Steven M. Horvath

The effects of age on finger temperature responses to local cooling

Abstract Finger temperature measurements were made before, during, and after a period of immersion of the hand in a 10° C. water bath on healthy individuals varying in age from 6 to 83 years. The hunting reaction tended to occur less frequently with the advancing age of the subjects. Similarly the rates of cooling and rewarming of the finger appeared to be influenced by the age of the individual. It is suggested that these differences in response to a local cold stimulus were related to changes in vascular reactivity.

Cardiac dynamics and coronary blood flow consequent to acute hemorrhage.

Abstract The rapid removal of a large volume of blood from an animal leads to a lowered arterial pressure, cardiac output, coronary blood flow and an increased extraction of oxygen by the myocardium. These responses are not greatly modified during the first hour of adjustment to this stress. The major corrective responses observable at this time were increases in cardiac output and coronary vascular resistance accompanied by a decrease in total peripheral vascular resistance. The coronary blood flow had not returned to its normal value although the fraction of the cardiac output delivered to the left ventricular muscular mass was essentially normal.

Aortic obstruction and cardiac output.

Abstract Sudden complete occlusion of the thoracic aorta at the level of the fourth intercostal space resulted in a marked rise of aortic pressure above the occlusion, an elevation of pulmonary arterial systolic and diastolic pressures, a slowing of the heart rate, and essentially no change in cardiac output. This latter effect is somewhat spurious since the same cardiac output was now being delivered to a much smaller vascular bed. Therefore, it represented effectively an increase in the cardiac output for the prevailing situation. Atropinization of the experimental animals prior to the induction of the occlusive episode did not alter the pattern or degree of response except in two particulars, i.e., little change in pulmonary arterial pressures and a tendency for the cardiac output to decrease. The adjustments following release of the occlusion were similar in both groups of animals, with the exception of a significant fall in cardiac ouput during the first postrelease minute in the atropinized animals.

Pressure curves from the coronary sinus of the dog

Abstract Pressure curves recorded from the coronary sinus (at a depth of 1 to 2 cm.) of fifty-six anesthetized dogs were analyzed in respect to their absolute values and general contours. The relationship of pressure values to certain hemodynamic factors and events occurring in the cardiovascular system was investigated. Pressures in the coronary sinus were low, 6.1 and 1.9 mm. Hg for systolic and diastolic values, respectively. A statistically significant correlation was found between coronary sinus diastolic and right ventricular end diastolic pressures. Lower correlations were obtained between coronary sinus diastolic and mean pressures and all pulmonary pressures, as well as between coronary sinus mean pressure and total left ventricular blood flow. The pressure curves recorded were extremely variable, not only in different animals, but in the same animal during the course of an experiment. Although it was possible to group these pressure tracings into five major patterns, considerable variation was observed within each main type.

Hepatic Blood Flow in Chronically Splenectomized Dogs

Summary Hepatic blood flow of chronically splenectomized dogs estimated by the bromsulphalein method was found not to be significantly different than that found in normal intact anesthetized and unanesthetized dogs.

Catheterization of the coronary arteries of intact dog

Abstract Catheterization of the coronary arteries in the intact animal has been successfully accomplished in 12 animals. “Wedged” pressures have values similar to those observed in the arteriolar end of peripheral capillaries. “Free” pressures in the coronary artery are essentially the same as in the larger arteries. Catheters have remained in these vessels for periods exceeding 3 hours without producing evidence of injury. It is not, however, a procedure without danger. Potential applications of this technique to further understanding of cardiac dynamics have been illustrated by preliminary data from experimental work now in progress.

Comparison of blood cell counts from major vessels in the dog.

Summary Blood cell counts were compared in samples drawn simultaneously from the aorta, right ventricle, superior vena cava, caudal vena cava, hepatic vein, and/or peripheral veins in dogs. The study was done on normal and splenectomized dogs, either un-anesthetized or anesthetized with pentobarbital. No differences in erythrocyte or leukocyte distributions were demonstrated as a result of anesthetization or splenectomy. The erythrocyte and leukocyte counts were the same in arterial and venous blood samples and in venous samples from different major vessels. Some factors are discussed which may be responsible for apparently contradictory reports concerning cell count distribution in circulating blood.

Blood gas and plasma ion concentrations of asphyxiated hypothermic and normothermic rats

1. 1. Cardiac punctures were made in four groups of rats during and after the time they were subjected to the procedures described for the induction of hypothermia with subsequent cardiac arrest. 2. 2. The absolute amounts of oxygen were low and the carbon dioxide was high in the arterial and mixed venous blood. Even under these situations a large A-V oxygen and carbon-dioxide difference remained. 3. 3. Although animals in all groups were acidotic, fibrillation was not observed on the electrocardiographic recordings during immersion of the animals of Groups AAH (ambient asphyxiation followed by hypothermia) and HAH (hypothermic asphyxiation followed by hypothermia) in the ice baths. 4. 4. A decreased buffering capacity of the blood, as evidenced by the BHCO3/H2CO3 ratio, was prominent especially in those groups ambiently asphyxiated. 5. 5. Plasma K+ increased at least 80 per cent in all groups. However, plasma sodium exhibited a significant decrease only in Groups HA (hypothermic asphyxiation) and HAH. 6. 6. It is suggested that one of the limiting factors for the induction of hypothermia with cardiac arrest is the absolute amount of oxygen available to the animal after respiratory arrest.