Renal Blood Flow Index Research Articles

New Classification for the Combined Assessment of the Fractional Excretion of Urea Nitrogen and Estimated Plasma Volume Status in Acute Heart Failure.

Background The fractional excretion of urea nitrogen (FEUN) has been used as a renal blood flow index related to cardiac output, and the estimated plasma volume status (ePVS) as a body fluid volume index. However, the usefulness of their combination in acute decompensated heart failure (HF) management is unclear. We investigated the effect of 4 hemodynamic categories according to the high and low FEUN and ePVS values at discharge on the long-term prognosis of patients with acute decompensated HF. Methods and Results Between April 2011 and December 2018, we retrospectively identified 466 patients with acute decompensated HF with FEUN and ePVS values at discharge. Primary end point was postdischarge all-cause death. Secondary end points were (1) the composite of all-cause death and HF readmission, and (2) HF readmission in a time-to-event analysis. The patients were divided into 4 groups according to the high/low FEUN (≥35%, <35%) and ePVS (>5.5%, ≤5.5%) values at discharge: high-FEUN/low-ePVS, high-FEUN/high-ePVS, low-FEUN/low-ePVS, and low-FEUN/high-ePVS groups. During a median follow-up period of 28.1 months, there were 173 all-cause deaths (37.1%), 83 cardiovascular deaths (17.8%), and 121 HF readmissions (26.0%). The Kaplan-Meier curve analysis showed that the high-FEUN/low-ePVS group had a better prognosis than the other groups (log-rank test, P<0.001). In the multivariable Cox regression analysis, the low-FEUN/high-ePVS group had a higher mortality than the high-FEUN/low-ePVS group (hazard ratio, 2.92 [95% CIs, 1.73-4.92; P<0.001]). Conclusions The new classification of the 4 hemodynamic profiles using the FEUN and ePVS values may play an important role in improving outcomes in patients with stable acute decompensated HF.

Modelling acute antibody-mediated rejection of human kidney transplants using ex-vivo warm machine perfusion.

Transplant rejection is a major cause of graft loss and morbidity. Currently, no human models of antibody-mediated rejection (AMR) exist, limiting mechanistic investigation and organ-specific targeted therapy. Here, using 12 human kidneys and ex-vivo normothermic machine perfusion, we demonstrate phenotypes of AMR after addition of antibodies against either human HLA class I or blood group antigens (A, B), thus modelling clinical AMR that can follow HLA incompatible (HLAi) or blood group incompatible (ABOi) transplantation. Discarded human kidneys with wide ranging demographics and cold ischaemia times (11-54h) were perfused with red blood cells and fresh frozen plasma (FFP) as a source of complement/coagulation factors. For the HLAi model, 600μg of W6/32 anti-class 1 HLA antibody was added to the circuit (time '0'). For the ABOi model, high titre FFP of the relevant blood group antibody was added. Renal blood flow index (RBFi, mL/min/100 g), C3 desArg, prothrombin fragments 1+2 and histology were determined. Our endpoints included haemodynamic changes, thrombosis, and biopsy proven complement deposition. Compared to control kidneys perfused without anti-donor antibodies, both models demonstrated haemodynamic collapse after antibody perfusion with only the HLAi model showing glomerular C4d deposition. We show that a clinically relevant human kidney model of AMR is feasible, and anticipate that these models, with refinements, could provide a basis to test different strategies to prevent AMR. The Rosetrees and Stonygate Trust, The Royal College of Surgeons of England Fellowship Grant, NIHR Biomedical Research Centre/KCL Early Career Grant, Kidney Research U.K.

Vascular effects of combined vacuum interferential therapy in patients with urolithiasis after extracorporeal shock wave lithotripsy

