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J Appl Physiol 100: 1831-1836, 2006. First published January 19, 2006; doi:10.1152/japplphysiol.01367.2005
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Experimental determination of net protein charge, [A]tot, and Ka of nonvolatile buffers in bird plasma

Henry Stämpfli,1 Michael Taylor,1 Carl McNicoll,1 Ady Y. Gancz,1 and Peter D. Constable2

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

Submitted 27 October 2005 ; accepted in final form 16 January 2006


   ABSTRACT
TOP
 ABSTRACT
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 GRANTS
 REFERENCES
 
The quantitative mechanistic acid-base approach to clinical assessment of acid-base status requires species-specific values for [A]tot (the total concentration of nonvolatile buffers in plasma) and Ka (the effective dissociation constant for weak acids in plasma). The aim of this study was to determine [A]tot and Ka values for plasma in domestic pigeons. Plasma from 12 healthy commercial domestic pigeons was tonometered with 20% CO2 at 37°C. Plasma pH, PCO2, and plasma concentrations of strong cations (Na, K, Ca), strong anions (Cl, L-lactate), and nonvolatile buffer ions (total protein, albumin, phosphate) were measured over a pH range of 6.8–7.7. Strong ion difference (SID) (SID5 = Na + K + Ca – Cl – lactate) was used to calculate [A]tot and Ka from the measured pH and PCO2 and SID5. Mean (±SD) values for bird plasma were as follows: [A]tot = 7.76 ± 2.15 mmol/l (equivalent to 0.32 mmol/g of total protein, 0.51 mmol/g of albumin, 0.23 mmol/g of total solids); Ka = 2.15 ± 1.15 x 10–7; and pKa = 6.67. The net protein charge at normal pH (7.43) was estimated to be 6 meq/l; this value indicates that pigeon plasma has a much lower anion gap value than mammals after adjusting for high mean L-lactate concentrations induced by restraint during blood sampling. This finding indicates that plasma proteins in pigeons have a much lower net anion charge than mammalian plasma protein. An incidental finding was that total protein concentration measured by a multianalyzer system was consistently lower than the value for total solids measured by refractometer.

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

ACID-BASE BALANCE HAS TRADITIONALLY been evaluated by using the Henderson-Hasselbalch equation (17, 18) to characterize four primary acid-base disturbances (i.e., respiratory acidosis and alkalosis, metabolic acidosis and alkalosis) (2, 10, 28) and by calculating the anion gap (AG) to estimate the unmeasured anion concentration (4, 7, 9, 23). Because the traditional Henderson-Hasselbalch approach is more descriptive than mechanistic (9) and fails to provide an accurate method for quantifying the unmeasured strong ion charge in animals with abnormal serum protein concentrations (4, 7, 10, 23, 28), alternative approaches to the clinical assessment of acid-base balance are required. A physicochemical approach derived from strong ion difference (SID) theory considers three independent variables (plasma SID, PCO2, and plasma nonvolatile buffer ion concentration) to directly determine plasma pH. This approach differs in three important areas from the traditional bicarbonate centric application of the Henderson-Hasselbalch equation (13): 1) acid-base balance is examined using a systems approach; 2) a clear conceptual distinction is made between dependent variables {such as pH and bicarbonate concentration ([HCO3–])} and the independent variables; and 3) the effects of protein concentration on acid-base balance are considered (10, 26, 28, 29). The strong ion approach characterizes six primary acid-base disturbances (i.e., respiratory acidosis and alkalosis, strong ion acidosis and alkalosis, nonvolatile buffer ion acidosis and alkalosis), and the unmeasured strong anion concentration is quantified by calculating the strong ion gap (SIG) (4, 13, 19).

The strong ion approach requires species-specific values for the total plasma concentration of nonvolatile weak acids ([A]tot; i.e., the total concentration of plasma nonvolatile buffers: albumin, globulin, and phosphate) and the effective dissociation constant (Ka) for plasma nonvolatile buffers (8, 26). Values for [A]tot and Ka have been experimentally determined in the plasma of horses (8, 27), humans (26), cats (21), dogs (6), and calves (5), and theoretically determined for the plasma of humans (11) and adult cattle (9). Values for [A]tot and Ka of bird plasma are presently unavailable. The objective of the study was to experimentally determine [A]tot and Ka values for avian plasma; to compare these values with [A]tot and Ka values for the plasma of horses, calves, cats, dogs, and humans; and to calculate the net protein charge in bird plasma. This information will facilitate our understanding of acid-base abnormalities in birds.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 GRANTS
 REFERENCES
 
