L3- Hypernatremia Flashcards
What are the 3 ways that Serum Na can be high?
Serum [Na] = Na/H2O = Sodium concentration = salt relative to water
Higher serum sodium concentration via 3 ways:
↓Na/↓↓↓ H2O - too much loss of water
↔Na/↓H2O = normal salt but loss of water
↑↑↑Na/↑H2O = exception to the rule!!! Rare where too much salt relative to increased water content
HYPERNATREMIA = DEHYDRATION!!!!! (too much water loss compared to salt)
Basically, can’t respond to sense of thirst or obtain water, too much salt or lack of ADH.
How do you calculate Serum Osm?
What is the value of Very Dilute urine w/ no ADH?
What is the value of very concentrated urine w/ high ADH?
Dilute - 50-100 mosms/kg
vs
1200 mosms/kg
What are the steps in the algorith for hypernatremia?
What are common presentations?
High Posm or high Na then Use physical exam to figure out volume status
Most commonly presents w/ Hypovolemia or Euvolemia
Hypovolemic hypernatremia:
What does it mean? Causes? Urinalysis?
Dehydrated AND volume depleted
Renal Causes: Diuretics or renal problems
Una >20 (should be less!)
Non-Renal Causes: Sweating, Burns, Fever, Diarrhea
Una <20
Normovolemic Hypernatremia:
What does it mean? Causes? Urinalysis?
Loss of water but normal Na - Dehydrated but volume ok
Renal Causes: Nephrogenic DI - can’t respond to ADH
Extrarenal causes: Central DI - cant make ADH, or Hypodypsia, or insensitive losses in lungs and skin
UNA can vary
Hypervolemic Hypernatremia:
What does it mean? Causes? Urinalysis?
RARE- Exception to the rule bc most about dehydration but this is excess Na intake
Causes - Eat Salt tablets or Infusion Hypertonic
Una >20 bc volume expanded
clinical manifestations of hypernatremia?
Increased muscle irritability
*Change in mentation - confusion to coma signs range classified as **Metabolic Encephalopathy **
Acute and chronic adaptations to changes in cell volume
What is the CNS defense to hypernatremia and how does that cause encephalopathy?
What are the treatments?
In response to high Na, cells shrink an dthen pump in electrolytes so water will follow back into cells and restore cell volume. The problem is that these electrolytes purturb neuronal functioning and lead to encephalopathy.
Acute Tx: Rapid hydration
Chronic Tx: Idiogenic Osmols to extrude perturbing electrolytes and replace them to maintain volume
- betain, sorbitol, phosphorylcholine, myoinositol
CAREFUL - slow correction otherwise Osmotic Demyelination Syndrome
1 mEq/L [Na]/hour
Treatment of Hypernatremia?
HYDRATION!!!!
Calculate the Electrolyte free water deficit
Water deficit = .6 x weight (kg) x (plasma [Na] - 140)/140
ADH replacement for central DI or partial nephrogenic DI
Diuretic therapy for RARE patient w/ hypervolemic hypernatremia
Volume depends on what?
Salt problems depend on what?
Volume depends on Na status
Salt problems - hypo or hypernatremia depend on WATER - hydraiton
Wha tis normal serum [Na}?
140!!
In Euvolemic Hypernatremia, what lab value is more helpful: Una or U-Osm?
Uosm more helpful bc patient is normovolemic
Uosm indicates if responding/releasing ADH or not
Uosm should be greater than Posm if responding to ADH
