Strong Ion Approach Research Articles

Traditional and quantitative analysis of acid-base and electrolyte imbalances in horses competing in cross-country competitions at 2-star to 5-star level.

BackgroundEarly recognition and management of acid‐base, fluid, and electrolyte disorders are crucial for the maintenance of health and performance in equine athletes.ObjectivesTo analyze changes in acid‐base and electrolyte status associated with exercise during cross‐country competitions at different levels using traditional and quantitative approaches.AnimalsThirty‐eight eventing horses.MethodsProspective observational study. Jugular venous blood samples were collected before and after the cross‐country test of 25 international eventing competitions ranging from 2‐star (formerly 1‐star) to 5‐star (formerly 4‐star) level. Blood gas analysis was performed to determine pH, pCO2, Na+, Cl−, and K+ and calculate HCO3 −, tCO2 base excess (BEECF), anion gap (AG), strong ion difference calculated from Na+, K+, Cl−, and lactate− (SID4), strong ion difference calculated from Na+, K+, and Cl− (SID3), strong ion gap (SIG), and total nonvolatile weak buffer concentration (Atot). Postexercise acid‐base imbalances, diagnosed on the basis of the traditional approach, and the simplified strong ion model were compared.ResultsSignificant decreases in pH, Cl−, SID4, pCO2, HCO3 −, tCO2, and BEECF as well as increases in K+, SID3, AG, TP, and Atot were observed between pre‐ and postexercise samples. The changes in acid‐base parameters were significantly affected by the competition level. Using the strong ion approach, a higher proportion of horses was diagnosed with postexercise metabolic acidosis.Conclusions and Clinical ImportanceRegarding the complex acid‐base changes in horses competing at cross‐country competitions, the quantitative approach provided a more detailed analysis of the different factors contributing to acid‐base balance than did the traditional approach.

The use of elements of the Stewart model (Strong Ion Approach) for the diagnostics of respiratory acidosis on the basis of the calculation of a value of a modified anion gap (AGm) in brachycephalic dogs.

Apart from the HH equation, the acid-base balance of an organism is also described by the Stewart model, which assumes that the proper insight into the ABB of the organism is given by an analysis of: pCO2, the difference of concentrations of strong cations and anions in the blood serum - SID, and the total concentration of nonvolatile weak acids - Acid total. The notion of an anion gap (AG), or the apparent lack of ions, is closely related to the acid-base balance described according to the HH equation. Its value mainly consists of negatively charged proteins, phosphates, and sulphates in blood. In the human medicine, a modified anion gap is used, which, including the concentration of the protein buffer of blood, is, in fact, the combination of the apparent lack of ions derived from the classic model and the Stewart model. In brachycephalic dogs, respiratory acidosis often occurs, which is caused by an overgrowth of the soft palate, making it impossible for a free air flow and causing an increase in pCO2--carbonic acid anhydride The aim of the present paper was an attempt to answer the question whether, in the case of systemic respiratory acidosis, changes in the concentration of buffering ions can also be seen. The study was carried out on 60 adult dogs of boxer breed in which, on the basis of the results of endoscopic examination, a strong overgrowth of the soft palate requiring a surgical correction was found. For each dog, the value of the anion gap before and after the palate correction procedure was calculated according to the following equation: AG = ([Na+ mmol/l] + [K+ mmol/l])--([Cl- mmol/l]+ [HCO3- mmol/l]) as well as the value of the modified AG--according to the following equation: AGm = calculated AG + 2.5 x (albumins(r)--albumins(d)). The values of AG calculated for the dogs before and after the procedure fell within the limits of the reference values and did not differ significantly whereas the values of AGm calculated for the dogs before and after the procedure differed from each other significantly. 1) On the basis of the values of AGm obtained it should be stated that in spite of finding respiratory acidosis in the examined dogs, changes in ion concentration can also be seen, which, according to the Stewart theory, compensate metabolic ABB disorders 2) In spite of the fact that all the values used for calculation of AGm were within the limits of reference values, the values of AGm in dogs before and after the soft palate correction procedure differed from each other significantly, which proves high sensitivity and usefulness of the AGm calculation as a diagnostic method.

