The Peak Concentration Hypothesis: A Urea Kinetic Approach to Comparing the Adequacy of Continuous Ambulatory Peritoneal Dialysis (CAPD) and Hemodialysis

Abstract

The KTIV urea index (K, clearance; T, treatment time; V, volume of urea distribution) has become an established index of hemodialysis (HD) adequacy, values of KTIV < 0.8 being associated with overt uremic toxicity. For the typical continuous ambulatory peritoneal dialysis (CAPD) regimen of 4 X 2 L exchanges/day, the equivalent KT/V -0.6. Paradoxically, overt uremic toxicity is not commonly observed in CAPD patients with this typical therapy prescription. Application of the urea kinetic model demonstrates that HD and CAPD have the same time-averaged urea concentration at the same KTIV. However, as HD is an intermittent therapy, the urea concentration in HD exceeds the time-averaged concentration for about half the hours in the week. If uremic toxicity is related to the peak rather than the time-averaged urea concentration, a higher KT/V would be required in HD to achieve a peak concentration at or below the steady state CAPD concentration. This peak concent ration hypothesis predicts, based on the results of the National Cooperative Dialysis Study, that underdialysis with CAPD would occur at KT/V < 0.4 for a protein intake of 1.1 gmlkglday.

Keywords

Hemodialysis adequacy urea kinetics therapy prescription uremic toxicity KT/V

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References

Sargent

, Gotch

The analysis of concentration dependence on uremic lesions in clinical studies.

Kidney Int. 1975; 7(Suppl 2): S35–S44.

Frost

, Kerr

Kinetics of hemodialysis: A theoretical study of the removal of solutes in chronic renal failure compared to normal health.

Kidney Int. 1977; 12: 41–50.

Gotch

, Sargent

J.A.

A mechanisitic analysis of the National Cooperative Dialysis Study (NCDS).

Kidney Int. 1985; 28: 526–534.

Dyck

P.J.

, Johnson

W.J.

, Lambert

E.H.

Comparison of symptoms, chemistry, and nerve function to assess adequacy of hemodialysis.

Neurology. 1979; 29: 1361–1368.

Teschan

P.E.

, Ginn

H.E.

, Bourne

J.R.

A prospective study of reduced dialysis.

ASAIO J. 1983; 6: 108–122.

Lowrie

E.G.

, Laird

N.M.

, Parker

T.F.

Effect of the hemodialysis prescription on patient morbidity.

N Engl J Med. 1981; 20: 1176–1181.

Parker

T.F.

, Laird

N.M.

, Lowrie

E.G.

Comparison of the study groups in the National Cooperative Dialysis Study and a description of morbidity, mortality and patient withdrawal.

Kidney Int. 1983; 23(Suppl): S42–S49.

Keshaviah

P.K.

, Collins

Hemodialysis: How much is enough?

Seminars Dial. 1988; 1: 3–4.

EMMES Corporation. Final report of the National CAPD Registry of the NIH. Bethesda, MD: EMMES Corporation; 1988.

10.

Rottembourg

, Issad

, Gallego

J.L.

Evolution of residual renal function in patients undergoing maintenance haemodialysis or continuous ambulatory peritoneal dialysis.

Proc EDTA. 1982; 19: 397–403.

11.

Randerson

D.H.

, Chapman

G.V.

, Farrell

P.C.

Amino acid and dietary status in long-term CAPD patients. In: Atkins

R.C.

, Farrell

P.C.

, Thomson

, eds. Peritoneal dialysis. Edinburgh: Churchill-Livingstone; 1981: 179–191.

12.

Borah

M.F.

, Schoenfeld

P.Y.

, Gotch

F.A.

, Sargent

J.A.

, Wolfson

, Humphreys

M.H.

Nitrogen balance during intermittent dialysis therapy of uremia.

Kidney Int. 1978; 14: 491–500.

13.

Whelton

, and Neu

, eds. The aminoglycosides. New York: Marcel Dekker; 1982: 179–181.

14.

Black

R.E.

, Lau

W.K.

, Weinstein

R.J.

Ototoxicity of amikacin.

Antimicrob Agents Chemother. 1976; 9: 956–961.