What are the lab findings in hyperchloremic acidosis?

From the Guidelines

Hyperchloric acidosis is characterized by a decreased serum pH, reduced serum bicarbonate concentration, and elevated serum chloride levels, with a normal anion gap, as evidenced by recent studies 1. The primary lab findings in hyperchloric acidosis include a decreased serum pH (below 7.35), reduced serum bicarbonate (HCO3-) concentration (below 22 mEq/L), and elevated serum chloride levels (above 106 mEq/L) 1. Some key points to consider in the lab findings of hyperchloric acidosis are:

• Decreased serum pH (below 7.35)
• Reduced serum bicarbonate (HCO3-) concentration (below 22 mEq/L)
• Elevated serum chloride levels (above 106 mEq/L)
• Normal anion gap (8-12 mEq/L)
• Low partial pressure of carbon dioxide (PaCO2) due to compensatory respiratory alkalosis
• Serum potassium may be elevated or decreased depending on the underlying cause
• Urinary pH is often low (acidic urine), and urine anion gap can help determine if renal tubular acidosis is present
• Elevated blood urea nitrogen (BUN) and creatinine if renal dysfunction is contributing to the acidosis, as seen in studies where administration of large volumes of 0.9% saline can cause hyperchloraemic acidosis, renal vasoconstriction, and AKI 1. These laboratory abnormalities reflect the underlying pathophysiology where excess chloride relative to sodium disrupts the normal electrolyte balance, leading to decreased bicarbonate reabsorption or increased bicarbonate loss, ultimately resulting in metabolic acidosis with normal anion gap.

From the Research

Lab Findings in Hyperchloremic Acidosis

• Decreases in plasma bicarbonate are associated with hyperchloremic acidosis and lactic acidosis, as seen in a study of 300 critically ill patients 2.
• The plasma strong-ion difference, both with and without lactate, has a stronger association with plasma bicarbonate than plasma chloride alone, with correlations of r = 0.60, r = 0.42, and r = -0.27, respectively 2.
• In patients with traditional hyperchloremic acidosis, the measured strong-ion difference (without lactate) has a stronger correlation with bicarbonate than chloride, with correlations of r = 0.85 versus r = -0.60 2.

Metabolic Acidosis

• Metabolic acidosis is defined as a pathologic process that increases the concentration of hydrogen ions (H+) in the body and reduces the bicarbonate (HCO3-) concentration 3.
• Metabolic acidosis can be of a kidney origin or an extrarenal cause, and assessment of urinary ammonium excretion can help distinguish between these two causes 3.
• Hyperchloremic normal gap metabolic acidosis can occur due to a primary defect in renal acidification or increased loss of bicarbonate from the body 3.

Treatment with Sodium Bicarbonate

• The use of sodium bicarbonate for metabolic acidosis has been debated, but a recent study suggests that hyperchloremic metabolic acidosis may potentially benefit from sodium bicarbonate therapy 4.
• The study found an interaction between baseline chloride, anion gap levels, and sodium bicarbonate therapy on patients' in-hospital death, with high chloride levels (≥112 mmol/L) associated with a higher incidence of hypernatremia, hypokalemia, and hypocalcemia at 24 h 4.
• Patients with high chloride levels who received sodium bicarbonate therapy had a lower simulated mortality and a lower incidence of hyperchloremia 4.