JH IM Board Review - Acid-Base Disorders and Renal Tubular Acidosis I

Question 1

The body never FULLY corrects for a single acid-base disorder except perhaps for …

Answer 1

Resp alkalosis.

Question 2

Does a normal pH exclude an acid-base disorder?

Answer 2

NO.

Coexisting met acidosis + met alkalosis.

Question 3

Calculation of the … may be helpful in evaluating normal AG acidosis.

***to ddx RTA from other causes.

Answer 3

URINE anion gap.

Question 4

Formula for urine AG:

Answer 4

Urine (Na + K - Cl).

Question 5

In a metabolic acidosis WITHOUT RTA, the urine AG is …

Answer 5

Negative.

If positive, then think RTA I and IV

Question 6

Metabolic acidosis w/ DECREASED AG are rare, and may be caused by …

Answer 6

1. Hypoalbuminemia.
2. MM.
3. Ingestion of bromide.

**little clinical significance.

Question 7

Toluene exception:

Answer 7

Presents first w/ AG acidosis ==> THEN metabolized resultin in NORMAL AG metabolic acidosis.

Question 8

Osmolar gap increase meaning:

Answer 8

Toxic compounds (methanol, ethylene glycol, toluene).

Question 9

Normal osmolar gap should be …

Answer 9

<10.

Question 10

Osmolality formula:

Answer 10

2Na + BUN/2.8 + Glu/18.

Question 11

Winter’s formula for respiratory compensation in metabolic acidosis:

Answer 11

PaCO2 = [1.5 x HCO3 + 8] +/- 2.

***If PaCO2 > than predicted then COEXISTING RESP ACIDOSIS.

If PaCO2 < than predicted then COEXISTING RESP ALKALOSIS.

Question 12

The presence of metabolic alkalosis always implies that 2 events have occurred:

Answer 12

1. Initiation of alkalosis ==> Gain of HCO3 or loss of acid.

2. Maintenance of alkalosis ==> Always by the kidneys.

Question 13

Maintenance of alkalosis by the kidney is favored by:

Answer 13

1. Volume depletion.
2. Chloride depletion — Urine Cl is low in volume depletion, low urine Cl impairs the renal secretion of HCO3.
3. Hypokalemia — stimulates ammoniagenesis and net acid secretion.
4. Mineralocorticoid excess.

Question 14

Measurement of which urine electrolyte is helpful in evaluating the cause of the metabolic alkalosis?

Answer 14

Urine Cl.

Question 15

If urine Cl <10mEq/L, then the causes of saline-responsive met alkalosis are:

Answer 15

1. NG suction.
2. Vomiting.
3. Diuretics.
4. Posthypercapnia.

Question 16

If urine Cl >10mEq/L, then the causes of metabolic alkalosis are (saline-resistant alkalosis) are further divided according to BP:

Answer 16

UP BP ==> Conn — Cushing — CAH — Liddle syndrome — Licorice ingestion — RAS — Renal failure + alkali admin.

NORMAL BP ==> Hypomagnesemia — Severe hypokalemia — Bartter and Gitelman syndromes — Milk-alkali syndrome — Congenital chloride diarrhea (!).

Question 17

Maximum PaCO2 in respiratory compensation for metabolic alkalosis is …

Answer 17

55-60mmHg.

Question 18

Note the 2 conditions that can result in both metabolic acidosis and respiratory alkalosis:

Answer 18

1. SEPSIS.

2. Aspirin.