How is metabolic alkalosis managed?

Management of Metabolic Alkalosis

The most effective treatment for metabolic alkalosis depends on identifying and addressing the underlying cause, with chloride-responsive alkalosis typically requiring normal saline administration and chloride-resistant cases requiring specific interventions targeting the underlying disorder.

Diagnosis and Classification

• Metabolic alkalosis is characterized by elevated pH and plasma bicarbonate levels above normal range 1
• Classification into chloride-responsive and chloride-resistant types guides treatment approach 2
• Common laboratory findings include elevated serum bicarbonate, compensatory increase in pCO2, and often hypokalemia and hypochloremia 1, 2

Chloride-Responsive Metabolic Alkalosis

Causes

• Diuretic therapy (especially loop and thiazide diuretics) 2
• Gastrointestinal losses (vomiting, nasogastric suction) 3
• Volume contraction with chloride depletion 1

Treatment

• Normal saline (0.9% NaCl) administration is the cornerstone of treatment for chloride-responsive metabolic alkalosis 1
• Potassium chloride supplementation when hypokalemia is present (20-60 mEq/day to maintain serum potassium in 4.5-5.0 mEq/L range) 2
• Discontinuation or reduction of diuretic doses when possible 2

Chloride-Resistant Metabolic Alkalosis

Causes

• Mineralocorticoid excess (primary hyperaldosteronism, Cushing syndrome) 3
• Bartter syndrome and Gitelman syndrome 2
• Severe potassium depletion 3

Treatment

• Address the underlying cause (e.g., treatment of primary hyperaldosteronism) 3
• For Bartter syndrome: sodium chloride supplementation (5-10 mmol/kg/day), potassium chloride, and consideration of NSAIDs 2
• Consider gastric acid inhibitors together with NSAIDs in Bartter syndrome patients 2

Pharmacologic Interventions

Acetazolamide

• Effective for diuretic-induced alkalosis in patients with adequate kidney function 2
• Mechanism: Decreases serum strong ion difference (SID) by increasing renal excretion ratio of sodium to chloride 4
• Single dose of acetazolamide can effectively correct metabolic alkalosis in critically ill patients 4

Potassium-Sparing Diuretics

• Amiloride is the most effective potassium-sparing diuretic for metabolic alkalosis (initial dose 2.5 mg daily, can be titrated up to 5 mg daily) 2
• Spironolactone can be used at an initial dose of 25 mg daily, titrated up to 50-100 mg daily 2
• Caution: Avoid combining potassium-sparing diuretics with ACE inhibitors without close monitoring due to hyperkalemia risk 2

Severe or Refractory Cases

• For severe metabolic alkalosis unresponsive to conventional therapy, dilute hydrochloric acid (0.1-0.2 N HCl) may be administered intravenously through a central venous catheter 5, 1
• Ammonium chloride is an alternative but should be avoided in patients with hepatic dysfunction 5
• Dialysis with higher K+, Cl- and low HCO3- bath may be appropriate in emergency situations with severe hypokalemia 1

Special Considerations

• In heart failure patients with metabolic alkalosis, consider adding an aldosterone antagonist (spironolactone) to the diuretic regimen 2
• Avoid potassium salts other than potassium chloride (such as potassium citrate) as they can worsen metabolic alkalosis 2
• Monitor serum electrolytes, acid-base status, and volume status regularly during treatment 2

Common Pitfalls to Avoid

• Overlooking the possibility of Bartter syndrome in patients with unexplained metabolic alkalosis, especially with history of polyhydramnios and premature birth 2
• Using potassium-sparing diuretics in patients with significant renal dysfunction or existing hyperkalemia 2
• Treating the alkalosis without addressing the underlying cause, which often leads to recurrence 3