Metabolic acidosis: Difference between revisions

Latest revision as of 15:12, 22 July 2017

Clinical Features

Compensatory respiratory tachypnea

Differential Diagnosis

Anion gap metabolic acidosis

Lactic acidosis
- Sepsis, shock, liver disease, CO, CN, metformin, methemoglobin
- Short bowel syndrome
- Propylene glycol infusions for lorazepam and phenobarbital
Renal failure
- Uremia
Ketoacidosis
Ingestions
- Acetaminophen toxicity
- Aspirin toxicity
- Increased osm gap
  - Methanol
  - Ethylene glycol
- Normal osm gap

Non-gap

Hyperkalemia
- Resolving DKA
- Early uremic acidosis
- Early obstructive uropathy
- RTA Type IV
- Hypoaldosteronism
- K-sparing diuretics
Hypokalemia
- RTA Type I
- RTA Type II
- Acetazolamide
- Acute diarrhea
  - (May be assoc with gap if hypoperfusion -> lactic acidosis)
CKD
Intestinal, pancreatic, biliary fistula
Hyperchloremic IVF infusions
Hyperalimentation

Evaluation

Osm gap = measured osm - calculated osm (normal 10-15)
Calculated Osm = 2(Na)+(glucose/18)+(BUN/2.8)+(BAL/5)

Primary acidosis if pH <7.38
HCO3 <24 = metabolic acidosis
Always determine if there is another acid/base process occurring
- Primary respiratory acidosis if pCO2 > pCO2expected
- Primary respiratory alkalosis if pCO2 < pCO2expected
  - use Winter's formula: PCO2 (expected) = (1.5 x [HCO3–] + 8) ± 2
  - In acute setting PCO2 should fall by 1 mmHg for every 1 mEq fall in HCO3
- Concurrent metabolic alkalosis if delta-delta > 28
- Delta-Delta = (AG - 12) + HCO3

Management

Treat source
Correct any respiratory acidosis
Bicarbonate
- HCO3 dose in mEq = 0.5(wt in kg) x (24 - measured HCO3)
- Each bicarb 0.5mEq/kg causes 1 meq/L rise in HCO3
- Consider for:
  - Bicarb <4
  - pH <7.20 AND shock/myocardial irritability
  - Severe hyperchloremic acidemia
  - lower threshold with non-AG acidosis (greater HCO3 loss)
    - Lost bicarbonate would take days to replenish

References

Authors:

@@ Line 1: / Line 1: @@
-==DDX==
+==Clinical Features==
+*Compensatory respiratory tachypnea
+==Differential Diagnosis==
+{{Anion gap metabolic acidosis}}
-I. GAP
+===Non-gap===
+{{Non anion gap acidosis}}
-) Lactic acidosis
+==Evaluation==
+;Osm gap = measured osm - calculated osm (normal 10-15)
-) Renal failure
+;Calculated Osm = 2(Na)+(glucose/18)+(BUN/2.8)+(BAL/5)
-) Ketoacidosis
-          a) DM
-          b) ETOH
-          c) Starvation
-          d) High fat diet
-) Tox ingestion
-          a) Inc osm gap
-               i) Methanol
-               ii) Ethylene glycol
-          b) Nl osm gap
-               i) Salicylate
-               ii) Paraldehyde
-               iii) Cyanide
-II. NON-GAP
-) Tendancy hyperKalemia
-          a) Resolving DKA
-          b) Early uremic acidosis
-          c) Early obstructive
-          d) RTA Type IV
-          f) Hypoaldo
-          g) K-sparing diuretics
-) Tendancy hypoKalemia
-          a) RTA Type I
-          b) RTA Type II
-          c) Acetazolamide
-          d) Acute diarrhea
-==Treatment==
-===Bicarbonate Indications===
-) Bicarb <4
-) pH <7.20 + Sx shock/myocardial irritability
-) Severe hyperchloremic acidemia + Sx shock/myocardial irritability
-==Source ==
-/21/06 DONALDSON (adapted from Tintinalli)
+*Primary acidosis if pH <7.38
+*HCO3 <24 = metabolic acidosis
+*Always determine if there is another acid/base process occurring
+**Primary respiratory acidosis if pCO2 > pCO2expected
+**Primary respiratory alkalosis if pCO2 < pCO2expected
+***use Winter's formula: PCO2 (expected) = (1.5 x [HCO3–] + 8) ± 2
+***In acute setting PCO2 should fall by 1 mmHg for every 1 mEq fall in HCO3
+**Concurrent metabolic alkalosis if delta-delta > 28
+**Delta-Delta = (AG - 12) + HCO3
+==Management==
+*Treat source
+*Correct any [[respiratory acidosis]]
+*[[Bicarbonate]]
+**HCO3 dose in mEq = 0.5(wt in kg) x (24 - measured HCO3)
+**Each bicarb 0.5mEq/kg causes 1 meq/L rise in HCO3
+**Consider for:
+***Bicarb <4
+***pH <7.20 AND shock/myocardial irritability
+***Severe hyperchloremic acidemia
+***lower threshold with non-AG acidosis (greater HCO3 loss)
+****Lost bicarbonate would take days to replenish
+==See Also==
+*[[Acid-base disorders]]
+==References==
+<references/>
 [[Category:FEN]]
+[[Category:Toxicology]]