The clearance of iohexol as a measure of the glomerular filtration rate in children with chronic renal failure.

The plasma clearances of technetium-99m-labelled DTPA ([99Tcm]-DTPA) and the non-ionic contrast medium iohexol were estimated in 11 children with chronic renal failure for determination of the glomerular filtration rate (GFR). Equal values were obtained with the two substances provided plasma sampling was simultaneous, but when plasma was sampled within 3.5 h after injection of iohexol and [99Tcm]-DTPA the GFR was overestimated by more than 50%. For clearance values below 20 ml min-1 1.73 m-2, valid GFR estimates were obtained both from two plasma samples taken 3 h and 24 h after the injection of iohexol and from a single plasma sample taken 24 h after the injection.

A single plasma sample method for estimation of the glomerular filtration rate in infants and children using iohexol, I: Establishment of a body weight-related formula for the distribution volume of iohexol.

This study was performed in order to develop a method for estimation of the glomerular filtration rate (GFR) from a single plasma sample based upon the plasma disappearance rate of the non-ionic contrast medium iohexol. The apparent distribution volume for iohexol was measured in 100 infants and children and used for establishment of a weight-related empirical formula for the distribution volume. Using the distribution volume obtained by this formula, a preliminary GFR was calculated from the iodine concentration measured in a plasma sample taken 3 h after injection of iohexol. When this estimate was corrected by another empirically established correction factor, a high degree of agreement was found between a GFR reference method and the 3-h single plasma sample method. In another group of 13 children the 3-h single plasma sample GFR was estimated twice with a 2-day interval, and the day-to-day variations were found to be similar to those obtained with other standard methods.

A single plasma sample method for estimation of the glomerular filtration rate in infants and children using iohexol, II: Establishment of the optimal plasma sampling time and a comparison with the 99Tcm-DTPA method.

The glomerular filtration rate (GFR) can be determined from the plasma disappearance rate of the non-ionic contrast medium iohexol. A preceding study established the empirical formulae enabling the development of a single plasma sample method for estimation of GFR in infants and children. In the present study the validity of these empirical formulae was confirmed in examinations in 143 patients. The results of the single plasma sample method were similar to those of a standard 99Tcm-DTPA method, and also with those of a two plasma sample iohexol method. Evaluation of the results obtained with plasma sampling 1 h, 2 h, 3 h and 4 h after the injection of the contrast medium showed that the optimal sampling time was about 3 h after the injection.

Glomerular filtration rate: a comparison between Cr-EDTA clearance and a single sample technique with a non-ionic contrast agent.

An algorithm for the calculation of the glomerular filtration rate (GFR) from a single-point determination of the serum concentration of the non-ionic contrast medium iohexol has been evaluated. The algorithm is based upon the assumption that the distribution volumes of iohexol and 51Cr-EDTA are similar. It includes correction factors for non-immediate mixing and irregular extracellular distribution during the elimination phase. The calculated GFR from single-point determinations of iohexol obtained at 180, 200, 220 and 240 min after injection of 5 mL of this compound (300 g iodine/L) were compared with the results from simultaneously performed 51Cr-EDTA clearance in 98 patients. The single-point iohexol clearance values calculated from the different sampling times showed a coefficient of correlation of more than 0.95 to 51Cr-EDTA clearance.

Plasma and renal clearance of iohexol--a study on the reproducibility of a method for the glomerular filtration rate.

The reproducibility of iohexol clearance as a determination of the glomerular filtration rate was assessed in 12 healthy subjects during triplicate constant-rate infusions. Renal and plasma clearance of iohexol demonstrated a total within-subject variation (CV) ranging between 0% and 16%. The inter-individual variation in renal clearance was about 10%, the clearance values being (mean +/- SD) 116 +/- 10, 117 +/- 9 and 110 +/- 12 ml/min 1.73 m2 in the three experiments and corresponding figures for the plasma clearance were 120 +/- 17, 118 +/- 12 and 112 +/- 14 ml/min 1.73 m2. The renal clearance (CLR) and the plasma clearance (CL) showed good correlation (regression equation CL = 11.80 + 0.93 CLR, rs = 0.67). The method is simple and reproducible; thus, it is suitable for both clinical examinations and research.

Measurement of the plasma clearance of urographic contrast media for the determination of glomerular filtration rate.

Further experience with a new method to determine glomerular filtration rate is presented. The method depends on measurement by an x-ray fluorescence technique of the plasma disappearance of the injected iodine in standard nonionic radiographic contrast media used during excretory urography. The results of comparison of contrast clearance with 99m technetium-diethylenetriaminepentaacetic acid clearance in 33 cases showed excellent agreement with a correlation coefficient of 0.95. Reproducibility of the contrast clearance method was confirmed by repeated examination of 10 plasma samples at weekly intervals for 6 weeks, the results of which showed no significant differences. The contrast clearance technique for the measurement of glomerular filtration rate during excretory urography is simple, quick and accurate, and merits further development.

Excretion of iohexol and metrizoate in human breast milk.

Six lactating women undergoing contrast media examination had milk and blood taken to determine the rate and extent of excretion of iohexol (Omnipaque) (four mothers) and metrizoate (Isopaque) (two mothers). Blood samples were taken up to 45 minutes and milk samples up to 48 hours after the contrast medium injection. The excretion was low, reaching a maximum at 3 to 6 hours and showing a slow decay curve (t1/2 = 15 to 108 hours). One mother, who was weaning her baby, showed a different excretion pattern. The amount excreted during 24 hours was about 0.5 per cent of the weight adjusted maternal dose for both iohexol and metrizoate. It is not likely, that such a low dose of poorly absorbed drug would cause any adverse effects in the infant, unless it is hypersensitive to the drug already. The authors consider breast feeding to be acceptable for mothers receiving iohexol or metrizoate.