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A Quick Reference on Hyperchloremic Metabolic Acidosis
A Q u i c k R e f e ren c e o n H y p e rc h l o re m i c M e t a b o l i c A cidos is Silvia Funes,
a DVM ,
Helio Autran de Morais,
DVM, PhD
b,
*
KEYWORDS Acidosis Anion gap Chloride Hyperchloremia KEY POINTS Hyperchloremic metabolic acidosis is identified by a decrease in pH, an increase in chloride, decrease in HCO3 or base excess, decrease in strong ion difference and normal anion gap. Chloride constitutes approximately two-thirds of the anions in plasma and in the remainder of extracellular fluid. When hyperchloremia is secondary to a decrease in free water, the concentration of Na1 also changes. Corrected chloride accounts for changes in plasma free water.
INTRODUCTION
Metabolic acidosis results from an increase in the concentration of a strong anion. Metabolic acidosis is divided in hyperchloremic metabolic acidosis and high anion gap (AG) acidosis based on the changes in the AG. The AG represents the difference between unmeasured cations and unmeasured anions, and it is calculated on any patient using commonly measured chemistry values as follows: AG 5 (Na1 1 K1) – (Cl 1 HCO3 ). Whenever there is an increase in unmeasured anions (eg, lactate, ketoanions) or chloride, HCO3 concentration decreases to maintain electroneutrality. - If the decrease in HCO3 is matched by an increase in chloride, the AG does not change and the acidosis is classified as hyperchloremic or normal AG acidosis. - If the acidosis is secondary to the addition of unmeasured anions, the decrease in HCO3 is not accompanied by an increase in chloride concentration. Thus, the AG increases resulting in the so-called high AG acidosis.
The authors have nothing to disclose. a Department of Clinical Sciences, College of Veterinary Medicine, Oregon State University, 700 Southwest 30th Street, Corvallis, OR 97331, USA; b College of Veterinary Medicine, Oregon State University, 700 Southwest 30th Street, Corvallis, OR 97331, USA * Corresponding author. E-mail address: [email protected] Vet Clin Small Anim - (2016) -–http://dx.doi.org/10.1016/j.cvsm.2016.11.001 0195-5616/16/ª 2016 Elsevier Inc. All rights reserved.
vetsmall.theclinics.com
2
Funes & de Morais
Chloride is the most abundant strong anion in plasma and extracellular fluid. It is also the most prevalent anion in gastric juices, small and large intestinal fluids, and glomerular ultrafiltrate. Chloride and Na1 concentrations are affected by increase and decrease in free water and the concentration of chloride needs to be corrected to identify acid-base disturbances. CORRECTED CHLORIDE
Chloride concentration must be corrected to account for changes in plasma free water. Primary chloride disorders have abnormal corrected chloride, whereas changes in free water do not. Corrected chloride is estimated as [Cl ]corrected 5 [Cl ]measured 146/[Na1]measured (dogs) [Cl ]corrected 5 [Cl ]measured 156/[Na1]measured (cats) where [Cl ]measured and [Na1] measured, respectively, are the patient’s serum chloride and sodium concentrations. The values 146 and 156 reflect the mean value for serum sodium concentration in dogs and cats. Normal [Cl ]corrected is approximately 107 to 113 mEq/L in dogs and 117 to 123 mEq/L in cats. These values may vary among laboratories and analyzers. ANALYSIS
Indications: HCO3 and chloride concentration should be measured in patients with systemic diseases (eg, vomiting, diarrhea, polyuria, and polydipsia), patients receiving fluidotherapy, and patients receiving total parenteral nutrition. Artifacts: Changes in free water can affect chloride and sodium concentration. To determine if a change in chloride is secondary to free water or an acid-base disturbance, the chloride concentration needs to be corrected. Potassium bromide therapy may lead to pseudohyperchloremia because bromide and other halides (eg, fluoride, iodide) are measured as chloride. CAUSES
