice to maintain an organism vitality of a patient before heart transplantation or for preservation of organs.

*By Invitation