E. B. Brown

Influence of Respiratory Acidosis on EGG and Pressor Responses to Epinephrine, Norepinephrine and Metaraminol.∗:

Summary and Conclusions 1. Sympathomimetic agents were administered to intact dogs under conditions of respiratory acidosis and at normal blood pH. Arterial pressure responses and electrocardiograms were obtained. In the presence of respiratory acidosis, the pressor responses were somewhat diminished and ECG abnormalities were absent or minimal as compared to the control state. 2. The same agents were administered to dogs subjected to total cardiac by-pass. Pressor responses under conditions of respiratory acidosis were uniformly much less in these animals than responses subsequently obtained in the same animals in which the arterial blood pH was at or near normal values.

Changes in Patterns of Seasonal Growth of Microtus Pennsylvanicus

A field study of growth, in terms of both linear dimensions and weight, was made by successively trapping the small winter—active mammals found in a study area in a region with persistent winter snow cover. The animals trapped were primarily Microtus pennsylvanicus, with some data also on Blarina brevicauda, Clethrionomys gapperi, and Peromyscus sp. The reliability of the field measurements was determined by comparing successive measurements made on individual animals within short time spans. The results of these comparisons indicate that linear measurements can be made accurately on live, conscious animals in the field, and that linear measurements are much more reliable than weight measurements. Microtus pennsylvanicus young born in the spring and early summer reach adult size in 12 weeks or less. These animals undergo a fall loss in weight. Animals born in middle to late summer stop growing in the fall, maintain their weight and linear dimensions throughout the winter, and resume growth again in the spring. Blarina brevicauda individuals grow little in linear dimensions after entering the trappable population and do not appear to lose weight in the fall.

Role of hyperkalemia in production of ventricular fibrillation following hypercapnia.

Summary and Conclusions 1. Dogs regularly show an increase in plasma potassium concentration during breathing of 30% and 40% CO2 mixtures. Immediately following return to air breathing, there is a further sharp rise in this concentration. This secondary rise reaches a peak after 5 minutes of air breathing. 2. Concentration of plasma potassium following 4 hrs of high CO2 breathing is not as high as that which is necessary to produce fibrillation or arrest when KCl solution is administered as an intravenous drip to normal or acidotic dogs. 3. Rapid return to air breathing following 30 minutes of high CO2 breathing does not produce cardiac arrhythmias, ventricular fibrillation, or cardiac arrest in dogs. However, when this rapid elevation in blood pH and/or fall in pCO2 takes place in the presence of sub-lethal but elevated plasma potassium concentrations, cardiac arrest or ventricular fibrillation may occur. Although this does not provide an explanation of the mechanism involved, it appears that the combination of elevated but sub-lethal plasma potassium concentration and a rapid fall in CO2 tension and/or hydrogen ion concentration, work together to produce the damage to the heart.

Plasma ultrafiltrable magnesium in respiratory alkalosis and acidosis.

Summary (1) Ultrafiltrable magnesium shows a significant increase within 25 minutes after cessation of hyperventilation in dogs as compared to the sample taken during hyperventilation, whereas total magnesium showed no changes. (2) Total and ultrafiltrable magnesium showed no significant changes during respiratory acidosis, as compared to the initial sample. A significant decrease in level of ultrafiltrable magnesium after 25 minutes on return to air breathing, as compared to the sample taken during 30% CO2 breathing, was noted. A shift of magnesium ion intracellulary is a possible explanation. (3) The results obtained in in vitro experiments show that increased phosphate level and pH changes, under the conditions of the experiments, show no effect on ultrafiltrable magnesium level, in contrast to changes previously observed with respect to ultrafiltrable calcium.

Maintenance of Respiratory Function with Isolated Lung Lobes During Cardiac Inflow Occlusion.

Summary 1. Dogs withstood and recovered from 30 minutes of total inflow occlusion to the right heart with extracorporeal cardiorespiratory maintenance at an average flow of 35 cc/kg/minute. 2. Biologic oxygenators (autologous and homologous lung lobes) and a pump (Sigma-motor) were used and the following precautions seemed essential (a) patency of the pulmonary veins—i.e. no cannulization whatever, (b) depulsator in pulmonary artery perfusion limb of the circuit, (c) care as to ventilatory mechanics of the isolated lobes. 3. The “open” system employed herein permitted rather exact balance between venous aspiration from bypassed dogs and arterial return to the dogs, and enabled flow measurements to be made. Note added in proof. Since submission of this manuscript, human blood has been perfused through the isolated dog lung with flows up to 1400 cc/minute, and the clinical applicability of this system (pump-biological oxygenator) as a means of cardiorespiratory maintenance during cardiac by-pass has been tested by the successful closure of a traumatic interventricular septal defect in a 55 kg male. In this patient the heart was partially by-passed for 20 minutes and totally by-passed for 15 minutes.

Plasma potassium changes during rebreathing in the dog.

Summary Plasma potassium was determined on dogs before and during 90 minutes of rebreathing, and immediately following return to air breathing. Potassium concentration rose gradually with increasing CO2 tensions during the first 60 minutes of rebreathing and remained essentially constant for the last 30 minutes. On changing from the high CO2 concentration to air breathing, a further rapid rise in plasma potassium concentration appeared. No evidence of a transient early rise in potassium concentration was observed.