Masanaru Toyoda

Measurement of Cerebral Hemispheric Blood Flow by Intracarotid Injection of Hydrogen Gas: VALIDATION OF THE METHOD IN THE MONKEY

To develop a reliable method for measuring hemispheric blood flow and metabolism in man, the clearance of hydrogen was measured in the cerebral lateral sinus blood of macaque monkeys after intracarotid injection. Hydrogen is an inert gas and its clearance from cerebral venous blood depends solely on arterial inflow, and since it is highly diffusible, rapid equilibrium is maintained between brain tissue and its capillary-venous blood. Cerebral venous clearance curves for hydrogen appeared to provide accurate and reproducible measures of cerebral blood flow. A bolus of 0.2 to 0.3 ml of saline saturated with hydrogen was injected rapidly into the internal carotid artery. Electrodes placed on the cortex showed that the bolus was almost exclusively distributed to the ipsilateral cerebral hemisphere. Blood flow of each hemisphere was calculated by Meier and Zierlers formula based on the Stewart-Hamilton principle, as well as by compartmental analysis. The values obtained for hemispheric blood flow were in good agreement with average cerebral blood flow measured by inhalation of hydrogen using the Fick principle. Values for hemispheric blood flow were the same whether the intracarotid injection of hydrogen was rapid or slow.

A new method for continuous sampling of cerebral venous blood without extracranial contamination in man: Bilateral transbrachial catheterization of the cerebral venous sinuses

IN ORDER to accurately measure cerebral blood flow and metabolism, reliable samples of cerebral venous blood must be obtained without extracranial contamination. A new method will be described which appears to have attained these objectives with minimum discomfort to the patient. Before describing this, the history of various methods for sampling cerebral venous blood will be briefly reviewed. In 1927, Myerson et a1.l introduced a technique for percutaneous puncture of the internal jugular bulb by the use of a needle for obtaining samples of cerebral venous blood. The needle was introduced at the tip of the mastoid process and advanced through the edge of the sternocleidomastoid muscle perpendicularly to the skin until dark venous blood was aspirated. In 1945, Gibbs et a1.2 utilized this approach for obtaining cerebral venous blood simultaneously f o m both internal jugular veins. The technique was modified slightly by Kety and Schmidt3 in 1945 when they introduced the nitrous oxide method for quantitative determination of cerebral blood flow and metabolism, using the Fick principle. Since then, this method of direct puncture, or minor modifications of it, have been used in many thousands of measurements of cerebral blood flow and metabolism. Shenkin et al.4 showed that brood obtained by puncturing the internal jugular bulb with the Myerson technique is contaminated by at least 3% of blood from extracerebral sources. They, and others, also showed that at least two-thirds of the blood from each jugular vein was derived from the ipsilateral hemisphere. Scheinberg, in 1950: measured cerebral blood flow and metabolism after puncturing the internal jugular vein by the Myerson method and inserting a catheter 5 cm. below the bulb in order to compare the results obtained with blood withdrawn from this point with

Evidence for a Pasteur effect regulating cerebral oxygen and carbohydrate metabolism in man

BEFORE RATIONAL THERAPY of occlusive cerebral vascular disease can be instituted, the nature of the metabolic accompaniments of cerebral ischemia in man should be well defined. I t is well known that some neurological deficits resulting from occlusion of a cerebral blood vessel recover, while others persist. If the metabolic changes responsible for recovery of neurological function in stroke were well understood, then it is possible that therapy could be directed along lines that would hasten restitution of neurological function. At the present time, some investigators have already begun to define certain patterns of disordered cerebral blood flow and metabolism that may result from cerebral ischemia and may be influenced by alterations of cerebral blood flow and oxygen delivery.*-10 Progress to date may be briefly summarized as follows: It is generally agreed that, in occlusive cerebral vascular disease, cerebral blood flow, oxygen consumption. and energy production are reduced and cerebral vascular resistance is increased. Evidence is accumulating that cerebral lactate production is also increased, particularly in acute cases. Cerebral blood flow and oxygen delivery may be temporarily reduced by hyperventilation, and this has been shown to be accompanied by an increase in cerebral lactate production. It has been postulated that the increased cerebral lactate production caused by cerebral ischemia is due to reduction of oxygen available to the brain, resulting in increased anaerobic glucose metabolism. This may be called thc