The aim of this study was to verify the correlation between mean blur rate (MBR) obtained with CCD-equipped laser speckle flowgraphy (LSFG) and capillary blood flow (CBF) obtained by the hydrogen gas ...clearance method in rabbit optic nerve head (ONH). Using Japanese white rabbits under systemic anesthesia, a hydrogen electrode was inserted an area of the ONH free from superficial capillaries. MBR was measured with LSFG near the hydrogen electrode. CBF and MBR were measured in the range of 32.4–83.5 mL/min/100 g and 3.5–6.0, respectively. MBR and CBF were significantly correlated (r = 0.73, P < 0.01, n = 14). After inhalation of carbon dioxide (CO2) or intravenous administration of endothelin-1 (ET-1), MBR and CBF were changed in the relative range of 0.74–1.27 and 0.76–1.35, respectively. The relative changes in MBR and CBF induced by CO2 and ET-1 were also significantly correlated (r = 0.67, P < 0.01). The current results suggest that MBR may correlate with CBF and also change with CBF, as an index of blood flow in the ONH, linearly.
► CCD-equipped LSFG was compared with hydrogen gas clearance method in rabbits. ► ONH blood flow was measured simultaneously by LSFG and hydrogen gas clearance method. ► Absolute values of MBR and capillary blood flow were significantly correlated. ► Relative changes of MBR and capillary blood flow were also significantly correlated.
Dynamic contrast CT with Patlak plot analysis can be used to determine the glomerular filtration rate (GFR). However, several studies have shown different GFR values and they are most likely less ...than the values by the standard techniques. The purpose of this prospective, experimental, and method comparison study was to evaluate the GFR using a CT technique (CT‐GFR) in 12 healthy dogs compared to serum iohexol clearance (SIC‐GFR). All dogs were anesthetized and placed in the right lateral recumbency position and the caudal part was lifted inside the CT gantry. A single‐slice dynamic CT of the aorta and both kidneys was scanned sequentially every 2 s for 2 min after a bolus injection (3 mL/s) of iohexol (300 mg/kg). Time attenuation curves (TAC) were constructed and the GFR per volume of kidney was calculated using the Patlak plot analysis method based on 30‐120 s time intervals, and results were compared to global GFR from SIC that was determined with eight blood samples for up to 240 min. The CT‐GFR value (1.85 ± 0.48 mL/min/kg) was significantly less than the SIC‐GFR value (3.40 ± 0.80 mL/min/kg; P < .05). The CT‐GFR was correlated with SIC‐GFR by the coefficient of correlation (r) at 0.61 (P = .046). In conclusion, the CT‐GFR underestimated SIC‐GFR and should be used carefully. We suggest that the GFR should be calculated using the equation derived from linear regression between CT‐GFR and the standard GFR method. With its own particular parameters, each institute should have its own prediction equation.
Aim
Accurate and precise estimation of glomerular filtration rate (GFR) is essential in kidney disease. We evaluated the usefulness of the mean of creatinine clearance (CCr) and urea clearance (CUN) ...examined over a 1‐h urine collection period (1‐h (CCr + CUN)/2) in a retrospective, cross‐sectional study across two centres, as a relatively simple method for estimating GFR in children.
Methods
Children aged ≤18 years who underwent inulin clearance (CIn) tests were eligible. Two clearance values were obtained during a 2‐h test consisting of two periods of 1 h each. The mean clearance in two periods was defined as 1‐h clearance. 1‐h (CCr + CUN)/2, 1‐h CCr, 1‐h CUN and GFR estimated by Cr‐based and cystatin C (CysC)‐based formulas for Japanese children were compared with CIn. Bland–Altman plots were used to evaluate correlations. The primary outcome measure was the correlation between 1‐h (CCr + CUN)/2 and CIn.
