L48

Question 1

What are 2 relationships between Na and H2O that may yield hypernatremia?

Answer 1

Normal Na/↓H2O = euvol hyperNa
↓Na/↓↓H2O = hypovol hyperNa = drop in water out of proportion to salt loss
↑↑↑Na/↑H2O = hypervol hyperNa

Question 2

What is the sensor for ECF volume?

Answer 2

Baroreceptors in the carotid sins and atrium

Watch for drop in BP: hemorrhage, vomiting, diarrhea

Question 3

What is the response invoked by baroreceptors when sense drop in BP?

Answer 3

Catecholamines
RAAS
ADH (non-osmotic regulation)
Net: ↑Na + H2O reabsorbed

Question 4

What are 3 scenarios that simulate a drop in effective circulating volume? Aka probably volume overloaded but all fluid is edema not in vasculature.

Answer 4

CHF
Cirrhosis
Nephrotic syndrome

Question 5

Where are osmoreceptors located?

Answer 5

Ant hypothalamus

↑osm -> ↑ADH

Question 6

Would you rather be hypovolemic or hyponatremic?

Answer 6

You will release ADH to repair hypovolemia and remain hypoNa

If you lose too much volume, you’ll suffer CV collapse before you notice the effects of low Na

Question 7

Where is ADH made?

Answer 7

Supraoptic + paraventricular nuclei

Stored in the post pituitary

Question 8

Mechanism of ADH

Answer 8

Binds V2 receptors in collecting duct
Causes aquaporin 2 to the apical surface - re-uptake of water
Urine gets concentrated

Question 9

Describe hypovol hyperNa. What is the cause if U Na > 20?

Answer 9

Lost more H2O than Na - both dehydrated and intravasc vol depleted
U Na > 20 = renal problem b/c you should be holding on to that Na to retain water
- Either on diuretic
- Or intrinsic renal disease

Question 10

What is the cause of hypovol hyperNa if U Na

Answer 10

U Na

Question 11

Describe euvol hyperNa. Name the 3 possible causes.

Answer 11

Dehydrated (lost H2O) but normal intravasc vol (no change to amt Na)

1. Diabetes insipidus
2. Hypodipsia (no drinking enough)
3. Extra-renal loss in lungs or skin

Question 12

Describe 2 types of diabetes insipidus

Answer 12

1. Central DI = ADH deficient
2. Nephrogenic DI = ADH isn’t working at kidney
   Either way, can’t concentrate urine so at risk for hyperNa

Question 13

What are the 3 possible causes of hypervol hyperNa?

Answer 13

U Na > 20 - makes sense b/c you’re trying to lose water and salt

1. Psych pt ate NaCl
2. Doctor did it - infusion of saline or NaHCO3
3. Hypertonic dialysis

Question 14

Why would hyperNa state be maintained?

Answer 14

Can’t get water: obtunded, infant

Question 15

Clinical presentation of hyperNa

Answer 15

AMS - range confusion -> coma, watch out for metabolic encephalitis
+/- muscle irritability

Question 16

Explain encephalitis in acute and chronic response to hyperNa

Answer 16

Cells shrink b/c lost water to hypertonic environment
Acute = (under 24 hrs) +electrolytes to pull water back in, bad SE on cell fxn
Chronic = +non-electrolytes to hold water, harder to remove but less impact on fxn

Question 17

Treat acute hypernatremia

Answer 17

Hydration

Question 18

Treat chronic hyperNa

Answer 18

Worry!!! Osmotic demyelinating syndrome // cerebral edema
Correct:
- ↓1 mEq/L [Na+] / hr
- ↓2 mosm/kg H2O / hr

Question 19

Treat DI

Answer 19

ADH replacement

Question 20

Do you use diuretics for hypervol hyperNa pts?

Answer 20

RARE

Question 21

Equation for calculating pts water deficit (aka how much you need to replace)

Answer 21

H2O def = 0.6 x weight kg x (plasma Na - 140/140)