Ventricular output in conscious dogs following acute vagal blockade.

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Abstract
The effect of vagal blockade on ventricular output, mean right and left atrlal pressures, heart rate, stroke volume, and mean arterial pressure was studied in 8 conscious dogs without the use of blocking drugs. A coll was implanted around the right vagus nerve trunk in the neck and the left vagus nerve was isolated and cut. Electromagnetic flow probes or Doppler ultrasonic flow probes were implanted around the root of the aorta and catheters were placed in the right and left atria under sterile surgical conditions. Vagal blockade was accomplished on 24 occasions in the 8 animals by pumping cold alcohol through the coil around the vagus nerve trunk. Control measurements were taken prior to and during vagal blockade. When the vagus nerve was cold blocked, the ventricular output rose significantly as did the mean arterial pressure. The right atrlal pressure tended not to change while the mean left atrlal pressure decreased. As the heart rate increased, a linear decline in stroke volume occurred, and this decline could be described by the equation for a straight line. The changes in ventricular output and stroke volume are discussed.