Renal Artery Flow Velocity Research Articles

Fetal Renal Artery Doppler in Cases of Isolated Oligohydramnios: Can it Predict Adverse Neonatal Outcome?

Aims and Objectives: This study compares the fetal renal artery flow velocity waveforms of pregnancies complicated by oligohydramnios with normal pregnancies and to detect any statistically significant difference between the two Groups and to further determine the relationship of these findings with neonatal outcome. Method: All pregnant women in IIIrd trimester with gestational age between 32 weeks to 36 weeks with isolated oligohydramnios were included as cases (Group-A). Normal IIIrd trimester pregnancies (Group-B) with gestational age between 32 weeks to 36 weeks served as controls between the study period of Jan 2018 to Dec 2019. Results: The mean umbilical artery pulsatility index (PI; mean ± SD) in patients of Group-A was 1.0730 ± 0.0637 and that of patients in Group-B was 1.0012 ± 0.1400 with P = 0.0023. The mean umbilical artery S/D ratio (mean ± SD) in patients of Group-A, was 2.9120 ± 0.2476 and that of patients in Group-B was 2.5135 ± 0.2751 with P < 0.0001. The mean renal artery PI (mean ± SD) in patients of Group-A was 2.5863 ± 0.2608 and that of patients in Group-B was 2.4737 ± 0.2648 with P = 0.0240. The mean birth weight and Apgar Score were also found to be statistically significant between the two Groups. Conclusion: The distribution of mean renal artery PI and umbilical artery PI, in oligohydramnios cases, was higher in comparison to normal cases. As the Neonatal intensive care unit (NICU) admission was higher in the oligohydramnios group with abnormal renal artery doppler indices, our recommendation is that abnormal fetal renal artery Doppler indices are an indication for early referral to tertiary care setup, as the majority of these neonates will require NICU care postdelivery.

Impact of different conditions of breath-holding on the results of renal artery Doppler sonography: A pilot study.

To investigate the impact of different breath-holding conditions on the results of renal artery Doppler ultrasonography (RADS). In 45 healthy volunteers, we performed RADS examination during breath-holding while breathing naturally and after a deep inspiration. We measured and compared peak systolic flow velocity (PSV), end diastolic velocity (EDV), and resistance index (RI) of the right (RRA) and left (LRA) renal artery, and PSV, EDV, RI, acceleration time and acceleration index (AI) of the right and left interlobar arteries. The RRA and LRA PSV were, respectively, 76 ± 13 cm/s and 77 ± 15 cm/s under natural breathing and 93 ± 18 cm/s and 89 ± 24 cm/s after deep inspiration (P ≤ .001). The RRA and LRA EDV were also greater at deep inspiration (P < .001 and P = .019, respectively). There was no significant difference in RRA or LRA RI. The PSV, RI, and AI of the right and left interlobar arteries were greater after deep inspiration (P ≤ .001), without difference in AI. Breath-holding conditions may influence Doppler measurements of renal artery flow velocity and should be reported and taken into account.

Effects of intravenous bolus injection of nicorandil on renal artery flow velocity assessed by color Doppler ultrasound