Twelve healthy domestic meat pigeons were acclimated for 5 days before the start of the blood sampling. The birds were physically restrained for venipuncture of the basilic vein of one wing. Five to ten milliliters of venous blood were thus collected into lithium-heparin vacuum tubes from each bird. One aliquot of whole venous blood was immediately analyzed anaerobically in duplicate on an automated blood-gas analyzer to characterize the normal values for this group of birds. The following parameters were measured simultaneously at 37°C (Statprofile M, NOVA Biomedical, Canada, Mississauga, Ontario): blood-gas analysis (pH, PCO2) and determination of [Na+], [K+], [Ca2+], [Cl–], and [L-lactate–] (where brackets denote concentration). Plasma was harvested from the remaining blood aliquot by centrifugation within 30 min of collection, and CO2 tonometry was performed on all samples within 60 min of collection. An untonometered plasma aliquot was analyzed in duplicate for determination of the strong cation magnesium and nonvolatile buffer ion (total protein, albumin, and inorganic phosphate) concentrations (Hitachi 911 with Roche reagents). Duplicate values from each bird were averaged, and the average was used from each parameter of each bird to calculate mean and SD of all birds (normal venous blood values).

CO2 tonometry of plasma.   Plasma samples were tonometered (model IL235, Instrumentation Laboratory, Lexington, MA) for 20 min at 37°C over a PCO2 range of 20–145 Torr and a pH range of 6.80–7.65 using a mixture of humidified 20% CO2 and 80% normal air alternating with 100% normal air as washout. Previous experience with tonometry has shown that the changes in PCO2 occur rapidly, and, therefore, individual samples were aspirated at empiric intervals anaerobically into a capillary tube and analyzed directly using the automated blood-gas analyzer, as detailed above. A total of 88 CO2 tonometered plasma samples were analyzed, representing four to nine tonometered samples from each bird. PCO2 varied from 20 to 145 Torr, yielding pH values between 6.8 and 7.8. All tonometered plasma samples were analyzed once for blood/plasma gas analysis (pH, PCO2) and determination of [Na+], [K+], [Ca2+], [Cl–], and [L-lactate–] simultaneously.

Calculation of SID.   A fixed value for SID during in vitro CO2 tonometry is one of the assumptions of the strong ion approach; SID is invariant over the physiological range of pH, because strong ions are fully dissociated at physiological pH (8, 26, 29). Therefore, all strong cation (Na+, K+, Ca2+, Mg2+) and strong anion (Cl–, L-lactate) concentrations were assumed to be constant during CO2 tonometry, and an ionic equivalency using ion-selective potentiometry (Mg2+) was assigned to those variables not measured. Accurate measurements of SID are difficult to obtain in plasma because of cumulative measurement error, presence of unknown strong anions (13, 19, 26), and differences in equipment and methodology used to measure strong ion concentrations (25). SID was initially calculated for each bird's titration using the following four formulas: SID3 = {([Na+] + [K+]) – [Cl–]}; SID4 = {([Na+] + [K+]) – ([Cl–] + [lactate])}; SID5 = {([Na+] + [K+] + [Ca2+]) – ([Cl–] + [L-lactate])}; SID6 = {([Na+] + [K+] + [Ca2+] + [Mg2+]) – ([Cl–] + [lactate])}. Mean ± SD of all titrations of each bird was obtained as constants for each SID3–6 (data not shown) for use in linear regression analyses.

Estimation of [A]tot and Ka.   Measured values for pH and PCO2, each bird's individual constant SID3–6, the simplified strong ion electroneutrality equation (8), and the Marquardt nonlinear regression procedure (14) (PROC NLIN, SAS 8e, SAS Institute, Cary, NC) were used to simultaneously estimate values for [A]tot and Ka for each bird. This required application of the simplified strong ion electroneutrality equation:

Formula 1(1)
in which the net nonvolatile buffer ion concentration in plasma ([A–]) was evaluated. To assist in estimating values for [A]tot and Ka, Eq. 1 was expressed in the following form:

