Metabolic Alkalosis

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Contents 1 Etiology 2 Clinical-manifestations 3 Management 4 More General Terms 5 References

Etiology

• chloride-responsive (urine Cl- < 10 meq/L)

• contraction alkalosis ( volume depletion)

• vomiting/ NG suction: upper GI loss of HCl
• thiazide & loop diuretics: renal loss of HCl

• cystic fibrosis
• villous adenoma
• congenital chloridorrhea

• chloride-resistant (urine Cl- > 20 meq/L) [much less common]

• hypertensive

• primary hyperaldosteronism
• Cushing's syndrome
• renal artery stenosis
• glucocorticoid/ mineralocorticoid therapy
• inhibitors of 11-beta hydroxysteroid dehydrogenase

• licorice ingestion
• tobacco chewing
• Liddle's syndrome

• diuretics & K+ depletion
• hypercalcemia
• hypoparathyroidism

• normotensive or hypotensive

• Bartter's syndrome
• Gitelman's syndrome

• pCO2 higher than expected

• COPD & diuretics
• ARDS & diuretics

• pCO2 lower than expected

• CHF & diuretics
• cirrhosis & diuretics
• hyperemesis

Clinical-manifestations

• respiratory compensation with hypoventilation
• weakness
• muscle cramps
• hyperreflexia
• dysrhythmias Labaratory:
• arterial blood gas

• increased pH
• increased pCO2

• electrolytes

• serum bicarbonate: increased HCO3-
• serum K+: hypokalemia
• serum chloride: hypocloremia

• serum aldosterone: may be increased
• urine chloride

• < 15 meq/L (chloride-responsive
• > 15 meq/L (chloride-resistant)

• * Predicted pCO2 ( respiratory) compensation for pure metabolic alkalosis ( PaCO2, arterial)

• pCO2 ( mm Hg) +/- 5 = 0.9 x HCO3- ( meq/L) + 15
• pCO2 increases 10 mm Hg for each 7 meq/L rise in [[[Hco3- | HCO3-]]]
• response is limited by hypoxemia [2]

Management

• correct underlying disorder

• remove renin- secreting tumor
• remove aldosterone- secreting tumor
• discontinue offending agents

• chloride-responsive ( saline-responsive) alkalosis

• NaCl tablets
• saline
• treat hypokalemia with KCl
• acetazolamide 250-500 mg PO or IV every 8 hours

• CHF with edema present
• cor pulmonale
• hepatic cirrhosis
• post-hypercapnic state

• reduction of gastric HCl loss

• proton-pump inhibitor

• lansoprazole
• omeprazole

• H2-receptor antagonist

• ranitidine
• cimetidine

• chloride-resistant alkalosis

• discontinue offending agents

• thiazides
• loop diuretics

• correct Mg+2 deficiency
• correct K+ deficits
• amiloride, triamterene or spironolactone

• treatment of severe metabolic alkalosis ( pH > 7.55)

• particularly if contraindication to NaCl administration

• heart failure
• renal failure

• HCl solution

• 150 mL of 1.0 N HCL in 1 L H2O (H+ 130 meq/L)
• administer through central line @< 0.2 meq/kg/ hr
• do not infuse directly into the right atrium
• H+ deficit:

• 0.5 x LBM* (measured - desired) [[[Hco3- | HCO3-]]]
• replace 1/2 the deficit in the 1st 12 hours, & the remainder in the following 24 hours

• hemodialysis
  

• * LBM: lean body mass in kg.

More General Terms

• alkalosis

References

1. Manual of Medical Therapeutics, 28th ed, Ewald & McKenzie (eds), Little, Brown & Co, Boston, 1995, pg 62-63
2. Medical Knowledge Self Assessment Program (MKSAP) 14, 15 American College of Physicians, Philadelphia 2006, 2009

metabolic alkalosis