BackgroundPrevious animal studies have shown that a potassium channel opener, nicorandil, provokes vasodilation in renal microvasculature and increases renal blood flow. We conducted a clinical study that aimed to evaluate the effect of nicorandil on renal artery blood flow in comparison with nitroglycerin by using color Doppler ultrasound. MethodsThe present study enrolled 40 patients with stable coronary artery disease who had no renal arterial stenosis and renal parenchymal disease. The patients received intravenous administration of nicorandil (n=20) or nitroglycerin (n=20). Before and after the administration, renal artery blood flow velocity was measured by color-guided pulsed-wave Doppler. ResultsThe peak-systolic, end-diastolic, and mean renal artery blood flow velocities before the administration were not different between the nicorandil group and the nitroglycerin group. The peak-systolic (79±15cm/s to 99±21cm/s, p<0.001; and 78±19cm/s to 85±19cm/s, p=0.004), end-diastolic (22±5cm/s to 28±8cm/s, p<0.001; and 24±6cm/s to 26±6cm/s, p=0.005) and mean (41±6cm/s to 49±9cm/s, p<0.001; and 43±9cm/s to 45±9cm/s, p=0.009) renal artery flow velocities increased significantly in either group. The nominal changes in the peak-systolic (20±10cm/s vs. 7±8cm/s, p<0.001), end-diastolic (5±4cm/s vs. 2±3cm/s, p=0.001), and mean (8±5cm/s vs. 2±2cm/s, p<0.001) renal artery blood flow velocities were significantly greater in the nicorandil group compared with the nitroglycerin group. ConclusionIntravenous nicorandil increased renal artery blood flow velocity in comparison with nitroglycerin. Nicorandil has a significant effect on renal hemodynamics.

Predictive value of second and third trimester fetal renal artery Doppler indices in idiopathic oligohydramnios and polyhydramnios in low-risk pregnancies: a longitudinal study.

Intermittent assessment of renal artery flow velocity waveforms during the early stages of pregnancy may help in predicting changes in amniotic fluid dynamics. The current study sought to determine the relation of renal artery and umbilical artery flow velocity waveforms with normal pregnancies and pregnancies complicated by either polyhydramnios or oligohydramnios. Renal and umbilical artery Doppler values were evaluated at 22, 28 and 34 weeks' gestation in 300 low-risk pregnant women with singleton pregnancies. Pulsatility index (PI) and resistance index (RI) were recorded and the amniotic fluid volume was evaluated. Three groups were formed according to the amniotic fluid volume at birth. Group I consisted of 264 pregnant women with normal amniotic fluid, group II included 30 pregnant women with oligohydramnios and group III included six pregnant women with polyhydramnios. Doppler parameters were compared between the groups and within each group according to gestational age. Renal artery PI values were higher in group II than group I at 22 weeks, 28 weeks and 34 weeks. The PI value at 28 weeks' gestation was statistically significant (P = 0.011). At 28 weeks' gestation, group II also had higher umbilical artery PI and RI values than group I. An increase in renal artery PI develops in early pregnancy before the development of oligohydramnios. In pregnancies developing polyhydramnios, renal artery PI was lower; however, our study included a small number of women with polyhydramnios.

A Randomized, Controlled, Double-Blind Crossover Study on the Effects of 1-L Infusions of 6% Hydroxyethyl Starch Suspended in 0.9% Saline (Voluven) and a Balanced Solution (Plasma Volume Redibag) on Blood Volume, Renal Blood Flow Velocity, and Renal Cortical Tissue Perfusion in Healthy Volunteers

We compared the effects of intravenous administration of 6% hydroxyethyl starch (maize-derived) in 0.9% saline (Voluven; Fresenius Kabi, Runcorn, United Kingdom) and a "balanced" preparation of 6% hydroxyethyl starch (potato-derived) [Plasma Volume Redibag (PVR); Baxter Healthcare, Thetford, United Kingdom] on renal blood flow velocity and renal cortical tissue perfusion in humans using magnetic resonance imaging. Hyperchloremia resulting from 0.9% saline infusion may adversely affect renal hemodynamics when compared with balanced crystalloids. This phenomenon has not been studied with colloids. Twelve healthy adult male subjects received 1-L intravenous infusions of Voluven or PVR over 30 minutes in a randomized, double-blind manner, with crossover studies 7 to 10 days later. Magnetic resonance imaging proceeded for 60 minutes after commencement of infusion to measure renal artery blood flow velocity and renal cortical perfusion. Blood was sampled, and weight was recorded at 0, 30, 60, 120, 180, and 240 minutes. Mean peak serum chloride concentrations were 108 and 106 mmol/L, respectively, after Voluven and PVR infusion (P = 0.032). Changes in blood volume (P = 0.867), strong ion difference (P = 0.219), and mean renal artery flow velocity (P = 0.319) were similar. However, there was a significant increase in mean renal cortical tissue perfusion after PVR when compared with Voluven (P = 0.033). There was no difference in urinary neutrophil gelatinase-associated liopcalin to creatinine ratios after the infusion (P = 0.164). There was no difference in the blood volume-expanding properties of the 2 preparations of 6% hydroxyethyl starch. The balanced starch produced an increase in renal cortical tissue perfusion, a phenomenon not seen with starch in 0.9% saline.