Formula 2(2)
using known values for solubility coefficient for CO2 (S) (0.0307 mmol·l–1·mmHg–1) (3) and –log of first dissociation constant of carbonic acid (pK1) (6.120 at [NaCl] = 0.16 mmol/l) (15). Using the value of 6.120 for pK1 calculates actual plasma [HCO3–] in millimoles per liter at 37°C (24); likewise, the methods used to calculate SID3–6 provide a value in terms of concentration. This means that Eq. 2 estimates a value for [A]tot in terms of concentration (mmol/l) (8). Initial estimates for [A]tot of 5–30 mmol/l in increments of 5 mmol/l and initial estimates for Ka of 0.1 x 10–7 to 3.0 x 10–7 in increments of 0.1 x 10–7 were used for the nonlinear regression procedure (14). For each pigeon's nonlinear regression procedure, the accuracy of the estimated values for [A]tot and Ka were evaluated using the number of iterations required to converge to a solution, the R2 value, comparison of actual vs. predicted values for [HCO3–], calculation of standardized residuals, studentized residuals, Cook's distance, examination of residual plots (plot of the difference between measured and predicted [HCO3–] values on the y-axis vs. pH on the x-axis), and normal probability plots of the residuals (14); the R2 value was considered to be the most important measure of model fit. A value of P < 0.05 was regarded as significant. Means ± SD (all birds combined) of SID3–6, [A]tot, and Ka for all birds were calculated.

The calculated [A]tot values for each bird were evaluated as the [A]tot indexed to the total protein concentration ([A]tot-tp), the [A]tot indexed to the albumin concentration ([A]tot-alb), and the [A]tot indexed to total solids ([A]tot-ts). Mean (±SD) values for [A]tot, [A]tot-tp, [A]tot-alb, [A]tot-ts, and Ka were determined.

Total solids as measured with a refractometer (Veterinary refractometer: Leica vet 360) were graphically compared with total protein estimation on an automatic analyzer (Hitachi 911 with Roche reagents) to examine agreement between the two methods.

Comparison of calculated and measured pH values.   pH was calculated from the measured value for SID and PCO2, estimated values for [A]tot (based on plasma albumin concentration) and Ka, known values for S (0.0307 mmol·l–1·mmHg–1) (3) and pK1 (6.120 at [NaCl] = 0.16 mmol/l) (15), and the simplified strong ion equation expressing pH as a function of the three independent factors (SID, PCO2, [A]tot) and three constants (Ka, S, pK1) (8). The calculated pH value was regressed against the measured pH value using linear regression analysis, and the relationship was compared with the line of identity (14).

Comparison of [A]tot and Ka values.   The estimated values for [A]tot and Ka in plasma of birds were compared with results from studies using identical experimental methodology for plasma of calves (5), horses (8, 27), humans (26), cats (21), and dogs (6) by using an unpaired t-test. Because five multiple comparisons were being performed, the P value for significance was Bonferroni adjusted for the number of comparisons, producing a P <0.01 as significant.

Sensitivity of plasma pH and [HCO3–] to changes in SID, PCO2, and [A]tot.   Sensitivity of the dependent variables (plasma pH and [HCO3–]) to the three independent factors, SID, PCO2, and [A]tot, was conveyed by a spider plot (11), which graphically depicted the relationship between the dependent variables and percentage change in one independent factor, while the remaining two independent factors were held constant at typical values. The spider plots were created using Eq. 1 solved for the dependent variable pH and [HCO3–] using mean SID and PCO2 values for the plasma of healthy pigeons (determined in this study) and estimated values for [A]tot and Ka (29). In addition, the derivatives of pH and HCO3– with respect to the three independent factors (SID, PCO2, [A]tot) were then calculated using an Excel software program to provide an index of the sensitivity of plasma pH and HCO3– to changes in each of the independent factors at physiological pH.


   RESULTS
TOP
 ABSTRACT
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 GRANTS
 REFERENCES
 
Blood and plasma analyses.   The values for venous blood from 12 meat pigeons are presented in Table 1. Mean sodium and chloride plasma concentrations of pigeons were comparable to dogs and were higher compared with humans (6, 26). Pigeons had high mean plasma [L-lactate] induced by manual restraint for blood sampling.


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  		Table 1. Mean (±SD) biochemical values of plasma obtained from venous blood samples collected from the basilic vein of 12 pigeons

 
Calculation of SID.   Much larger differences in the mean value for SID3–6 were observed compared with other species (dogs, horses, cats, and ruminants) (Table 2). The larger differences in SID3–6 values were mainly due to the high plasma [L-lactate] in pigeons (Table 1).


