Hypernatremia/Hyponatremia Flashcards
What is normal plasma osmolality?
275-290
What is the equation to calculate plasma osm?
2*Na + Glu/18 + BUN/2.8
What are some causes of hyperosmolarity?
Hypernatremia, high glucose, renal failure (BUN high)
What is normal urine Osm?
60-1200
no ADH- max ADH
What does ADH control?
Vasopressin controls water homeostasis (works by plugging water channels into the cell membrane)
What does aldosterone regulate?
Volume homeostasis, works through Na channels
What does high ADH correlate with?
High urine osmolality
High serum osmolality
Low urine output
Is the threshold for ADH release or thirst higher?
ADH release threshold is lower than that for thirst
What is the stimuli for ADH release?
high serum osm, low blood volume, angiotensin II, nausea (NAUSEA is MOST POWERFUL)
How much water intake per day for normal adult?
1-1.5 L + 350-500 ml (cell metabolism)
How to calculate water loss?
Water intake - (lost through skin, lungs, GI, urine)
What is hypernatremia refer to?
Dehydration
What are some symptoms of hypernatremia?
Thirst, AMS (irritable, coma, stupor), seizures, focal neuro deficits
What are some causes of hypernatremia?
Hypothalamic disorders (primary hypodipsia, neuro disorders, lack of access to water)
- Extrarenal: GI (osm diarrhea, vomiting, NGT
- Insensible losses: Fever, sweating, burns, respiratory
- Renal Loss: Diabetes insipidus, Osmotic diuresis (glucose, mannitol, urea), loop diuretics
- Other: Hypertonic IVF, high aldosterone
- Intracellular osmoles- metabolites made during seizures + exercise (transient hypernatremia)
What are some causes of nephrogenic diabetes insipidus?
Lithium, amp B, hypercalcemia, severe hypokalemia, post-obstruction, ATN recovery phase
What causes diabetes inspidus (central)?
Trauma, hypoxic encephalopathy, anorexia, alcohol
What labs do you need for hypernatremia?
Urine osmolality, Urine Sodium
How is the diagnosis made?
Usually obvious
How do you diagnose Diabetes Insipidus?
Hypernatremic
Urine Osmolality is LOW (central
What is the treatment for hypernatremia?
1) Calculate Water deficit
- 0.6weight(Na-140)/140
2) Estimate water losses
- sensible and insensible
3) Restore water (2-3 days)
- Access to water
- IV fluids
- AVOID OVERCORRECTION (brain will shrink)
Causes Cerebral Edema
How much should you correct for in hypernatremia?
8-12 mEq per 24 hours or
What disease is most likely if you have Hypernatremia with Uosm > 700-800 with a UANa
Extrarenal H20 losses
- GI h2o loss
- Insensible loss
- Increased Intracellular osmoles
What is you have hypernatremia with Urine Osm >700-800 with a UANa >100?
Na Overload
- NaCl/NaHCOe IVF
- Mineralcorticoids
What is you have hypernatremia with Uosm
Renal H20 Losses DI
- Uosm
How do you treat central DI?
Desmopressin