Systemic Arterial Hemodynamics and the “Renal Resistive Index:” What is in a Name?

Systemic Arterial Hemodynamics and the “Renal Resistive Index:” What is in a Name?

A Randomized, Controlled, Double-Blind Crossover Study on the Effects of 2-L Infusions of 0.9% Saline and Plasma-Lyte® 148 on Renal Blood Flow Velocity and Renal Cortical Tissue Perfusion in Healthy Volunteers

We compared the effects of intravenous infusions of 0.9% saline ([Cl] 154 mmol/L) and Plasma-Lyte 148 ([Cl] 98 mmol/L, Baxter Healthcare) on renal blood flow velocity and perfusion in humans using magnetic resonance imaging (MRI). Animal experiments suggest that hyperchloremia resulting from 0.9% saline infusion may affect renal hemodynamics adversely, a phenomenon not studied in humans. Twelve healthy adult male subjects received 2-L intravenous infusions over 1 hour of 0.9% saline or Plasma-Lyte 148 in a randomized, double-blind manner. Crossover studies were performed 7 to 10 days apart. MRI scanning proceeded for 90 minutes after commencement of infusion to measure renal artery blood flow velocity and renal cortical perfusion. Blood was sampled and weight recorded hourly for 4 hours. Sustained hyperchloremia was seen with saline but not with Plasma-Lyte 148 (P < 0.0001), and fall in strong ion difference was greater with the former (P = 0.025). Blood volume changes were identical (P = 0.867), but there was greater expansion of the extravascular fluid volume after saline (P = 0.029). There was a significant reduction in mean renal artery flow velocity (P = 0.045) and renal cortical tissue perfusion (P = 0.008) from baseline after saline, but not after Plasma-Lyte 148. There was no difference in concentrations of urinary neutrophil gelatinase-associated lipocalin after the 2 infusions (P = 0.917). This is the first human study to demonstrate that intravenous infusion of 0.9% saline results in reductions in renal blood flow velocity and renal cortical tissue perfusion. This has implications for intravenous fluid therapy in perioperative and critically ill patients. NCT01087853.

Local intra-renal fenoldopam infusion causes greater increases in renal artery flow velocity than systemic intravenous fenoldopam infusion: a pilot study.

Typical intravenous fenoldopam doses result in only minimal increases in renal blood flow and glomerular filtration, while higher doses are associated with systemic hypotension. We hypothesized that local infusion of fenoldopam into the renal arteries would enhance renal perfusion with reduction of arterial hypotension. Of 20 patients with renal impairment undergoing coronary intervention, 10 received infusion of fenoldopam into the left renal artery (IR). Doses were increased progressively (0.1,0.2,0.4 mcg/kg/min) at 5 min intervals, separated by a 10 min "wash out" period without drug application. Average and maximum peak renal blood flow velocities (APV and MPV) were measured using a flow-wire. A comparison group of 10 patients received renal flow measurements during IV fenoldopam application using the same escalating dose protocol without a drug-free period.The average peak flow velocity increased from 29.9+/-10.7 cm/s in the IR group and 25.9+/-7.7 cm/s in the IV group at baseline (p=ns) to 50.0+/-13.1 cm/s (IR) versus 31.0+/-11.9 cm/s (IV) at the maximum dose level (p=0.011). There was a trend towards attenuated reduction of the systemic pressure in the IR group compared to the IV group. In patients with renal insufficiency, local renal infusion of fenoldopam resulted in an approximately 50% increase in renal artery velocities without substantial blood pressure reduction compared to IV fenoldopam.