To study the combined vacuum-interference therapy effect on the renal blood flow in patients with urolithiasis after ECSWL. Forty patients aged 33 to 64 years old with urolithiasis after ECSWL were included in the study. Patients were assigned into two groups by simple randomization. Starting the second day after ECSWL, along with drug therapy, the patients of the main group (n=20) received vacuum-interference therapy with the carrier frequency of 5 kHz, frequency range 80-150 Hz, and the vacuum of 0.3-0.4 bar for 15 min daily, 6-8 procedures in total. Patients in the control group (n=20) received antibacterial and anti-inflammatory drug therapy, the same as the main group. To evaluate the severity of impaired renal blood flow due to nephrolithotripsy, we studied renal blood flow by the basic hemodynamic characteristics of renal ultrasound dopplerography (USDG): renal blood flow indices at the level of renal, segmental, interlobar, and arch arteries, including measurement of systolic linear blood flow velocity (Vps) and diastolic blood flow velocity (Vsd), as well as pulsatility index (PI) and resistance index (RI). The ultrasound examination prior to ECSWL revealed a statistically significant increase in all studied parameters. Thus, Vsd in renal arteries was increased by 32.7% (p<0.01) and 17.8% (p<0.05), respectively; in segmental arteries by 14.5% (p<0.05) and 29.5% (p<0.05), respectively; in interlobar arteries by 14.5% (p<0.05) and 29.5% (p<0.05), respectively, and in the arcus arteriosus by 10.7% (p<0.05) and 21.4% (p<0.05), respectively; the renal vein blood flow was within the reference range. When assessing PI in UL patients before lithotripsy, a statistically significant increase in all studied indices was also observed: in the renal arteries by 19.0% (p<0.05), in the segmental arteries by 12.5% (p<0.05), and in the interlobar and arch arteries by 11.6% (p<0.05) and 11.8% (p<0.05), respectively. After the treatment course, the most pronounced change was observed in the patients of the main group, in which all indices differed from the reference values only by 3.5-8.3%. It is important to note an increase in linear velocity in the renal vein by 21.4% (p<0.05), indicating a significant improvement of renal blood flow due to improved venous outflow and increased arterial inflow in the renal arteries. In the control group patients, statistically significant improvement was observed only for systolic and diastolic blood flow velocity, as well as the renal vein blood flow velocity, which increased by 22.1% (p<0.05), 6.3% and 17.8% (p<0.05), respectively; the other parameters remained unchanged. When assessing PI and RI values after the treatment course, the most marked improvement was also observed in the main group of patients, in which all indices were close to the reference values (p<0.05). In the control group patients, the indices were 11.6-14.0% higher than reference values (p<0.05). According to obtained data, it was concluded that vacuum interference therapy has a pronounced vascular effect that promotes an earlier recovery of blood flow and normalization of the kidney function in patients with urolithiasis after extracorporeal lithotripsy and can be recommended for routine clinical practice.

Diagnosis and Treatment of Renal Artery Stenosis in China in the Era of Donation After Cardiac Death.

BackgroundThe aim of this study was to investigate the clinical features and treatment strategies of transplant renal artery stenosis (TRAS) with kidneys from donation after cardiac death (DCD).Material/MethodsWe collected the clinical data of donors and recipients of single-center DCD-induced TRAS from January 2015 to June 2017.ResultsAll the 8 cases of TRAS were from hypertensive cerebrovascular accident DCD-originated kidneys. The mean donor age was 53.5 (45~57) years, with mean BMI 27.8 (26.4~32.3) kg/m2, atherosclerosis index 5.8 (4.9~7.0), and renal atherosclerotic plaque. Clinical features of TRAS were: refractory hypertension with elevated serum creatinine >50%, and negative urine protein and occult blood. Ultrasound of transplanted kidneys showed renal blood flow index 0.49 (0.43~0.55). Angiography confirmed the diagnosis of renal artery trunk or secondary branch stenosis. There were 2 cases of moderate stenosis and 6 cases of severe stenosis. Six patients underwent stent implantation and 2 patients underwent balloon dilatation. Seven patients had serum creatinine recovery after interventional therapy during follow-up. The transplanted kidney of 1 patient ruptured 6 h after interventional therapy and was then resected.ConclusionsThe incidence of TRAS with hypertensive cerebrovascular accident DCD-originated kidneys is relatively high, which is a warning to kidney transplant physicians. Digital subtraction angiography (DSA) is the most reliable diagnostic means of TRAS and can be performed concurrently with intervention therapy. If the donor has severe atherosclerosis, plaques that are visible to the unaided eye in the renal artery trunk should be removed as completely as possible.

Elevated Renal Oxygen Extraction During Open Abdominal Aortic Aneurysm Repair Is Related to Postoperative Renal Dysfunction.

