| Background and Objective:A simple and reliable method for quantifying regional renal tissue blood perfusion is not currently available due to the complication of renal vessel structure and renal function. There is an important meaning in quantifying regional renal tissue perfusion since that the functions of kidney are influenced in large part by the change of actual regional tissue nutrient blood flow. Contrast-Enhanced Ultrasound (CEU) as a new method has been used to quantify solid tissue blood perfusion. However, the accuracy of CEU to quantify renal tissue perfusion need further determine. Furthermore, dopamine (DA) and noradrenaline (NE) have been commonly used in daily clinics as vascular active drugs, but the effects of DA and NE on renal tissue perfusion are not clear. Therefore, the purposes of this study were to evaluate the ability of CEU in quantifying renal blood perfusion and the effects of DA and NE on renal tissue perfusion. Methods:After induction of anesthesia successfully, 10 experimental dogs were incubated and ventilated. Both femoral veins and the right femoral artery were exposed and cannulated with 7F catheters. An incision was made in the left flank to expose the left kidney and its vascular supply. An ultrasonic probe was placed proximally on the renal artery. Blood pressure, heart rate and the left renal artery flow (RAF) were required and CEU were performed at baseline and during different doses of DA and NE. DA and NE wereadministered in random. 3 incremental doses of DA (3, 8 and 16ug/kg/min) and 3 incremental doses of NE (0.2, 0.6 and 1.0 ug/kg/min) were intravenously infused. In order to avoid the mutual effect between DA and NE, 30 minutes interval was required between the both drugs administration. CEU was performed during a continuous venous infusion of microbubbles, pulsing interval (PI) was progressively increased from 0 to 10 second. Regions of interest (ROIs) were carefully selected in the cortex and medullar. Using the Video intensity (VI) analyzing system, VI in the ROIs were automatically measured and then background-subtracted. PI versus background-subtracted VI plots were generated and fitted to an exponential function: Y=A (1-e- B t), where A is the plateau VI representing blood volume fraction, and B represents mean microbubble velocity. Blood flow was calculated by multiplying A by B. At the end of the experiment, renal weight was accounted. Normalized RAF (ml/min/g) was calculated using RAF (ml/min) divided by renal weight (g). Results:As compared to baseline, a dose-depend increase in ultrasonic flow probe-derived normalized RAF was showed with DA up to a dose of 8ug/kg/min (P<0.05). Above this dose, the increase in the normalized RAF was attenuated (P<0.05). At baseline and during low-, middle- and high-doses of DA, the normalized RAF was 1.26+0.17ml/min/g, 2.01+0.17 ml/min/g, 2.45+0.21 ml/min/g and 1.63+0.26ml/min/g, separately. As expected, the increases in CEU-derived cortical nutrient blood flow (A*B) were similar to the increases in the normalized RAF in the presence of DA. At baseline and during low-, middle- and high-doses of DA, the CEU-derived cortical blood flow (A*B) was 93.98+10.73, 119.30+10.85, 147.93+9.46 and 108.38+10.36, separately. In the presence of low-, middle- and high-doses of NE, a dose-depend progressive decrease in the normalized RAF compared with baseline was seen (P<0.05). Again, the same dose-depend decrease was found in CEU-derived cortical nutrient blood flow (A*B) during NE. At baseline and during low-, middle- and high-doses of NE, the normalized RAF was1.26+0.13 ml/min/g, 1.15+0.11 ml/min/g, 1.01+0.14 ml/min/g and 0.87+0.12 ml/min/g, separately. Most importantly, an excellent positive correction was seen between ultrasonic flow probe-derived normalized RAF and CEU-derived cortical nutrient blood flow (y=38.60x+42.73, r=0.86, p<0.01).In the presence of low-, middle- and high-doses of DA, CEU-derived B was significantly higher in the cortex compared to baseline (P<0.05). However, CEU-derived A was significantly higher...
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