ADAPTATION OF A SINGLE INJECTION CLEARANCE METHOD TO PHYSIOLOGICAL AND PATHOPHYSIOLOGICAL FACTS A Review of Data Obtained in Infancy and Childhood

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Abstract
A retrospective analysis of 395 51Chromium/EDTA single injection clearances performed in infants and children was presented. In 61% of infants and 30% of the children the clearance values were calculated on the basis of a plasma disappearance half time of the reference substance, which was longer than the standard study, i.e., on the basis of extrapolated data. Plasma creatinine and urea levels were appropriate indicators for predicting the plasma disappearance half time of the marker substance. Additional patients (14) were studied prospectively with a duration of the study predicted by means of the plasma creatinine and urea levels. In these patients, separate determinations of the clearances using either the data obtained during the standard time of procedure only, or the data of the entire study, demonstrated that the clearances obtained by means of the standard procedure overestimated glomerular filtration rate. The analysis of the data in infants showed that the plasma urea level was a reasonably good indicator for predicting the time schedule of the study; plasma creatinine should not be used. The retrospective data indicated that a prolongation of the study should be recommended in all infants. The necessity and means of adapting the time schedule of isotope single injection clearances to physiological and pathophysiological facts was demonstrated.