Open abdominal aortic aneurysm repair is often followed by elevated plasma creatinine, likely due to impaired renal blood flow. We evaluated whether postoperative elevation in creatinine relates to renal oxygen extraction during surgery as an index of renal blood flow and also monitored frontal lobe oxygenation. For 19 patients (66 ± 10 years; mean ± SD) undergoing open infrarenal abdominal aortic aneurysm repair, renal oxygen extraction was determined by arterial and renal vein catheterization. Near-infrared spectroscopy determined frontal lobe oxygenation. During surgery mean arterial pressure (from 102 ± 14 to 65 ± 11 mm Hg; P < .0001), arterial hemoglobin (from 7.7 ± 0.7 to 6.6 ± 0.8 mmol/L; P < 0.0001), and frontal lobe oxygenation (from 74 ± 6% to 70 ± 6%; P = .0414) decreased, while renal oxygen extraction increased (from 5.3% [4.3-8.1]; median [interquartile range] to 10.8% [5.8-17.5]; P = .0405). Plasma creatinine became significantly elevated on the second day after the operation (from 83 [73-101] to 105 µmol/L [79-143]; P = .0062) with a peak increase observed after 2 days (1-2). The peak increase in creatinine correlated to intraoperative renal oxygen extraction ( r = 0.51; P = .026). Kidney function was affected after open abdominal aortic aneurysm repair likely related to limited renal blood flow. We take the increase in renal oxygen extraction and reduction in frontal lobe oxygenation to suggest that mean arterial pressure and hemoglobin were too low to maintain renal and cerebral circulation in vascular surgical patients.

THE EFFECTS OF FENOLDOPAM ON RENAL FUNCTION AND METABOLISM IN AN OVINE MODEL OF SEPTIC SHOCK.

The importance of renal perfusion and metabolism in septic acute kidney injury (AKI) remains unclear. Prophylactic administration of the dopaminergic agent, fenoldopam, has been suggested to reduce the occurrence of AKI, but its effects in septic shock are poorly defined. Sepsis was induced in 15 adult female sheep by injecting autologous feces into the abdominal cavity. Two hours later, the animals were randomized to one of three groups: low-dose fenoldopam (1.0 μg/kg/min, n = 5), high-dose fenoldopam (5.0 μg/kg/min, n = 5), or placebo (control, n = 5). A perivascular flow probe was placed around the renal artery and a catheter in the renal vein for measurement of renal blood flow index (RBFI) and oxygen consumption (VO2renI). Metabolism in the renal cortex was evaluated using microdialysis. Serum creatinine was measured 6-hourly and the sublingual microcirculation assessed using sidestream dark-field videomicroscopy. High-dose fenoldopam was associated with a lower RBFI at 18 h (P = 0.032) than in the control group, but VO2renI was maintained by a higher oxygen extraction (P < 0.05 vs. baseline). Sublingual microcirculatory alterations at 18 h were more severe in the high-dose than in the control and low-dose groups (P = 0.021 and P = 0.032). Renal cortex lactate and pyruvate levels increased earlier in the high-dose group than in the other two groups (P < 0.001 vs. baseline). Fenoldopam did not affect creatinine clearance or urine output. In this model of septic shock, fenoldopam did not improve renal blood flow, worsened microcirculatory alterations, and induced metabolic changes that were indicative of increased glycolysis.

Measurement of renal blood flow by phase-contrast magnetic resonance imaging during septic acute kidney injury

In septic patients, decreased renal perfusion is considered to play a major role in the pathogenesis of acute kidney injury. However, the accurate measurement of renal blood flow in such patients is problematic and invasive. We sought to overcome such obstacles by measuring renal blood flow in septic patients with acute kidney injury using cine phase-contrast magnetic resonance imaging. Pilot observational study. University-affiliated general adult intensive care unit. Ten adult patients with established septic acute kidney injury and 11 normal volunteers. Cine phase-contrast magnetic resonance imaging measurement of renal blood flow and cardiac output. The median age of the study patients was 62.5 yrs and eight were male. At the time of magnetic resonance imaging, eight patients were mechanically ventilated, nine were on continuous hemofiltration, and five required vasopressors. Cine phase-contrast magnetic resonance imaging examinations were carried out without complication. Median renal blood flow was 482 mL/min (range 335-1137) in septic acute kidney injury and 1260 mL/min (range 791-1750) in healthy controls (p = .003). Renal blood flow indexed to body surface area was 244 mL/min/m2 (range 165-662) in septic acute kidney injury and 525 mL/min/m2 (range 438-869) in controls (p = .004). In patients with septic acute kidney injury, median cardiac index was 3.5 L/min/m2 (range 1.6-8.7), and median renal fraction of cardiac output was only 7.1% (range 4.4-10.8). There was no rank correlation between renal blood flow index and creatinine clearance in patients with septic acute kidney injury (r = .26, p = .45). Cine phase-contrast magnetic resonance imaging can be used to noninvasively and safely assess renal perfusion during critical illness in man. Near-simultaneous accurate measurement of cardiac output enables organ blood flow to be assessed in the context of the global circulation. Renal blood flow seems consistently reduced as a fraction of cardiac output in established septic acute kidney injury. Cine phase-contrast magnetic resonance imaging may be a valuable tool to further investigate renal blood flow and the effects of therapies on renal blood flow in critical illness.

