Sodium

Question 1

What is the normal value of Fractional Excretion of sodium ?

Answer 1

FE (Na+) < 1% (adults and foals)
FE > 1% is due to tubulopathies

Question 2

What is pseudohyponatremia ?

Answer 2

Dosage below the true plasma [Na+] due to hyperproteinemia and hyperlipemia

Question 3

DDX of hyponatremia ?

Answer 3

1- Increased losses : diarrhea, salivary losses (mild), renal failure, sweat
2- Dilutional hypoNa+ : free water adm°/consumption in excess or without access to Na+ (feed deprivation), bladder rupture
3- Adrenal insufficiency : ↘︎ aldosterone → urinary Na+ excretion + hyperkalemia
4- Rhabdomyolysis : unclear mechanism

Question 4

Clinical effects of hyponatremia ?

Answer 4

Water moves from eC to iC space in case of hypoNa+ → edema (brain ++)
Mild hypoNa+ : no clinical signs
Severe hypoNa+ : dysphagia, seizures, coma or death (brain swelling)

Question 5

What is the target rate of correction of hypoNa+ ?

Answer 5

0,5 mEq/L/h or 0,5 mmol/L/h, recheck q2h
This is a target rate of correction, which will determine the supplementation required (contrary to K+)
*The rate of increase or decrease of Na+ is much more important to control than for K+. *

Question 6

What is the risk associated with too rapid correction of Na+ deficiency ?

Answer 6

Can lead to dangerous mouvement of fluid out of brain cells → demyelination syndrome and neuro. damages

Question 7

How to treat hyponatremia ?

Answer 7

Target change : 0,5 mEq/L/h
1- Hyponatremia + dehydration/volume deficits : isotonic crystalloid solution
2- Hyponatremia + volume overload : CRI of furosemide + isotonic crystalloid solution
Recheck q2h

Question 8

What is pseudohypernatremia ?

Answer 8

May be due to hypoproteinemia

Question 9

Causes of hypernatremia ?

Answer 9

1- Hypernatremia associated with hypervolemia :
* Salt poisoning.
* Iatrogenic: hypertonic saline solution for resuscitation or milk replacer mixed incorrectly
* Hyperaldosteronism or hypercortisolism

2- Hypernatremia associated with normovolemia
* Primary hypodipsia
* Inadequate access to water
* Diabetes insipidus (central or nephrogenic)
* High environmental temperature or prolonged exercise (exhausted horse syndrome).

3- Hypernatremia associated with hypovolemia
* Gastrointestinal losses (reflux, early stage diarrhea)
* Third space loss (SI obstruction, peritonitis)
* Burns
* Renal losses (of water)

Question 10

Clinical effects of hypernatremia ?

Answer 10

Water moves from iC to eC space in case of hyperNa+ → cell dehydration
Mild hyperNa+ : no clinical signs
**Severe hyperNa+ : prolapse of the 3rd eyelid, myoclonus of head and neck muscles, tail swishing **

Question 11

How to treat hypernatremia ?

Answer 11

Acute → rapid correction
Chronique or unknown duration → slow correction
⚠️ Rapid decrease in serum Na+ with large amounts of water → cerebral edema

• Dehydration + hypernatremia : Correction of hypernatremia is achieved by free water replacement.
  1- Half of the water deficit can be replaced in 12-24h with close monitoring of neuro status (Water deficit = % dsh x BW)
  2- Remaining deficit can be corrected over the subsequent 48h
  3- Max rate of decrease in plasma [Na+] < 0,5 mEq/L/h or 0,5 mmol/L/h → recheck q2h
• Fluid overload + hypernatremia : furosemide + isotonic cristalloid
  The rate of increase or decrease of Na+ is much more important to control than for K+.