Metabolic acidosis causes
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Low anion gap
A low anion gap is relatively rare but may occur from the presence of abnormal positively charged proteins, as in multiple myeloma, or in the setting of a low albumin level. The mnemonic for low anion gap is BAM
- B - Bromism
- A - (Low) Albumin (hypoalbuminism)
- M - Multiple myeloma
Normal anion gap (hyperchloremic acidosis)
Usually the HCO3- lost is replaced by a chloride anion, and thus there is a normal anion gap. In normal anion gap acidosis, the increased anion is chloride, which is measured, so the anion gap does not increase. Thus, normal anion gap acidosis is also known as hyperchloremic acidosis. Urine anion gap is useful in evaluating a patient with a normal anion gap (see above).
The mnemonic for the most common causes of a normal-anion gap metabolic acidosis is "DURHAM."
- D- Diarrhea
- M- Miscellaneous (chloridorrhea, amphotericin B, toluene - toluene causes high anion gap metabolic acidosis followed by normal anion gap metabolic acidosis.
High anion gap
The bicarbonate lost is replaced by an unmeasured anion and thus you will see a high anion gap. Low serum albumin will decrease the apparent anion gap. To correct the anion gap for low serum albumin, we have to add 2.5 to the anion gap for every 1g/dl that serum albumin is decreased from the normal value of 4g/dl. The mnemonic "MUDPILES" is used to remember the causes of a high anion gap.
M - methanol/metformin
U - uremia
D - diabetic ketoacidosis
P - paraldehyde/propylene glycol
I - Infection/ischemia/isoniazid
L - lactate
E - ethylene glycol/ethanol
S - salicylates/starvation
Some people, especially those not in the emergency room, find the mnemonic KIL-U easier to remember and also more useful clinically:
K - Ketones
I - Ingestion
L - lactic acid
U - uremia
All of the components of "mudpiles" are also covered with the "KIL-U" device, with the bonus that these are things that can kill you.
Ketones: more straightforward than remembering diabetic ketosis and starvation ketosis, etc.
Ingestion: methanol, metformin, paraldehyde, propylene glycol, isoniazid, ethylene glycol, ethanol, and salicylates are covered by ingestion. These can be thought of as a single group: "ingestions" during the initial consideration, especially when not triaging a patient in the emergency room.
Lactate: including that caused by infection and shock
Coexistent elevated anion gap and normal anion gap metabolic acidosis
- An elevated anion gap can coexist with a normal anion gap metabolic acidosis.
- In a single acid-base disorder of elevated anion gap metabolic acidosis, serum bicarbonate (HCO3) will decrease by the same amount that the anion gap increases.
- However, a situation in which the anion gap increases less and serum bicarbonate decreases significantly indicates that there is another metabolic acidosis present, which is decreasing the the serum bicarbonate, but not affecting the anion gap i.e. normal anion gap metabolic acidosis is also present.
- Thus, it is advised to compare the changes in the anion gap with the changes in the serum bicarbonate.
- This is often referred as the delta-delta equation, or the corrected bicarbonate equation.
- Delta-Delta equation: Change in anion gap = Change in bicarbonate
Causes by Organ System
Causes in Alphabetical Order