Fluid Therapy Flashcards
What are the sources of water gain and loss?
Gain: Drinking, eating, metabolic water
Loss: Insensible (i.e. body cannot control)- respiration and skin. Sensible (i.e. body can control) - urine, faeces
What are the normal ranges for insensible and sensible losses?
Insensible - Approx 10-20mls/kg/day
Sensible - Approx 30-40mls/kg/day
What is the maintenance fluid rate?
50mls/kg/day
What are electrolytes?
Minerals that are dissolved in bodily fluids. They are ions within a solution
Define osmosis
The movement of water across a semi-permeable membrane from an area of lower concentrated solution to an area of higher concentrated solution => in order to equalise the concentrations
Describe the movement of fluid between capillaries and cells
High pressure capillary. Due to high pressure, fluid leaks out into the ISF and is then drawn into the cells to balance concentrations. The cells then push fluid and waste out of the cell into ISF and, as the capillary now has a higher concentration (as fluid was previously lost), the fluid is drawn back into the capillaries. Any leftover fluid is collected by the lymphatic system
What could cause oedema?
Decreased plasma proteins (prevents the capillaries from having osmotic draw to get fluid back into them)
or
Ineffective lymphatic drainage
What 3 mechanisms are in place for when an animal becomes dehydrated (i.e. plasma osmolarity increases)
- Osmoreceptors in hypothalamus detect changes and stimulate thirst
- Posterior pituitary gland activated and releases ADH which acts on the permeability of the DCT and causes reabsorption of water in the kidneys
- RAA system - drop in blood pressure causes kidney to release Renin which converts A-A1- (ACE) - A2. A2 then causes vasoconstriction increasing blood pressure, and also causes the adrenal gland to release aldosterone which causes salt retention in kidney (water follows) therefore increasing blood pressure
What signs would you see in a mild-moderately dehydrated patient?
dry MM decrease in skin elasticity decreased urine output mild tachycardia slightly prolonged CRT
What signs would you see in a severely dehydrated patient?
Skin tenting Sunken eyes 3rd eyelid protrusion Oliguria/anuria Weak pulse Long CRT Then collapse, shock etc
What is the normal urine output?
1-2mls/kg/hr
What are the normal specific gravity values for dogs and cats?
Dog: 1.015-1.045
Cat: 1.020-1.060
What is the normal PCV values for dogs and cats?
Dog: 37-55%
Cat: 24-45%
What is the normal body pH?
7.4 approx
What pulmonary regulation takes place if the blood becomes too acidic?
Detected by arterial chemoreceptors which increases tidal volume (deeper) or respiration rate (faster).
Combine H+ ions with bicarb which is then breathed out as CO2 and water.
What renal regulation takes place if the blood becomes too acidic?
Adjusts H+ and bicarbonate to form ammonium and excretes this in the urine to get rid of the excess H+ ions and bring blood pH back up
Which is quicker? Pulmonary or renal regulation of blood pH?
Pulmonary
What is metabolic acidosis?
Where an acid state in the body occurs due to altered metabolism. I.e. unable to excrete acid or losing excess alkali
When would metabolic acidosis occur?
- Vomiting/diarrhoea (in normal vomiting lose more alkaline bile than stomach acid)
- Renal failure (aren’t excreting acid as efficiently)
- Shock ( not enough blood reaching kidneys to be filtered)
What is metabolic alkalosis?
Where an alkaline state in the body occurs due to altered metabolism
When would metabolic alkalosis occur?
- Vomiting stomach contents only (e.g. pyloric obstruction)
2. Over-administration of bicarbonate
What is respiratory acidosis?
Where an acid state in the body occurs when the respiratory system cannot excrete acid
When would respiratory acidosis occur?
- Respiratory obstruction ( prevents exit of H+)
- Acute respiratory failure (reduces RR, build up acid)
- Hypoventilation
- Anaesthetic problems
