Hypernatremia

Question 1

hypernatremia is a problem w/

Answer 1

WATER deficit

Question 2

clinical shortcut to calculate free water deficit

Answer 2

pt [Na+] minus 140 divided by 3

Question 3

free water clearance calculation

Answer 3

urine volume - ((urine osm/plasma osm) x urine volume)

Question 4

electrolyte free water clearance calculation

Answer 4

urine volume - ((urine Na+ + K+/plasma Na+) x urine volume)

Question 5

polyuria from water diuresis

Answer 5

> 3 l/day d/t;

• polydipsia
• hypotonic solution
• impaired urinary concentration (central or nephrogenic DI)

Question 6

polyuria from solute diuresis

Answer 6

> 3 l/day d/t;

• isotonic solution
• osmotic diuresis (DM, mannitol)
• solute diuresis (diuretics)

Question 7

if polyuria (UOP > 3 l/day) next step

Answer 7

check urine Osm

Question 8

if polyuria and urine Osm < 100 mosm/kg, ML diagnosis

Answer 8

• primary polydipsia

- central or nephrogenic DI

Question 9

if polyuria and urine Osm < 100 mosm/kg (water diuresis), next step

Answer 9

water deprivation test

Question 10

if polyuria and urine Osm 100-300 mosm/kg (mixed polyuria), ML diagnosis

Answer 10

• partial DI (central and nephrogenic)
• simultaneous water and solute intake
• CKD

Question 11

if polyuria and urine Osm 100-300 mosm/kg (mixed polyuria), next step

Answer 11

water deprivation test or 24-hour urine collection (urine Na+, K+, glucose, and urea)

Question 12

if polyuria and urine Osm > 300 mosm/kg (solute diuresis), ML diagnosis

Answer 12

• hyperglycemia
• azotemia
• high solute intake

Question 13

if polyuria and urine Osm > 300 mosm/kg (solute diuresis), next step

Answer 13

water deprivation test or 24-hour urine collection (urine Na+, K+, glucose, and urea)

Question 14

if primary polydipsia water deprivation test (WDT) result

Answer 14

will be able to concentrate urine

Question 15

if DI WDT result

Answer 15

still have water diuresis; unable to concentrate urine

Question 16

after WDT, DDAVP response test; expected response if central DI

Answer 16

urine concentrates

Question 17

after WDT, DDAVP response test; expected response if nephrogenic DI

Answer 17

NO response; unable to concentrate urine

Question 18

causes of nephrogenic DI

Answer 18

• congenital = V2 receptor mutation
• medications = Li+, amphotericin, etc
• electrolyte abnormalities = hypokalemia, hypercalcemia
• intrinsic renal diseases = polycystic kidney disease, medullary cystic disease, SCD, obstruction

Question 19

gestational DI

Answer 19

• placenta produces vasopressinase usually in 3rd trimester

Question 20

causes of central DI

Answer 20

• congenital (Wolfram syndrome)
• head trauma
• suprasellar tumors (either primary or metastatic)
• granulomatous disease (TB, sarcoid, etc)
• Histiocytosis
• vascular (cerebral thrombosis, Sheehan syndrome, etc)