Hypernatremia/Hyponatremia

Question 1

What is normal plasma osmolality?

Answer 1

275-290

Question 2

What is the equation to calculate plasma osm?

Answer 2

2*Na + Glu/18 + BUN/2.8

Question 3

What are some causes of hyperosmolarity?

Answer 3

Hypernatremia, high glucose, renal failure (BUN high)

Question 4

What is normal urine Osm?

Answer 4

60-1200

no ADH- max ADH

Question 5

What does ADH control?

Answer 5

Vasopressin controls water homeostasis (works by plugging water channels into the cell membrane)

Question 6

What does aldosterone regulate?

Answer 6

Volume homeostasis, works through Na channels

Question 7

What does high ADH correlate with?

Answer 7

High urine osmolality
High serum osmolality
Low urine output

Question 8

Is the threshold for ADH release or thirst higher?

Answer 8

ADH release threshold is lower than that for thirst

Question 9

What is the stimuli for ADH release?

Answer 9

high serum osm, low blood volume, angiotensin II, nausea (NAUSEA is MOST POWERFUL)

Question 10

How much water intake per day for normal adult?

Answer 10

1-1.5 L + 350-500 ml (cell metabolism)

Question 11

How to calculate water loss?

Answer 11

Water intake - (lost through skin, lungs, GI, urine)

Question 12

What is hypernatremia refer to?

Answer 12

Dehydration

Question 13

What are some symptoms of hypernatremia?

Answer 13

Thirst, AMS (irritable, coma, stupor), seizures, focal neuro deficits

Question 14

What are some causes of hypernatremia?

Answer 14

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)

Question 15

What are some causes of nephrogenic diabetes insipidus?

Answer 15

Lithium, amp B, hypercalcemia, severe hypokalemia, post-obstruction, ATN recovery phase

Question 16

What causes diabetes inspidus (central)?

Answer 16

Trauma, hypoxic encephalopathy, anorexia, alcohol

Question 17

What labs do you need for hypernatremia?

Answer 17

Urine osmolality, Urine Sodium

Question 18

How is the diagnosis made?

Answer 18

Usually obvious

Question 19

How do you diagnose Diabetes Insipidus?

Answer 19

Hypernatremic

Urine Osmolality is LOW (central

Question 20

What is the treatment for hypernatremia?

Answer 20

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

Question 21

How much should you correct for in hypernatremia?

Answer 21

8-12 mEq per 24 hours or

Question 22

What disease is most likely if you have Hypernatremia with Uosm > 700-800 with a UANa

Answer 22

Extrarenal H20 losses

• GI h2o loss
• Insensible loss
• Increased Intracellular osmoles

Question 23

What is you have hypernatremia with Urine Osm >700-800 with a UANa >100?

Answer 23

Na Overload

• NaCl/NaHCOe IVF
• Mineralcorticoids

Question 24

What is you have hypernatremia with Uosm

Answer 24

Renal H20 Losses DI

- Uosm

Question 25

How do you treat central DI?

Answer 25

Desmopressin