Acid-base disorders in calves with chronic diarrhea.

The aim of this study was to analyze disorders of acid-base balance in calves with chronic diarrhea caused by mixed, viral, bacterial and Cryptosporydium parvum infection. We compared results ob- tained with the classic model (Henderson-Hasselbalch) and strong ion approach (the Steward model). The study included 36 calves aged between 14 and 21 days. The calves were allocated to three groups: I - (control) non-diarrheic calves, group II - animals with compensated acid-base imbalance and group III calves with compensated acid-base disorders and hypoalbuminemia. Plasma concentrations of Na+, K+, Cl-, C12+, Mg2+, P, albumin and lactate were measured. In the classic model, acid-base balance was determined on the basis of blood pH, pCO2, HCO3-, BE and anion gap. In the strong ion model, strong ion difference (SID), effective strong anion difference, total plasma concentration of nonvolatile buffers (A(Tot)) and strong ion gap (SIG) were measured. The control calves and the animals from groups II and III did not differ significantly in terms of their blood pH. The plasma concentration of HCO3-, BE and partial pressure of CO2 in animals from the two groups with chronic diarrhea were significantly higher than those found in the controls. The highest BE (6.03 mmol/l) was documented in calves from group II. The animals from this group presented compensation resulted from activation of metabolic mechanisms. The calves with hypoal- buminemia (group III) showed lower plasma concentrations of albumin (15.37 g/L), Cl (74.94 mmol/L), Mg2+ (0.53 mmol/L), P (1.41 mmol/L) and higher value of anion gap (39.03 mmol/L). This group III presented significantly higher SID3 (71.89 mmol/L), SID7 (72.92 mmol/L) and SIG (43.53 mmol/L) values than animals from the remaining groups (P < 0.01), whereas A(Tot) (6.82 mmol/L) were significantly lower. The main finding of the correlation study was the excellent relationship between the AGcorr and SID3, SID7, SIG. In conclusion, chronic diarrhea leads to numerous water-electrolyte disorders. Characterization of acid-base disturbance in these cases suggests that classic model have some limitations. This model can not be recommended for use whenever serum albumin or phosphate concentrations are markedly abnormal.

Quantitative physicochemical analysis of acid-base balance and clinical utility of anion gap and strong ion gap in 806 neonatal calves with diarrhea.

BackgroundAcid‐base abnormalities in neonatal diarrheic calves can be assessed by using the Henderson‐Hasselbalch equation or the simplified strong ion approach which use the anion gap (AG) or the strong ion gap (SIG) to quantify the concentration of unmeasured strong anions such as d‐lactate.Hypothesis/ObjectivesTo determine and compare the clinical utility of AG and SIG in quantifying the unmeasured strong anion charge in neonatal diarrheic calves, and to examine the associations between biochemical findings and acid‐base variables by using the simplified strong ion approach. We hypothesized that the SIG provides a more accurate prediction of unmeasured strong anions than the AG.AnimalsEight hundred and six neonatal diarrheic calves admitted to a veterinary teaching hospital.MethodsRetrospective study utilizing clinicopathologic findings extracted from medical records.ResultsHyperphosphatemia was an important predictor of venous blood pH. Serum inorganic phosphorus and plasma d‐lactate concentrations accounted for 58% of the variation in venous blood pH and 77% of the variation in AG and SIG. Plasma d‐ and total lactate concentrations were slightly better correlated with SIG (r s = −0.69; −0.78) than to AG (r s = 0.63; 0.74).Conclusions and Clinical ImportanceStrong ion gap is slightly better at quantifying the unmeasured strong anion concentration in neonatal diarrheic calves than AG. Phosphorus concentrations should be included as part of the calculation of A tot when applying the simplified strong ion approach to acid‐base balance to critically ill animals with hyperphosphatemia.