Transesophageal Doppler Measurement of Renal Arterial Blood Flow Velocities and Indices in Children

Doppler-derived renal blood flow indices have been used to assess renal pathologies. However, transesophageal ultrasonography (TEE) has not been previously used to assess these renal variables in pediatric patients. In this study, we (a) assessed whether TEE allows adequate visualization of the renal parenchyma and renal artery, and (b) evaluated the concordance of TEE Doppler-derived renal blood flow measurements/indices compared with a standard transabdominal renal ultrasound (TAU) in children. This prospective cohort study enrolled 28 healthy children between the ages of 1 and 17 years without known renal dysfunction who were undergoing atrial septal defect device closure in the cardiac catheterization laboratory. TEE was used to obtain Doppler renal artery blood velocities (peak systolic velocity, end-diastolic velocity, mean diastolic velocity, resistive index, and pulsatility index), and these values were compared with measurements obtained by TAU. Concordance correlation coefficient (CCC) was used to determine clinically significant agreement between the 2 methods. The Bland-Altman plots were used to determine whether these 2 methods agree sufficiently to be used interchangeably. Statistical significance was accepted at P ≤ 0.05. Obtaining 2-dimensional images of kidney parenchyma and Doppler-derived measurements using TEE in children is feasible. There was statistically significant agreement between the 2 methods for all measurements. The CCC between the 2 imaging techniques was 0.91 for the pulsatility index and 0.66 for the resistive index. These coefficients were sensitive to outliers. When the highest and lowest data points were removed from the analysis, the CCC between the 2 imaging techniques was 0.62 for the pulsatility index and 0.50 for the resistive index. The 95% confidence interval (CI) for pulsatility index was 0.35 to 0.98 and for resistive index was 0.21 to 0.89. The Bland-Altman plots indicate good agreement between the 2 methods; for the pulsatility index, the limits of agreement were -0.80 to 0.53. The correlation of the size of the measurement and the mean difference in methods (-0.14; 95% CI = -0.28, 0.01) was not statistically significant (r = 0.31, P = 0.17). For the resistive index, the limits of agreement were -0.22 to 0.12. The correlation of the size of the measurement and the mean difference in methods (-0.05; 95% CI = -0.09, -0.01) was not statistically significant (r = 0.10, P = 0.65). This study confirms the feasibility of obtaining 2-dimensional images of kidney parenchyma and Doppler-derived measurements using TEE in children. Angle-independent TEE Doppler-derived indices show significant concordance with those derived by TAU. Further studies are required to assess whether this correlation holds true in the presence of renal pathology. This technique has the potential to help modulate intraoperative interventions based on their impact on renal variables and may prove helpful in the perioperative period for children at risk of acute kidney injury.

Oral Rehydration Therapy for Preoperative Fluid and Electrolyte Management

Preoperative fluid and electrolyte management is usually performed by intravenous therapy. We investigated the safety and effectiveness of oral rehydration therapy (ORT) for preoperative fluid and electrolyte management of surgical patients. The study consisted of two studies, designed as a prospective observational study. In a pilot study, 20 surgical patients consumed 1000 mL of an oral rehydration solution (ORS) until 2 h before induction of general anesthesia. Parameters such as serum electrolyte concentrations, fractional excretion of sodium (FENa) as an index of renal blood flow, volume of esophageal-pharyngeal fluid and gastric fluid (EPGF), and patient satisfaction with ORT were assessed. In a follow-up study to assess the safety of ORT, 1078 surgical patients, who consumed ORS until 2 h before induction of general anesthesia, were assessed. In the pilot study, water, electrolytes, and carbohydrate were effectively and safely supplied by ORT. The FENa value was increased at 2 h following ORT. The volume of EPGF collected following the induction of anesthesia was 5.3±5.6 mL. In the follow-up study, a small amount of vomiting occurred in one patient, and no aspiration occurred in the patients. These results suggest that ORT is a safe and effective therapy for the preoperative fluid and electrolyte management of selected surgical patients.

