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Recent experimental studies and clinical application of deep hypothermia for cardiovascular surgery are reviewed. At most institutions, surface hypothermia alone or in combination with limited cardiopulmonary bypass has been employed. Circulatory dynamics were well maintained following prolonged cardiac arrest at 20°C. Some degree of acidosis usually developed after the arrest period but was gradually corrected during rewarming. Total circulatory occlusion could be maintained for at least one hour at 20°C. without evidence of cerebral damage in infants. Many complex congenital cardiac anomalies, including transposition of the great arteries, total anomalous pulmonary venous return, ventricular septal defect, and tetralogy of Fallot, have been successfully corrected in the first few weeks of life. Less encouraging results have been achieved in patients with infradiaphragmatic total anomalous pulmonary venous return, complete atrioventricular canal, or pulmonary atresia.

Direct tracheoscopy was employed to assess tracheal damage following prolonged intubation. Comparison of conventional and low-pressure cuffs showed that there was less trauma from the low-pressure cuff. Comparison of tube sizes showed a reduction in injury with 8-mm diameter tubes compared with larger ones.

Combined use of intra-aortic balloon counterpulsation (IABCP) and coronary revascularization was utilized in 28 patients with acute and chronic left ventricular power failure (LVPF) and ischemic dysrh

Singh, H. M., and Baker, J. T. (1974). Thorax, 29, 68-74. Jaundice following open-heart surgery. A study was made into the factors influencing the onset of jaundice in 102 patients undergoing valve replacement during cardiopulmonary bypass. Postoperative jaundice appeared to be correlated with double valve replacement, the co-existence of an uncorrected valvular lesion, length of perfusion and myocardial ischaemia times, and also the age of the patient. Factors appearing not to be correlated with the onset of jaundice included preoperative pulmonary artery pressure, cardiac index, parameters of preoperative renal and hepatic function, and the amount of blood used during bypass. The biochemical features of the jaundice seemed to follow a pattern not previously recognized in this context, with sometimes considerably raised bilirubin levels in association with virtually normal levels of transaminases and alkaline phosphatase.

Two patients developed a false aneurysm of the right ventricle after Rastelli’s operation for transposition of the great arteries (TGA) with ventricular septal defect (VSD) and left ventricular outflow tract obstruction (LVOTO). The clinical features and hemodynamic data are presented. The most likely etiologic cause was an excessively long conduit in 1 patient and postoperative infection in the other. Operative technique consisted of cannulation of peripheral arteries, right thoracotomy, and establishment of cardiopulmonary bypass with moderate hypothermia before transection of the sternum. A left ventricular vent was inserted through the right upper pulmonary vein. Both patients are well 7 and 5 months after their second operation.

A case of Staphylococcus aureus endocarditis associated with a retained pacemaker electrode fragment is presented. Antibiotic therapy was to no avail. The electrode fragment was eventually removed by cardiotomy with cardiopulmonary bypass, and the infection then cleared. The mechanism of electrode entrapment and the various alternative methods of treatment are discussed. When a foreign body cannot be removed by closed techniques, cardiotomy with cardiopulmonary bypass is necessary.

In a randomly selected group of 20 dogs undergoing a three-hour cardiopulmonary bypass, a marked fall in total plasma protein, serum albumin and serum globulins was noted. Operative trauma, and the dilution produced by priming fluid, were responsible for these changes. The weak relationships noted between serum albumin and serum globulin levels on the one hand, and BSP retention levels on the other, suggested an altered hepatic function. The alteration was not significant enough to play an important part during prolonged cardiopulmonary bypass in open-heart surgery.

Jastrzebski, J., Sykes, M. K., and Woods, D. G. (1974).Thorax, 29, 534-538. Cardiorespiratory effects of protamine after cardiopulmonary bypass in man. The cardiorespiratory changes following the injection of protamine sulphate (6 mg/kg) were studied in 15 patients who had undergone cardiopulmonary bypass. There was a transient fall in arterial pressure and a more prolonged increase in pulmonary artery pressure. There was a significant fall in arterial oxygen tension which was mainly due to a reduction in mixed venous oxygen tension resulting from a fall in cardiac output. Dead space/tidal volume ratio and percentage shunt did not change significantly.

