hydration Flashcards
how much water is intracelular
66%
how much water is extracellular
33%
What are signs of water loss
loss of moisture of skin
sunken appearance
drying of mucus membranes
Measurable losses
Urination
other secretory functions
Non-measurable losses
Evaporation form body surface
During respiration
Body water loss is exacerbated in the event of
High ambient temp
Aridity
Increased exercise
Fever
Open body cavities
Certain pathological processes
Causes of water intoxication
Iatrogenic - excessive fluid therapy is most common cause
Endocrine problems (excess ADH)
o Behavioral overconsumption (seen in young calves, habitual training, with psychological disorders
Pathological changes during water intoxication
Increased volume in blood vessels → decreases oncotic pressure and osmotic pressure in blood vessels → fluid leaves blood vessels and enters interstitial space → decreases osmotic pressure in the interstitial space → fluid enters into cells
Pathological effects of over hydration
Increased demand on heart
▪ Increased water added to the blood vessels increased BP
Diuresis
Increased blood flow through the kidneys will increase urine production
Pulmonary hypertension
fluid enters in lungs and pleural space
▪ Due to a combination of high BP and decreased oncotic pressure in the blood vessels.
▪ If the heart cannot push the fluid through fast enough, there will be increased pressure in the pulmonary vessels; if significant may force fluid into lungs and pleural space
▪ Decreasing the oncotic pressure in the blood vessels will cause fluid to enter into the interstitial spaces (e.g., lungs and pleural space)
PULMONARY EDEMA – Increased fluid in the lungs
PLEURAL EFFUSION – Fluid in the pleural space (around the lungs)
Cerebral edema and brain compression
▪ Increased water causes the concentration of Na+ to drop and this decreases the osmotic pressure in the interstitial space.
▪ Water moves from the extracellular space into the intracellular space
causing the cells to swell up. The brain has a limited volume that is determine by the size of cranial vault; swelling of cells causes cerebral edema and compression
CEREBRAL EDEMA – Swelling due to excessive fluid in the brain
Clinical signs of over hydration
Increased HR
o Increased BP
o Increased respiratory rate
o DYSPNEA = Increased respiratory effort; may be seen as open-mouth breathing; heavy breathes; using abdominal effort to breathe; very shallow and rapid breathing
o Increased urination; dilute urine
o Neurological signs: headache → behavioral changes→ ataxia, tremors, central blindness → seizures → coma
Treating over hydration
Stop any fluids
o Diuretics – drugs that promote urine production
o Correct any underlying endocrine condition
Patient at increased risk for over hydration
Heart failure
Kidney failure
End-stage liver disease
Small animals
Increased loses
Lactating animal require more water (i.e., dairy cows can produce 40 L milk/day)
o Animals that work and athletes need increased water intake to account for
increased evaporation and sweat
o Hot weather, hyperthermia, prolonged fever – increases the amount of evaporation, sweat
o Losses from vomit and diarrhea
o Renal losses - polyuria due to renal disease, hormonal causes
o Iatrogenic – due to excessive use of diuretics
o Loss of blood/plasma (hemorrhage, trauma, 3rd space loss)
o Small animals are at higher risk than large animal
Percent dehydrated and what is shown
<3%
Subclinical- No clinical signs on PE
- Long-term may alter production and performance
- Changes appear on diagnostic testing (packed
cell volume, total proteins, azotemia, urine concentration
Treat by getting them to drink more
3-5% dehydrated
Mild
Treat with oral fluids
Often subclinical
- If clinical: lethargic, mucus membrane texture may be questionable, questionable weight change
- Changes on diagnostic testing (see above)
- Diagnosis often based on history
5-8% dehydrated
Moderate
Treat with IV fluids
- Weight loss, lethargic, prolonged CRT, tacky mm, mild skin tent
- Clearly seen on diagnostic tests
8-10% dehydrated
Marked
treat with IV fluids and correct electrolytes
- Weight loss, lethargic to depressed, prolonged CRT, tacky to dry mm, skin tent, mild tachycardia and may appear sunken
- Clearly seen on diagnostic tests
10-12% dehydrated
Severe
IV fluids and organ support
Significant weight loss, depressed, prolonged CRT, dry mm, skin tent, sunken eyes, tachycardic, cool extremities
- Diagnostic tests show other changes to electrolytes and other organ functions.
> 12% dehydrated
Moribund
Shock fluids, possible CPR
This animal is in shock and dying
Adult dog maintenance volume
40-60mL/kg/DAY
Adult cat maintenance volume
50mL/kg/day
Small animal pediatric maintenance volume
80 -120 mL/kg/day
Large animal maintenance volume
40mL/kg/day
Large animal pediatric maintenance volume
80mL/kg/day
Oncotic pressure is affected by
affected by the amount of soluble proteins in the blood vessels, most importantly, albumin
Osmotic pressure
Based on concentration of electrolytes
Deficient volume
Deficit volume in mls = (% dehydration) x (patient’s weight in kg) x 1 L/1kg x 1000 ml/1L
Body water and blood volume
Adult: 60% body weight is water; neonates: 80%
Blood volumes: dog: 90mL/kg; cat: 60mL/kg
This corresponds to 7-9% of body weight in dogs about 6.5% in cats
Max blood draw: not more than 1% body weight (10mL/kg)
