Instantaneous aortic blood flow measurement with range-gated Doppler flowmeter in anesthetized rat

The availability of a range-gated Doppler flowmeter system enabled us to construct miniaturized probes using piezoelectric crystals that emit an 8 MHz signal and receive the reflected sound waves from passing blood cells. The finished flow probe are 4 mm long and 3 mm in external diameter with lumen diameter appropriate to be placed around the ascending aorta in the rat. The accuracy of the Doppler method in measuring cardiac output in the rat was established by the demonstration of a significant correlation between cardiac output simultaneously measured from ultrasonic (Qd) and thermodilution (Qt) procedures in anesthetized Wistar rats (Qd = 0.55, Qt - 6.67 cm3/min, r = 0.69, p less than 0.001). An average Qd determination is 52.5% +/- 16% of average Qt. From aortic blood pressure and phasic aortic blood velocity, we have compared hemodynamic and cardiovascular functions in 15 spontaneously hypertensive rats and in 15 control Wistar-Kyoto rats under pentobarbital sodium anesthesia. The present study demonstrates that phasic aortic blood flow can be quantified easily and accurately in anesthetized rats by using a range-gated Doppler flowmeter and an implantable perivascular flow probe, and should provide a relatively simply method for investigating hemodynamic characteristics in models of disease such as ventricular hypertrophy and hypertension.