Fluid Therapy And Parenteral Nutrition Flashcards
What are the two considerations when giving fluid therapy?
Replacement of fluids lost
Maintenance of fluid needs
How can fluids be lost?
Haemorrhage
Excessive urination (polyuria)
Vomiting and diarrhoea
Sequestered fluid
What percentage of body weight is made up of total body water?
60%
What can total body water be subdivided into?
What proportions?
Extracellular fluid (1/3) and intracellular fluid (2/3)
What can extracellular fluid be subdivided into?
Interstitial fluid 3/4
plasma (intravascular volume) 1/4
How can we calculate blood volume?
Plasma volume / (1-haematocrit)
Why are fluids indicated for general anaesthesia?
Replacement of blood lost from surgical bleeding
Counteract CV depression from anaesthetic drugs - vasodilation leads to lowered BP
Replace insensible fluid loss
Maintain normal fluid volumes despite reduced intake pre and post op
Warmed fluids can help maintain body temp
What is meant by insensible fluid losses?
Evaporation from surgical site etc.
What are some other indications for fluid therapy ?
Flushing things out
Animals with azotaemia (pre, renal and post) may help improve glomerular filtration rate and removing renal toxins
Animals intoxicated with water soluble substances - flush out - e.g. chocolate, NSAIDs
Correction of acid-base disturbances
How can fluids be used to correct electrolyte disorders?
Fluids may be supplemented with potassium and glucose if needed .
When might drugs be delivered using fluid therapy?
Some drugs have to be diluted before administration
Some drugs require constant infusion over sever hours
What are the common types of fluids available?
Crystalloids
Synthetic colloids
Blood products
Osmotic diuretics
What are the three types of crystalloids?
Isotonic
Hypertonic
Hypotonic
What is the most common type of fluid to administer?
Isotonic crystalloids
What are crystalloids composed of ?
Water and small molecules which can freely move out of the intravascular space.
Vary in exact composition
- Electrolytes - Na+,Cl-, K+, Mg2+, Ca2+
- Buffers - lactate, gluconate
- Dextrose
How does hypertonic fluid affect blood volume?
Water is attracted into blood
How does hypotonic fluid affect blood volume?
fluid moves into interstitial space
Causes cellular oedema
What are some examples of isotonic crystalloids?
Hartmann’s
Compound Sodium Lactate (CSL)
0.9% NaCl
Lactated Ringer’s Solution (LRS)
What happens after isotonic fluid is administered?
Fluid distributes equally amongst all fluid compartments
Only a third of volume remains intravascularly after equilibration due to the movement of sodium
What are the complications which can be associated with isotonic crystalloid therapy?
-Inadequate volume resuscitation or replacement
- VOLUME OVERLOAD
- Peripheral oedema formation
- Pulmonary oedema or pleural effusion
-Possible dilutional coagulopathy
When might hypertonic saline be indicated?
SEVERE shock, particularly larger patients
Cerebral oedema - attracts water into blood from brain
MUST NOT USE AS A CONSTANT INFUSION
What is a contraindication of hypertonic fluids?
Dehydration / hypernatremia
When might hypotonic crystalloids be indicated?
Hypernatraemic patient or for some drug infusions
NOT USED OFTEN
What are synthetic colloid fluids composed of?
LARGE molecules (>30 KDa) suspended in an ISOTONIC crystalloid
How are Synthetic Colloids useful?
Need molecules which persist in the vascular space and continue to attract water - Generate COLLOID OSMOTIC PRESSURE with PROLONGED EFFECT
This delays equilibration of fluid with other compartments
When may synthetic colloids be considered?
Hypoperfusion (shock)
To restore circulating volume
When are synthetic colloids indicated?
Require rapid intravascular resuscitation - mainly haemorrhagic
Want to increase COP in patients with low protein
- hepatic synthetic failure, protein losing conditions (e.g. PLE, PLN), haemorrhage
TYPICALLY when the patient is oedematous or does not respond to isotonic crystalloids
What are some possible complications of using synthetic colloids?
Fluid overload (more likely than isotonic crystalloids) - NOT AS SAFE
Coagulopathy
-Dilution of platelets and clotting factors and other additional effects
Inaccuracy of total solids and urine specific gravity measurements
Risk of acute kidney injury
How can synthetic colloids potentially result in a coagulopathy?
Dilute platelets and clotting factors
Additional direct effects on coagulation
What lab diagnostics can be effected by the use of synthetic colloids?
Total solids
Urine specific gravity
What are natural colloid solutions?
Blood products
- whole blood, plasma, packed RBCs
Concentrated albumin solutions
-human or canine
Give an example of an osmotic diuretic.
What is its effect?
Mannitol
Shift fluid into intravascular space to be excreted by kidneys - Increased vascular volume
When is mannitol indicated?
Most common: BRAIN OEDEMA
Also, acute glaucoma, oliguric acute kidney injury (AKI)
What do you need to monitor when giving mannitol?
Fluid depletion or volume overload
What does parenteral nutrition contain?
When should it be given?
A mixture of amino acid solutions, dextrose, and lipids (via IV line)
When animals cannot receive nutrition via the GIT (enteral nutrition)
What are the advantages of enteral nutrition?
Directly supports enterocytes
Preserves mucosal barrier - prevents bacterial translocation
Immunomodulatory
Stimulates motility, secretions and neuroendocrine pathways
Fewer complications
Relatively inexpensive
IF THE GUT WORKS, USE IT !!!
What are some options for enteral nutrition?
Nasogastric feeding tube
Oesophagostomy feeding tube
Gastrotomy/PEG tube
Jejunostomy tube (bypass stomach)
When is parenteral nutrition indicated?
Uncontrolled GI dysfunction - V/R
Existing malnutrition or high risk malnutrition
Individualised feeding
Contraindication for enteral feeding (e.g. CV instability or unable to protect airway)
Reserved for cases of convincing GIT failure
What are some negatives associated with parenteral nutrition?
More expensive than enteral feeding
More challenging to manage in practice
Needs a central venous catheter
Can cause sepsis
Why does total parenteral nutrition need to be delivered via the jugular vein?
High osmolarity fluid
Can cause vasculitis in small peripheral vessels
When would you see parenteral nutrition used?
In referral practice
- requires special expertise and equipment for patient specific prescriptions
Needs to be handled COMPLETELY ASEPTICALLY
Metabolic complications possible
What negatives are associated with parenteral nutrition?
Expensive Often can give nutrition enterally Can cause sepsis Need a central venous catheter Need 24/7 monitoring