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  		Table 2. Summary of mean (±SD) estimated values for SID, Ka, [A]tot, [A]tot-alb, [A]tot-tp, and [A]tot-ts for 12 pigeons

 
Estimation of [A]tot and Ka.   The R2 values for nonlinear regression models using SID5 and SID6 were >0.990, indicating excellent fit to the data, whereas the R2 values using SID3 and SID4 were always numerically lower (data not shown). Mean ± SD values for [A]tot and Ka derived from SID3, SID4, SID5, and SID6 indicated that the estimates derived from SID5 and SID6 were more precise (Table 2). Either pair of [A]tot and Ka values derived from SID5 and SID6 would be suitable; however, we selected those derived from SID5 for further evaluation because the SD value for Ka was numerically smaller.

Comparison of calculated and measured pH values.   Calculation of pH from the measured values for the three independent factors (SID5, PCO2, [A]tot) and three constants (Ka, S, pK'1) indicated excellent agreement between calculated and measured pH values over a physiologically large range of pH (6.83–7.68; R2 = 0.974, Fig. 1). The slope (0.981) and intercept (0.132) for the linear regression equation relating calculated pH to measured pH were similar to the line of identity (slope = 1, P = 0.23; intercept = 0, P = 0.27).


Figure 1
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  		Fig. 1. Relationship between calculated and measured pH values. pH was calculated using the simplified strong ion equation (Eq. 1), expressing pH as a function of the 3 independent factors strong ion difference (SID5), PCO2, total plasma concentration of nonvolatile weak acids ([A]tot)} and 3 constants (Ka, S, pK'1) (8). The dashed line is the line of identity, and the solid line is the linear regression line (slope = 0.981; intercept = 0.132; R2 = 0.974).

 
Comparison of [A]tot and Ka values.   The [A]tot values of pigeon plasma were lower than that of cat, calf, human, dog, and equine plasma (Table 3). In contrast, the Ka values were similar to those of horse plasma but higher (P < 0.001) than those for dog, cat, calf, and human plasma.


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  		Table 3. Mean (±SD) values for [A]tot, [A]tot-alb, [A]tot-tp and Ka of plasma from different species

 
Sensitivity of plasma pH and [HCO3–] to changes in SID, PCO2, and [A]tot.   Analysis of the spider plots revealed that pigeon plasma pH was most sensitive to changes in SID (Fig. 2) at physiological pH. Likewise, analysis of the spider plots depicted that pigeon plasma [HCO3–] was most sensitive to changes in SID at physiological pH (Fig. 3).


Figure 2
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  		Fig. 2. Spider plot revealing the dependence of plasma pH on changes in the 3 independent variables (SID, PCO2, and [A]tot). The spider plot was obtained by systematically varying 1 independent variable while holding the other 2 independent variables at their reference values for pigeon plasma. Reference values for the 3 independent variables were as follows: SID5, 33.5 meq/l ({blacklozenge}); PCO2, 41.4 Torr ({blacksquare}); [A]tot, 7.8 mmol/l ({blacktriangleup}). The vertical solid line at 0 indicates that pH = 7.43 when SID, PCO2, and [A]tot are at their reference values.

 

Figure 3
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  		Fig. 3. Spider plot revealing the dependence of plasma bicarbonate (HCO3–) concentration on changes in the 3 independent variables (SID, PCO2, and [A]tot). The spider plot was obtained by systematically varying 1 independent variable while holding the other 2 independent variables at their reference values for pigeon plasma. Reference values for the 3 independent variables were as follows: SID5, 33.5 meq/l ({blacklozenge}); PCO2, 41.4 Torr ({blacksquare}); [A]tot, 7.8 mmol/l ({blacktriangleup}). The vertical solid line at 0 indicates that plasma HCO3– concentration = 26.0 mmol/l when SID, PCO2, and [A]tot are at their reference values.

