Metabolic Acidosis

Question 1

What is the main pathology behind metabolic acidosis?

Answer 1

Academia caused by either a high hydrogen ion concentration or a reduction in extracellular bicarbonate producing a low blood pH.

Question 2

How is Carbonic acid, a volatile acid, mainly excreted, how is the remainder excreted?

Answer 2

Mainly excreted via ventilation
The remainder non-volatile is buffered by extracellular bicarbonate

Question 3

What is renal ammoniagenesis

Answer 3

The excretion of ammonia chloride and the generation of new bicarbonate
Ammonia chloride is a type of acid
This process is triggered by acidemia and hypokalemia
This process is inhibited by alkalemia and hyperkalemia

Question 4

What is the formula for anion gap and what is the normal value?

Answer 4

(Na)-(Cl + HCO3)
Normal gap = 6

Question 5

What does hypoalbuminemia and alkalemia do to the anion gap?

Answer 5

Hypoalbuminemia can cause a falsely low anion gap
Alkalemia can cause a falsely high anion gap

Question 6

Causes of high anion gap metabolic acidosis

Answer 6

Lactic acid is the most common
Propylene glycol
Alcohol
Ketoacidosis
Starvation
Intoxications
Salicylates

Question 7

What is the most common cause of high anion gap metabolic acidosis?

Answer 7

Lactic acidosis

Question 8

What are examples of medications that contain propylene glycol that can produce a high anion gap metabolic acidosis?

Answer 8

Ativan, nitroglycerin, etomidate, phenytoin

Question 9

What are the two types of high anion gap metabolic acidosis and what are the differences? Include examples of each type.

Answer 9

Type A: imbalance of tissues demand vs supply. Ex: Shock, anemia, carbon monoxide poisoning, grand mal seizure, exercise
Type B: All other causes. Ex: Cyanide poisoning, pharmaceuticals, HIV, ETOH, propofol, diabetes, alkalemia, malignancy, phenochromocytoma, liver failure.

Question 10

How does renal tubular acidosis contribute to non-gapped metabolic acidosis?

Answer 10

Bicarbonate is lost or hydrochloric acid is gained - Bicarbonate concentration falls - Cl is displaced to the extracellular space buffering the gap

Question 11

How does post hypo-capanic metabolic acidosis produce a non-gapped acidosis?

Answer 11

Bicarbonate falls in compensation for chronic respiratory alkalosis

Question 12

How does dilutional hypochloremic acidosis produce a non-gapped acidosis?

Answer 12

Typically just a result of isotonic fluid resuscitation, blood bicarbonate is diluted

Question 13

What is classified as severe acidemia?

Answer 13

PH<7.20

Question 14

What are the cardiac, hepatic, renal, and metabolic clinical manifestations of metabolic acidosis?

Answer 14

Cardiac: venoconstriction, diminished myocardial contractility, malignant arrhythmia, increase in pressure arterial vasodilation
Hepatic: Reduced lactic acid uptake and metabolism
Renal: Compromised renal perfusion
Metabolic: Sympathetic hyperactivity, diminished catecholamine responsiveness, insulin resistance, suppressed glycolysis

Question 15

Which diagnostic tests would you order to rule out Metabolic acidosis?

Answer 15

CMP, BMP

Question 16

Diagnosis for low bicarbonate and high gap

Answer 16

High anion gap metabolic acidosis

Question 17

Diagnosis for low HCO3 and normal anion gap

Answer 17

Hyperchlooremic metabolic acidosis or respiratory alkalosis with metabolic compensation

Question 18

When do you correct metabolic acidosis?

Answer 18

PH <7.10

Question 19

How do you treat metabolic acidosis?

Answer 19

Treat underlying cause
Treat respiratory etiology FIRST
Sodium Bicarbonate infusion (Beware of hypocalcemia and hypervolemia) goal pH 7.20
If lactic acidosis is present treat underlying cause
HD/CRRT for lactic acidosis or metformin induced acidosis