Hyperchloremic metabolic acidosis is the result of chloride retention, excessive loss of sodium relative to chloride, or excessive gain of chloride relative to sodium (Box 1). Excessive Loss of Sodium Relative to Chloride
Gastrointestinal losses of HCO3 in dogs with diarrhea can lead to hyperchloremic metabolic acidosis. Intestinal fluid is rich in HCO3 but has a lower chloride concentration. Excessive Gain of Chloride Relative to Sodium
Administration of fluids with higher concentration of chloride than sodium as compared with the normal extracellular fluid concentration (eg, 0.9% NaCl, 7.2% NaCl, KCl). Total parenteral nutrition with amino acid–containing fluids, which metabolism leads to an increase in production of H1. Salt poisoning
Quick Reference on Hyperchloremic Metabolic Acidosis
Box. 1 Causes of hyperchloremic metabolic acidosis 1. Pseudohyperchloremia: potassium bromide therapy 2. Excessive loss of sodium relative to chloride a. Diarrhea 3. Excessive gain of chloride relative to sodium a. Fluid therapy (eg, 0.9% NaCl, hypertonic saline, KCL supplementation) b. Total parenteral nutrition with amino acid–containing fluids c. Salt poisoning 4. Chloride retention a. Early stages of chronic kidney disease b. Renal tubular acidosis (proximal or distal) c. Hypoadrenocorticism d. Spironolactone treatment e. Correction phase of diabetic ketoacidosis
Chloride Retention
Early stages of chronic renal failure as a consequence of chloride retention. Renal tubular acidosis (RTA) secondary to either decreased HCO3 reabsorption (proximal RTA) or a defect in acid excretion (distal RTA). Hypoadrenocorticism is associated with a deficit in aldosterone and an increase in concentrations of Cl (corrected chloride), H1, and K1. Treatment with spironolactone has similar effects. Patients with diabetes mellitus and ketoacidosis may have a normal AG because the ketones are excreted through the kidneys and chloride is retained in place of them. CLINICAL SIGNS
Clinical signs are related to the underlying disease that accompanies the metabolic acidosis. Treatment of hyperchloremic acidosis is based on addressing the underlying disease process. SUGGESTED READINGS
de Morais HA, Constable PD. Strong ion approach to acid-base disorders. In: DiBartola SP, editor. Fluid, electrolyte, and acid-base disorders. 4th edition. St Louis: Elsevier; 2012. p. 316–29. DiBartola SP. Metabolic acid-base disorders. In: DiBartola SP, editor. Fluid, electrolyte, and acid-base disorders. 4th edition. St Louis: Elsevier; 2012. p. 253–86.
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a DVM ,
Helio Autran de Morais,
DVM, PhD
b,
*
KEYWORDS Acidosis Anion gap Chloride Hyperchloremia KEY POINTS Hyperchloremic metabolic acidosis is identified by a decrease in pH, an increase in chloride, decrease in HCO3 or base excess, decrease in strong ion difference and normal anion gap. Chloride constitutes approximately two-thirds of the anions in plasma and in the remainder of extracellular fluid. When hyperchloremia is secondary to a decrease in free water, the concentration of Na1 also changes. Corrected chloride accounts for changes in plasma free water.
INTRODUCTION
Metabolic acidosis results from an increase in the concentration of a strong anion. Metabolic acidosis is divided in hyperchloremic metabolic acidosis and high anion gap (AG) acidosis based on the changes in the AG. The AG represents the difference between unmeasured cations and unmeasured anions, and it is calculated on any patient using commonly measured chemistry values as follows: AG 5 (Na1 1 K1) – (Cl 1 HCO3 ). Whenever there is an increase in unmeasured anions (eg, lactate, ketoanions) or chloride, HCO3 concentration decreases to maintain electroneutrality. - If the decrease in HCO3 is matched by an increase in chloride, the AG does not change and the acidosis is classified as hyperchloremic or normal AG acidosis. - If the acidosis is secondary to the addition of unmeasured anions, the decrease in HCO3 is not accompanied by an increase in chloride concentration. Thus, the AG increases resulting in the so-called high AG acidosis.