Changes in fetoplacental vessel flow velocity waveforms following maternal administration of betamethasone.

To determine the timing of the onset of the umbilical artery flow velocity waveform changes following maternal administration of betamethasone in pregnancies complicated by umbilical artery absent end-diastolic flow, and to explore whether these changes are associated with flow velocity waveform changes in other fetoplacental vessels. This was a prospective study of 12 women with pregnancies complicated by umbilical artery absent end-diastolic flow. Flow velocity waveforms were recorded from the umbilical artery, fetal middle cerebral artery, renal artery, aorta and ductus venosus, before and after maternal betamethasone administration, using real-time pulsed wave Doppler. In all 12 pregnancies, the administration of maternal betamethasone was followed by the return of end-diastolic flow within 24 h. End-diastolic flow was first observed at 4 h and was present in all women studied at 8 h. In addition, there was a statistically significant decrease in the pulsatility index in the fetal aorta at 8 h and the middle cerebral artery at 24 h. No change was observed in the ductus venosus or the renal artery flow velocity waveforms. The findings suggest that, in pregnancies complicated by absent end-diastolic flow in the umbilical artery, maternally administered betamethasone induces a return in umbilical artery end-diastolic flow as early as 4 h, along with widespread vasodilatation throughout the fetoplacental vasculature.

Comparison of Steerable Continuous-Wave Versus Pulsed-Wave Doppler Ultrasonography to Renal Artery Angiography in Diagnosing Renal Artery Stenosis

Pulsed-wave Doppler ultrasonography is widely used to noninvasively diagnose renal artery stenosis. The use of steerable continuous-wave Doppler has never been tested. We compared pulsed and steerable continuous-wave Doppler ultrasonography, demonstrating that although both methods are highly sensitive for severe stenoses, continuous-wave Doppler shows a better sensitivity for mild to moderate stenoses.

Sequential external counterpulsation increases cerebral and renal blood flow

The purpose of this study was to evaluate the effect of sequential external counterpulsation (SECP) on cerebral and renal blood flow. The effect of SECP on carotid and renal artery blood flow was studied in 35 and 18 patients, respectively. With a portable unit, cuffs were applied to the calves and thighs, sequentially inflated with air at the onset of diastole, and deflated at the onset of systole. Carotid and renal artery Duplex studies were performed during intermittent SECP. Flow velocity and flow velocity integral were measured at baseline and during SECP. Diastolic augmentation of carotid and renal artery flow velocity was observed in all patients. The mean carotid flow velocity integral increased by 22% from 27.7 ± 1.8 cm to 33.1 ± 2.3 cm ( P = 0.001). The mean renal artery flow velocity integral increased by 19% from 21 ± 1 cm to 25 ± 1 cm ( P = 0.0001). With SECP, a new diastolic Doppler flow velocity wave was observed, with an average peak carotid diastolic flow velocity of 56 ± 4 cm/sec and an average peak renal artery diastolic flow velocity of 40 ± 2.5 cm/sec. This diastolic wave was 75% (carotid) and 68% (renal) as high as the systolic wave during SECP. In addition, with SECP the systolic wave increased by 6% and 8% in the carotid and renal artery, respectively ( P = 0.02 and 0.006, respectively). In conclusion, SECP significantly increases carotid and renal blood flow. This noninvasive, harmless treatment may be useful to support patients with decreased cerebral and renal perfusion.