Analysis of acid–base disorders in calves with lactic acidosis using aclassic model and strong ion approach

The objective of this study was to analyze the disorders of acid-base balance in calves with lactic acidosis using the classic model and the strong ion approach. The study included 40 calves: group I was the control group (n = 20) and group II consisted of calves with diarrhea and lactic acidosis (n = 20). The highest lactate concentration (5.49 ± 2.58 mmol/L) was documented in diarrheic calves. The diarrheic calves presented with significantly lower pH, pCO2, and concentrations of HCO3- (P < 0.01), and with higher anion gap (AG), strong ion difference (SID3, SID7), and strong ion gap (SIG) (P < 0.01) than the controls. In the group of diarrheic calves lactic acid correlated with AG (r = 0.684, P < 0.01), SID3 (r = 0.718, P < 0.01), SID7 (r = 0.494, P = 0.03), and SIG (r = 0.561, P = 0.01). There was a negative correlation between lactate and effective SID (SIDEff) (r = -0.499, P = 0.02), and total plasma concentration of nonvolatile buffers (ATot ) (r = -0.361, P = 0.04). The results indicated that in lactic acidosis there were specific disturbances with an increased concentration of unmeasured strong ions.

Blood gas analysis in dogs in veterinary practice. A review

Blood gas analysis is useful to obtain information about acid-base state and gas exchange of the lung. Interpretation is based on the Henderson-Hasselbalch equation. This approach has its limitations especially in interpretation of complex disturbances of acid-base status and has been complemented by base excess and anion gap. Peter Stewart described a model of quantitative approach to the acid-base disturbances which has been further developed and is known as the strong ion approach. This model differs from the traditional approach in the assessment of metabolic disorders of acid base status. Both models complement each other but also have their advantages and disadvantages. For simple disorders of the acid-base state the Henderson-Hasselbalch approach can be used, however in complex disturbances of acid-base balance, especially with abnormalities of serum albumin and phosphate concentrations, the strong ion approach is recommended. With the understanding of both models and of the clinical presentation of blood gas abnormalities, optimal case management and therapy can be provided.

Acid‐Base Alterations in Barrel Racing Quarter Horses of Different Fitness Levels Assessed Via The Simplified Strong Ion Approach

IntroductionThe evaluation of acid‐base balance of horses is important because it detects alterations that affect their performance and health. There are studies relating these changes with endurance type effort, but few regarding sprint exercise. The purpose of this study was to determine whether the fitness level of Quarter Horses performing barrel racing could be differentiated by quantitative acid‐base analysis.MethodsFor this purpose, 10 horses were distributed into two groups: high (HF) and lower (LF) fitness as defined by the trainer. GPS and frequency meter were used for the measurements. Venous blood gas analysis was performed using a portable analyzer (I‐stat) before and after exercise. Strong ion difference (SID), anion gap (AG), strong ion gap (SIG) and concentration of non‐volatile buffers (Atot) were determined. Variables before and after exercise were compared within and between groups by t‐test (P&lt;0.05).ResultsThe average track distance was 125 m. There were no differences between maximum or average velocity and heart rate, which were 30.76 ± 0.53 km/h, 22.85 ± 0.28 km/h, 206 bpm ± 3.91 versus 27.7 ± 2.4 km/h, 21.94 ± 0.3 km/h and 203 bpm ± 5.77 for the HF and LF groups, respectively. SID values before exercise were significantly lower for the LF group. Both groups showed a significant increase in Atot and AG, while pH, HCO3‐, SIG and SID decreased significantly after exercise.ConclusionsMetabolic acidosis was observed using both the traditional and the quantitative approach. It was not possible to differentiate the fitness level of horses in the study.Ethical Animal ResearchAll procedures were approved by the institutional animal care and use committee of the university (CEUA, Process: 008481/11). Explicit owner informed consent for participation in this study is not stated. Sources of funding: UNESP Reitoria (PIBIC). Competing interests: none.

