One or two samples for determination of total plasma clearance of a nonionic contrast medium in patients undergoing...

Plasma clearance of nonionic iopamidol (300 mg I/ml) was measured in 50 patients in connection with enhanced CT. Before injection of either 50 or 100 ml of the contrast medium, S-creatinine and urine osmolality were measured. Employing Renalyzer PRX 90, the plasma concentration of iodine was determined in blood samples drawn approximately 3 and 4 h after injection of iopamidol. The glomerular filtration rate was calculated by the Renalyzer using 2 different formulas, one requiring only a single sample, and one requiring at least 2 samples (standard). Both the 3- and 4-h single sample values correlated well with the glomerular filtration rate expressed by the standard sample value. The result was independent of whether 50 or 100 ml had been administered and whether or not water soluble contrast medium had been given orally before CT. As could be expected S-creatinine and urine osmolality correlated poorly with the clearance values. It is concluded that in patients receiving either 50 or 100 ml contrast medium for enhanced CT, the glomerular filtration rate can be determined in a single sample as well as with 2 samples taken between 3 and 4 h after contrast medium injection.