 
Net protein charge for model with SID5.   Net protein charge has two components: nonvolatile buffer ion charge and SID charge. The value for [A–] at pH = 7.43 reflects the net negative buffer ion charge of protein and phosphate; [A–] = [A]tot/(1 + 10Formula 2– pH) = 7.8 mmol/l/(1 + 106.67 – 7.43) = 6.65 meq/l (assuming nondissociated portion of the weak acids) is uncharged, A– has a valence of –1, and pKa is the negative logarithm to base 10 of the calculated Ka value. Because the net negative buffer ion charge of phosphate at pH = 7.43 approximates 0.96 meq/l (0.8 x [phosphate]; Table 1), the nonvolatile buffer ion charge of protein was 6.65 – 0.96 {approx} 6 meq/l. The true value for SID calculated using algebraic rearrangement of Eq. 2 when pH = 7.43 (Table 1), PCO2 = 41.4 Torr (Table 1), [A]tot = 7.8 mmol/l (Table 2), and Ka = 2.15 x 10–7 (Table 2) is 33.5 meq/l, which approximated the value for SID5 (32.8 meq/l; Table 1). This result suggests that plasma proteins have a SID charge of approximately zero; net protein charge, therefore, results primarily from nonvolatile buffer ion charge and approximates 6 meq/l.

The normal Gamble gram of birds.   Figure 4 demonstrates the composition of the normal Gamble gram of bird plasma based on the results of 12 healthy meat pigeons (Table 1).


Figure 4
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  		Fig. 4. Simplified Gamblegram of normal avian plasma {electroneutrality: ([Na+] + [K+]) – [Cl–] + [HCO3–] + [A–] – [Lac–] = 0; 0.94 meq/l}, where brackets denote concentration.

 
Concentration of total solids (refractometer) and total protein concentrations.   Figure 5 shows relationship between total protein concentration and total solids as measured with refractometry.


Figure 5
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  		Fig. 5. Total plasma protein concentration compared with total solid concentration of each bird. {blacklozenge}, Total solids; {blacksquare}, total protein.

 

   DISCUSSION
TOP
 ABSTRACT
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
GRANTS
 REFERENCES
 
Use of the strong ion approach to evaluate acid-base status requires species-specific values for [A]tot and Ka (26). In this study, mean values for [A]tot (0.32 mmol/g of total protein or 0.51 mmol/g of albumin; or 0.23 mmol/unit of total solids) and Ka (2.15 x 10–7) were experimentally established for plasma of meat pigeons.

An interesting finding was that the [A]tot value of pigeon plasma was lower than that of cat, calf, human, dog, and equine plasma (Table 3) and that the Ka values were similar to horse plasma but higher to those for dog, cat, calf, and human plasma. Because the main determinants of [A]tot and Ka are the plasma albumin concentration and number and mean pKa value of histidine residues on albumin (6, 8, 9, 11, 21, 26), it is not surprising that values for [A]tot and Ka of avian plasma are different from those of mammalian plasma. As a group, the albumin and total protein concentrations in avian plasma are much lower than those of mammalian plasma (Table 3) (16); however, when [A]tot was indexed to the albumin ([A]tot-alb) or total protein concentration ([A]tot-tp), the values for avian plasma were similar to mammalian values. This indicates that the main reason for the low [A]tot value of pigeon plasma is the low plasma albumin and total protein concentrations. Differences in the Ka value of avian plasma and most mammalian species were most likely due to small differences in the mean pKa value of histidine moieties on albumin.

The mean AG was ~13 meq/l, comprising 7 meq/l of L-lactate and 6 meq/l of plasma protein charge. The AG in healthy pigeons differs from that in small-animal species (dog, cat), because the AG of pigeons reflects the plasma protein concentration and the [L-lactate]; the latter was increased markedly due to restraint for blood sampling and represents a "restraint artifact." Our results suggest that the normal AG of an unrestrained pigeon is ~7 meq/l, assuming a normal [L-lactate] of 1 mmol/l (28).

A useful clinical application of SID theory is calculation of the SIG instead of the AG (4, 10). The SIG provides an estimate for the difference between the unmeasured strong anion charge (mostly due to L-lactate, D-lactate, sulfate, nonesterified fatty acids, ketoacids, pH-independent protein and phosphate charge, and very few other strong anions) and unmeasured strong cation charge (Ca2+, Mg2+). The SIG is also referred to as the difference between a measured SID and an effective SID (26). Total protein or albumin concentrations can be used to calculate [A]tot for calculation of the SIG. Based on estimated values for [A]tot and Ka, the following equations for calculating SIG (in meq/l) in the plasma of pigeons are proposed:

Formula 3(3)
where [total protein] is in g/l and the AG (in meq/l) = ([Na+] + [K+]) – ([Cl–] + [HCO3–]). The major component of SIG in pigeons is L-lactate (Table 1), and this equation may be used to estimate the [L-lactate] in laboratories where lactate measurements are not available.

