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P&T Block 5 Renal > L48 > Flashcards

Flashcards in L48 Deck (21)
1

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

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

2

What is the sensor for ECF volume?

Baroreceptors in the carotid sins and atrium
Watch for drop in BP: hemorrhage, vomiting, diarrhea

3

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

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

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.

CHF
Cirrhosis
Nephrotic syndrome

5

Where are osmoreceptors located?

Ant hypothalamus
↑osm -> ↑ADH

6

Would you rather be hypovolemic or hyponatremic?

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

7

Where is ADH made?

Supraoptic + paraventricular nuclei
Stored in the post pituitary

8

Mechanism of ADH

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

9

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

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

10

What is the cause of hypovol hyperNa if U Na

U Na

11

Describe euvol hyperNa. Name the 3 possible causes.

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

12

Describe 2 types of diabetes insipidus

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

13

What are the 3 possible causes of hypervol hyperNa?

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

14

Why would hyperNa state be maintained?

Can't get water: obtunded, infant

15

Clinical presentation of hyperNa

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

16

Explain encephalitis in acute and chronic response to hyperNa

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

17

Treat acute hypernatremia

Hydration

18

Treat chronic hyperNa

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

19

Treat DI

ADH replacement

20

Do you use diuretics for hypervol hyperNa pts?

RARE

21

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

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