Evaluation of pulmonary dysfunctions and acid–base imbalances induced by Chlamydia psittaci in a bovine model of respiratory infection

Background: Chlamydia psittaci (Cp) is a respiratory pathogen capable of inducing acute pulmonary zoonotic disease (psittacosis) or persistent infection. To elucidate the pathogenesis of this infection, a translational large animal model was recently introduced by our group. This study aims at quantifying and differentiating pulmonary dysfunction and acid–base imbalances induced by Cp.&#x0D; Methods: Forty-two calves were grouped in (i) animals inoculated with Cp (n = 21) and (ii) controls shaminoculated with uninfected cell culture (n = 21). For pulmonary function testing, impulse oscillometry, capnography, and FRC (functional residual capacity) measurement were applied to spontaneously breathing animals. Variables of acid–base status were assessed in venous blood using both (i) traditional Henderson-Hasselbalch and (ii) strong ion approach.&#x0D; Results: Both obstructive and restrictive pulmonary disorders were induced in calves experimentally inoculated with Cp. Although disorders in respiratory mechanics lasted for 8–11 days, the pattern of spontaneous breathing was mainly altered in the period of acute illness (until 4 days post inoculation, dpi). Expiration was more impaired than inspiration, resulting in elevated FRC. Ventilation was characterised by a reduction in tidal volume (−25%) combined with an increased percentage of dead space volume and a significant reduction of alveolar volume by 10%. Minute ventilation increased significantly (+50%) due to a compensatory doubling of respiratory rate. Hyperventilatory hypocapnia at 2–3 dpi resulted in slightly increased blood pH at 2 dpi. However, the acid–base equilibrium was additionally influenced by metabolic components, i.e. the systemic inflammatory response, all of which were detected with help of the strong ion theory. Decreased concentrations of albumin (2–10 dpi), a negative acute-phase marker, resulted in a decrease in the sum of non-volatile weak acids (Atot), revealing an alkalotic effect. This was counterbalanced by acidic effects of decreased strong ion difference (SID), mediated by the interplay between hypochloraemia (alkalotic effect) and hyponatraemia (acidic effect).&#x0D; Conclusions: This bovine model was found to be suitable for studying pathophysiology of respiratory Cp infection and may help elucidating functional host-pathogen interactions in the mammalian lung.

Response to: Strong ion approach in cardiogenic shock: formula and patients

Response to: Strong ion approach in cardiogenic shock: formula and patients

Importance of the Effective Strong Ion Difference of an Intravenous Solution in the Treatment of Diarrheic Calves with Naturally Acquired Acidemia and Strong Ion (Metabolic) Acidosis

The effect of sodium bicarbonate on acid-base balance in metabolic acidosis is interpreted differently by Henderson-Hasselbalch and strong ion acid-base approaches. Application of the traditional bicarbonate-centric approach indicates that bicarbonate administration corrects the metabolic acidosis by buffering hydrogen ions, whereas strong ion difference theory indicates that the co-administration of the strong cation sodium with a volatile buffer (bicarbonate) corrects the strong ion acidosis by increasing the strong ion difference (SID) in plasma. To investigate the relative importance of the effective SID of IV solutions in correcting acidemia in calves with diarrhea. Twenty-two Holstein-Friesian calves (4-21 days old) with naturally acquired diarrhea and strong ion (metabolic) acidosis. Calves were randomly assigned to IV treatment with a solution of sodium bicarbonate (1.4%) or sodium gluconate (3.26%). Fluids were administered over 4 hours and the effect on acid-base balance was determined. Calves suffered from acidemia owing to moderate to strong ion acidosis arising from hyponatremia and hyper-D-lactatemia. Sodium bicarbonate infusion was effective in correcting the strong ion acidosis. In contrast, sodium gluconate infusion did not change blood pH, presumably because the strong anion gluconate was minimally metabolized. A solution containing a high effective SID (sodium bicarbonate) is much more effective in alkalinizing diarrheic calves with strong ion acidosis than a solution with a low effective SID (sodium gluconate). Sodium gluconate is ineffective in correcting acidemia, which can be explained using traditional acid-base theory but requires a new parameter, effective SID, to be understood using the strong ion approach.

