Drugs for Hypo/Hypernatremia Flashcards
how do content and concentration of sodium differ in reference and meaning
concentration cares about sodium relative to water regardless of what the amount is.
what is the equation for for plasma osmolality
2(Na) + Glucose/18 + BUN/2.8
What is the effect of .9 NaCl on ICF and ECF volume
increases ECF volume
What is the effect of .45 NaCl on ICF and ECF volume
Increases both ICF and ECF volume with majority of expansion in ECF
What is the effect of 3 or 5% NaCl solution on ICF and ECF
Expand ECF
Shrink ICF
What is the effect of 5% dextrose
increases total body water.
What value constitutes hypernatremia
> 145 mEq/L
What value constitutes hyponatremia
<135 mEq/L
what is normal serum osmolality
285-295 mOsm/kg
What is the mnemonic of hyponatremia symptoms
SALT LOSS
Stupor/coma
Anorexia, N/V
Lethargy
Tendon reflexes decreased
Limp muscles
Orthostatic hypotension
Seizures/headache
Stomach Cramping
what must be avoided when treating a sodium imbalance
overly rapid correction can cause osmotic demyelination syndrome
if you have acute symptomatic hyponatremia, what is the limit of rise?
can use 2.5 mEq/L/hr
not to exceed 20 mEq/L/day
If you have chronic symptomatic hyponatremia, what is the limit of rise
.5 mEq/L/h until 120 mEq/L not to exceed 8-12 mEq/L/day and no more than 18 mEq/L in first 48 hrs
What is the MOA of conivaptan
blocks Vasopressin receptor (ADH) which promotes excretion of water
What are the clinical applications and toxicities of conivaptan (IV)
treats euvolemic and hypervolemic hyponatremia in people who are hospitalized and not responsive to fluid restriction.
Can cause orthostatic hypotension, fatigue, thirst, polyuria
why must tolvaptan (PO) be used less than 30 days for hyponatremia
can lead to liver toxicity
What enzyme metabolizes Vaptans
CYP3A4
What are the main causes of hypernatremia
Unreplaced Water loss
Water loss into cells (exercise)
Sodium overload
What is the mnemonic for hypernatremia symptoms
TRIP
T - twitching, tremors, hyperreflexia
R - Restlessness, irritable, confusion
I - intense thirst, dry mouth, decreased urine output
P - pulmonary and peripheral edema
what is the treatment of hypovolemic hypernatremia
use isotonic saline
-in other patients use hypotonic IV solutions
correct slowly and long duration
What is the MOA of desmopressin
analogue of ADH
V2 selective agonist
What is the clinical indication of desmopressin
central diabetes insipidus
primary nocturnal enuresis
What are the toxicities ofdesmopressin
Fluid retention - hyponatremia (especially in CF, renal impairment, HF)
hypotension
What is the most common cause of nephrogenic diabetes insipidus
Li treatment
What drug is used to treat nephrogenic diabetes insipidus if not caused by lithium?
and if it is?
Thiazides if not caused by lithium
Amiloride if it is
