ASN QBank Pearls - Fluid Compartments and Electrolyte Disorders

Question 1

how much volume of 0.9% saline contributes to increasing the volume of the intravascular space?

Answer 1

25%

Question 2

illicit drug that can cause AKI 2/2 nontraumatic rhabdomyolysis

Answer 2

MDMA (ecstasy)

Question 3

most efficient and effective means of removing lithium

Answer 3

HD

Question 4

normal kidneys echogenicity

Answer 4

less than that of pancreas and equal or less than that of liver and spleen

Question 5

hypercholesterolemia with lipoprotein X associated with cholestatic or obstructive jaundice is a cause of

Answer 5

pseudohyponatremia

Question 6

risk factors for osmotic demyelination syndrome (ODS)

Answer 6

• alcoholism
• serum Na+ ≤ 105 mEq/L
• liver disease
• malnutrition

Question 7

complication of hypomagnesemia or hypermagnesemia

Answer 7

hypocalcemia

Question 8

differential diagnosis for hypercalcemia with low PTH, normal 25(OH)D, and low 1,25(OH)2D

Answer 8

• hyperthyroidism
• malignancy
• immobilization
• Paget’s disease
• milk-alkali syndrome

Question 9

initial therapy of moderate to severe hypercalcemia includes

Answer 9

simultaneous administration of;

• isotonic saline
• calcitonin
• bisphosphonate

Question 10

classic triphasic response following injury or transection of the pituitary stalk

Answer 10

1. DI occurs because vasopressin cannot be released from nerve terminals d/t interruption of nerve impulses
2. SIADH results from unregulated release of stored vasopressin from degenerating neurons
3. permanent DI once vasopressin stores are depleted

Question 11

can cause central pontine and extrapontine myelinolysis, similar to what occurs after rapid correction of chronic hyponatremia

Answer 11

acute hypernatremia; should be rapidly corrected

Question 12

ODS prognosis even if initially ventilator dependent

Answer 12

complete neurological recovery in up to 1/3 of cases

Question 13

mechanism by which hypermagnesemia causes hypocalcemia

Answer 13

binds to calcium-sensing Rs and reduces PTH

Question 14

complications of acute hypermagnesemia

Answer 14

• hypotension
• hyperkalemia
• hypocalcemia
• at higher levels, heart block and cardiac arrest

Question 15

familial hypomagnesemia with hypercalciuria and nephrocalcinosis (FHHNC) gene mutations

Answer 15

claudin-16 gene

Question 16

medication class that inhibits claudin-16 gene

Answer 16

calcineurin inhibitors (cyclosporine, tacrolimus, and pimecrolimus)

Question 17

medications that cause hypomagnesemia d/t renal magnesium wasting in distal tubule

Answer 17

cetuximab, panitumumab, and matuzumab

Question 18

calcineurin inhibitors primarily reduce expression of claudin 16 where?

Answer 18

ascending limb in LOH

Question 19

what test BEST demonstrates pseudohyponatremia?

Answer 19

plasma osmolality

Question 20

MOST appropriate therapy for hyperuricemia prior to tumor-specific chemotherapy if G6PD deficiency?

Answer 20

allopurinol

Question 21

no longer recommended for tumor lysis syndrome (TLS)

Answer 21

urinary alkalinization d/t r/o calcium-phosphate crystal deposition (acute phosphate nephropathy) and hypoxanthine/xanthine crystal deposition

Question 22

renal complications of cisplatin

Answer 22

• hyponatremia 2/2 cisplatin-induced renal salt wasting
• ATN
• tubulopathies:
• proximal tubulopathy/Fanconi syndrome
• Mg2+ wasting
• nephrogenic DI
• CKD

Question 23

MOST common electrolyte disturbance associated with cetuximab

Answer 23

hypomagnesemia

Question 24

complications of ecstasy toxicity

Answer 24

• hyponatremia 2/2 SIADH and excessive hypotonic fluid ingestion
• seizures (from hyponatremia)
• lactic acidosis
• AKI 2/2 rhabdomyolysis

Question 25

mechanisms of hyponatremia 2/2 IVIG

Answer 25

• pseudohyponatremia from the immunoglobulin

- true hyponatremia from the associated carrier (sucrose, maltose)

Question 26

women who donate a kidney before becoming pregnant

Answer 26

increased risk for adverse outcomes DURING pregnancy

Question 27

use of ACE inhibitors during pregnancy?

Answer 27

contraindicated, but can be used during breastfeeding postpartum

Question 28

polyuria d/t high solute intake

How to calculate daily solute excretion:
Urine studies:
24hr urine vol: 6L
Na 27 mEq/L / K 13 mEq/L
Urea 32g/24hrs
Uosm 267 mOsm/H20

Answer 28

Consider solute diuresis if :
- Uosm >300 mOsm/day (lab result)
- Daily solute excretion >1000mg/day (you calculate this)

-> Calc daily solute excretion (approximates daily solute intake)
-> Uosm (mOsm/kg) x Uvol (L/day) = daily urinary solute (mOsm/day)
note: typical daily solute intake 600-900 mOsm/day

Question 29

How to determine the major contributor to urinary osmoles in the daily solute excretion:

Urine studies:
24hr urine vol: 6L
Na 27 mEq/L / K 13 mEq/L
Urea 32g/24hrs
Uosm 267 mOsm/H20

Answer 29

Uosm (mOsm/kg) x Uvol (L/day) = daily urinary solute (mOsm/day)
- 267 x 6 = 1602 mOsm/day
=> convert urea to mOsm:
32g/ 6L = 5.3g/L -> 530mg/dL urine urea
=> divide by 2.8 to get mOsm/L
530 mg/dL / 2.8 = 189 mOsm/L (x6L for this patient in 24hrs)
= 1135 mOsm/day is urine urea

=> 2x [UNa + UK] x vol per day = remaining mOsm
2x [27 + 13] x 6L = 480 mOsm
**1135 mOsm urine urea > 480 mOsm urine Na +K

Question 30

how to calculate protein intake:
50kg patient
Urine studies:
24hr urine vol: 6L
Na 27 mEq/L / K 13 mEq/L
Urea 32g/24hrs
Uosm 267 mOsm/H20

Answer 30

urine urea used to estimate protein intake:
Calculated protein intake = [urine urea + (kg × 0.031 g nitrogen/kg/day) × 6.25.
In this case:
[32 g/d + (50 kg × 0.031g nitrogen/kg/day)] × 6.25 = 210 g calculated daily protein intake.

Daily target protein 0.8g/kg/day without CKD