779-5 The Effect of Endothelial Stimulation on the Renal Circulation in Patients with Chronic Heart Failure

Impairment of renal blood flow (RBF) is common in pts with chronic heart failure (CHF) and may lead to renal dysfunction. Although abnormal RBF may be due to depressed cardiac output, individual correlations are weak and suggest for local vasoregulatory mechanisms. We assessed the role of endothelium (END) derived nitric oxide (NO) on the renal circulation in 12 pts with CHF. Acetylcholine (ACh) (END-dependent vasodilator) and nitroglycerin (NTG) (END-independent vasodilator) were infused in a randomized, crossover design into the renal artery (RA). Effects on renal arterial (RAP) and renal venous IRVP) pressures, RA cross sectional area (CSA), RBF and renal vascular resistance (RVR) were studied. CSA was measured by intravascular ultrasound and RA flow velocity by a Doppler flow wire. The results were as follows:Empty CellRAP mmHgRVP mmHgCSA mm2RBF ml/minRVR dynes.cm-5BLl91 ± 410 ± 1.03.7 ± 0.3610 ± 4611171 ± 1295ACh 10-8M88 ± 410 ± 0.93.8 ± 0.4*1015 ± 118*6685 ± 723* 10-7M87 ± 410 ± 0.83.9 ± 0.3*l360 ± 154*5188 ± 805* 10-6M90 ± 411 ± 0.94.0 ± 0.3*1499 ± 181*4868 ± 660*BL291 ± 310 ± 1.03.5 ± 0.3635 ± 3010275 ± 931NTG 10-7M91 ± 410 ± 1.037 ± 0.3†782 ± 808842 ± 1060 10-6M95 ± 410 ± 1.03.9 ± 0.3†753 ± 789972 ± 1415 10-5M89 ± 310 ± 1.13.9 ± 0,3†755 ± 588595 ± 809*p &lt; 0.05 vs Baseline 1 (BL1)†p &lt; 0.05 vs Baseline 2 (BL2) p &lt; 0.05 vs Baseline 1 (BL1) p &lt; 0.05 vs Baseline 2 (BL2) 1) Exogenous NO (NTG) causes a vasodilatory effect on renal conductance but not on resistance vessels; 2) In contrast, stimulation of endothelium-derived NO results in a significant vasodilation of both conductance and resistance vessels. This effect leads to reduction in RVR and increase in RBF and may be an important regulatory mechanism of renal circulation in pts with CHF.

Fetal renal artery flow velocity waveforms in the presence of congenital renal tract anomalies

Colour Doppler flow mapping of the renal arteries and subsequent pulsed Doppler measurement of impedance to flow in these vessels were attempted in 33 fetuses with postnatally confirmed renal pathology. The majority presented with unilateral or bilateral hydronephrosis (n = 21) and bilateral renal agenesis (n = 8). Renal artery blood flow could be visualized in all, except for the eight cases of bilateral renal agenesis. Bilateral flow velocity recordings were collected in six out of 12 cases of bilateral hydronephrosis and in five out of nine cases of unilateral hydronephrosis. The pulsatility index (PI), as a measure of downstream impedance, was in the normal range in 16 out of 18 kidneys (88 per cent) in bilateral hydronephrosis and in 12 out of 14 kidneys (85 per cent) in unilateral hydronephrosis. The PI was significantly higher in severe hydronephrosis compared with mild hydronephrosis. In four cases of unilateral multicystic kidney, the PI was always higher on the affected side. Colour Doppler flow mapping and pulsed Doppler evaluation may be helpful in our understanding of renal vascularization in renal pathology and in confirming the diagnosis of renal agenesis.

Inability of color and spectral Doppler to identify fetal renal obstruction.

Color flow Doppler imaging was used to obtain fetal renal artery flow velocity waveforms in 130 normal fetuses at various gestational ages to build a database for the establishment of normal ranges for the Pulsatility Index in the fetal renal arteries throughout pregnancy. Twenty-nine cases of fetal renal tract dilation (greater than 5 mm anteroposterior diameter of the renal pelvis) of various causes were investigated. We found that measurements of the pulsatility index were not significantly altered from the normal range, so that color flow Doppler does not appear to be helpful in the differential diagnosis of fetal renal dilation.