Comparison of the utility of the classic model (the Henderson-Hasselbach equation) and the Stewart model (Strong Ion Approach) for the diagnostics of acid-base balance disorders in dogs with right sided heart failure

Classically, the acid-base balance (ABB) is described by the Henderson-Hasselbach equation, where the blood pH is a result of a metabolic components--the HCO3(-) concentration and a respiratory component--pCO2. The Stewart model assumes that the proper understanding of the organisms ABB is based on an analysis of: pCO2, Strong Ion difference (SID)--the difference strong cation and anion concentrations in the blood serum, and the Acid total (Atot)--the total concentration of nonvolatile weak acids. Right sided heart failure in dogs causes serious haemodynamic disorders in the form of peripheral stasis leading to formation of transudates in body cavities, which in turn causes ABB respiratory and metabolic disorders. The study was aimed at analysing the ABB parameters with the use of the classic method and the Stewart model in dogs with the right sided heart failure and a comparison of both methods for the purpose of their diagnostic and therapeutic utility. The study was conducted on 10 dogs with diagnosed right sided heart failure. Arterial and venous blood was drawn from the animals. Analysis of pH, pCO2 and HCO3(-) was performed from samples of arterial blood. Concentrations of Na+, K+, Cl(-), P(inorganic), albumins and lactate were determined from venous blood samples and values of Strong Ion difference of Na+, K+ and Cl(-) (SID3), Strong Ion difference of Na+, K+, Cl(-) and lactate (SID4), Atot, Strong Ion difference effective (SIDe) and Strong Ion Gap (SIG4) were calculated. The conclusions are as follows: 1) diagnosis of ABB disorders on the basis of the Stewart model showed metabolic alkalosis in all dogs examined, 2) in cases of circulatory system diseases, methodology based on the Stewart model should be applied for ABB disorder diagnosis, 3) if a diagnosis of ABB disorders is necessary, determination of pH, pCO2 and HCO3(-) as well as concentrations of albumins and P(inorganic) should be determined on a routine basis, 4) for ABB disorder diagnosis, the classic model should be used only when the concentrations of albumins and P(inorganic) are normal.

Acid‐base imbalances during a 120 km endurance race compared by traditional and simplified strong ion difference methods

Acid-base disturbances are traditionally assessed using the Henderson-Hasselbach equation. The simplified strong ion approach describes more accurately the complex acid-base and electrolyte abnormalities present in endurance horses. To describe acid-base and electrolytes changes in fit horses competing in a FEI*** 120 km endurance race and to compare the traditional vs. strong ion approaches. Thirty horses were initially enrolled in the study. Venous blood samples were obtained before the race (n = 25), at the second (n = 29; 65.4 km) and third vet-gates (n = 23, 97.4 km) and upon race completion (n = 17). Blood gas analysis was performed to determine pH, PCO(2), PO(2), Na(+), K(+) and iCa(++), and calculate HCO(3)(-), base excess and tCO(2). Packed cell volume and total protein, globulin, albumin, lactate, phosphate, glucose and creatinine concentrations, as well as muscle enzymes activities, were also determined. Calculated variables included strong ion difference (SIDm), strong ion gap (SIG) and nonvolatile buffer concentration (A(tot)). A longitudinal linear model using the general estimating equation methodology was used for statistical analysis. Mild but significant increases in PCO(2), SIDm, lactate, plasma protein, globulins and A(tot), as well as a decrease in potassium concentrations were observed from the second vet-gate to race finish when compared to prerace values (P < 0.05). Using the strong ion approach, 67% samples showed acid-base disturbances vs. 70% when using the traditional method, but their interpretations only matched in 24% of measurements. A complex acid-base imbalance characterised by a mild strong ion alkalosis (hypochloraemia attenuated by hyperlactataemia), nonvolatile buffer acidosis and compensatory mild respiratory acidosis were present in most horses, although pH did not significantly change during a 120 km endurance race. The strong ion approach to interpretation of acid-base balance should be favoured over the traditional approach in endurance horses, given the frequent and complex alterations in PCO(2), SIDm and A(tot) during a race.