Results
Fifty‐three children were analysed. Their median age was 10.9 (interquartile range IQR 5.3–14.2) years, and median CIn and 1‐h (CCr + CUN)/2 were 77.0 (IQR: 51.5–95.1) and 81.0 (IQR: 64.1–97.7) ml/min/1.73 m2, respectively. Percentage difference of CIn and 1‐h (CCr + CUN)/2 in the Bland–Altman plot was −11.2% (95% confidence interval − 15.3% – −7.1%), with 95% lower and upper limits of agreement of −40.3% and 18.0%, respectively. Thus, 1‐h (CCr + CUN)/2 was 1.12 times CIn.
Conclusion
1 h (CCr + CUN)/2 was almost concordant with CIn. 1‐h (CCr + CUN)/2 can estimate GFR accurately and precisely, making it a simple and speedy test for use in clinical practice.
SUMMARY AT A GLANCE
The importance of better measures of kidney function in children is highlighted in this cross‐sectional study, which evaluated the use of a 1‐h urine collection for the determination of the mean of creatinine clearance and urea clearance, and showed a good agreement with measured inulin clearance. The authors propose this urine collection as a quick and reliable measure of kidney function in children and suggest that it may be more accurate than other endogenous clearance methods.
Isotopic glomerular filtration rate (iGFR) measurement is comparable to the inulin method. In this study, we compared urinary and plasma iGFR methodologies in patients with diabetic nephropathy.
A ...total of 147 patients from 3 sites in the Diabetic Intervention with Vitamins to Improve Nephropathy (DIVINe) trial provided 213 sets of urine and blood collections, at baseline, 18 and 36 months.
The mean (with standard deviation) plasma iGFR of 60.7 (24.9) ml/min/1.73 m(2) compared to urinary iGFR of 52.0 (28.0) ml/min/1.73 m(2) was statistically significant (p value <0.001). Although plasma and urinary iGFRs were highly related (R(2) = 0.86), plasma iGFR increasingly overestimated urinary iGFRs at lower GFRs. In contrast to the cross-sectional analyses, the two measures of iGFR were weakly related (R(2) = 0.32) in regard to patients' change over 18 months of follow-up.
Plasma iGFR may not be a suitable method for accurately measuring GFR in patients with advancing degrees of chronic kidney disease from diabetic nephropathy.
INTRODUCTIONThe aim of this study was to compare two gamma camera-based methods (Gates’ method and Inoue’s method) for measuring glomerular filtration rate (GFR) with Russell’s two plasma sample ...clearance method (2-PSC), which was taken as the gold standard.
MATERIALS AND METHODSIn 94 healthy potential kidney donors (25 women and 69 men), GFR was measured by means of the 2-PSC method and was compared with Gates’ and Inoue’s methods of assessing GFR after technetium-99m-labeled diethylene triamine penta-acetic acid (Tc-DTPA) injection.
RESULTSInoue’s method showed no statistically significant difference (P=0.22) with the gold standard (2-PSC); there was good correlation (r=0.69) and least bias (−1.91 ml/min/1.73 m, root mean squared error=11.85 ml/min/1.73 m). Gates’ method showed weak correlation (r=0.36) and tended to underestimate GFR by 21% with bias of 25 ml/min/1.73 m and root mean squared error of 29.97.
CONCLUSIONFor a normal healthy adult population, Inoue’s method gives a better measure of GFR in contrast to Gates’ method when compared with 2-PSC method of GFR calculation.
Transcranial Doppler ultrasound-determined middle (MCA) and anterior (ACA) cerebral artery mean flow velocities (Vmean) and pulsatility indexes (PI) were measured during "no-load" 21, 60, and 102 ...revolutions/min (rpm) and loaded cycling (30, 60, and 149 W) at approximately 60 rpm. At rest Vmean MCA was 51 (36-55) cm/s (median and range; n = 10) and Vmean ACA was 41 (36-49) cm/s (n = 7; P < 0.05). With no load on the cycle Vmean MCA increased 4 (2-36), 10 (0-47), and 27% (4-58) (P < 0.05) at the three pedaling frequencies, respectively; arterial PCO2 (PaCO2) remained constant. During loaded cycling the increases were 19 (6-42), 25 (2-45), and 32% (12-67) (P < 0.01), respectively, with only a minimal change in PaCO2. No significant changes were observed in Vmean ACA. Changes in Vmean MCA were similar to those recorded by the initial slope index (ISI) of the 133Xe clearance method (n = 11), which in turn were smaller than increases recorded by the fast-compartment flow. PI ACA followed PI MCA during no-load as well as loaded exercise and increased with work rate, perhaps reflecting an increase in pulse pressure from 56 (48-63) mmHg at rest to 109 (88-123) mmHg at 149 W (P < 0.01). Data demonstrate a graded increase in regional cerebral perfusion during dynamic exercise corresponding to the MCA territory.