A worrisome observation was the discrepancy between total protein plasma concentrations (Hitachi 911e) and total protein concentrations estimated by refractometer as total solids. Normally there is excellent agreement between refractometer readings of total solids and biuret estimation of total protein concentrations in domestic species (12). The literature on correlation for avian biuret plasma protein concentrations compared with total solid estimation varies, and some studies showed good agreement (chicken, turkey, duck) (1, 22), whereas one study in pigeons showed poor to no agreement that was attributed to interference by high concentrations of other refractive compounds in plasma, such as chromagens, lipids, and glucose (16, 20). The exact cause of the difference is not known. Physiologically, the higher total protein concentrations estimated by refractometry appear to make sense. This aspect needs further investigation.

We did not measure plasma urate concentration in the pigeons. Failure to account for the urate concentration in plasma could theoretically lead to an error in estimating SID, because the pKa of uric acid is 5.6; urate, therefore, is categorized as a strong anion at physiological pH (8). However, the serum urate concentration in birds is <0.8 mmol/l, with the normal range for Columba livia (pigeon) being 0.15–0.77 mmol/l (16). The plasma urate concentration is, therefore, quantitatively small relative to the measurement error in SID and can, therefore, be ignored.

In conclusion, application of the experimentally determined values for [A]tot, Ka, and net protein charge of pigeon plasma should improve our understanding of the mechanism for complex acid-base disturbances in critically ill pigeons.


   GRANTS
TOP
 ABSTRACT
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 GRANTS
REFERENCES
 
Funding for this project was obtained from Pet Trust Ontario Veterinary College, University of Guelph, Guelph, Canada.


   FOOTNOTES
 

Address for reprint requests and other correspondence: H. Stämpfli, Dept. of Clinical Studies, Ontario Veterinary College, Univ. of Guelph, Guelph, Ontario, Canada N1G 2W1 (e-mail: hstaempf{at}uoguelph.ca)

The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.