A 4-month-old infant with anomalous origin of the left coronary artery from the pulmonary artery developed a large left ventricular aneurysm with intractable myocardial decompensation. The aneurysm was excised and the anomalous coronary artery was ligated at its origin. High-flow cardiopulmonary bypass with moderate hypothermia (30° C.) was used during the operation. The child made an uneventful recovery and 8 months after the operation appears to be perfectly healthy. This method of treatment is applicable in those infants who have had a large infarction and a definite loss of ventricular muscle mass.

The acutely injured patient may require emergency thoracotomy as an integral part of resuscitation. In critical circumstances, thoracotomy in the emergency center for control of hemorrhage, cardiac massage, and direct repair of crucial injuries can be lifesaving. Such an approach may be required for urgent repair of cardiac injuries. Between January, 1970, and December, 1973, over 6,000 emergency operations were performed for blunt and penetrating trauma at Ben Taub General Hospital. Emergency thoracotomy was required in more than 400 cases. Of these, 148 patients required thoracotomy in the Emergency Center due to rapid deterioration in their clinical condition. Forty-eight of these patients had injury to the heart. This aggressive approach allowed salvage of 67.5 per cent of these critically wounded patients with cardiac injuries who had any sign of life on arrival at the hospital. Autotransfusion, emergency cardiopulmonary bypass, and fine-screen filtration of transfused blood have been valuable adjuncts to this lifesaving measure. Thoracotomy in the Emergency Center should be considered as a primary modality in the management of moribund patients with penetrating wounds of the chest.

We have reported a series of 320 patients anaesthetized for operations with cardiopulmonary bypass using a combination of diazepam and pentazocine sup-plemented with nitrous oxide and oxygen. We found it to be a satisfactory tech-nique for the anaesthetic management of patients with poor cardiac reserve. Ease of induction and maintenance were noteworthy with this technique, with minimal side effects during anaesthesia and in the post-operative period. Although the use of pentazocine in large dosage has not been officially approved, we feel that use of a combination of diazepam and pentazocine in the technique we have described has many advantages in anaesthesia for operations with cardiopul-monary bypass.

The performance of cardiac surgery in the community hospital not concerned with postgraduate medical education has not been encouraged. It has been stated that the moderate-sized community hospital cannot offer sufficient support or patient volume to maintain a cardiac surgical team. The advent of a successful myocardial revascularization procedure has been instrumental in altering this concept. The first procedure requiring cardiopulmonary bypass in a Lubbock, Texas, hospital was performed on November 24, 1970. To date, 550 cardiac procedures requiring total cardiopulmonary bypass have been performed at Methodist Hospital, Lubbock. The cumulative mortality for this group of patients has been 2.9%. The development of a comprehensive cardiac surgical program has been very well accepted, and it is our consensus that it has been not only a feasible undertaking but a strong asset to the community.

The details of 60 patients scheduled for emergency coronary artery surgery are presented. Forty-two patients were categorized as having "impending" infarctions and 18 were operated on within 4 hours of sustaining acute myocardial infarctions. The patients presented with different haemodynamic disturbances and the selection of anaesthetic drugs was modified accordingly. We have found that conventional anaesthetic methods, conservatively applied, can be used safely in this group. The induction of anaesthesia and the increase in arterial oxygen tensions obtained by controlled ventilation produced an improvement in e.c.g. signs of ischaemia, and also reduced myocardial irritability. Circulatory complications were treated according to information obtained from simple monitoring techniques. The responsibility of the anaesthetist in postoperative care is emphasized and a regime of postoperative ventilatory management is described.

Surgical correction of aortic arch aneurysms can be technically difficult and present hazards related to central nervous system and myocardial viability. Temporary circulatory arrest may be necessary, and in the age group in which most aneurysms are found, coronary and peripheral vascular disease increase the risk of ischemic damage. A patient is presented in whom hypothermia and cardiopulmonary bypass were utilized for resection of an aneurysm of the distal two-thirds of the aortic arch. Flow to the head through the right brachial and left common carotid arteries was regulated by monitoring pressure tracings from bilateral temporal artery catheters. Anoxic cardiac arrest for 70 minutes was well tolerated. No neurological deficit or cardiac dysfunction was evident postoperatively. Hypothermia with cardiopulmonary bypass is the approach of choice with aneurysms of the aortic arch. It affords the best protection for the central nervous system and myocardium.

