Flashcards in Fluid Therapy Deck (40)
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
- excessive urination
- 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?
How much of the ECF is interstitial fluid and how much is plasma?
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?
- electrolytes (Na, Cl, K, Mg, Ca)
- ± buffers (citrate, lactate)
- ± dextrose
How may fluid types be classified?
- Crystalloid (water and electrolytes)
- Colloids: natural (plasma) OR synthetic (starches/gelatin) mimic proteins in plasma
Which type of fluid is most common? What are the complications associated with this?
- 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%
Give some examples of available colloid solutions
Pentastarch, tetrastarch (voluven), Gelatins (gelofusine) - UK available, Dextrans, Oxyglobin
Why is oxyglobin rarely used? What is its purpose?
Has oxygen carrying capacity
Ridiculously expensive (£400/125ml)
How does tonicity of the solution affect distribution?
Hypotonic = shifts water to cells -> cellular oedema [BE CAREFUL!]
Isotonic = fluid distributed equally
Hypertonic = draws fluid from intracellular and interstitial compartements -> intravascular
What hypertonic fluids are available?
- 3% and 7% saline
- 20% mannitol [for diuresis as cannot be metabolised so will be wholly excreted]
- 50% dextrose [glucose gets rapidly metabolised]
Q:"Why do you want to give this animal isotonic crystalloid fluids?"
- rescucitation (hypovolaemia)
- correcting acid/base balance
- delivering drugs
- induce diuresis
Q:"Why do you want to give this animal colloid fluids?"
- rapid rescusitation
- resuscitation needs to last longer than 1 hour
- used for oedematous animals
Are most colloids isotonic, hyper or hypo?
What is a standard colloid dose? How would a crystalloid dose differ from this?
Crystalloid 4x this
When would hypertonic saline be indicated? Is this commonly used?
-Rapid resuscitation - very effective
-Patient must already be WELL HYDRATED
-Treatment of brain oedema
What is a standard hypertonic saline dose?
4ml/kg (v small)
What is mannitol indicated for use in?
> Brain oedema
> Acute glaucoma
> Oliguric renal failure
- An osmotic diuretic -> main effect is to shift fluid into intravascular space to be excreted by kidneys
Where are hypotonic saline indicated? Is this commonly used?
NO! Devils fluid - cheap but easily causes severe electrolyte imbalance.
- should NOT be given to sick animals
- maintainence during elective surgery of healthy patient potentially use short term
- rarely used except in referral practice
> can be used in extreme hypernatreaemic patients
Is parenteral nutrition carried out in general practice?
Rarely (referral procedure)
- expensive (£100/day)
- difficult to manage
- expertise in formulation, compounding and delivering required
When is parenteral nutrition indicated?
- Convincing case of bowel failure
- Dysfuntinal GI (VD+)
- Existing malnutrition or risk of becoming malnourished
- Enteral feeding contraindicated - pancreatitis or unable to protect airway
Give 4 options for enteral nutrition
- force/syringe feed
- nasogastric feeding tube
- oesophagostomy tube
- gastrostomy/PEG tube