How is metabolic alkalosis treated?

Treatment of Metabolic Alkalosis

The treatment of metabolic alkalosis should focus on correcting the underlying cause, with isotonic saline (0.9% NaCl) administration as first-line therapy for chloride-responsive alkalosis to correct both volume depletion and chloride deficit. 1

Classification and Diagnostic Approach

Metabolic alkalosis is characterized by:

• Elevated serum bicarbonate (>26 mEq/L)
• Decreased serum chloride (<98 mmol/L)
• Elevated arterial pH (>7.45)
• Often accompanied by hypokalemia (<3.5 mEq/L)

Classification based on urinary chloride:

• Chloride-responsive alkalosis (urinary chloride <20 mEq/L)
  • Caused by volume depletion, vomiting, nasogastric suction
• Chloride-resistant alkalosis (urinary chloride >20 mEq/L)
  • Caused by diuretics, mineralocorticoid excess, Bartter syndrome

Treatment Algorithm

1. Chloride-Responsive Metabolic Alkalosis (Urinary Cl <20 mEq/L)

• First-line therapy: Isotonic saline (0.9% NaCl) administration 1
  • Corrects volume depletion
  • Replaces chloride deficit
  • Promotes renal bicarbonate excretion
  • Suppresses the renin-angiotensin-aldosterone system
• Potassium supplementation: Add potassium chloride if hypokalemia is present 1
  • Target potassium level: 4.0-5.0 mEq/L

2. Diuretic-Induced Metabolic Alkalosis

• Reduce or discontinue the offending diuretic 1
• Consider adding spironolactone to counteract hypokalemia and metabolic alkalosis 2
• Caution: High doses of furosemide can cause severe electrolyte disturbances and metabolic alkalosis 2

3. Severe or Refractory Metabolic Alkalosis

• For patients who cannot tolerate fluid therapy or require rapid correction:
  • Ammonium chloride infusion (first choice for patients with normal hepatic function) 3
  • Dilute hydrochloric acid (0.1-0.2 N) via central venous catheter for patients with hepatic dysfunction 3, 4
  • Consider dialysis with low-bicarbonate bath in patients with kidney failure and severe alkalosis 1, 4

Special Considerations

Hypokalemia Management

• Potassium chloride supplementation is essential when hypokalemia is present 1
• Check magnesium levels and correct if deficient, as hypomagnesemia can perpetuate hypokalemia 1
• Avoid non-chloride potassium salts when hypochloremia is present 1

Monitoring

• Check serum electrolytes within 24 hours of initiating therapy 1
• More frequent monitoring for IV replacement 1
• Adjust fluid and electrolyte therapy based on renal function 1

Common Pitfalls to Avoid

• Avoid potassium-sparing diuretics in contraction alkalosis as they can worsen volume depletion 1
• Avoid thiazides as they may lead to life-threatening hypovolemia 1
• Avoid correcting potassium too rapidly to prevent complications 1
• Do not use potassium supplements with potassium-sparing diuretics without close monitoring 1
• Be alert for surreptitious causes of metabolic alkalosis (vomiting, laxative abuse, diuretic abuse, alkali ingestion) in unexplained cases 5

Specific Clinical Scenarios

Vomiting-Induced Alkalosis

• Potassium chloride infusion restores the kidney's ability to excrete bicarbonate 6
• Correct volume depletion with isotonic saline 1, 6

Bartter Syndrome

• Long-term potassium chloride supplementation 1
• Consider NSAIDs in symptomatic patients 1

By addressing the underlying cause and correcting electrolyte imbalances, most cases of metabolic alkalosis can be effectively managed, reducing associated morbidity and mortality.