Fluid therapy Flashcards
need for fluid therapy
Replacement of fluids “lost”
Maintenance of fluid “needs”
ways to loose fluid
Blood loss Dehydration excessive urination Vomiting, diarrhoea Sequestered fluid (“third space”– in bowel, in cavities)
“flushing things out”
azotaemia (pre-renal, renal, post-renal) may require fluid therapy as a means of increasing Glomerular Filtration Rate (GFR)
Animals intoxicated with water soluble substances may also benefit from fluid therapy
whats in a fluid bag
Water
Electrolytes - Sodium, Chloride, Potassium, Magnessium, Calcium
± Buffers - Lactate, Citrate
± Dextrose
Fluid Therapy to Deliver Nutrients
When animals cannot receive nutrition through the gastrointestinal tract (enteral nutrition) animals may be fed parenterally
fluid types
Crystalloids
Colloids - Natural, Synthetic
fluid tonicities
Isotonic
Hypertonic
Hypotonic
Crystalloids - Components
Water + small molecules
Electrolytes - Sodium, Chloride, Potassium, Magnessium, Calcium
± Buffers - Lactate, Citrate
± Dextrose
crystalloids
Most common used fluid in practice
Cheapest
Can be administered PO, IV, SQ, IO, IP
After administered, distributes equally amongst all fluid compartments - Only a third of volume remains intravascularly after equilibration
Complications only related to amounts of fluid used (too little/too much)
Synthetic Colloids - Components
water + large molecules
electrolytes - sodium, chloride
+/- buffers - lactate, citrate
Synthetic Colloids
Some form of colloid available in most practices
Can be rather expensive
Generates colloid osmotic pressure - This delays equilibration of fluid with other compartments, Useful for resuscitation of intravascular volume
Complications include fluid overload and coagulopathy
unavailable in UK
possible harm to patients – kidney injury mainly
natural colloids
Blood products - Fresh whole blood, Packed red blood cells, Fresh frozen plasma
Concentrated albumin solutions
parenteral nutrition
Mixture of amino acids solutions, dextrose, lipids (all crystalloids)
Provides energy and building blocks for protein synthesis
Effects of Tonicity
Isotonic = same tonicity as blood
Hypertonic = much higher than blood
Hypotonic = less than blood
Tonicity determines distribution of fluid between compartments, i.e., tonicity is what can move fluids from one compartment to another
Isotonic fluid administered IV - effect
fluid distributed equally amongst all compartments
Hypertonic fluid administered IV - effect
Draws fluid from intracellular and interstitial compartments into intravascular compartmen
Hypotonic fluid administered IV - effect
Fluid shifts to the intracellular compartment – cellular oedema
isotonic crystalloid use
Rehydration Resuscitation – treatment of hypovolaemia Correction of acid/base electrolytes Deliver drugs Induce diuresis
Considerations for colloid use
Require rapid resuscitation Want to increase COP Need resuscitative effect to last more than 1 hr Most colloids are isotonic Typically used when animal is oedematous
hypertonic saline use
Not used very much extremely rapid resuscitation Very effective! Patient has to be well hydrated for hypertonic saline to work Can be used to treat brain oedema Very small doses required
mannitol
Most commonly used for brain oedema
Treatment for acute glaucoma
Sometimes used for oliguric renal failure
Osmotic diuretic – main effect is to shift fluid into the intravascular space to be excreted by the kidneys
hypotonic fluid use
Not used very much at all
Supposed to be a true “maintenance fluid”
For short term use – only a few hours
Only really useful if you are treating extremely hypernatraemic patients
Nicknamed “Devil’s Fluid” - Causes too many complication with electrolytes and cellular oedema
Parenteral Nutrition - Indications
Dysfunctional GI tract - vomiting, diarrhoea
Existing malnutrition or risk of becoming malnourished
contraindicated enteral feeding
Pancreatitis (?)
Unable to protect airway
Total Parenteral Nutrition
Meets 100% of energy requirements Very hypertonic (hyperosmolar) Needs to be delivered via jugular catheters
Partial or Peripheral Parenteral Nutrition
Only meets 40-70% of energy
Lower osmolarity
can be given peripherally
parenteral nutrition in use
used in referral practices - Requires special expertise, equipment
Needs to be handled completely aseptically
Amino acids and dextrose ready to use
Meets 40-70% energy depending on case
