A New Technic for the Continuous Recording of the Cardiac Output. ∗

Abstract

The output of the heart, or a portion of it, has been measured directly in the anesthetized animal with different types of flowmeters inserted either into the venae cavae (1,2) or the aorta (3,4). Recently Seely and Gregg (5) designed a technic for the measurement of the pulmonary artery outflow by means of an electromagnetic rotameter. The technic described in this paper permits the continuous recording with an electromagnetic rotameter(6,7) of the output of the left ventricle in the anesthetized dog with cerebral circulation intact.

In dogs anesthetized with sodium pentobarbital, the chest is opened through a midsternal incision. Under artificial respiration, the brachiocephalic trunk, a segment of the left subclavian artery close to the aorta, a segment of both common carotid arteries and a segment of the thoracic aorta distal to the left subclavian artery are dissected free. Heparin is then administered, first a dose of 5 mg per kg of body weight, then 3 mg per kg every half hour. As seen in Fig. 1, the aortic end of the left subclavian artery A is first connected to the tubing B leading into the flowmeter (rotameter) C. Then the cephalic end of the right carotid artery D is cannulated and thereby connected to the tubing F coming from the flowmeter C. At this time, the blood flows from the aorta G into the right carotidartery D via the left subclavian artery A, inflow tube B, flowmeter C and outflow tube F. The left common carotid artery E is then also cannulated. At this point, the aortic end of the brachiocephalic trunk H is cannulated and connected to the inflow tube B. The aorta is then ligated at J, just beyond the origin of the left subclavian artery, then cannulated at K and connected to the outflow tube F.