Approximately 90% of the body’s water intake comes via the gastro-intestinal tract. The remaining 10% is called metabolic water and is produced as the result of various chemical reactions in the cells of the body’s tissues.
Once an ingested meal enters the GI tract, fluids shift from the plasma, making the contents isotonic. Water movement into and out of the GI tract follows the osmotic gradients created by electrolyte movement. For this reason, providing solid food to a dehydrated animal is contradicted, and could prove fatal.
Estimated Percentage Dehydration |
Physical
Examination Findings |
<5 |
History of fluid loss but no findings on
physical examination |
5 |
Dry oral mucous membranes but no panting or
pathological tachycardia; slight loss of skin elasticity |
7 |
Mild to moderate decreased skin turgor, dry oral
mucous membranes, slight tachycardia, and normal pulse pressure; definite loss of skin elasticity; slight prolongation of capillary refill; slight sinking of eyes into orbit;
slight dryness of oral mucous membranes. |
10 |
Moderate to marked degree of decreased skin
turgor, dry oral mucous membranes, tachycardia, and decreased pulse pressure. prolonged capillary refill; eyes sunken in orbits; dry mucous membranes; possible signs of shock
|
12 |
Marked loss of skin turgor, dry oral mucous
membranes, and significant signs of shock. |
How much fluid to use |
135 X Weight (in kgs) = Maintenance Requirements per day |
1. Determine the maintenance requirement (replacement of normal fluid losses via urine, feces, respiration, skin). Requirements are usually 40-60 ml/kg/day but very young animals require 135 ml/kg/day. |
Maintenance X Percentage of Deficit |
2. Establish the percentage of dehydration using the table and multiply the percentage of dehydration by the maintenance requirement to determine the deficit amount. |
Deficit X .75 |
3. Provide 75% of the deficit amount during the first 24 hours. |
|
4. Must also add “daily maintenance volumes” to your calculated deficit volume if the animal is not eating nor drinking. |
Route to administer |
PO: | Oral route; The absorption of fluids, electrolytes and foods from the stomach is slow. Obviously the oral route of delivery of fluids is contraindicated if the animal needs rapid fluid loading, such as in states of shock. Hypertonic solution, such as 50% dextrose should not be given orally, as the osmotic draw of these hypertonic solutions will bring water into the stomach, causing gastric distension. (concentrations of 20-50% are used to treat hypoglycemia). Gastric distension is one stimulus for vomiting. Whenever the oral route of administration is used, there is always the danger of aspiration of fluid and food into the airways. |
Sub-Cutaneouly: | (hypodermoclysis); The administration of fluids subcutaneously is a rapid, easy method of providing fluids. The absorption of fluids from the subcutaneous space is relatively slow, occurring over 6-8 hours. If the animal is severely dehydrated, blood is shunted away from the subcutaneous tissues to more vital structures, and absorption of fluids will be delayed even longer. Place about 10-20 ml/kg/hour per site. |
IV: | large fluid volumes can be administered rapidly; 10 ml/kg/hour; can only be administered by lisenced professional. |
Which fluid to use |
Select a replacement fluid that closely matches the osmolality of the extracellular fluid (plasma) to acheive the highest rate of safe absorption. The osmolality of blood plasma sets the standard. Fluids in the range of 240 to 340 mOsm/liter are considered isotonic. Fluids with tonicities above 340 mOsm/liter are hypertonic; those with tonicities below 240 mOsm/ liter are hypotonic. |