Mathematical modelling of the acid–base chemistry and oxygenation of blood: a mass balance, mass action approach including plasma and red blood cells

Mathematical models of the acid-base chemistry of blood based upon mass action and mass balance equations have become popular as diagnostic tools in intensive care. The reference models using this approach are those based on the strong ion approach, but these models do not currently take into account the effects of oxygen on the buffering characteristics of haemoglobin. As such these models are limited in their ability to simulate physiological situations involving simultaneous changes of O(2) and CO(2) levels in the blood. This paper describes a model of acid-base chemistry of blood based on mass action and mass balance equations and including the effects of oxygen. The model is used to simulate the mixing of venous blood with the same blood at elevated O(2) and reduced CO(2) levels, and the results compared with the mixing of blood sampled from 21 healthy subjects. Simulated values of pH, PCO(2), PO(2) and SO(2) in the mixed blood compare well with measured values with small bias (i.e. 0.000 pH, -0.06 kPa PCO(2), -0.1% SO(2), -0.02 kPa PO(2)), and values of standard deviations (i.e. 0.006 pH, 0.11 kPa PCO(2), 0.8% SO(2), 0.13 kPa PO(2)) comparable to the precision seen in direct measurement of these variables in clinical practice. These results indicate that the model can reliably simulate the mixing of blood and has potential for application in describing physiological situations involving the mixing of blood at different O(2) and CO(2) levels such as occurs in the mixing of lung capillary and shunted pulmonary blood.

Application of strong ion difference theory to urine and the relationship between urine pH and net acid excretion in cattle

To develop an equation expressing urine pH in terms of independent variables, derive an equation relating urine pH to net acid excretion (NAE), and apply this new knowledge to determine the role that monitoring urine pH should play when diets with low cationanion difference are fed to dairy cattle. 11 Holstein-Friesian cows. A physicochemical strong ion approach was used to develop a general electroneutrality equation for urine that involved urine pH and strong ion difference (SID [difference between strong cation and strong anion concentrations]), PCO(2), the concentration of ammonium ([NH(4)(+)]) and phosphate ([PO(4)]), and 3 constants. The general electroneutrality equation was simplified for use in bovine urine and applied to 321 data points from 11 cows fed different diets. Urine pH was dependent on 4 independent variables (urine SID, [NH(4)(+)], PCO(2), and [PO(4)]) and 3 constants. The simplified electroneutrality equation for bovine urine was pH approximately {pK(1)' - log(10)(S PCO(2))} + log(10)([K(+)] + [Na(+)] + [Mg(2+)] + [Ca(2+)] + [NH(4)(+)] - [Cl(-)] - [SO(4)(2-)]). The relationship between urine pH and NAE (in mEq/L) for cattle fed different diets was pH = 6.12 + log(10)(-NAE + [NH(4)(+)] + 2.6). A change in urine SID, [NH(4)(+)], PCO(2), or [PO(4)] independently and directly led to a change in urine pH. Urinary [K(+)] had the greatest effect on urine pH in cattle, with high urine [K(+)] resulting in alkaline urine and low urine [K(+)] resulting in acidic urine. Urine pH provided an accurate assessment of NAE in cattle when pH was > 6.3.

