Howard L. Gadboys

Homologous-Blood Syndrome during Extracorporeal Circulation in Man

IT has previously been demonstrated that circulating blood volume significantly diminishes after perfusion despite careful replacement of all measured blood loss.1 Clinical and experimental evidenc...

Experimental and clinical aspects of surgical heart block

Summary Surgical heart block has assumed a major experimental and clinical position in the overall picture of heart block. Anatomical studies of the conduction system have revealed moderately consistent patterns in various cardiac anomalies, but sufficient variations exist to influence the development of block during cardiac surgery. Moreover, the local arterial and venous circulations may be of significance. Many experimental methods have been employed to interrupt the conduction system including asphyxia, heating, crushing, application of drugs, suture ligation, and incision. Physiologic studies of these animals have demonstrated early reduction of cardiac output with eventual partial restoration toward normal, and evidence of heart failure frequently appears. The clinical incidence of surgical heart block during ventricular septal defect repair has been as high as 30 per cent in the past. In one series with permanent heart block, 14 of 19 patients succumbed. Heart block has been reported following operation for many lesions including low lying interatrial septal defect, A-V canal, ventricular septal defect, Tetralogy of Fallot, single ventricle, corrected transposition, congenital subvalvular aortic stenosis, and calcific aortic stenosis. Moreover, traction on the interventricular septum, local hemorrhage, and division of anomalous coronary arteries have also been responsible for surgical heart block. Bundle branch block, although clinically of minor importance, not infrequently occurs during cardiac surgery. Technics for prevention of surgical heart block in recent years have lowered the incidence of permanent disability to less than 4 per cent. Principal factors have been avoidance of the posteroinferior border of ventricular septal defects by utilization of the septal leaflet attachments of the tricuspid valve. cardiac hypothermia, crossclamping of the aorta during placement and tying of sutures and increased utilization of patches to reduce tension. Vital staining and conduction locator technics have met with only limited enthusiams. Major therapeutic advances in the treatment of surgically induced heart block have occurred with the perfection of percutaneous pacemakers for acute management and totally implantable units for long-term pacing. Temporary experimental success has been observed with nodal and endocrine transplants.

Base line for left heart catheterization

Abstract 1. 1. X-ray and somatic measurements show that the left atrium is at approximately the same elevation with the subject supine and lying on the right or the left side. The elevation is equal to 1 2 the chest thickness measured at the second costochondral junction. 2. 2. Left atrial and ventricular diastolic pressures recorded in relation to any fixed base line are the same in all three positions. 3. 3. A base line at an elevation above the table equivalent to 1 2 of chest thickness at the second or fourth costochondral junction minimizes variability of pressures recorded in subjects of different sizes. Hydrostatic error is probably least if the second costochondral reference level is used. 4. 4. A base line fixed in relation to the table top offers some advantage in simplicity with no loss of meaning and little sacrifice of consistency from patient to patient. Chest dimensions and reference level should be stated to permit correlation with measurements made against any other base line. 5. 5. Previously reported “normal” pulmonary “capillary” pressures provide a basis for judging the normality of left atrial and ventricular diastolic pressures measured with patients supine or lying on the right or left side. 6. 6. Hydrostatic pressure differences are not recorded against a common base line. Vertical displacement of pulmonary arterial catheter tip introduced no problem in interpretation of pressure records.

Anaphylactoid Shock from Blood Exchange as a Factor in Experimental Cardiopulmonary Bypass

During 75 cardiopulmonary bypass experiments in dogs, a fall in arterial pressure or a tendency for the animal to take up blood from the extracorporeal circuit was noted at the onset of perfusion. To determine the mechanism of these reactions, the effect of homologous blood exchange in the dog was studied using a variety of techniques, including total and partial cardiac bypass. METHODS In the 75 preliminary total cardiopulmonary bypass studies a vertical-screen oxygenator and rotary pumps were used. The priming volume was approximately 3 litres and blood from four or five donors was required. Subsequent total bypass experiments were performed with a rotating-disc oxygenator and a pump driven by compressed air (Hufnagel, McAlinden, Vardar, DeVenecia, and Real, 1958). The volume of this circuit was somewhat smaller and only three donors were needed in most experiments. The two partial cardiac bypass techniques used were veno-arterial pumping and left heart bypass. Venoarterial pumping consists of transferring the superior vena caval return to the lower aorta without oxygenation (Hamer, Dickson, and Dow, 1959), and left heart bypass involves pumping oxygenated blood from the left atrium to the aorta. A simple circuit with a closed venous reservoir and a capacity of 800 ml. was used for both these procedures, and was usually filled with blood from one donor. Blood exchange with constant volume was performed by placing 200 ml. of blood from each of one to four donor animals in a closed flask suspended above the recipient and connected to cannulae in the femoral artery and vein. When the cannulae were opened pressure in the flask rose 25 to 30 mm. Hg and blood exchange occurred, the volume of blood in the flask increasing by less than 50 ml. Mongrel dogs weighing 15 to 25 kg. were used throughout. Donor blood was obtained from animals lightly anaesthetized with pentothal (15 mg./kg. body weight) by arterial exsanguination into bottles