THE GENDER FEATURES OF THE RENIN-ANGIOTENSIN-ALDOSTERONE SYSTEM IN HYPERTENSIVE PATIENTS

Aim. To study the correlation of the renin-angiotensin-aldosterone system (RAAS) activity with the female sex hormone levels and markers of target organ damage in patients with arterial hypertension (HT). Material and methods. Patients with HT (20 men and 39 postmenopausal women) were involved into the study. The dynamic renal angioscintigraphy and echocardiography were performed, plasma rennin activity (PRA), levels of aldosterone, estradiole and 17-hydroxiprogesterone were determined by radioimmunoassay. Results. Higher aldosterone level was found in women in comparison with men (212,5±123,9 pg/ml and 148,9±82,5 pg/m, respectively, р=0,03). Negative relations between aldosterone and estradiol levels (r=-0,3; p=0,04), and between aldosterone and 17-hydroxyprogesterone levels (r=-0,318; p=0,04), and positive relations between aldosterone concentration and PRA (r=0,555; p=0,04) was found in women. Besides, correlation between levels of female sex hormones, aldosterone and renal blood flow indicators, glomerular filtration rate, left ventricular mass index (LVMI) were found in women. These correlations were not found in men. Conclusion. The gender differences of RAAS activity were revealed with higher aldosterone level in postmenopausal hypertensive women in comparison with men. Relationships between PRA, levels of aldosterone and female sex hormones and renal blood flow indices, LVMI were also found in women.

Preoperative fluid and electrolyte management with oral rehydration therapy

We hypothesized that oral rehydration therapy using an oral rehydration solution may be effective for preoperative fluid and electrolyte management in surgical patients before the induction of general anesthesia, and we investigated the safety and effectiveness of oral rehydration therapy as compared with intravenous therapy. Fifty female patients who underwent breast surgery were randomly allocated to two groups. Before entry to the operation room and the induction of general anesthesia, 25 patients drank 1000 ml of an oral rehydration solution ("oral group") and 25 patients were infused with 1000 ml of an intravenous electrolyte solution ("intravenous group"). Parameters such as electrolyte concentrations in serum and urine, urine volume, vital signs, vomiting and aspiration, volumes of esophageal-pharyngeal fluid and gastric fluid (EPGF), and patient satisfaction with the therapy (as surveyed by a questionnaire) were assessed. After treatment, the serum sodium concentration and the hematocrit value, which both declined within the normal limits, were significantly higher in the oral group than in the intravenous group (sodium, 140.8 +/- 2.9 mEq x l(-1) in the oral group and 138.7 +/- 1.9 mEq x l(-1) in the intravenous group; P = 0.005; hematocrit, 39.03 +/- 4.16% in the oral group and 36.15 +/- 3.41% in the intravenous group; P = 0.01). No significant difference was observed in serum glucose values. Urine volume was significantly larger in the oral group (864.9 +/- 211.5 ml) than in the intravenous group (561.5 +/- 216.0 ml; P < 0.001). The fractional excretion of sodium (FENa), as an index of renal blood flow, was increased in both groups following treatment (0.8 +/- 0.5 in the oral group and 0.8 +/- 0.3 in the intravenous group). Patient satisfaction with the therapy favored the oral rehydration therapy, as judged by factors such as "feeling of hunger", "occurrence of dry mouth", and "less restriction in physical activity". The volume of EPGF collected following the induction of anesthesia was significantly smaller in the oral group than in the intravenous group (6.03 +/- 9.14 ml in the oral group and 21.76 +/- 30.56 ml in the intravenous group; P < 0.001). No adverse events or adverse reactions were observed in either group. The results suggest that the oral rehydration therapy with an oral rehydration solution before surgery is superior to the current preoperative intravenous therapy for the provision of water, electrolytes, and carbohydrates, and this therapy should be considered as an alternative to the intravenous therapy for preoperative fluid and electrolyte management in selected surgical patients in whom there is no reason to suspect delayed gastric emptying.

POST‐TRANSFUSIONAL VARIATION IN URINARY OXYGEN TENSION IN SURGICAL PATIENTS

Prior studies have suggested urinary oxygen tension (P(u)O2) as a putative index of renal blood flow (RBF) and tissue oxygenation. In the present study, we collected intraoperative data from eight anaemic, bladder-catheterized patients who received erythrocyte transfusions during various surgical procedures under general anaesthesia. Urinary and arterial blood gas analysis and co-oximetry were performed before and after transfusion, during an interval in which RBF was assumed to be constant. Pre- and post-transfusion haematocrit levels were 23 +/- 4.8 and 27 +/- 6.4%, respectively, and arterial oxygen content (C(a)O2) was 10.5 +/- 2.5 and 12.4 +/- 3.1 mL/dL, respectively (P = 0.012). Pre- and post-transfusion P(u)O2 was 90 +/- 14 and 108 +/- 20 mmHg, respectively (P = 0.036). 4. These results, although limited, suggest that under conditions of stable haemodynamics, systemic oxygenation and renal function, intraoperative blood transfusion may increase P(u)O2 in anaemic anaesthetized patients. If confirmed by subsequent clinical and laboratory studies, P(u)O2 measurement could become a simple, non-invasive way to monitor renal medullary oxygenation and tissue oxygen availability and help determine whether red blood cells should be transfused.

