Local thermodilution: a reliable technique for estimating renal blood flow in the rabbit

1. A thermistor probe designed for determination of renal blood flow in rabbits, consisted of a fast-responding bead thermistor and an injection port which was also used to measure renal venous pressure between injections. 2. By an in vitro calibration system, actual measured flow (Qa) correlates well with the thermodilution calculated flow (Qc), where Qc = 0.99 Qa + 4.9 (r = 0.97, n = 42). 3. The renal blood flow (RBF) as determined by the thermodilution technique in 3 control groups was 53 +/- 3 (8), 60 +/- 6 (8), and 62 +/- 3 (3) ml/min/kidney or about 9% of the cardiac output. 4. Hypovolemia (-10%) reduced RBF by 19% from the control value, whereas, hypervolemia (+10%) did not alter RBF. 5. Smoke-induced apnea resulted in hypertension (+30%) and bradycardia (-39%), and was associated with changes in RBF (-55%) and renal vascular resistance (+183%). 6. We conclude that the local thermodilution technique is a relatively easy and reliable method for estimating RBF in rabbits.