What is the treatment approach for metabolic alkalosis?

Treatment of Metabolic Alkalosis

The treatment of metabolic alkalosis depends on classifying it by urinary chloride concentration and addressing the underlying cause: chloride-responsive alkalosis (urinary Cl <20 mEq/L) requires saline and potassium chloride replacement, while chloride-resistant alkalosis (urinary Cl >20 mEq/L) requires potassium-sparing diuretics or treatment of the underlying disorder. 1

Initial Assessment and Classification

• Measure urinary chloride concentration immediately to determine if the alkalosis is chloride-responsive (<20 mEq/L) or chloride-resistant (>20 mEq/L), as this guides the entire treatment strategy 1
• Check serum potassium, as hypokalemia (<3.5 mmol/L) commonly accompanies metabolic alkalosis and must be corrected to >3.5 mmol/L for successful treatment 1
• Assess volume status clinically, as volume depletion is the most common perpetuating factor 2
• Consider Bartter or Gitelman syndrome in patients with chloride-resistant alkalosis, especially with a history of polyhydramnios and premature birth 1

Treatment Based on Etiology

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

This includes diuretic-induced alkalosis, vomiting, and nasogastric suctioning.

• Administer normal saline (0.9% NaCl) for volume repletion, which allows the kidneys to excrete excess bicarbonate 2, 3
• Give potassium chloride 20-60 mEq/day to maintain serum potassium in the 4.5-5.0 mEq/L range; potassium chloride is essential as other potassium salts (like potassium citrate) will worsen the alkalosis 1
• Discontinue or reduce diuretic doses if possible, as loop and thiazide diuretics perpetuate metabolic alkalosis 1

Chloride-Resistant Alkalosis (Urinary Cl >20 mEq/L)

This includes hyperaldosteronism, severe hypokalemia, and Bartter/Gitelman syndrome.

• Amiloride is the first-line potassium-sparing diuretic, starting at 2.5 mg daily and titrating up to 5 mg daily as needed 1
• Spironolactone 25 mg daily (titrate to 50-100 mg daily) is an alternative, particularly in heart failure patients 1
• Avoid combining potassium-sparing diuretics with ACE inhibitors without close monitoring due to hyperkalemia risk 1
• For Bartter or Gitelman syndrome: sodium chloride supplementation 5-10 mmol/kg/day plus potassium chloride, with NSAIDs for symptomatic patients (use gastric acid inhibitors concurrently) 1

Pharmacologic Interventions for Severe or Refractory Cases

Acetazolamide

Acetazolamide 500 mg IV as a single dose is highly effective in patients with heart failure and adequate kidney function, causing rapid fall in serum bicarbonate with normalization of pH within 2 hours and maximal effect at 15.5 hours 1, 4, 5

• Acetazolamide inhibits carbonic anhydrase in the kidney, causing renal loss of bicarbonate along with sodium, water, and potassium 4
• The effect is still apparent at 48 hours with no adverse effects noted in clinical studies 5
• Do not use acetazolamide in patients with significant renal dysfunction 1
• Monitor for hypokalemia, as acetazolamide increases potassium excretion 4

Hydrochloric Acid (HCl)

For refractory cases unresponsive to conventional therapy, dilute hydrochloric acid (0.1-0.2 N) may be administered through a central venous catheter at a maximum rate of 0.2 mmol H+/kg/hour 6, 3

• This is particularly indicated in patients with hepatic dysfunction who cannot metabolize ammonium chloride or arginine monohydrochloride 6
• Hemodialysis with low-bicarbonate/high-chloride dialysate is the treatment of choice for refractory metabolic alkalosis with concurrent renal failure 1, 2
• Ammonium chloride is an alternative but requires hepatic conversion and should be avoided in liver disease 6

Special Situations

Heart Failure Patients

• Manage circulatory failure appropriately as this is integral to treatment 1
• Add spironolactone to the diuretic regimen to counter metabolic alkalosis while treating volume overload 1
• Switch to longer-acting loop diuretics or add potassium-sparing diuretics if diuretic-induced alkalosis persists 1

Severe Metabolic Alkalosis with Anasarca

• Avoid sodium bicarbonate or alkalinization strategies, as these are contraindicated and will worsen the alkalosis 1
• Do not use furosemide unless hypervolemia, hyperkalemia, or renal acidosis are present, as loop diuretics perpetuate alkalosis 1

Monitoring

• Monitor serum electrolytes, acid-base status (pH, bicarbonate, base excess), and volume status frequently 1
• Adjust therapy based on clinical response and laboratory parameters 1
• Resolution is indicated by serum bicarbonate ≥18 mEq/L, venous pH >7.3, and anion gap ≤12 mEq/L 7

Common Pitfalls to Avoid

• Never use potassium salts other than potassium chloride (such as potassium citrate or potassium bicarbonate), as these worsen metabolic alkalosis 1
• Do not overlook Bartter or Gitelman syndrome in patients with unexplained chloride-resistant alkalosis 1
• Avoid potassium-sparing diuretics in patients with significant renal dysfunction or existing hyperkalemia 1
• Do not use bicarbonate therapy in metabolic alkalosis—this is only for metabolic acidosis with pH <6.9 7