HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Free Full Text (PDF) Free All Versions of this Article: 95/2/620    most recent 00100.2003v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (20) Citing Articles via Google Scholar Google Scholar Articles by Staempfli, H. R. Articles by Constable, P. D. Search for Related Content PubMed PubMed Citation Articles by Staempfli, H. R. Articles by Constable, P. D.

Experimental determination of net protein charge and A_tot and K_a of nonvolatile buffers in human plasma

¹Department of Clinical Studies, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada N1G 2W1; and ²Department of Veterinary Clinical Medicine, College of Veterinary Medicine, University of Illinois, Urbana, Illinois 61802

Submitted 31 January 2003 ; accepted in final form 26 March 2003

The mechanism for an acid-base disturbance can be determined by using the strong ion approach, which requires species-specific values for the total concentration of plasma nonvolatile buffers (A_tot) and the effective dissociation constant for plasma weak acids (K_a). The aim of this study was to experimentally determine A_tot and K_a values for human plasma by using in vitro CO₂ tonometry. Plasma PCO₂ was systematically varied from 25 to 145 Torr at 37°C, thereby altering plasma pH over the physiological range of 6.90–7.55, and plasma pH, PCO₂, and concentrations of quantitatively important strong ions (Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl^-, lactate) and buffer ions (total protein, albumin, phosphate) were measured. Strong ion difference was estimated, and nonlinear regression was used to calculate A_tot and K_a from the measured pH and PCO₂ and estimated strong ion difference; the A_tot and K_a values were then validated by using a published data set (Figge J, Rossing TH, and Fencl V, J Lab Clin Med 117: 453–467, 1991). The values (mean ± SD) were as follows: A_tot = 17.2 ± 3.5 mmol/l (equivalent to 0.224 mmol/g of protein or 0.378 mmol/g of albumin); K_a = 0.80 ± 0.60 x 10^-7; negative log of K_a = 7.10. Mean estimates were obtained for strong ion difference (37 meq/l) and net protein charge (13+.0 meq/l). The experimentally determined values for A_tot, K_a, and net protein charge should facilitate the diagnosis and treatment of acid-base disturbances in critically ill humans.

plasma pH; strong ion difference; anion gap; metabolic acidosis

This article has been cited by other articles:

				B.-V. Nguyen, J.-L. Vincent, J. B. Hamm, J.-H. Abalain, J.-L. Carre, E. Nowak, M. O. Ahmed, C. C. Arvieux, and G. Gueret The Reproducibility of Stewart Parameters for Acid-Base Diagnosis Using Two Central Laboratory Analyzers Anesth. Analg., November 1, 2009; 109(5): 1517 - 1523. [Abstract] [Full Text] [PDF]

				D. Boning and N. Maassen Point:Counterpoint: Lactic acid is/is not the only physicochemical contributor to the acidosis of exercise J Appl Physiol, July 1, 2008; 105(1): 358 - 359. [Full Text] [PDF]

				I. Kurtz, J. Kraut, V. Ornekian, and M. K. Nguyen Acid-base analysis: a critique of the Stewart and bicarbonate-centered approaches Am J Physiol Renal Physiol, May 1, 2008; 294(5): F1009 - F1031. [Abstract] [Full Text] [PDF]

				H. Stampfli, M. Taylor, C. McNicoll, A. Y. Gancz, and P. D. Constable Experimental determination of net protein charge, [A]tot, and Ka of nonvolatile buffers in bird plasma J Appl Physiol, June 1, 2006; 100(6): 1831 - 1836. [Abstract] [Full Text] [PDF]

				C. M. Anstey Comparison of three strong ion models used for quantifying the acid-base status of human plasma with special emphasis on the plasma weak acids J Appl Physiol, June 1, 2005; 98(6): 2119 - 2125. [Abstract] [Full Text] [PDF]

				R. M. Effros and P. D. Constable Stewart Approach Is Not Always a Practical Clinical Tool * Response Anesth. Analg., January 1, 2004; 98(1): 271 - 272. [Full Text] [PDF]