Caval long‐circuit in the dog

Abstract

In order to further studies on the relations between the vascular and cerebrospinal fluid pressures begun in the cat (Grundy & Howarth, 1957;Howarth, 1962), it was found necessary, because of its more suitable intracranial vascular architecture, to perfuse the dog. In addition, it was felt that if a satisfactory preparation of this type could be devised, it would greatly facilitate physiological and pharmacological study of the vascular system of the whole animal, since with but little modification such a preparation would allow simultaneous study of blood flows through selected vascular beds. A new procedure for caval long-circuit in the dog was developed, and in this paper it is proposed to describe the characteristics of the preparation and discuss the measurements of caval flows. METHODSThe object of these experiments was to long-circuit blood passing via the venae cavae through an apparatus before returning it to the heart. In the first series of experiments the technique was substantially that described for the cat (Howarth, 1962). After each experiment the apparatus was dismantled and carefully washed, first in detergent (dilute Teepol), then in running water followed by distilled water. The glass parts were heat-sterilized and the tubing dried in air. The apparatus was then re-assembled and before use washed by successively circulating several litres of sterile distilled water and Ringer-Locke solution. The animal was prepared with clean but not sterile technique.In view of the results obtained in the dog with this technique, it was decided to attempt to reach the same objective in a spontaneously breathing animal under sterile conditions and with minimal surgery. The procedure for the modified caval long-circuit was as follows.Extracorporeal circuit. A diagram of the system is shown in Fig.

The effect of haemorrhage on venous return and regional blood flow in the anaesthetized cat

“…Data on regional blood flows in the cat are very few. The proportion of the venous return draining from the superior vena cava in our experiments is in close agreement with other work in both cat and dog (Greenway & Howarth, 1963). Our mean hepatic blood flow of 48 ml./kg .…”

“…Our values for the venous return (minus coronary and bronchial flows) are in good agreement with cardiac output determinations in the cat reported in the linastratur (aer, Cunningham &i Pearce, 1952;Cross, Groom, Mottram &ftRowlands, 1957;Grundy&rv Howarth, 1957)s As in the dog (Greenway A Howarth, 1963), comparison between different animals 868 HAEMORRHAGE AND REGIONAL BLOOD FLOW and different species is difficult, due to the lack of a close correlation between cardiac output and body weight or surface area, the varying effects of the anaesthetic agents and the varying durations for which the animal has been anaesthetized. Data on regional blood flows in the cat are very few.…”

“…The extracorporeal circuit was similar to, but smaller than, that described for the dog (Greenway & Howarth, 1963). Blood draining from the four segments of the venae cavae passed to outflow cylinders (F, Fig.…”

“…The technique of long-circuiting the venae cavae in the cat and dog has been used by several workers and the method was discussed critically by Greenway & Howarth (1963). It provides a useful and inexpensive means of studying venous return and regional blood flows.…”