In previous studies white retinal emboli have been observed during open heart surgery in patients who postoperatively developed neurological complications and in patients who failed to survive (Williams, 1973). In the present study similar white retinal emboli were experimentally produced in dogs undergoing total cardiopulmonary bypass and were shown to comprise blood platelets. Trypsin digest flat preparations of the retina showed multiple capillary occlusions, some having characteristics of denatured cellular material and fat, others resembling silicone grease in vessels. The incidence of experimentally produced emboli comprising blood platelets and other cellular material was significantly reduced by adding dipyridamole (Persantin-Boehringer Ingelheim) a substance which impairs aggregation and adhesiveness of platelets, to the perfusate.

A case of supravalvular stenosing ring of the left atrium without an associated cardiac lesion and the youngest (four-month-old) patient ever reported to survive operation with this lesion is presented. The importance of careful diganostic studies including clinical examination, angiocardiography and echocardiography before operation is emphasized. Since this lesion is potentially curable by operation, repair with use of cardiopulmonary bypass should be performed without delay once the diagnosis has been made.

Several reports have demonstrated that the lungs are the most important site of conversion of angiotensin I to angiotensin II. The purpose of the present study was to assess the extent of extra-pulmonary conversion hi man, during cardiopulmonary bypass. Plasma concentrations of angiotensin I and immunoreactive angiotensin II, and plasma renin activity were simultaneously determined, using specific radioimmunoassays, during extra-corporeal circulation in 13 patients undergoing major cardiac surgery. Generally the renin-angiotensin system was stimulated during cardiopulmonary bypass with maximum values occurring at different time. A highly significant correlation was found between plasma renin activity and angiotensin I and II concentrations respectively, as well as between these two peptides. Positive correlations were also obtained between arterial and venous samples for plasma renin activity and angiotensin I and II. Thus the presence of angiotensin II in plasma in the absence of pulmonary circulation and its parallel variations with plasma renin activity indicate that converting activity by extra-pulmonary sources is not negligible.

Presented at Canadian Anaesthetists' Society Annual Meeting, Vancouver, June, 1973. THE use of eardiopulmonary bypass and of the pump oxygenator has increased as newer surgical techniques have been developed. Pulmonary complications, particularly those of the left lower lobe, have remained frequent following bypass 1 despite the decrease in the post-perfusion syndrome or "pump lung" attributed to improved venting of the left ventricle and atrium s and/or the use of low molecular weight dextran? This study is an attempt to present the nature and frequency of these complications and to correlate these changes with pulmonary function during the first post-operative week. Pulmonary function was assessed using alveolo-arterial oxygen gradients (A-aDO2), arterio-alveolar carbon dioxide gradients (a-ADCO2), steady-state diffusing capacity for carbon monoxide (Dco.~.~), and physiological dead space-tidal volume ratios (VD/VT) in association with the roentgenologic changes. MATERIALS AND METHODS Nineteen patients were studied. They were clinically free of chest disease or overt uncontrolled congestive heart failure with the exception of one (case No. 11). Seventeen had coronary artery bypass grafts for refractory or intractable angina pectoris; one (No. 11) had mitral and aortic valve replacement because of refractory congestive heart failure and the remaining one (No. 15) had an aortic valve replacement. The clinical details are shown in Table I. All patients had cardiopulmonary bypass using a Sarns roller pump with the Bentley "Temptrol" reservoir and bubble oxygenator. Prime consisted of three units of heparinized homologous blood (3-5 days old) mixed with 1.5 to 2.0 litres of two-thirds 5 per cent G/W with one-third N/S. Blood flow was maintained at 9..2 liters/M s minute at 35 ~ C. with a minimum perfusion pressure of 60 mm Hg after adequate venting of left atrium and ventricle. During bypass the lungs were kept statically inflated with a mixture of nitrous oxide and oxygen 50:50 at 10 cm H20 pressure and humidified using an ultrasonic nebulizer. Three "sighs" were administered during most periods of bypass and again after the patient had come off bypass. The clinical and operative records were reviewed for factors which might have

