Improved clearance of iohexol with longer haemodialysis despite similar Kt/V for urea.
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.


CONCLUSIONS
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.
Johnsson
E
E
Department of Nephrology, Sahlgrenska University Hospital, Göteborg, Sweden.
Attman
P O
PO
Samuelsson
O
O
Haraldsson
B
B
D000368:Aged; D003287:Contrast Media / Q000032:analysis / Q000493:pharmacokinetics*; D005260:Female; D006801:Humans; D007472:Iohexol / Q000032:analysis / Q000493:pharmacokinetics*; D008297:Male; D008875:Middle Aged; D009994:Osmolar Concentration; D006435:Renal Dialysis; D013997:Time Factors; D014508:Urea / Q000097:blood*
D003287:Contrast Media; D007472:Iohexol; D014508:Urea