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Flashcards in Sodium disorders Deck (28)
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1
Q

What is normal serum sodium?

A

135-145 mEq/L

2
Q

How do you calculate normal serum osmolality?

A

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

3
Q

What is the cause of neurological symptoms in hyponatremia?

A

extracellular hypo-osmolality causes swelling of brain cells leading to N/V, HA, AMS, seizure, coma, death

4
Q

What is the cause of neurological symptoms in hyper-natremia?

A

extracellular hyperosmolality causes dehyrdration and shrinkage of brain cells leading to fatigue, weakness, twitch, seizure, coma, death, cerebral vessel rupture

5
Q

What are the main triggers of ADH release?

A

plasma osmolality over 295 and decreased baroreceptor input/ hypovolemia

6
Q

What is the MOA of ADH?

A

binds V2 receptors in collecting tubule, to send Aqp 2 from cytoplasm to lumen to increase water re absorption and decrease serum osmolality

7
Q

What does urinary osmolality indicate about ADH and water reabsorption?

A

high UOsm (>100) ADH present and H2O reabsorption, low UOsm (<100) no ADH and no H2O reabsorption

8
Q

What does urinary sodium indicate about extra-cellular volume?

A

low UNa+ (10) kidney thinks ECV high (or acid base or unable to retain) secreting Na+

9
Q

Pseudohyponatremia with normal POsm is caused by what?

A

hyperlipidemia or hyperproteinemia

10
Q

Pseudohyponatremia with high POsm is caused by what?

A

hyperglycemia or hypertonic mannitol

11
Q

What tests should you run if you suspect hyponatremia and why?

A

1 POsm (hyperosmolar?)
2 UOsm (ADH?)
3 UNa+ (kidney ~ ECV?)
4 H&P (clinical, electrolytes, renal fn)

12
Q

What clinical signs would support hyponatremia?

A

volume losses (diarrhea, vomit, bleed, diuresis), medication, pain, surgery, edema, rales, S3, orthostatic vitals, skin tenting

13
Q

What are the three causes of hyponatremia with UOsm <100 and ADH is appropriately not produced?

A

1 primary polydipsia (too much H2O intake, psych)
2 beer potomania
3 tea and toast syndrome (low osmolar load)

14
Q

At what rate should you correct a sodium imbalance?

A

0.5 mEq/L/hr

15
Q

What happens if you correct hyponatremia too fast?

A

central pontine myelinolysis/ osmotic demyelination syndrome

16
Q

What does the body produce to compensate for gradual development of hyponatremia?

A

idiogenic osmoles

17
Q

What is SIADH?

A

syndrome of inappropriate ADH excretion= production of fixed amount of ADH with no input from osmotic or volume factors resulting in high UOsm

18
Q

What are some causes of hyponatremia with low UNa+ and low ECV with appropriate ADH production?

A

GI volume loss, burns, diuretics, cortisol deficiency, treat by giving saline

19
Q

How do you treat hyponatremia with low UNa+ and high ECV with inappropriate ADH production?

A

treat underlying CHF, cirrhosis, nephrosis

20
Q

What are some causes of hyponatrmia with high UNa+ and low ECV with inappropriate ADH production?

A

adrenal insufficiency, genetic salt wasting diseases, vomit, hypothyroidism, treat with fluid restriction

21
Q

What are some causes of hyponatremia with high UNa+ and high ECV with appropriate ADH production?

A

abnormal ADH production (oat cell carcinoma, SIADH), TB/pneumonia/asthma, CKD, reset osmostat

22
Q

How do you treat hyponatremia with increased ECV?

A

fluid restriction with high sodium high protein diet to increase osmolar load and ADH antagonists (Tolvaptan, conivaptan)

23
Q

What are the two causes of sodium retention that can lead to hypernatremia?

A

drinking salt water, infusion of hypertonic NaCl

24
Q

What are the sources of water loss that can lead to hypernatremia?

A
insensible (sweat)
renal (diabetes insipidus)
GI
loss into cells (rhabdomyolysis)
inadequate water intake (reset osmostat)
25
Q

What are the two types of diabetes insipidus and ?

A

central - don’t make ADH b/c hypothalamus/pituitary problem

nephrogenic- collecting tubule doesn’t respond to ADH b/c receptor problem/Li+/osmotic diuretic

26
Q

How can you differentiate between central and nephrogenic diabetes insipidus?

A

if you give desmopressin (ADH) and UOsm increases then it’s central diabetes insipidus

27
Q

How do you treat diabetes insipidus?

A
low Na+ diet
thiazide diuretic
carbamazepine/chlorpropamide to increased ADH effect
NSAIDs to block PG's (which block ADH)
if central then give ADH
28
Q

What fluids can you give to treat hypernatremia?

A

D5W
1/4 saline if low Na+ and low ECV
normal saline if low Na+ and low ECV with low BP