Short-term Lipid-Lowering Treatment with Atorvastatin Improves Renal Function But Not Renal Blood Flow Indices in Patients with Peripheral Arterial Disease

Some studies have suggested that lipid lowering with statins exerts favorable effects on the progression of chronic kidney disease. Therefore, the authors assessed the effects of short-term atorvastatin treatment on biochemical markers of renal function and evaluated duplex indices of renal blood flow (RBF) in patients with peripheral arterial disease. Hyperlipidemic claudicants (n = 18), aged 44-85 years, were treated for 8 weeks with 20 mg/day atorvastatin. Blood tests at baseline and after 8 weeks included serum fasting lipids, creatinine, urate, and cystatin C (a sensitive indicator of renal function) levels. RBF was also assessed (n = 9) by measuring pulsatile and resistance duplex indices. As expected, there was a significant improvement in total cholesterol, low-density lipoprotein cholesterol, and triglycerides. There was also a significant (p < 0.0001) fall in serum creatinine from 89 (58-125) to 79 micromol/L (54-119) and an increase in calculated creatinine clearance (CrCl) from 72 (40-129) to 80 mL/minute (47-138; p < 0.0001). Serum cystatin C values decreased significantly (p = 0.0002) from 1.04 (0.57-1.56) to 0.90 mg/L (0.47-1.47). There were no detectable changes in the RBF duplex indices. Treatment of stable claudicants with atorvastatin for 8 weeks was associated with improved renal function (as assessed by serum creatinine, cystatin C, and calculated CrCl) without changes in RBF. Further studies are required to identify the mechanisms involved in this phenomenon.

The effects of prone positioning on intraabdominal pressure and cardiovascular and renal function in patients with acute lung injury.

To detect any harmful effects of prone positioning on intraabdominal pressure (IAP) and cardiovascular and renal function, we studied 16 mechanically ventilated patients with acute lung injury randomly in prone and supine positions, without minimizing the restriction of the abdomen. Effective renal blood flow index and glomerular filtration rate index were determined by the paraaminohippurate and inulin clearance techniques. Prone positioning resulted in an increase in IAP from 12 +/- 4 to 14 +/- 5 mm Hg (P < 0.05), PaO(2)/fraction of inspired oxygen from 220 +/- 91 to 267 +/- 82 mm Hg (P < 0.05), cardiac index from 4.1 +/- 1.1 to 4.4 +/- 0.7 L/min (P < 0.05), mean arterial pressure from 77 +/- 10 to 82 +/- 11 mm Hg (P < 0.01), and oxygen delivery index from 600 +/- 156 to 648 +/- 95 mL. min(-)(1). m(-)(2) (P < 0.05). Renal fraction of cardiac output decreased from 19.1% +/- 12.5% to 15.5% +/- 8.8% (P < 0.05), and renal vascular resistance index increased from 11762 +/- 6554 dynes. s. cm(-)(5). m(2) to 15078 +/- 10594 dynes. s. cm(-)(5). m(2) (P < 0.05), whereas effective renal blood flow index, glomerular filtration rate index, filtration fraction, urine volume, fractional sodium excretion, and osmolar and free water clearances remained constant during prone positioning. Prone positioning, when used in patients with acute lung injury, although it is associated with a small increase in IAP, contributes to improved arterial oxygenation and systemic blood flow without affecting renal perfusion and function. Apparently, special support to allow free chest and abdominal movement seems unnecessary when mechanically ventilated, hemodynamically stable patients without abdominal hypertension are proned to improve gas exchange. Prone positioning is increasingly used to improve gas exchange in patients with acute lung injury. However, during prone positioning an increase in intraabdominal pressure in these critically ill patients may promote dysfunction of other organs. Therefore, we performed a randomized study in mechanically ventilated patients with acute lung injury to investigate the cardiovascular and renal effects of prone positioning.