After exposure of the hearts of eight dogs to a total of 45 min of myocardial ischaemia during cardiopulmonary bypass, mean left ventricular hydraulic output power (MLVP) decreased to an average of 49·5% of the original value and Vmax to 95·2% of its original value. During a constant intravenous infusion of isoproterenol, MLVP and Vmax expressed as a percentage of the depressed value noted after ischaemia, increased to an average of 229 and 164%, respectively. During epinephrine infusion MLVP and Vmax increased to an average of 171 and 123%, respectively, relative to the post-ischaemic levels. MLVP was shown to quantitate practically all of the mechanical output power of the left ventricle. Thus, if preload, afterload, and heart rate are controlled, MLVP should be representative of the contractile state of the left ventricle. Since changes of Vmax in response to positive and negative inotropic intervention did not correlate with MLVP, we concluded Vmax did not accurately reflect quantitative change of the contractile state of the left ventricle.

Three patients with aortic dissection originating from a thoracic aortic cannulation site are discussed and recommendations are made for preventing this complication.

Sixty-three infants with transposition of the great arteries (TGA) aged 3 weeks to 12 months, have had Mustard's operation between 1967 and 1973. Their weights ranged from 3.7 to 9.5 kilograms. Fifty-two had TGA and atrial septal defect (ASD), 10 had TGA and ventricular septal defect (VSD), and 1 had TGA, VSD, and left ventricular outflow tract obstruction (LVOTO). Fifty-eight infants were operated upon with cardiopulmonary bypass, while deep hypothermia and circulatory arrest was used in 5. Fifty of 52 infants with TGA and ASD survived the operation. In the group with complex transposition, 4 out of 10 infants with VSD survived the operation. The only infant who had TGA and LVOTO survived the operation after a prolonged postoperative period. Among 17 survivors in whom pericardium was used for the patch (1967 to 1970), fatal pulmonary venous obstruction occurred in 1. In a later group of 28 infants in whom Dacron was used, all survived the operation, but 10 developed SVC and/or IVC obstruction. This was severe enough to require operative revision in 9 (one death). Since September, 1972, pericardium has been used exclusively for the patch. Our early and late results confirm the view that early primary repair in patients with simple TGA is a preferable method of treatment

The Kety-Schmidt method of measuring coronary blood flow using radioactive iodoantipyrine as the indicator has been used in man after cardiopulmonary bypass and other states. However, the validity of this method has not been established. We found the method to be both precise and accurate in measuring left ventricular coronary flow in normal dogs. The highest precision of coronary blood flow measurement by this method was obtained by using only the successive 15 or 30 sec coronary sinus and arterial samples that gave the best exponential fit. This usually fell within the first 3 min of antipyrine infusion.

The screen filtration pressure (SFP) and its derivative, the screen filtration resistance (SFR), were measured in blood in the extracorporeal circuit of humans during cardiopulmonary bypass. It was confirmed that blood from the suction line had very high SFP and SFR. These were returned to normal by filtration through Dacron wool. During the first few minutes of bypass the SFR of venous blood was high, but thereafter it remained low. The SFR of oxygenated blood was elevated continuously during the procedure, especially after nearly 2 hours of bypass. Arterial blood consistently had a low SFR after Dacron-wool filtration. The high SFR values following oxygenation are interpreted as being due to particle (microemboli) production by the oxygenator. These were uniformly removed by a Dacron-wool arterial filter.

Twenty-six puppies, 4 to 6 weeks of age, underwent preoperative determination of alveolar ventilation, venoarterial shunting, static pulmonary compliance, and diffusion capacity. The animals were divided into four groups: Group I underwent a left thoracotomy alone for 3 hours and served as a control; Group II underwent total cardiopulmonary bypass for 1 hour with a membrane oxygenator; Group III underwent total cardiopulmonary bypass for 1 hour with a bubble oxygenator; and Group IV underwent total cardiopulmonary bypass for 3 hours with a membrane oxygenator. After the operation, pulmonary function studies were repeated in each animal. It was found that pulmonary function deteriorated in all groups. Alveolar ventilation and venoarterial shunting grew worse in the two groups that had been supported by the membrane oxygenator, whereas decrease in compliance seemed to be related to duration of the procedure. Diffusing capacity decreased equally in all groups.

