Disorders of Na and K Regulation Flashcards
What is osmolarity?
the concentration of a solution expressed as the total number of solute particles per liter
What is normal serum osmolarity?
280-290
What is serum osmolarity regulated by?
ADH and thirst
What are the osmotic stimuli that cause ADH release?
from increases in serum osmolarity detected by osmorecptors in the anterior hypothalamus
What are non-osmotic stimuli that cause ADH release?
from decreases in BP or blood volume detected by arterial baroreceptors; other cases include nausea, hypoxia, pain, meds (opiates and antidepressants), pregnancy, multiple other stimuli
What are some causes for someone with hypotonic hypovolemic hyponatremia with Uosm >300 and Urine Na >20?
Renal fluid losses such as diuretic excess, adrenal insufficiency, osmotic diuresis, post obstructive digress, RTA, cerebral salt wasting, salt losing nephropathy
What are some causes for someone with hypotonic hypovolemic hyponatremia with Uosm >300 and Urine Na <20?
Extrarenal fluid losses such as vomiting, diarrhea, third spacing fluids (burns, pancreatitis), blood loss, excessive sweating, lung losses
What are some causes for someone with hypotonic euvolemic hyponatremia with Uosm <100?
primary polydipsia
What are some causes for someone with hypotonic euvolemic hyponatremia with Uosm >300 and urine Na >20?
SIADH (tumor, CNS or pulmonary disorder, drugs (SSRI), nausea, pain, hypoxia), hypothyroidism, adrenal insufficiency, thiazides
What are some causes for someone with hypotonic hypervolemic hyponatremia with Uosm >300 and urine Na <20?
nephrotic syndrome, heart failure and cirrhosis
What are some causes for someone with hypotonic hypervolemic hyponatremia with Uosm >300 and urine Na >20?
acute or chronic kidney failure
What must be ruled out when determining if a pt has SIADH?
cortisol deficiency, hypothyroidism, and other causes
What is the MC malignancy associated with ectopic ADH production?
Small cell lung cancer
Which drugs are associated with SIADH?
Antidepressants, anticonvulsants, antipyschotics, anti-DM drugs, vasopressin analogs, misc
What is the tx for hypovolemic hypotonic hyponatremia?
isotonic saline if no sx; hypertonic saline if symptomatic
What is the treatment for primary polydipsia?
water restriction and hypertonic saline if symptomatic
What is the treatment for hypotonic euvolemic hyponatremia with Uosm >300 and UrineNa >20?
Hypertonic saline if symptomatic; if SIADH then water restriction, furosemide, salt or urea tablets, vaptans, demeclocycline; thyroid replacement for hypothyroidism; prednisone for cortisol deficiency; discontinue thiazides if that’s the cause
What is the treatment for hypervolemic hypotonic hyponatremia?
water restriction and furosemide
Excess K is removed from the body primarily by what?
the kidneys with some loss in the feces
The distribution of Na and K is maintained by what?
Na K ATPase pump
What is the effect of K on RMP?
makes membrane potential less negative –> long term leads to a net decrease in membrane excitability leading to impaired cardiac conduction and neuromuscular weakness/paralysis
Review EKG changes
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