OnlineMedEd: Intern Content - "Sodium"

Question 1

In _______-natremia, the cells swell.

Answer 1

hypo

Question 2

It isn’t the amount of cell shrinkage or swelling that causes symptoms, but rather the _______________.

Answer 2

rate at which it happens

Thus, the rate of change of sodium is the real important marker.

Question 3

Review Dr. Williams’ three categories of hypo- and hypernatremia.

Answer 3

Hyponatremia:

• Mild (no symptoms): give PO sodium
• Moderate (headache, dizziness): IV NS
• Severe (obtunded, seizing): give hypertonic saline

Hypernatremia:

• Mild (no symptoms): PO free water
• Moderate (headache, dizziness): IV NS
• Severe (coma, seizing): IV 1/2 NS or D5

Question 4

Goal correction of sodium should be _____________, unless they are actively seizing.

Answer 4

0.5 per hour

Question 5

Give the formula for serum osmolarity.

Answer 5

(2 x Na) + (glucose/18) + (BUN/2.8)

Remember 2, 1, 8

Question 6

Once you compare the calculated to the measured serum Osms, give the three possible outcomes with their respective differentials.

Answer 6

Hypertonic: meaning calculated > measured

• ingestions (alcohol)
• hyperglycemia

Isotonic: calculated = measured
- fats and proteins elevated

Hypotonic:

• hypervolemic: CHF
• euvolemic: RATS (RTA, Addison’s, thyrotoxicosis, SIADH)
• hypovolemic: thiazide overuse, dehydration, heat exposure

Question 7

Explain the hyperglycemia/sodium conversion.

Answer 7

For every 100 mg/dL glucose greater than 100, increase sodium by 1.6.

Example: glucose of 1,100 and sodium of 120 means an actual sodium of 136.

Question 8

If you can’t figure out if the person with isotonic hyponatremia is hypo-, hyper-, or euvolemic, you can do what?

Answer 8

Give fluids and see how they respond. If they worsen, they were hyper- or euvolemic. If they improve, it was hypovolemia.

Question 9

The macula densa makes renin in response to _____________.

Answer 9

low flow through the ascending loop of Henle (think of Dustyn’s backward switch)

Question 10

In the volume down state, your urine sodium should be ______________ and your urine osmolarity should be ______________.

Answer 10

low; high

Sodium < 20 (from high aldosterone)
Osmolarity > 300 (from high ADH)

Question 11

How will urine sodium and urine osmolarity be affected in SIADH?

Answer 11

UNa: > 20 (because aldosterone is off)
UOsm: > 300 (because ADH is high)

Question 12

In the volume up state, your urine sodium should be ______________ and your urine osmolarity should be ______________.

Answer 12

high; low

Sodium > 20 (from low aldosterone)
Osmolarity < 300 (from low ADH)