Effects of Increased Renal Parenchymal Pressure on Renal Function

Acute renal failure is seen with the acute abdominal compartment syndrome (AACS). The cause of acute renal failure in AACS is thought to be multifactorial, including increased renal venous pressure, renal parenchymal pressure (RPP), and decreased cardiac output. Previous studies have established the role of renal venous pressure as an important mediator of this renal derangement. In this study, we evaluate the role of renal parenchymal compression on renal function. Two groups of swine (20-26 kg) were studied after left nephrectomy and placement of a renal artery flow probe and ureteral cannula. Two hours were allowed for equilibration, and an inulin infusion was begun to calculate inulin clearance as a measurement of glomerular filtration. In group 1 animals (n = 6), RPP was elevated by 30 mm Hg for 2 hours with renal parenchymal compression. RPP then returned to baseline for 1 hour. In group 2 (n = 6), the RPP was not elevated. The cardiac index, preload, and mean arterial pressure remained stable. Blood samples for plasma renin activity and plasma aldosterone were taken at baseline and at hourly intervals. Elevation of RPP in the experimental group showed no significant decrease in renal blood flow index or glomerular filtration when compared with control animals. There were no significant elevations of plasma aldosterone or plasma renin activity in the experimental animals when compared with control. Elevated renal compression alone did not create the pathophysiologic derangements seen in AACS. However, prior data from this laboratory found that renal vein compression alone caused a decreased renal blood flow and glomerular filtration and an increased plasma renin activity, plasma aldosterone, and urinary protein leak. These changes are partially or completely reversed by decreasing renal venous pressure as occurs with abdominal decompression for AACS. These data strengthen the proposal that renal vein compression, and not renal parenchymal compression, is the primary mediator of the renal derangements seen in AACS.

Captopril renography in the diagnosis of renal artery stenosis: accuracy and limitations

purpose: The purpose of this study was to determine the sensitivity, specificity, and clinical usefulness of renography performed in combination with captopril administration (“captopril renography”) in diagnosing renal artery stenosis. patients and methods: Fifty-five patients with suspected renal artery stenosis underwent renography prior to performance of renal angiography. Renography was performed on two consecutive days using technetium-99m-diethylenetiamine pentaacetic acid (DTPA) as an index of glomerular filtration rate and iodine-131orthoiodohippurate (OIH) as an index of renal blood flow. Captopril (25 mg orally, crushed) was administered 1 hour before the second study. Renal artery stenosis was defined as a stenosis exceeding 70%. Renographic criteria were then established, retrospectively, to differentiate renal artery stenosis from essential hypertension based on (1) asymmetry of function and (2) the presence of captopril-induced changes. results: Renal artery stenosis was detected in 35 of 55 patients (21 with unilateral and 14 with bilateral stenosis). Three criteria were established for diagnosing renal artery stenosis: (1) a percent uptake of DTPA by the affected kidney of less than 40% of the combined bilateral uptake, (2) a delayed time to peak uptake of DTPA, which was more than 5 minutes longer in the affected kidney than in the contralateral kidney, (3) a delayed excretion of DTPA, with retention at 15 minutes, as a fraction of peak activity, more than 20% greater than in the contralateral kidney. The presence of one or more of these criteria was diagnostic of renal artery stenosis, with a sensitivity and specificity of 71% and 75%, respectively before captopril administration, and 94% and 95% after captopril administration. Lesser degrees of asymmetry (i.e., uptake of 40% to 50%) had very poor diagnostic specificity. Among patients with bilateral, stenoses, asymmetry identified the more severely affected kidney, but the presence or absence of stenosis in the contralateral kidney could not be reliably determined. When pre- and post-captopril studies were compared, the presence of captopril-induced scintigraphic changes was a highly specific finding for renal artery stenosis, but occurred in only 51% of the cases. OIH scintigraphy provided similar results, with slightly lower sensitivity and specificity. conclusion: Asymmetry of DTPA uptake, time to peak uptake, or retention seen on a single post-captopril renogram is a highly sensitive and specific finding in detecting renal artery stenosis but does not distinguish unilateral from bilateral disease. If renograms are obtained both before and after captopril administration, the presence of captopril-induced change is a highly specific finding for the detection of renal artery stenosis, but the sensitivity of this finding is low.