Acid-base analysis: a critique of the Stewart and bicarbonate-centered approaches

When approaching the analysis of disorders of acid-base balance, physical chemists, physiologists, and clinicians, tend to focus on different aspects of the relevant phenomenology. The physical chemist focuses on a quantitative understanding of proton hydration and aqueous proton transfer reactions that alter the acidity of a given solution. The physiologist focuses on molecular, cellular, and whole organ transport processes that modulate the acidity of a given body fluid compartment. The clinician emphasizes the diagnosis, clinical causes, and most appropriate treatment of acid-base disturbances. Historically, two different conceptual frameworks have evolved among clinicians and physiologists for interpreting acid-base phenomena. The traditional or bicarbonate-centered framework relies quantitatively on the Henderson-Hasselbalch equation, whereas the Stewart or strong ion approach utilizes either the original Stewart equation or its simplified version derived by Constable. In this review, the concepts underlying the bicarbonate-centered and Stewart formulations are analyzed in detail, emphasizing the differences in how each approach characterizes acid-base phenomenology at the molecular level, tissue level, and in the clinical realm. A quantitative comparison of the equations that are currently used in the literature to calculate H(+) concentration ([H(+)]) is included to clear up some of the misconceptions that currently exist in this area. Our analysis demonstrates that while the principle of electroneutrality plays a central role in the strong ion formulation, electroneutrality mechanistically does not dictate a specific [H(+)], and the strong ion and bicarbonate-centered approaches are quantitatively identical even in the presence of nonbicarbonate buffers. Finally, our analysis indicates that the bicarbonate-centered approach utilizing the Henderson-Hasselbalch equation is a mechanistic formulation that reflects the underlying acid-base phenomenology.

Influence of Stewart acid–base variables on plasma pH in critically ill patients

The study objective was to determine and quantify the influence of strong-ion approach variables on the plasma pH in critically ill patients.

Hyperchloraemic metabolic acidosis following open cardiac surgery

Aims: To describe acid–base derangements in children following open cardiac surgery on cardiopulmonary bypass (CPB), using the Fencl–Stewart strong ion approach. Methods: Prospective observational study set in the paediatric intensive...

Use of a Quantitative Strong Ion Approach to Determine the Mechanism for Acid—Base Abnormalities in Sick Calves with or without Diarrhea

Acid‐base abnormalities are frequently present in sick calves. The mechanism for an acid‐base disturbance can be characterized using the strong ion approach, which requires accurate values for the total concentration of plasma nonvolatile buffers (Atot) and the effective dissociation constant for plasma weak acids (Ka). The aims of this study were to experimentally determineAtot,Ka, and net protein charge values for calf plasma and to apply these values quantitatively to data from sick calves to determine underlying mechanisms for the observed acid‐base disturbance. Plasma was harvested from 9 healthy Holstein‐Friesian calves and concentrations of quantitatively important strong ions (Na+, K+, Ca2+, Mg2+, Cl‐, L‐lactate) and nonvolatile buffer ions (total protein, albumin, phosphate) were determined. Plasma was tonometered with CO2at 37°C, and plasma PCO2and pH measured over a range of 15–159 mm Hg and 6.93‐7.79, respectively. Strong ion difference (SID) was calculated from the measured strong ion concentrations, and nonlinear regression was used to estimate values forAtotandKafrom the measured pH and PCO2and calculated SID. The estimatedAtotandKavalues were then validated using data from 2 in vivo studies. Mean (± SD) values for calf plasma wereAtot= 0.343 mmol/g of total protein or 0.622 mmol/g of albumin;Ka= (0.84 ± 0.41) × 10‐7;pKa= 7.08. The net protein charge of calf plasma was 10.5 mEq/L, equivalent to 0.19 mEq/g of total protein or 0.34 mEq/g of albumin. Application of the strong ion approach to acid‐base disturbances in 231 sick calves with or without diarrhea indicated that acidemia was due predominantly to a strong ion acidosis in response to hyponatremia accompanied by normochloremia or hyperchloremia and the presence of unidentified strong anions. These results confirm current recommendations that treatment of acidemia in sick calves with or without diarrhea should focus on intravenous or PO administration of a fluid containing sodium and a high effective SID.

