NA disorders Flashcards
What is normal serum sodium?
135-145 mEq/L
How do you calculate normal serum osmolality?
(Na+ x 2) + (BUN/2.8) + (Glucose/18)
What is the cause of neurological symptoms in hyponatremia?
extracellular hypo-osmolality causes swelling of brain cells leading to N/V, HA, AMS, seizure, coma, death
What is the cause of neurological symptoms in hyper-natremia?
extracellular hyperosmolality causes dehyrdration and shrinkage of brain cells leading to fatigue, weakness, twitch, seizure, coma, death, cerebral vessel rupture
What are the main triggers of ADH release?
plasma osmolality over 295 and decreased baroreceptor input/ hypovolemia
What is the MOA of ADH?
binds V2 receptors in collecting tubule, to send Aqp 2 from cytoplasm to lumen to increase water re absorption and decrease serum osmolality
What does urinary osmolality indicate about ADH and water reabsorption?
high UOsm (>100) ADH present and H2O reabsorption, low UOsm (<100) no ADH and no H2O reabsorption
What does urinary sodium indicate about extra-cellular volume?
low UNa+ (10) kidney thinks ECV high (or acid base or unable to retain) secreting Na+
Pseudohyponatremia with normal POsm is caused by what?
hyperlipidemia or hyperproteinemia
Pseudohyponatremia with high POsm is caused by what?
hyperglycemia or hypertonic mannitol
What tests should you run if you suspect hyponatremia and why?
1 POsm (hyperosmolar?)2 UOsm (ADH?)3 UNa+ (kidney ~ ECV?)4 H&P (clinical, electrolytes, renal fn)
What clinical signs would support hyponatremia?
volume losses (diarrhea, vomit, bleed, diuresis), medication, pain, surgery, edema, rales, S3, orthostatic vitals, skin tenting
What are the three causes of hyponatremia with UOsm <100 and ADH is appropriately not produced?
1 primary polydipsia (too much H2O intake, psych)2 beer potomania3 tea and toast syndrome (low osmolar load)
At what rate should you correct a sodium imbalance?
0.5 mEq/L/hr
What happens if you correct hyponatremia too fast?
central pontine myelinolysis/ osmotic demyelination syndrome
What does the body produce to compensate for gradual development of hyponatremia?
idiogenic osmoles
What is SIADH?
syndrome of inappropriate ADH excretion= production of fixed amount of ADH with no input from osmotic or volume factors resulting in high UOsm
What are some causes of hyponatremia with low UNa+ and low ECV with appropriate ADH production?
GI volume loss, burns, diuretics, cortisol deficiency, treat by giving saline
How do you treat hyponatremia with low UNa+ and high ECV with inappropriate ADH production?
treat underlying CHF, cirrhosis, nephrosis
What are some causes of hyponatrmia with high UNa+ and low ECV with inappropriate ADH production?
adrenal insufficiency, genetic salt wasting diseases, vomit, hypothyroidism, treat with fluid restriction
What are some causes of hyponatremia with high UNa+ and high ECV with appropriate ADH production?
abnormal ADH production (oat cell carcinoma, SIADH), TB/pneumonia/asthma, CKD, reset osmostat
How do you treat hyponatremia with increased ECV?
fluid restriction with high sodium high protein diet to increase osmolar load and ADH antagonists (Tolvaptan, conivaptan)
What are the two causes of sodium retention that can lead to hypernatremia?
drinking salt water, infusion of hypertonic NaCl
What are the sources of water loss that can lead to hypernatremia?
insensible (sweat)renal (diabetes insipidus)GIloss into cells (rhabdomyolysis)inadequate water intake (reset osmostat)
What are the two types of diabetes insipidus and ?
central - don’t make ADH b/c hypothalamus/pituitary problemnephrogenic- collecting tubule doesn’t respond to ADH b/c receptor problem/Li+/osmotic diuretic
How can you differentiate between central and nephrogenic diabetes insipidus?
if you give desmopressin (ADH) and UOsm increases then it’s central diabetes insipidus
How do you treat diabetes insipidus?
low Na+ dietthiazide diureticcarbamazepine/chlorpropamide to increased ADH effectNSAIDs to block PG’s (which block ADH)if central then give ADH
What fluids can you give to treat hypernatremia?
D5W1/4 saline if low Na+ and low ECVnormal saline if low Na+ and low ECV with low BP
