12 Metabolic Acidosis

Anion Gap

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• blood: total number of + must equal -

• chem 7 only tells some of the positive and negative charges

• Na and K (positive) minus Cl and bicarb (negative) is the gap

• in reality no gap, just other ions not measured

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• albumin predominantly responsible for negative anions besides Cl/bicarb

  • for every 1 g decrease in albumin, add 2.5 to AG

• IgG push Na out and retain K in plasma: shrink anion gap

A low anion gap is frequently caused by hypoalbuminemia. Albumin is a negatively charged protein and its loss from the serum results in the retention of other negatively charged ions such as chloride and bicarbonate. As bicarbonate and chloride anions are used to calculate the anion gap, there is a subsequent decrease in the gap.

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• if lose bicarb, compensate with Cl to maintain normal charge

• Cl part of anion gap ion, thus normal AG

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• top: bicarb decreased (met acidosis). Cl increased, normal 95 (non-AG)

• bottom: met acidosis, Cl not high, AG

• Cl up: non-AG; Cl down: AG

Winter's Formula

[_](Winter's formula and delta ratio uses)..

[_](winter's formula use when)..

Delta Delta

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• Winter's tell if there's secondary respiratory, Delta ratio tells if secondary metabolic

• <1: bicarb driven down by metabolic acidosis also by something else

• more than 2: chronic respiratory acidosis causing chronic retention of bicarb

Non- AG Causes

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• anything that lowers aldosterone, decreases bicarb level, or increases H+ levels

• addison: can't make aldosterone

• saline: low aldosterone result

• hyperalimentation: IV nutrition

• calculate urinary AG

• Na+K-Cl = urine bicarb

• positive: renal loss

• negative: GI loss

• TB: adrenal insufficiency

AG Acidosis Causes

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• MUD PILES

Methanol

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• destroy optic disc

• child, suicide, etc.

• very important: visual symptoms

Ethylene Glycol

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• calcium oxalate in tubules

• kidney symptoms instead of visual

• formaldehyde: formic acid

• glycoladehyde: glycolate, oxalate

Propylene Glycol

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Isopropyl Alcohol

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• someone ingest toxic product but no AG acidosis

Uremia

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• at first: can't excrete H

• later: can't excrete organic acids

• association with other uremic symptoms (pericarditis, confusion, hyperkalemia)

DKA

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• or diabetic who didn't take insulin

Lactic Acidosis

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• seizures: so much muscle contraction

Iron

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• usually child

• highly prone to bleeding

• later phase: AG acidosis

• ferric irons: unmeasured anions

INH

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• Motion lines: INH may cause seizures

• MUD PILES: INH may cause anion gap metabolic acidosis

Aspirin

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• Mudpile: aspirin toxicity can cause an anion gap metabolic acidosis (S in MUDPILES)

• Blowing “OH-” bubbles: aspirin causes a respiratory alkalosis, stimulate respiratory center directly