Several simple equations exist for the calculation of Kt/V from predialysis (Cpre) and postdialysis (Cpost) measurements of urea concentration. Analogous equations are needed for precise determination of patient protein catabolic rate (nPCR) from Cpre and Cpost. In this study we develop three simple nPCR equations from urea mass balance theory. The equations, which include a term for residual function, may be applied to any session of the week for patients dialyzed three times weekly who are in steady state with respect to dialysis dose and protein catabolism. The precision of each equation was tested with Cpre, Cpost data obtained from steady state simulations of 540 patients without residual renal clearance (KR) and 972 simulated patients with significant residual Kr. The simplest equation has the form: nPCR = a[kt/V+ Kr/V](Cpre+ Cpost)+0.17 where V is urea distribution volume, and a and d are constants varying with session of the week. When compared to nPCR values calculated from formal urea kinetic modelling, the error determined with this formula never exceeded 5 % for the midweek or final session. A more complicated equation of the form: nPCR =a{[1-bCpost/Cpre][1-Cpost/Cpre+ΔBW/V]Cpre/(1-0.0003t)+d KR/V(Cpre+ Cpost)}+0.17 provided nPCR estimates with a maximum error < 1.3% for any dialysis session of the week and for Kr up to 4 ml/min for a 70-kg patient. The only data required for the latter equation are Cpre, Cpost, length of dialysis session, volume ultrafiltered (ΔBW), and an approximate value of the patient’s urea distribution volume. The proposed equations permit nPCR to be calculated simply and accurately for stable patients dialyzed three times a week.

Keywords:
Hemodialysis, Mathematical modelling, Protein catabolic rate, Residual renal function, Urea kinetic modelling
This content is only available via PDF.
© 1997 S. Karger AG, Basel
1997
Copyright / Drug Dosage / Disclaimer
Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher.
Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug.
Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.
You do not currently have access to this content.