Abstract
Aim:
Many investigators have proved the usefulness of acetazolamide provocation and the carbon dioxide test for assessment of the local cerebrovascular reactivity by measurement of the ...regional cerebral blood flow in patients with occlusive cerebrovascular disease. Data originating from a comparison of these two different vasomotor stimuli as concerns the differences in sensitivity to them in various parts of the central nervous system are scarce. Our aim was to compare the cerebral blood flow responses to hypercapnic and acetazolamide stimuli in different brain regions.
Methods:
The cerebral blood flow was measured in the cerebrum (cortex and caudate nucleus) and cerebellum (cortex), as measured by a hydrogen clearance method in anaesthetized, artificially ventilated rabbits.
Results:
In normocapnia, the cerebral blood flow values in the cerebrum and the cerebellum differed significantly. The cerebral blood flow responses to both vasodilatory stimuli were to be significantly higher in the cerebrum than in the cerebellum, but the relative increases, i.e. the mean relative reactivities, were similar in the different regions measured.
Conclusion:
The regional dissimilarity might explain to some extent the different sensitivities of the various brain areas to sudden blood pressure changes (infarction or haemorrhage). The results further suggest that heterogeneity in cerebrovascular reactivity should be considered in the assessment of vasoreactivity in patients with occlusive cerebrovascular disease. Since the comparison of the carbon dioxide and acetazolamide – induced cerebrovascular reactivities revealed a strong linear relationship, it was concluded that acetazolamide provocation is equivalent to the carbon dioxide test in the evaluation of cerebrovascular reactivity.
The aim of the present study was to elucidate the influence of the hepatic sympathetic and parasympathetic (vagal) nerves on the hepatic blood flow (HBF), both tonically and when stimulated, using ...urethane-anesthetized rats as an in vivo experimental model. HBF was measured at the surface of the lateral left lobe of the liver using laser Doppler flowmetry and the hydrogen gas clearance method. Denervation of the hepatic sympathetic nerves had no influence on the HBF, while electrical stimulation of the hepatic sympathetic nerves caused the HBF to decrease in a frequency-dependent manner. This decrease was shown to occur via α-adrenergic receptors. In contrast, neither denervation nor electrical stimulation of the hepatic vagal nerves elicited significant changes in the HBF. These results demonstrate that the sympathetic and vagal hepatic nerves have little or no tonic influence on the HBF of rats under urethane anesthesia, whereas the HBF decreases in response to activation of the hepatic sympathetic nerves.
Microcirculation in the optic nerve head (ONH) in the ocular fundus was measured noninvasively using the recently developed laser speckle circulation analyzer. Results were compared with capillary ...blood flow (CBF) measurements made by the hydrogen clearance method. The ONH blood flow of six normal rabbits was measured simultaneously by both methods. Inhalation of 10% carbon dioxide (CO2) increased the CBF by 22% (hydrogen clearance method). Intravenous injection of endothelin-1 (ET-1) (10(-10) mol/kg) decreased the CBF by 19%. Significant correlations were found between the NB (normalized blur) value by the laser speckle method and CBF (r = 0.38, P < 0.05, n = 30) and also between the relative change of NB and CBF (r = 0.92, P < 0.01, n = 30) in the ONH. This indicates that evaluation of the NB change in the ONH is as accurate with the laser speckle method as with the hydrogen clearance method, giving a basis for the clinical application of the laser speckle method of measuring ONH circulation.
