Flashcards in Dysnatremia Deck (24):
Effective osmole definition and examples
does not diffuse freely across membrane. Na and K (due to ATPase). Not urea.
What is the principle cause of hyponatremia
kidneys are unable to excrete free water
What are the principle causes of hypernatremia?
sodium gain or water loss
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.
What are the thresholds for thirst and ADH
A little bit higher threshold for thirst than ADH. Adh first then thirst
Definition of hyponatremia/hypernatremia
serum sodium 145
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
causes of hyponatremia with high osmolality
hyperglycemia, mannitol infusion
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
Fraction of excreted Na. 1% otherwise
hypervolemic hyponatremia: what is it? causes?
total body fluid volume ^, effective circulating volume decreased. CHF, cirrhosis
Euvolemic hyponatremia: causes
Syndrome of inappropriate ADH secretion (almost any brain or lung disorder). hypothyroidism, adrenal insufficiency, polydipsia
Signs of polydipsia
max urine production (10-15L/d), urine osmolarity <100 mosm/L
Symptoms of hyponatremia and their causes
H2O moves across BBB into brain cells. Headache, nausea, vomiting,
How much can plasma [Na] be changed in 24 hrs? why?
10mmol. Osmotic demyelination syndrome or central pontine myelinolysis. Esp if hyponatremia is chronic
Tx for acute or sever hyponatremia (plasma Na<100)
Which diuretics can cause volume depletion? Hyponatremia?
loop and thiazide. Thiazide (Na loss> H2O loss)
Hypernatremia is always a state of ____
Causes of hypernatremia
Decreased H2O intake (handicapped, not drinking), increased H2O loss (Renal:diuretics,Diabetes insipidus), Na gain (hypertonic saline administration)
Central Diabetes Insipidus
impaired ADH secretion (trauma, tumor, genetic)
Nephrogenic Diabetes insipidus
Resistance to ADH (inherited mutation, acquired from lithium, pregnancy, hypokalemia, hypercalcemia)
Differentiation of CDI from NDI
water restriction followed by desmopressin. in cdi, urine osms increase by at least 50% after DDAVP.
Tx of hypernatremia due to water loss
water thru GI route or D5w or HNS