Observations on the cerebro‐spinal fluid pressure in the perfused cat preparation

Caval long‐circuit in the dog

“…The method of caval long-circuit used successfully for the cat (Grundy & Howarth, 1957;Howarth, 1962) proved unsatisfactory for the dog. The reasons for this are uncertain.…”

“…As in the perfused cat (Grundy & Howarth, 1957), the size of the total caval flow in our experiments was an inaccurate index of the physiological state of the perfused dog. Further, the mean values obtained by ourselves and others with whose work we are familiar vary between 900 and 1400 ml./ min, yet the preparations include those with gross disturbance of the vascular variables (Wegria, Rojas & Wiggers, 1943;Rashkind, Lewis, Henderson, Heiman & Dietrick, 1953;our open-chest preparations) and those with relatively stable vascular variables and the capacity for rapid recovery (our closed-chest experiments).…”

“…It should be noted that in the second of these three groups of experiments the azygos vein was intact, while in the other two it was tied. In the cat the superior vena cava carried 25 %, of the combined caval flow excluding azygos flow and 29-30 % when the flow through the azygos vein was included (Grundy & Howarth, 1957;Howarth, 1962).…”

“…It has been shown that the cardiac output of both cats (Baxter, Cunningham & Pearce, 1952; Grundy & Howarth, 1957) and dogs (Nash, Davis & Woodbury, 1956; declines during the course of prolonged pentobarbitone anaesthesia and many of our dogs had been anaesthetized for 3-4 hr before total caval long-circuit was established. In intact dogs the mean cardiac outputs after 3-4 hr of pentobarbitone anaesthesia were 1300 ml./min by a dye-dilution method, 1700 ml./min by a pulse-contour method and 1400 ml./min by a Fick procedure (Nash et al 1956;, while in our preparations the mean total venous return which omits azygos, coronary and bronchial flows was 963 ml./min.…”

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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.

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