Effect of Neosynephrin ∗ on Gaseous Exchange of the Brain. †

Abstract

The effects of neosynephrin on the cerebral arterio-venous oxygen difference were studied on large dogs, narcotized with Dial,† 0.5 cc per kilo. The cranium was trephined above the superior longitudinal sinus, the trachea was exposed and cannulated and both femoral arteries were also exposed. The first pair of femoral arterial and cerebral venous blood samples was collected while the animals were breathing air and the second after they had come to equilibrium while respiring a gas mixture containing approximately 11% oxygen. Neosynephrin was then administered and when blood pressure had risen significantly the third pair of blood samples was collected. Blood flow of the cerebral longitudinal sinus was determined by Daly's modification of the thermostromuhr. 1 Blood pressure was recorded by means of a cannula inserted into a femoral artery. Blood samples were analyzed for oxygen and carbon dioxide contents and oxygen capacity, 2 for glucose, 3 and for lactic acid. 4 The oxygen tension of the blood was estimated by using the nomogram of Bock et al. for humans 5 which may also be applied to dogs. 6 In addition, the effects of neosynephrin on the cerebral arteriovenous oxygen difference were determined on dogs breathing room air. In most experiments 2 cc of 1% neosynephrin solution were administered intramuscularly, portions of the 2 cc being injected at various sites. In a few experiments, however, 1-10,000 neosynephrin solution was injected intravenously and in these instances the amount of neosynephrin injected was much smaller than with intramuscular injection.

In Table I are presented the results of 2 out of 4 experiments on animals breathing reduced concentrations of oxygen. In all 4 experiments the blood became more alkaline as a result of the hyperpnea produced by breathing 11% oxygen and then less alkaline after injections of neosynephrin. Neosynephrin increased the concentrations of lactic acid and glucose in the blood.