Haemodynamic effects of precordial or carotid ultrasound application on the dog

Ultrasound (1.09 MHz, 1 to 2 W/cm2) was applied on the thoracic wall or on the neck of the anaesthetized, artificially ventilated dog. The heart rate, stroke volume and cardiac output remained almost unchanged during both applications. The aortic and pulmonary arterial pressures increased by 7 to 9 mmHg. Pulmonary arterial wedge pressure increased. The right atrial mean and aortic and pulmonary arterial pulse pressures did not change. The observed changes except the rise of wedge pressure returned to the control values within 5 min after the application. The present findings suggest an increase in systemic vascular and pulmonary arterial resistances in connection with both methods of ultrasound application. The precordial application was associated with pooling of blood in the pulmonary circuit. Since the ultrasound non-selectively affects several receptors and structures the final role of the sympathetic nervous system can be evaluated after experiments with isolated targets and selected denervations.