Acid Base Disorders - Determining the Etiologies.

Question 1

What are the first two steps of any acid base problem?

Answer 1

pH 7.4 = alkalemia.
In acidemia, CO2 > 40 = respiratory acidosis.
In alkaemia, CO2

Question 2

What are the causes of respiratory alkalosis?

Answer 2

Hyperventilation (pain, anxiety, hypoxemia, increased ICP, salicylates, high altitudes).

Question 3

What are the causes of respiratory acidosis?

Answer 3

Hypoventilation. Opiates, Asthma/COPD (rising CO2 = very bad sign in these), weakening of resp muscles, obesity/obstructive sleep apnea.

Question 4

If you have a metabolic acidosis, what’s the first step to determining etiology?

Answer 4

Gap or NonGap. Sodium - (Cl + Bicarb).

Question 5

If you have an anion gap acidosis, what is the acronym for potential causes?

Answer 5

Methanol
Uremia
DKA
Propylene glycol
Iron/INH
Lactic acidosis
Ethylene glycol (antifreeze)
Salicylates

Question 6

What two disturbances does salicylates cause?

Answer 6

Anion gap metabolic acidosis + respiratory alkalosis.

Question 7

What are the causes of non-gap metabolic acidosis?

Answer 7

Hyperalimentation
Addison's disease/adrenal insufficiency
RTA
Diarrhea
Acetozolamide
Spironolactone
Saline infusion
Ureteroenteric fistula
Pancreaticduodenal fistula

Question 8

When do you calculate the urine anion gap?

Answer 8

When you find non-gap metabolic acidosis

Question 9

What us the urine anion gap and what does it tell you?

Answer 9

Sodium + Potassium - Chloride. If positive, likely RTA, if negative, likely diarrhea.

Question 10

If you find metabolic alkalosis, what is the next step in finding the etiology?

Answer 10

Urine chloride.

Question 11

What does the urine chloride in metabolic alkalosis tell you?

Answer 11

Whether or not someone is volume responsive.

Question 12

What does volume responsiveness have to do with urine chloride?

Answer 12

When someone is volume down, the RAAS system is activated. Aldo brings in sodium, ADH holds in water, and Chloride should follow Na+. If someone is volume down, urine chloride should be low. (

Question 13

If urine chloride is low

Answer 13

Contraction alkalosis. Could be due to diuretics, dehydration, emesis, or NG suction.

Question 14

If urine chloride is high, >10, what is the next step?

Answer 14

Do they have HTN? If so, consider hyperaldo states like primary hyperaldosteronism, renal artery stenosis, or fibromuscular dysplasia. If they are not hypertensive, consider Barter’s (like having a loop diuretic), or Gitelman’s (like having a thiazide diuretic).