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Flashcards in Dysnatremia Deck (24):
1

Effective osmole definition and examples

does not diffuse freely across membrane. Na and K (due to ATPase). Not urea.

2

What is the principle cause of hyponatremia

kidneys are unable to excrete free water

3

What are the principle causes of hypernatremia?

sodium gain or water loss

4

What is the principle regulator of water excretion and what stimulates it?

AVP. Increased osmolality or decreased effective circulating volume. The first is extremely sensitive, the second is not.

5

What are the thresholds for thirst and ADH

A little bit higher threshold for thirst than ADH. Adh first then thirst

6

Definition of hyponatremia/hypernatremia

serum sodium 145

7

Cause of hyponatremia with normal plasma osmolality? Why?

hyperproteinemia, hyperlipidemia. Artifactual rise due to increased plasma vol w/o increase in water plasma. Use ion-selective electrode. Also, trans-urethral tumor resection

8

causes of hyponatremia with high osmolality

hyperglycemia, mannitol infusion

9

Causes of hypovolemic hyponatremia? What will the urine osmolality be? Urine Na? Exceptions? FENa?

sweating, vomiting, diarrhea, diuretics. Then thirst/adh. High. Low except w/ recent diuretics, vomiting (H loss>NaHCO3 loss). Low FENa

10

FENa

Fraction of excreted Na. 1% otherwise

11

hypervolemic hyponatremia: what is it? causes?

total body fluid volume ^, effective circulating volume decreased. CHF, cirrhosis

12

Euvolemic hyponatremia: causes

Syndrome of inappropriate ADH secretion (almost any brain or lung disorder). hypothyroidism, adrenal insufficiency, polydipsia

13

Signs of polydipsia

max urine production (10-15L/d), urine osmolarity <100 mosm/L

14

Symptoms of hyponatremia and their causes

H2O moves across BBB into brain cells. Headache, nausea, vomiting,

15

How much can plasma [Na] be changed in 24 hrs? why?

10mmol. Osmotic demyelination syndrome or central pontine myelinolysis. Esp if hyponatremia is chronic

16

Tx for acute or sever hyponatremia (plasma Na<100)

3% saline

17

Which diuretics can cause volume depletion? Hyponatremia?

loop and thiazide. Thiazide (Na loss> H2O loss)

18

Hypernatremia is always a state of ____

hyperosmolality

19

Causes of hypernatremia

Decreased H2O intake (handicapped, not drinking), increased H2O loss (Renal:diuretics,Diabetes insipidus), Na gain (hypertonic saline administration)

20

Central Diabetes Insipidus

impaired ADH secretion (trauma, tumor, genetic)

21

Nephrogenic Diabetes insipidus

Resistance to ADH (inherited mutation, acquired from lithium, pregnancy, hypokalemia, hypercalcemia)

22

Differentiation of CDI from NDI

water restriction followed by desmopressin. in cdi, urine osms increase by at least 50% after DDAVP.

23

Tx of hypernatremia due to water loss

water thru GI route or D5w or HNS

24

calculation of free water deficit

=total body H2O*[(serum Na/140)-1]