Experimental Determination of Net Protein Charge andAtotandKaof Nonvolatile Buffers in Canine Plasma

Acid-base abnormalities frequently are present in sick dogs. The mechanism for an acid-base disturbance can be determined with the simplified strong ion approach, which requires accurate values for the total concentration of plasma nonvolatile buffers (A(tot)) and the effective dissociation constant for plasma weak acids (K(a)). The aims of this study were to experimentally determine A(tot) and K(a) values for canine plasma. Plasma was harvested from 10 healthy dogs; the concentrations of quantitatively important strong ions (Na+, K+, Ca2+, Mg2+, Cl-, L-lactate) and nonvolatile buffer ions (total protein, albumin, phosphate) were determined; and the plasma was tonometered with CO2 at 37 degrees C. Strong ion difference (SID) was calculated from the measured strong ion concentrations, and nonlinear regression was used to estimate values for A(tot) and K(a), which were validated with data from an in vitro and in vivo study. Mean (+/- SD) values for canine plasma were A(tot) = (17.4 +/- 8.6) mM (equivalent to 0.273 mmol/g of total protein or 0.469 mmol/g of albumin); K(a) = (0.17 +/- 0.11) x 10(-7); pK(a) = 7.77. The calculated SID for normal canine plasma (pH = 7.40; P(CO2) = 37 mm Hg; [total protein] = 64 g/L) was 27 mEq/L. The net protein charge for normal canine plasma was 0.25 mEq/g of total protein or 0.42 mEq/g of albumin. Application of the experimentally determined values for A(tot), K(a), and net protein charge should improve understanding of the mechanism for complex acid-base disturbances in dogs.

Use of a Quantitative Strong Ion Approach to Determine the Mechanism for Acid–Base Abnormalities in Sick Calves with or without Diarrhea

Acid-base abnormalities are frequently present in sick calves. The mechanism for an acid-base disturbance can be characterized using the strong ion approach, which requires accurate values for the total concentration of plasma nonvolatile buffers (A(tot)) and the effective dissociation constant for plasma weak acids (K(a)). The aims of this study were to experimentally determine A(tot), K(a), and net protein charge values for calf plasma and to apply these values quantitatively to data from sick calves to determine underlying mechanisms for the observed acid-base disturbance. Plasma was harvested from 9 healthy Holstein-Friesian calves and concentrations of quantitatively important strong ions (Na+, K+, Ca2+, Mg2+, Cl-, L-lactate) and nonvolatile buffer ions (total protein, albumin, phosphate) were determined. Plasma was tonometered with CO2 at 37 degrees C, and plasma P(CO2) and pH measured over a range of 15-159 mm Hg and 6.93-7.79, respectively. Strong ion difference (SID) was calculated from the measured strong ion concentrations, and nonlinear regression was used to estimate values for A(tot) and K(a) from the measured pH and P(CO2) and calculated SID. The estimated A(tot) and K(a) values were then validated using data from 2 in vivo studies. Mean (+/- SD) values for calf plasma were A(tot) = 0.343 mmol/g of total protein or 0.622 mmol/g of albumin; K(a) = (0.84 +/- 0.41) x 10(-7); pK(a) = 7.08. The net protein charge of calf plasma was 10.5 mEq/L, equivalent to 0.19 mEq/g of total protein or 0.34 mEq/g of albumin. Application of the strong ion approach to acid-base disturbances in 231 sick calves with or without diarrhea indicated that acidemia was due predominantly to a strong ion acidosis in response to hyponatremia accompanied by normochloremia or hyperchloremia and the presence of unidentified strong anions. These results confirm current recommendations that treatment of acidemia in sick calves with or without diarrhea should focus on intravenous or PO administration of a fluid containing sodium and a high effective SID.