Cardiac output during cardiopulmonary bypass. Animal experiments as a guide to flow rate.

Superior total body perfusion during cardiopulmonary bypass in dogs is achieved by duplicating, in each individual case, the actual operative cardiac output, rather than by relying on the currently recommended perfusion flow rates.A highly accurate method of measuring the cardiac output is presented using the gated sinewave electromagnetic flowmeter. Simplicity and sensitivity of the method enable the operator to measure the flow in situ (in the intact canine ascending aorta) and thus to determine a truly representative cardiac output before the cardiopulmonary bypass is effected. An adjustable hydraulic pump in conjunction with the electromagnetic flowmeter is used to substitute the natural cardiac action in order to maintain the normal hemodynamic state by providing a pulsatile flow of proper magnitude. The procedure is technically simple and, supported by favorable experimental evidence, is recommended for clinical use in open heart operations.