Hemodynamic, renal, and neurohumoral effects of a selective oral DA 1 receptor agonist (fenoldopam) in patients with congestive heart failure

Fenoldopam mesylate (SK&F 82526-J) is a novel benzazepine derivative. It has selective agonist activity at post-junctional (DA 1) vascular dopaminergic receptors, which normally subserve renal artery vasodilation. Previous studies in normal subjects and in patients with hyportension indicate that fenoldopam increases renal blood flow and promotes a sodium diuresis. Drug efficacy was clinically evaluated in eight patients with chronic congestive heart failure (CHF) after a single oral dose of 100 mg of fenoldopam and following 3 days of therapy (100 mg four times daily). Stroke volume index acutely increased from 26 ± 7 (mean ± SD) to 30 ± 4 ml/beat/m 2 ( p < 0.05) and left ventricular filling pressure decreased from 26 ± 13 to 23 ± 11 mm Hg ( p < 0.05). Systemic vascular resistance decreased from 1513 ± 159 to 1128 ± 319 ( p < 0.05). Hemodynamic changes were seen as early as 30 minutes following fenoldopam and returned to control levels by 4 hours. Forearm blood flow, hepatic blood flow, and venous capacitance did not significantly change acutely, but renal blood flow index was significantly reduced (34 ± 4 to 30 ± 3 min −1 × 1000, p < 0.01). Plasma norepinephrine, plasma renin activity, plasma arginine vasopressin, and plasma aldosterone did not significantly change acutely. After 3 days of treatment, 100 mg of fenoldopam again reduced the renal blood flow index (35 ± 7 to 26 ± 7 min −1 × 1000, p < 0.01) and tended to increase plasma renin activity (11.7 ± 8 to 21.2 ± 19.4 ng/ml/hr, p = NS). Three days of fenoldopam, 100 mg four times daily, did not result in a sodium diuresis. We conclude that fenoldopam is a short-acting, orally effective vasodilator in patients with CHF that increases stroke volume and reduces filling pressure. However, contrary to its effects in normal subjects and in patients with hypertension, oral fenoldopam in this dose may reduce renal blood flow and it fails to promote a sodium diuresis in patients with CHF, thereby possibly limiting its utility.

Immediate and short-term hemodynamic effects of diltiazem in patients with hypertension.

The immediate effects of intravenous diltiazem effects and short-term (4 weeks) of the oral drug on systemic and regional hemodynamics, cardiac structure, and humoral responses were evaluated by previously reported methods in nine patients with mild-to-moderate essential hypertension and in one patient with primary aldosteronism. Diltiazem was first administered in three intravenous doses of 0.06, 0.06, and 0.12 mg/kg, respectively; patients were then treated for 4 weeks with daily doses ranging from 240 to 360 mg (average 300 mg). Intravenous diltiazem immediately reduced mean arterial pressure (from 115 +/- 3 to 96 +/- 3 mm Hg; p less than .01) through a fall in total peripheral resistance index (from 37 +/- 3 to 23 +/- 2 U/m2; p less than .01) that was associated with an increase in heart rate (from 66 +/- 2 to 77 +/- 3 beats/min; p less than .01) and cardiac index (from 3.3 +/- 0.3 to 4.3 +/- 0.4 liters/min/m2; p less than .01). These changes were not associated with changes in plasma levels of catecholamines or aldosterone or in plasma renin activity. After 4 weeks the significant decrease in mean arterial pressure persisted (104 +/- 3 mm Hg; p less than .01) and there were still no changes in the humoral substances or plasma volume. Renal blood flow index increased (from 368 +/- 52 to 462 +/- 57 ml/min/m2; p less than .01) and renal vascular resistance index decreased (from 0.37 +/- 0.06 to 0.26 +/- 0.04 U/m2; p less than .01), while splanchnic hemodynamics did not change.(ABSTRACT TRUNCATED AT 250 WORDS)

Noninvasive measurement of an index of renal blood flow.

A new technique for the noninvasive measurement of an index of renal blood flow is described. The method utilizes ultrasound determined renal volume and radionuclide assessment of the mean transit time of a pertechnetate bolus through the kidneys. From this information a value for flow is calculated according to compartmental analysis principles. There is good correlation between renal blood flow estimated by this technique and that determined by microsphere injection, r = 0.96.

Intrarenal blood flow distribution in the genetically hypertensive rat.

Distribution of intrarenal blood flow has been measured in genetically hypertensive (GH) and normotensive (N) rats (aged 17--23 weeks) by a 133Xe washout technique without opening the abdominal cavity. Three different specific flow compartments were found in the rats. The distribution of the intrarenal blood flow to the fast compartment was reduced in the GH rats when compared with the N rats and the rate of flow in it was also reduced. The flow rate in the second compartment was the same in the two strains, the distribution to it being relatively greater in the GH rats. The mean renal blood flow index (in ml/min/g of kidney) was reduced in the GH rats. It is not at present clear whether these differences are due to the hypertension or represent a causative factor in the hypertension.