Renal artery flow velocity waveforms in normal and hypertensive pregnant women.

Pregnancy is associated with marked changes in renal functions. Hypertensive disorders in pregnancy are frequently accompanied by deteriorated renal functions and by pathological lesions in the glomeruli. Using a pulsed Doppler ultrasound, we measured the resistance to flow in the renal artery in normal and hypertensive pregnant patients. We performed 176 pulsed Doppler ultrasound measurements of the renal arteries at various stages of gestation in 60 low risk pregnant patients. Another 111 Doppler measurements of the same vessels were obtained from 80 hypertensive pregnant patients throughout the third trimester. Twenty-six patients had preeclampsia, 35 patients had pregnancy-induced hypertension, and 19 patients had chronic hypertension. The resistance to flow in the renal arteries (expressed by the resistance index, RI) did not change significantly during pregnancy. The renal artery RI was not significantly different between the hypertensive group (RI = 0.61 +/- 0.06) and the low risk group (RI = 0.605 +/- 0.04). The RI values were also similar in all hypertensive patient categories: preeclampsia (RI = 0.62 +/- 0.07), pregnancy-induced hypertension (RI = 0.60 +/- 0.06), and chronic hypertension (RI = 0.61 +/- 0.05). The renal artery RI did not correlate with the severity of the hypertensive disease or with the status of renal functions. The outcome of pregnancy was worse in patients with abnormally elevated resistance index in the renal arteries. Patients with abnormally elevated resistance to flow in the uterine arteries also had a significant increase in the resistance index in the renal vessels.(ABSTRACT TRUNCATED AT 250 WORDS)

Renal artery flow-velocity waveforms in normal and hypoxemic fetuses

Color flow mapping was used to identify the fetal renal artery and to obtain flow-velocity waveforms. A reference range of the fetal renal artery pulsatility index with gestation was constructed from a cross-sectional study of 114 appropriate for gestational age fetuses of 17 to 43 weeks' gestation. The pulsatility index decreased linearly with gestation, indicating a fall in impedance to flow, and presumably an increase in renal perfusion. The renal artery pulsatility index was also determined in 18 small-for-gestational-age fetuses and was higher than the appropriate-for-gestational-age group. The small-for-gestational-age fetuses also had fetal blood sampling performed by cordocentesis. A significant, direct correlation was found between blood oxygen deficit and increased renal artery pulsatility index.

Renal artery flow velocity analysis: a sensitive measure of experimental and clinical renovascular resistance

Renal artery flow velocity analysis has recently been shown to be an indicator of renal parenchymal resistance. Noninvasive measurement of graded renovascular resistance is investigated with experimental models of canine gel microsphere embolization ( n = 15), canine renal allografts ( n = 4), and clinical renal allografts ( n = 6). Intraoperative pulsed Doppler recordings were made on the canine renal artery simultaneous to pressure and flow measurements with sequentially increasing resistance. Transcutaneous echo-Doppler (Duplex) measurements were made on acute patient renal allografts following chemical estimation of renal function. Noninvasive prediction of renovascular resistance in the experimental canine gel microsphere and allograft models correlates with invasive recordings of volume flow (pressure nearly constant), r = 0.93 and r = 0.90, respectively. Duplex estimation of clinical renal allograft resistance and chemical prediction of renal function are similarly interdependent, r = 0.81. Directional arterial flow analysis may be a useful indicator of native and acute allograft renovascular resistance.

Phasic Renal Artery Flow Velocity During Ventricular Tachycardia in Man: A Possible Mechanism of Renal Shutdown

Cardiac arrhythmias, particularly ventricular tachycardia, have long been recognized as a cause of tubular necrosis, anuria and renal failure.1 The graphic display of phasic, instantaneous blood flow velocity in the renal arteries of unanesthetized, conscious human subjects has afforded an opportunity to study the effect of transient or chronic arrhythmias on the renal circulation.