The authors have nothing to disclose. a Department of Clinical Sciences, College of Veterinary Medicine, Oregon State University, 700 Southwest 30th Street, Corvallis, OR 97331, USA; b College of Veterinary Medicine, Oregon State University, 700 Southwest 30th Street, Corvallis, OR 97331, USA * Corresponding author. E-mail address: [email protected] Vet Clin Small Anim - (2016) -–http://dx.doi.org/10.1016/j.cvsm.2016.11.001 0195-5616/16/ª 2016 Elsevier Inc. All rights reserved.
vetsmall.theclinics.com
2
Funes & de Morais
Chloride is the most abundant strong anion in plasma and extracellular fluid. It is also the most prevalent anion in gastric juices, small and large intestinal fluids, and glomerular ultrafiltrate. Chloride and Na1 concentrations are affected by increase and decrease in free water and the concentration of chloride needs to be corrected to identify acid-base disturbances. CORRECTED CHLORIDE
Chloride concentration must be corrected to account for changes in plasma free water. Primary chloride disorders have abnormal corrected chloride, whereas changes in free water do not. Corrected chloride is estimated as [Cl ]corrected 5 [Cl ]measured 146/[Na1]measured (dogs) [Cl ]corrected 5 [Cl ]measured 156/[Na1]measured (cats) where [Cl ]measured and [Na1] measured, respectively, are the patient’s serum chloride and sodium concentrations. The values 146 and 156 reflect the mean value for serum sodium concentration in dogs and cats. Normal [Cl ]corrected is approximately 107 to 113 mEq/L in dogs and 117 to 123 mEq/L in cats. These values may vary among laboratories and analyzers. ANALYSIS
Indications: HCO3 and chloride concentration should be measured in patients with systemic diseases (eg, vomiting, diarrhea, polyuria, and polydipsia), patients receiving fluidotherapy, and patients receiving total parenteral nutrition. Artifacts: Changes in free water can affect chloride and sodium concentration. To determine if a change in chloride is secondary to free water or an acid-base disturbance, the chloride concentration needs to be corrected. Potassium bromide therapy may lead to pseudohyperchloremia because bromide and other halides (eg, fluoride, iodide) are measured as chloride. CAUSES
Hyperchloremic metabolic acidosis is the result of chloride retention, excessive loss of sodium relative to chloride, or excessive gain of chloride relative to sodium (Box 1). Excessive Loss of Sodium Relative to Chloride
Gastrointestinal losses of HCO3 in dogs with diarrhea can lead to hyperchloremic metabolic acidosis. Intestinal fluid is rich in HCO3 but has a lower chloride concentration. Excessive Gain of Chloride Relative to Sodium
Administration of fluids with higher concentration of chloride than sodium as compared with the normal extracellular fluid concentration (eg, 0.9% NaCl, 7.2% NaCl, KCl). Total parenteral nutrition with amino acid–containing fluids, which metabolism leads to an increase in production of H1. Salt poisoning
Quick Reference on Hyperchloremic Metabolic Acidosis
Box. 1 Causes of hyperchloremic metabolic acidosis 1. Pseudohyperchloremia: potassium bromide therapy 2. Excessive loss of sodium relative to chloride a. Diarrhea 3. Excessive gain of chloride relative to sodium a. Fluid therapy (eg, 0.9% NaCl, hypertonic saline, KCL supplementation) b. Total parenteral nutrition with amino acid–containing fluids c. Salt poisoning 4. Chloride retention a. Early stages of chronic kidney disease b. Renal tubular acidosis (proximal or distal) c. Hypoadrenocorticism d. Spironolactone treatment e. Correction phase of diabetic ketoacidosis
Chloride Retention
Early stages of chronic renal failure as a consequence of chloride retention. Renal tubular acidosis (RTA) secondary to either decreased HCO3 reabsorption (proximal RTA) or a defect in acid excretion (distal RTA). Hypoadrenocorticism is associated with a deficit in aldosterone and an increase in concentrations of Cl (corrected chloride), H1, and K1. Treatment with spironolactone has similar effects. Patients with diabetes mellitus and ketoacidosis may have a normal AG because the ketones are excreted through the kidneys and chloride is retained in place of them. CLINICAL SIGNS
Clinical signs are related to the underlying disease that accompanies the metabolic acidosis. Treatment of hyperchloremic acidosis is based on addressing the underlying disease process. SUGGESTED READINGS
de Morais HA, Constable PD. Strong ion approach to acid-base disorders. In: DiBartola SP, editor. Fluid, electrolyte, and acid-base disorders. 4th edition. St Louis: Elsevier; 2012. p. 316–29. DiBartola SP. Metabolic acid-base disorders. In: DiBartola SP, editor. Fluid, electrolyte, and acid-base disorders. 4th edition. St Louis: Elsevier; 2012. p. 253–86.
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