Solute removal index correlates more with equilibrated Kt/V than with single pool Kt/V in haemodialysis patients.

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Solute removal index (SRI) is an adequacy index that estimates haemodialysis dose based on urea removal in the spent dialysate. We examined the SRI, single pool Kt/V (spKt/V) and equilibrated Kt/V (eKt/V) in two groups of chronic haemodialysis patients; group A, 25 patients received haemodialysis twice weekly and group B, 11 patients received haemodialysis thrice weekly. The Ing's partial dialysate collection method was used for spent dialysate collection. The SRI values of the first and second dialysis sessions in a week in group A were 68.7 +/- 4.7 and 69.7 +/- 4.1%, respectively, while that of the first, mid-week and third dialysis sessions in a week in group B were 56.5 +/- 5.3, 55.8 +/- 5.4 and 57.5 +/- 6.2%, respectively. The correlation coefficients (r) between SRI and spKt/V in the first and second dialysis sessions in a week in group A were 0.90 (P < 0.01) and 0.95 (P < 0.01), respectively, and that in the first, mid-week and third sessions for group B were 0.96 (P < 0.01), 0.94 (P < 0.01) and 0.91 (P < 0.01), respectively. The r values between SRI and eKt/V in the first and second sessions for group A were 0.97 (P < 0.01) and 0.99 (P < 0.01), respectively, and that in the first, mid-week and third sessions for group B were 0.98 (P < 0.01), 0.97 (P < 0.01) and 0.98 (P < 0.01), respectively. Therefore, the correlation between SRI and eKt/V (r values approaching one) was better than that between SRI and spKt/V in all dialysis sessions in a week for both group A and B patients. We conclude that the SRI, an index based on dialysate urea removal, correlates more with equilibrated Kt/V (an index that accounted for postdialysis urea rebound) than with single pool Kt/V.