   REFERENCES
TOP
 ABSTRACT
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 GRANTS
 REFERENCES
 

  1. Andreasen CB, Latimer KS, Kircher IM, and Brown J. Determination of chicken and turkey plasma and serum protein concentrations by refractometry and the biuret method. Avian Dis 33: 93–96, 1989.[CrossRef][ISI][Medline]
  2. Astrup P, Jorgensen K, Siggaard Anderson O, and Engel K. The acid-base metabolism. A new approach. Lancet 1: 1035–1037, 1960.[ISI][Medline]
  3. Austin WH, Lacombe E, Rand PW, and Chatterjee M. Solubility of carbon dioxide in serum from 15 to 38°C. J Appl Physiol 18: 301–304, 1963.[Abstract/Free Full Text]
  4. Constable PD, Hinchcliff KW, and Muir WW. Comparison of anion gap and strong ion gap as predictors of unmeasured strong ion concentration in plasma and serum from horses. Am J Vet Res 59: 881–887, 1998.[ISI][Medline]
  5. Constable PD, Stämpfli HR, Navetat H, Berchtold J, and Schelcher F. Use of a quantitative strong ion approach to determine the mechanism for acid-base abnormalities in sick calves with or without diarrhea. J Vet Intern Med 19: 581–589, 2005.[CrossRef][ISI][Medline]
  6. Constable PD and Stämpfli HR. Experimental determination of net protein charge and A(tot) and K(a) of nonvolatile buffers in canine plasma. J Vet Intern Med 19: 507–514, 2005.[CrossRef][ISI][Medline]
  7. Constable PD, Streeter RK, Koenig GR, Perkins NR, Gohar HM, and Morin DE. Determinants and utility of the anion gap in predicting hyperlactatemia in cattle. J Vet Intern Med 11: 71–79, 1997.[ISI][Medline]
  8. Constable PD. A simplified strong ion model for acid-base equilibria: application to horse plasma. J Appl Physiol 83: 297–311, 1997.[Abstract/Free Full Text]
  9. Constable PD. Calculation of variables describing plasma nonvolatile weak acids for use in the strong ion approach to acid-base balance in cattle. Am J Vet Res 63: 482–490, 2002.[CrossRef][ISI][Medline]
  10. Constable PD. Clinical assessment of acid-base status: comparison of the Henderson-Hasselbalch and strong ion approaches. Vet Clin Pathol 29: 115–128, 2000.[Medline]
  11. Constable PD. Total weak acid concentration and effective dissociation constant of nonvolatile buffers in human plasma. J Appl Physiol 91: 1364–1371, 2001.[Abstract/Free Full Text]
  12. George JW and O'Neill SL. Comparison of refractometer and biuret methods for total protein measurement in body cavity fluids. Vet Clin Pathol 30: 16–18, 2001.[ISI][Medline]
  13. Gilfix BM, Bique M, and Magder S. A physical chemical approach to the analysis of acid-base balance in the clinical setting. J Crit Care 8: 187–197, 1993.[CrossRef][ISI][Medline]
  14. Glantz SA and Slinker BK. Primer of Applied Regression and Analysis of Variance. New York: McGraw-Hill, 1990, p. 1–777.
  15. Harned HS and Bonner FT. The first ionization of carbonic acid in aqueous solutions of sodium chloride. J Am Chem Soc 67: 1026–1031, 1945.[CrossRef]
  16. Harr KE. Clinical chemistry of companion avian species: a review. Vet Clin Pathol 31: 140–151, 2002.[ISI][Medline]
  17. Hasselbalch KA. Die Berechnung der Wasserstoffzahl des Blutes aus der freien und gebundenen Kohlensäure desselben, und die Sauerstoffbindung des Blutes als Funktion der Wasserstoffzahl. Biochem Z 78: 112–144, 1916.[ISI]
  18. Henderson LJ. The theory of neutrality regulation in the animal organism. Am J Physiol 21: 427–428, 1908.[Free Full Text]
  19. Kellum JA, Kramer DJ, and Pinsky MR. Strong ion gap: a methodology for exploring unexplained anions. J Crit Care 10: 51–55, 1995.[CrossRef][ISI][Medline]
  20. Lumeij JT, de Bruijne JJ, and Kwant MM. Comparison of different methods of measuring protein and albumin in pigeon sera. Avian Pathol 19: 255–261, 1990.[Medline]
  21. McCullough SM and Constable PD. Calculation of the total plasma concentration of nonvolatile weak acids and the effective dissociation constant of nonvolatile buffers in plasma for use in the strong ion approach to acid-base balance in cats. Am J Vet Res 64: 1047–1051, 2003.[CrossRef][ISI][Medline]
  22. Morgan GW, Thaxton P, and Edens FW. Estimation of protein content in the plasma of young chickens by a refractometric method. Poult Sci 54: 1312–1314, 1975.[ISI][Medline]
  23. Oh MS and Carroll HJ. Current concepts. The anion gap. N Engl J Med 297: 814–817, 1977.[ISI][Medline]
  24. Putnam RW and Roos A. Which value for the first dissociation constant of carbonic acid should be used in biological work? Am J Physiol Cell Physiol 260: C1113–C1116, 1991.[Abstract/Free Full Text]
  25. Rodriguez-Garcia J, Sogo T, Otero S, and Paz JM. Transferability of results obtained for sodium, potassium and chloride ions with different analysers. Clin Chim Acta 275: 151–162, 1998.[CrossRef][ISI][Medline]
  26. Staempfli HR and Constable PD. Experimental determination of net protein charge and Atot and Ka of nonvolatile buffers in human plasma. J Appl Physiol 95: 620–630, 2003.[Abstract/Free Full Text]
  27. Stampfli HR, Misiaszek JH, Lumsden, Carlson GP, and Heigenhauser GJ. Weak acid-concentration Atot and dissociation constant Ka of plasma proteins in racehorses. Equine Vet J Suppl 30: 438–442, 1999.[Medline]
  28. Stämpfli HR and Carlson GP. How to use routine serum biochemical profile to understand and interpret acid-base disorders in the horse. AAEP Proc 47: 257–261, 2001.
  29. Stewart PA. Modern quantitative acid-base chemistry. Can J Physiol Pharmacol 61: 1444–1461, 1983.[ISI][Medline]
  30. Van Slyke DD. On the measurement of buffer values and on the relationship of buffer value to the dissociation constant of the buffer and the concentration and reaction of the buffer solution. J Biol Chem 52: 525–570, 1922.[Free Full Text]



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