Sodium

Question 1

What is the daily requirement for sodium?

Answer 1

3 mEq/kg/day

Question 2

What 2 categories causes hypernatremia?

Answer 2

Sodium excess

1. improper mixing of formula (not enough water)
2. ingestion of sea saltwater
3. Excessive sodium bicarbonate after resuscitation
4. Breast milk with excessive sodium
5. Iatrogenic

Water deficit

1. DI
2. Diarrhea

Question 3

What is nephrogenic diabetes?

Answer 3

X-linked disorder, ONLY in MALES. Kidneys don’t respond to ADH (vasopressin).

Question 4

What is the best study to decipher what type of hyponatremia you have? (hypovolemic, euvolemic, hypervolemic)

Answer 4

Fractional excretion of sodium (FENa).

Question 5

What causes hyponatremia?

Answer 5

1. Loss of sodium
   - ex. GI losses, will have low urine Na since kidneys trying to hold on to it
2. Increased water
   - Too much water: POLYDIPSIA
   - Too little out: SIADH (too much ADH, not peeing!)

Question 6

What causes SIADH?

Answer 6

S-surgery, esp. post-operatively (increased ADH secretion)
I-infection
A-axon (Guillain Barre, Brain Tumor)
D-day after post-op
H-head or hemorrhage

Medications: Vincristine, Cyclophosphamide, Carbamazapine

Question 7

What labs present with SIADH?

Answer 7

LOW sodium
LOW serum osmolality
NORMAL Potassium
NORMAL Cr and BUN
HIGH Urine Sodium >25mEq/L

Question 8

SIADH vs Hyponatremic dehydration

Answer 8

SIADH-
LOW serum osmolality
NORMAL Cr and BUN
Elevated Urine Sodium >25mEq/L

Hyponatremic dehydration-
NORMAL/ELEVATED serum osmolality
HIGH BUN
LOW Urine Sodium ,25mEq/L

Question 9

How do you treat SIADH?

Answer 9

1. Fluid restriction (2/3) maintenance IVF
2. Furosemide (never thiazide diuretics, worsens hyponatremia)
3. Hypertonic saline if Na < 120 mEq/L
4. Demeclocycline (blocks ADH), but must be >8yo (it’s related to doxycycline)

Question 10

What is dilutional hyponatremia?

Answer 10

Water intoxication
Total body sodium is NORMAL
Urine sodium > 100 mEg/L
Can have seizures secondary to cerebral swelling (water rushes from ECF–>ICF), Pontine damage

Question 11

What are causes of dilutional hyponatremia?

Answer 11

1. Swimming (swallowing lots of water)
2. Malnutrition
3. Hypotonic fluids
4. Glucocorticoid deficiency
5. Hypothyroidism

Question 12

What are the steps for pseudohyponatremia?

Answer 12

1. Elevated triglycerides and/or plasma proteins (aka nephrotic syndrome)
2. TGs take up a lot of room, so “less water”, but the “volume is the same”.
   Labs report sodium per volume NOT per water. The level would be low since water is the only part that actually contains sodium. Sodium level actually normal.
3. Lots of water outside circulation in conditions with edema. More water than usual which contains sodium. Total body sodium is elevated.