Electrolytes - Ex 5 Flashcards
1
Q
Restorative mechanisms - hypertonic dehydration (3)
A
- Osmoreceptors: very sensitive and act quickly –> ADH is secreted –> retention of water = restores volume & osmolality
- Thirst is increased (centrally) –> gain free water
- Volume receptors: less sensitive and slower –> cause change in vascular tone to maintain BP and in the long term (if necessary), engage RAAS –> increase Na retention & thus water
2
Q
Restorative mechanisms - isotonic dehydration
A
- Volume receptors: activate RAAS –> inc Na retention & thus water retention
- Volume receptors: also cause changes in vascular tone
3
Q
Restorative mechanisms - hypotonic dehydration
A
- Osmoreceptor activation –> release of ADH & gain of free water
- Volume receptors –> activation of RAAS –> restores Na and water levels
4
Q
Pseudohyponatremia
A
Artifactual increase in Na!
Can be due to hyperlipidemia
5
Q
True Hyponatremia - Differentials
A
- Loss of Na from the body
- secretory diarrhea
- hypertonic sweating (horses)
- renal tubular dz (w/inc natriuresis - exc of Na in urine)
- Addison’s dz - Dilution by excess water retention
- administration of osmotic diuretics (e.g. mannitol) –> pulls water into the vascular space
- Diabetes mellitus –> high glucose pulls water INTO the vascular space - “Third space” syndrome
- displaced abdomen (electrolyte trapping)
- hemoabdomen
- GI obstruction
- Mech: sequestration and accumulation of isotonic fluid –> perceived hypovolemia –> inc thirst w/gain of free water
6
Q
Most common cause of hypernatremia
A
Water loss from the body in excess of Na –> hypertonic dehydration
7
Q
Salt Toxicity
A
Excessive dietary intake (or limited access to water)
Iatrogenic administration
8
Q
Corrected Chloride Calculation
A
Ccl = Cl (measured) x [Na(normal)/Na(measured)
- If within normal range –> change in chloride is due to change in Na
**If outside of normal range –> true hypochloremia
