Related Experiment Videos
Improved clearance of iohexol with longer haemodialysis despite similar Kt/V for urea
E Johnsson1, P O Attman, O Samuelsson
1Department of Nephrology, Sahlgrenska University Hospital, Göteborg, Sweden.
Background:
The efforts to improve the quality of haemodialysis (HD) has renewed the interest in the consequences of blood-flow distribution for removal of solutes.
Methods:
To test the effects of HD time per se, 10 patients were studied in a cross-over fashion with HD for 3 h and 1 week later for 6 h, with similar blood urea Kt/Vs, achieved by adjusting the blood flow rate to 290 and 120 ml/min respectively. Injections of iohexol (MW 821 Dalton) were given 2 days prior to the dialysis sessions. Blood samples were taken before, during (6/HD), 1 and 24 h after the HD and analysed for concentrations of urea and iohexol. A urea on-line monitor (Gambro) was used for continuous recordings and sampling of dialysate.
Results:
According to the study design the blood Kt/V for urea (Daugirdas II) was similar for 3 and 6 h HD, close to 1.0 (n.s), while the removed mass of urea showed that Kt/V was slightly and significantly higher for the 6 h HD. The 'apparent' mass of iohexol, defined as plasma concentration times estimated distribution volume, fell to 29% and 21% of pre-dialysis levels after 3 h and 6 h HD, respectively (P<0.01), but increased after HD, and more so after the short dialysis, reaching 46% of the predialysis mass 24 h after 3 h HD vs. 36% after 6 h HD (P<0.05). The removed mass of iohexol was 920+/-110 mg with 6h HD and 700+/-81 mg with 3h HD, (P<0.01). Thus, the longer dialysis removed 32% more iohexol despite similar blood Kt/V for urea.
Conclusion:
The treatment time per se affects solute removal despite similar blood Kt/V for urea. This is particularly true for an intermediate-size molecule like iohexol.
Related Concept Videos
Drug Dosing in Renal Diseases: Dose Adjustments Based on Drug Clearance and Elimination Rate Constant
Renal Drug Clearance: Comparison Between Renal Excretion Methods
Renal clearance is often associated with the renal glomerular filtration rate (GFR), which represents the rate at which plasma is filtered through the glomeruli in the kidney. When drug reabsorption is minimal and there is no active secretion, renal clearance is closely related to the...
Renal Drug Excretion: Effect of Urine pH, Flow Rate, and Drug pKa
The pKa of a drug,...
Factors Affecting Renal Clearance: Drug Distribution and Drug Interactions
One important factor is the relationship between renal clearance and the apparent volume of distribution. Renal clearance tends to be inversely proportional to the apparent volume of distribution. Drugs with an extensive distribution volume or those...
Renal Drug Clearance: Overview
Renal clearance can be calculated using different methods. One approach is to divide the urinary drug excretion rate by the plasma drug concentration. This method directly measures renal clearance, indicating the kidneys' efficiency in...
Drug Elimination by Renal Route: Tubular Reabsorption