No abstract

Available evidence suggests that cerebral vascular resistance in man is primarily under chemical control. Past studies indicate that neurogenic stimuli, hormonal influences and most drugs have little ability to dilate cerebral vessels significantly. The potent chemical regulators which dilate cerebral vessels have been shown to be: 1) anoxia and 2) either CO2 retention or decrease in the pH of arterial blood (1, 2). Using the nitrous oxide technique, Kety found increased cerebral blood flow (CBF) in subjects breathing 10 per cent 02. He also showed that the increased CBF of respiratory acidosis produced by breathing 5 per cent or 7 per cent CO2 was associated with increased CO2 content and a lowered pH of arterial blood and decreased CBF of respiratory alkalosis following hyperventilation with a lowered CO2 content and elevated pH.Because of a tendency to an increase in CBF in late stages of diabetic acidosis, it was suggested originally by Kety, Polis, Nadler, and Schmidt (3) that the pH level might be more important than the CO2 content in regulation of cerebral vascular tone. This viewpoint has been stated by others (4,5). Some doubt about this interpretation is suggested by earlier findings of Bronk and Gesell (6). In 1927, they found that intravenous injection of sodium carbonate and sodium bicarbonate increased blood flow in the femoral and the carotid arteries of dogs under anesthesia.The present study attempts to separate the effect on cerebral vessels of changes in pH and CO2 spectively, were produced in man. The changes which occurred in CBF and cerebral vascular resistance were noted and compared to the changes previously reported after respiratory acidosis and alkalosis. METHODThe subjects studied were patients on the Medical Service of Duke Hospital. They were convalescing from a variety of illnesses and cannot be considered as a group of normal people. Six subj ects were patients at Butner State Hospital. These patients were ill with schizophrenia and presented no physical illnesses. Metabolic alkalosis was produced by intravenous infusion of 1000 ml. of 3 per cent NaHCO8 or 1000 ml. of 1.2 per cent NaHCOs over a period of sixty minutes. Metabolic acidosis was established by slower infusion of approximately 350 cc. of 0.8 per cent NHCl intravenously over a period of 60 to 90 minutes. NH4Cl caused slight hyperpnea, and nausea occurred if the speed of the infusion was increased. Changes in pulse rate and blood pressure did not occur if the drip rate was kept below the nausea threshold.The effect of changes in blood volume was determined by administering 1000 ml. of 0.85 per cent NaCl solution intravenously over a period of one hour. The effects of both volume change and hypertonicity on the cerebral circulation were observed after the intravenous administration of 1000 ml. of 2 per cent NaCl solution over a period of one hour.Cerebral blood flow (CBF) was measured, using the nitrous oxide technique described by Kety and Schmidt (7) and modified by Scheinberg and Stead (8). Oxygen differences in vol...

Evidence is presented which indicates that in certain instances pulsus alternans may be abolished or diminished in the presence of advanced congestive heart failure. The observations suggest that in severe congestive failure the ventricular filling pressure may increase to the point where it causes the diastolic stretch of the left ventricle to be more equal from one beat to the next. This in turn would bring about more uniform systolic ejections and hence ventricular alternation would disappear or be lessened in degree. P ULSUS ALTERNANS is considered a grave sign of heart disease, indicating myocardial insufficiency.1 Recent observations indicate that this phenomenon can be profoundly influenced by changes in the venous return to the heart. During the past two years we have encountered 12 patients with pulsus alternans and have noted that in certain instances advanced congestive failure may also influence pulsus alternans. We wish to report detailed studies of three of these patients. MATERIAL AND METHODSThree patients, all of whom showed pulsus alternans initially and who were on accepted treatment for cardiac failure were observed. One, who had rheumatic aortic insufficiency-, was in heart failure following treated subacute bacterial endocarditis. Two observations were made on this man; the first, when he showed early signs and symptoms of left heart failure, and the second, w-hen he was in intractable congestive failure seven months later. The remaining two patients had hypertensive heart disease with severe congestive failure as evidenced by dyspnea at rest, orthopnea, paroxysmal nocturnal dyspnea, venous distention, liver engorgement and peripheral edema. After the pulsus alternans was demonstrated, both were taken off all treatment for heart failure and were put on an unrestricted sodium diet for a period of 7 to 10 days. They were followed both symptomatically and by weight. Repeated

The theory, instrumentation and technique of a thermal method for measuring the blood flow in a small volume of tissue is described. With present instrumentation the volume sampled is about 4 or 5 mm3. The technique has been applied to the relation between tissue temperature and skin blood flow in the calf of the leg. In 25 observations on 3 subjects, values ranging from 1.3 to 82 x 10-4 gm of blood per gm of tissue per second have been obtained. An extension of the technique has led to the measurement of the temperature coefficient of flow, (1/F)(ΔF/ΔT), when flow is influenced by very local temperature changes. A mean value of +39%/° with a range of -57% to +81%/° was found. Periodic fluctuations in tissue temperatures of the frequencies of the heart beat and respiration are described. Submitted on August 29, 1958

It has been found that retinal arterial reactivity to oxygen is diminished in persons with retinal arteriosclerosis, and that cerebral blood flow and the increment in cerebral flow upon inhalation of carbon dioxide are diminished in persons with cerebral arteriosclerosis. The present study demonstrates that there is a significant positive correlation between retinal arterial reactivity on the one hand, and cerebral blood flow and reactivity, on the other. This finding is taken to mean that arteriosclerosis severe enough to affect measurements of this sort is apt to involve retinal and cerebral vessels together.