Metabolic alkalosis: Difference between revisions
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*[[Hypomagnesemia]] | *[[Hypomagnesemia]] | ||
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*pH > 7.42 = alkalemia | *pH > 7.42 = alkalemia | ||
*HCO3 > 28 = metabolic alkalosis | *HCO3 > 28 = metabolic alkalosis |
Revision as of 07:01, 24 July 2016
Background
Metabolic alkalosis generally occurs as a primary increase in serum bicarbonate (HCO3-) concentration, which can occur due to loss of H+ from the body or a gain in HCO3-.
Main Causes
- Hydrogen ion loss (via vomiting)
- Shift of hydrogen ions intracellularly (from hypokalemia)
- Bicarbonate administration
- Contraction alkalosis (Diuretic administration, diarrhea, or any excessive loss of volume)
Clinical Features
Differential Diagnosis
Chloride-Responsive
Urine Cl < 20 mEq/L
- Loss of gastric secretions;
- Loss of colonic secretions
- Diarrhea
- Congenital chloridorrhea
- Villous adenoma
- Thiazides/loop diuretics
- Cystic fibrosis
Chloride-resistant
Urine Cl > 20 mEq/L
- Exogenous alkali (Nabicarb + renal failure, metabolism of lactic acid, or ketoacids)
- Milk alkali syndrome
- Hypercalcemia (inability to concentrate urine leads to hypovolemia)
- Intravenous penicillin
- Refeeding alkalosis
- Massive blood transfusion
- Primary hyperaldosteronism
- CAH (11-Hydroxylase or 17-hydroxylase deficiency)
- Cushing syndrome
- Exogenous steroids
- Liddle syndrome
- Renovascular HTN
- Bartter syndrome (pediatrics)
- Gitelman syndrome (pediatrics)
- Severe K+ depletion
- Hypomagnesemia
Evaluation
- pH > 7.42 = alkalemia
- HCO3 > 28 = metabolic alkalosis
- Always determine if there is also a concurrent primary respiratory process
- expected pCO2 = 40 + 0.6(measured HCO3 - 24)
- if pCO2>pCO2 expected, then there is also a primary respiratory acidosis
- if pCO2<pCO2 expected, then there is also primary respiratory alkalosis
- Always calculate AG to determine if concurrent primary metabolic acidosis
Management
- Correct volume depletion
- Normal Saline
- Repletion of extracellular volume decr need for Na reaborption
- Delivery of Cl to distal tubule increases Cl/bicarb exchange
- Normal Saline
- Correct potassium depletion
- Giving K+ leads to movement of H+ out of cells -> acidosis
- Giving K+ stops hypokalemia-induced distal H+/K+ pump
- Correct chloride depletion
- Must give a reabsorbable anion to replace HCO3
- Correct mineralocorticoid excess
- Aldostorone antagonists if indicated (i.e. spironolactone)
- Note: if patient is edematous (CHF, cirrhosis), do NOT give normal saline
- If patient is hypokalemic KCl will correct both hypoK AND alkalosis