In a series of 75 patients undergoing cardiac operations with the assistance of cardiopulmonary bypass (CPB), 15 patients were subjected to relatively large hypotensive stresses during CPB as measured by the depth and duration of the fall in cerebral perfusion pressure. Of these 15 patients, eight manifested cerebral dysfunction postoperatively ranging from temporary exacerbation of pre-existing focal neurological deficits to irreversible coma. In each of these eight cases, EEG disturbances which first appeared at the time of hypotensive episodes during CPB persisted postoperatively and correlated with the nature and evolution of the clinical deficit. In two of the patients who did not regain consciousness postoperatively, neuropathological studies revealed bilateral laminar cortical necrosis, primarily involving cerebral cortex in one case and cerebellar cortex in the other, with accentuation in arterial border zones. Of seven other patients who suffered comparable exposures to hypotension during CPB, none evidenced cerebral dysfunction postoperatively. The most important determinants of this selective vulnerability to low extracorporeal perfusion pressure appeared to be the "reperfusion" pressure established after the hypotensive episode, postoperative blood pressure and cardiac output, and brain temperature at the time of the hypotension. Advanced age and history of cerebrovascular insufficiency were the greatest risk factors among patient variables.

Experience with intracardiac surgery in infants indicates that for most anomalies the operative and late mortality after primary total correction is lower than the combined mortality after early palliation and delayed correction. In addition, there are secondary benefits of primary total correction in terms of reversal of retarded physical growth and social development and alleviation of parental anxiety. The relative merits of conventional cardiopulmonary bypass versus profound hypothermia, circulatory arrest, and limited cardiopulmonary bypass are as yet incompletely elucidated, particularly regarding the long-term effects of the second method on cerebral function. Indications for the use of each method will undoubtedly become clearer as reports of longer follow-up become available. At the University of Oregon Medical School, intracardiac operation using conventional cardiopulmonary bypass has been carried out in 108 infants under 2 years of age. Late hemodynamic studies and intellectual and social developmental testing indicate gratifying long-term results with this technique.

Between 1967 and 1973, 86 patients underwent total correction of transposition of the great arteries. There were 6 hospital deaths for an in-hospital survival of 93% with three late deaths. Seventy-two patients had repair with standard cardiopulmonary bypass and 14 infants were corrected with profound hypothermia and circulatory arrest. The incidence of postoperative dysrhythmia was less in the group in whom the coronary sinus was not incised but yet placed into the systemic venous return. Postoperative rhythm disturbance was greatest when the coronary sinus was widely opened and placed with the venous return. This observed decrease in incidence of atrial dysrhythmia may be related to not incising the coronary sinus and placing the sutures very superficial in the area between the sinus and the tricuspid valve.

A simplified method of performing coronary artery surgery without the use of blood is described. Not only is the use of blood substantially decreased by this method (71 per cent of our patients did not require blood), but the time of cardiopulmonary bypass is decreased since the proximal anastomoses are performed before bypass. This method has allowed us to operate upon critically ill patients in congestive failure, with marked left ventricular impairment and an ejection fraction of 0.10 to 0.20 (normal 0.70). The mortality rate in 33 such patients was 9 per cent (three deaths).

If cardiopulmonary bypass is done with a hypooncotic prime, the initial fall in colloid osmotic pressure in the patient is followed by an incomplete compensatory rise. The mechanism of this rise has been investigated by studying the time course of the specific activity and the concentration of 125I albumin activity in the plasma. Albumin specific activity fell at a rate greater than that measured in the control subjects, thus indicating an increased influx of albumin into the circulating blood volume. The concentration of labeled albumin in the patients, in sharp contrast to that in the control subjects, rose during bypass. This indicated an efflux of water from the circulating blood volume. It is concluded that both albumin influx and water efflux contribute to the rise in colloid osmotic pressure during bypass. It is further concluded that at the end of bypass approximately 40 per cent of the rapidly exchangeable extravascular albumin pool will have been transferred to the intravascular compartment, while approximately 1 L. of water will have been added to the interstitial fluid.

