Fluid Therapy Flashcards
For what 2 reasons is fluid therapy indicated?
- replacement of lost fluids
- maintainence of fluid needs (homeostatic metabolic pathways require water)
Why would fluid replacement be needed for lost fluids?
- blood loss
- dehydration
- excessive urination
- VD+
- sequestered fluid - third space eg. bowel/cavities
How much of the total body weight is water?
60% (kg -> L)
How much of the total body water (TBW) is in the form of ECF? ICF?
ECF: 1/3
ICF: 2/3
How much of the ECF is interstitial fluid and how much is plasma?
ECF: 3/4
Plasma: 1/4
Which fluid “compartment” is being investigated when looking at mucous membrane moisture and skin pinch?
Interstitial fluid volume
Which compartments does dehydration affect?
ECF, ICF, Interstital fluid
How can blood volume be calculated from plasma volume and PCV?
BV = PV / (1-Heamatocrit)
What should decisions for use of fluid therapy be based on?
Physical findings, history (NOT PURELY BLOOD WORK)
Give an eg. of a situation where replacement fluids required. How would these be these given?
Hypovolaemic shock (tachycardia, tachypnoea, tall narrow pulses, pale MMs, prolonged CRF -> indicating attempted COMPENSATION for hypovolamia.) Given as rapid fluid bolus (over 10-20mins)
Give an eg. of a situation where maintainence fluids are required. How would these be given?
Dehydration (PU/PD cat, not drinking much over past few days, dry MMs, skin tent, lethargic -> indicates body is NOT trying to compensate so giving bolus of fluids would be pointless as they would be urinated out.)
Given as 24hr fluid drip to allow equilibration of fluids into all body compartments, and reverse the dehydration in interstital fluids
Can cases be dehydrated and hypovoleamic? How should this be treated? Which is most serious?
Yes - with severe dehydration (eg. VD+) can develop hypovoleamia, especially in puppys or small dogs (rare in large dogs)
Bolus (hypovoleamia most serious) followed by rehydration fluids
Why do animals undergoing GA require fluids?
Aneasthetic agents -> vasodilation and hypovolaemia, and depress most systems
In what situations may fluids be indicated other than dehydration, hypovolaemia and GA?
“flushing things out”
- Azotaemia (pre/renal/post) -> ^ GFR
- Animals intoxicated with water soluble substance may benefit
> correction of electrolyte disorders
> correction of acid/base disturbance
- delivering other drugs (may need diluting or constant rate infusion-if metabolised quickly but constant levels needed)
What may be in a fluid bag?
- water
- electrolytes (Na, Cl, K, Mg, Ca)
- ± buffers (citrate, lactate)
- ± dextrose
How may fluid types be classified?
By type - Crystalloid (water and electrolytes) - Colloids: natural (plasma) OR synthetic (starches/gelatin) mimic proteins in plasma By tonicity - Iso/hypo/hyper
Which type of fluid is most common? What are the complications associated with this?
Crystalloid Isotonic
- cheapest, administered PO, IV, SQ, IO, IP
- distributes equally amongst all fluid compartment (1/3 remains intravascular)
- Complications = too much or too little fluid given. Too much -> CHF
What may a crystalloid solution contain?
- Water + small molecules ( electrolytes, ± buffers, ± dextrose
Electrolytes will roughly match body levels but may be slightly off.
What are synthetic colloid mixtures composed of? When would they be indicated?
Water + large molecules (>30KD ~400KD!)
- act as “sponges” to generate colloid osmotic pressure and DELAY equilibration of fluid with other compartments
> Contain electrolytes (Na, Cl) ± buffers (lactate, citrate)
- Good for resucitation of intravascular volume
What are the risks associated with synthetic colloids?
Fluid overload, coagulopathy
In humans -> kidney risk, coagulopathy ^ risk of dialysis
Could the job of a synthetic colloid be carried out by crystalloids?
Yes but MUCH larger volume required. eg. 3l cyrystalloid needed for same effect as 600ml colloid
What types of natural colloid are available?
- Fresh whole blood (use with 24hours)
- Packed red cells (use within 30d)
- Fresh frozen plasma (use within 3-5years)
> concentrated albumin solutions (human, though may -> side effects)
What are parenteral nutrition solutions composed of?
AA, dextrose, lipids (all crystalloids)
-> energy and protein synthesis substrate
Give some examples of available crystalloid solutions
- 0.9% NaCl
- Hartmanns/Lactated Ringer Solution/Compound Sodium Lactate
- Half strength saline 0.45%
