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

Background

Early recognition and management of acid‐base, fluid, and electrolyte disorders are crucial for the maintenance of health and performance in equine athletes.

Objectives

To analyze changes in acid‐base and electrolyte status associated with exercise during cross‐country competitions at different levels using traditional and quantitative approaches.

Animals

Thirty‐eight eventing horses.

Methods

Prospective 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 (BE_ECF), 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 (A_tot). Postexercise acid‐base imbalances, diagnosed on the basis of the traditional approach, and the simplified strong ion model were compared.

Results

Significant decreases in pH, Cl⁻, SID₄, pCO₂, HCO₃⁻, tCO₂, and BE_ECF as well as increases in K⁺, SID₃, AG, TP, and A_tot 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 Importance

Regarding 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.

[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.

Hyperkalemia in neonatal diarrheic calves depends on the degree of dehydration and the cause of the metabolic acidosis but does not require the presence of acidemia

Hyperkalemia is a clinically important electrolyte imbalance in neonatal diarrheic calves that has previously been associated with skeletal muscle weakness and life-threatening cardiac arrhythmias. The aim of the present retrospective analysis was to identify risk factors for hyperkalemia in a convenience sample of 832 calves (≤ 21 d of age) with a clinical diagnosis of diarrhea admitted to a veterinary teaching hospital. Plasma potassium concentrations were most closely associated with parameters of dehydration and renal function such as serum creatinine [Spearman correlation (rs) = 0.61], urea (rs = 0.51), and inorganic phosphorus concentrations (rs = 0.64). Plasma potassium concentrations were weakly associated with venous blood pH (rs = -0.21). Although venous blood pH was not predictive in a multivariate linear regression analysis, the odds of having hyperkalemia (>5.8 mmol/L) in acidemic calves was found to be 8.6 times as high as in nonacidemic calves [95% confidence interval (CI): 4.8-15.4]. However, the presence of hyperkalemia depended on the nature of an existing acidosis, and the odds for the presence of hyperkalemia in acidemic calves with hyper-D-lactatemia (>3.96 mmol/L) were only 0.15 times as high as in acidemic calves with normal D-lactate concentrations (95% CI, 0.11-0.22). Acidemia in hyperkalemic diarrheic calves was associated with hyponatremia and increased concentrations of inorganic phosphorus, L-lactate, and unidentified strong anions that presumably included uremic anions such as sulfate. We conclude that hyper-D-lactatemia in neonatal diarrheic calves is not usually associated with elevated plasma potassium concentrations. Application of the simplified strong ion acid-base model indicated that dehydration is an important contributor to the pathogenesis of hyperkalemia and acidemia in neonatal calves with diarrhea.