The acutely injured patient may require emergency thoracotomy as an integral part of his resuscitation. Thoracotomy in the emergency center for control of hemorrhage, cardiac compression, preservation of available fluid volume, and direct repair of critical injuries can be lifesaving. Between January of 1970 and December of 1972, over 5,000 emergency operations were performed for blunt and penetrating trauma at Ben Taub General Hospital. Emergency thoracotomy was required in approximately 300 cases. In 106 patients the urgency of their condition required thoracotomy in the emergency center. Among these 106 patients, 67% of those who arrived with discernible vital signs and whose injuries were limited to the intrathoracic organs, were resuscitated. There were 33 initial survivors, eight of whom had both intrathoracic and extrathoracic injuries. Long term survivors, discharged from the hospital, totaled 27. Cardiac wounds were successfully controlled in 20 patients. Thoracotomy in the emergency center for cardiac resuscitation was rarely successful when injuries were limited to extrathoracic organs. Urgent thoracotomy in the emergency center environment is an adjunct to resuscitation and allows control of reversible intrathoracic injuries. Autotransfusion, emergency cardiopulmonary bypass, fine screen filtration of transfused blood, and intravascular shunts have been applied as extensions of this life saving measure.

This study assesses the effects of ventricular distention during spontaneously and electrically maintained ventricular fibrillation on coronary blood flow distribution, myocardial metabolism, and ventricular performance. Distention of the spontaneously fibrillating, adequately perfused, heart causes a redistribution of left ventricular coronary flow away from the subendocardial region and results in biochemical evidence of ischemia and moderately impaired ventricular function. While electrical fibrillation alone causes these deleterious effects on coronary flow distribution, myocardial metabolism, and performance, distention of the electrically fibrillating heart accentuates the degree of subendocardial underperfusion and metabolic and functional impairment. We conclude that overstretching of muscle fibers by ventricular distention is not the only cause of impaired ventricular function following cardiopulmonary bypass.

Eleven cardiac operations are reported in which there was electroencephalographic and/or clinical evidence of seizure activity during cardiopulmonary bypass (CPB). In four patients seizure activity appeared after acute episodes of cerebral ischaemia resulting from either hypotension or pump-generated emboli occurring at the beginning of CPB, or from air embolism occurring at the end of CPB when the myocardium was closed and defibrillated. In the remaining seven patients the seizures appeared to result from the synergistic action of a toxic substance in the perfusate with pre-existing or CPB-induced alterations in cerebral physiology.

Plasma glucose, insulin, and potassium were measured in patients before, during, and after cardiopulmonary bypass surgery. Five per cent dextrose was used for the pump prime. In all patients, plasma glucose rose rapidly during bypass but insulin secretion was suppressed. The concentration of plasma growth hormone rose rapidly at this time. Five patients (Group II) received isoproterenol (Isuprel) intravenously immediately after cardiopulmonary bypass, and their plasma insulin rose to high levels, statistically significantly above those of the control group of 5 patients who did not receive isoproterenol. Administration of isoproterenol did not suppress the growth hormone levels. The mean level of serum potassium was lower in the Group II patients (high plasma insulin) at that time, but later, when insulin levels had fallen to resting values, their mean potassium level was above that of the control group in spite of their having received less potassium intravenously.

The safe period of anoxic arrest of the heart is related to its individual metabolic activity rather than to a specific time interval. The capacity of the heart to produce energy through anaerobic metabolism, on which survival depends, has been assessed in this study by continuous monitoring of intramyocardial carbon dioxide tension (Pco2). Two groups of 12 dogs each were placed on total cardiopulmonary bypass at 38° C. and 28° C., respectively. Anoxic arrest of the heart was produced by cross-clamping of the ascending aorta and venting of the left ventricle. Intramyocardial Pco2 was measured by a mass spectrometer, and carbon dioxide accumulation curves were plotted. An initial period during which the Pco2 increased in a linear fashion was followed by a period during which the rate of rise gradually decreased until a plateau was reached. If the arrest was terminated at the transition point between these two periods, all hearts could be resuscitated. If the arrest was terminated when the carbon dioxide accumulation curve had reached a plateau, none of the hearts could be resuscitated. These results are given in the text. Our technique defines a point at which anoxic arrest can be safely terminated. This point can be significantly extended by reducing the metabolic activity of the heart by moderate hypothermia.