Fluid therapy Flashcards
What ways do we lose fluid?
Urine
Faeces/diarrhoea
Vomit
Blood loss
Third space loss
Inflammatory exudate
Insensible losses
Redistriubtion
Explain fluid loss via vomiting
Loss of acid (HCl) => metabolic alkalosis
Explain fluid loss via blood loss
Can be external or internal e.g., bleeding splenic haemangiosarcoma (tumour)
Loss of blood => loss of O2 supply => anareobic respiration => lactic acid formation => acidosis
Describe fluid loss via third space loss
Third space = body cavities e.g., abdomen
Fluid can be a transudate (low protein and cells), modified transudate (high protein, low cells) or exudate (high protein and cells) depending on disease
Loss of fluid +/- proteins => reduced blood volume => poor oxygen supply => anaerobic respiration => lactic acid formation => acidosis
Explain fluid loss via inflammatory exudate
Loss of fluid due to inflammation e.g., burns
Burns lead to fluid and protein loss from site
Explain fluid loss via insensible losses
e.g., sweating, breathing
can be significant e.g., sweating in exercising horses
Explain fluid loss via redistribution
a relative loss
Relates to hypovolaemia and distributive shock
In ‘distributive’ disease blood vessels dilate => more fluid needed to fill vessels back up
Peripheral vasodilation causes a relative hypovolaemia due to change in capacticance
Define dehydration
Loss of fluid from intracellular and interstitial compartments
Define hypovolaemia
loss of fluid from intravascular space
How can you check for hypovolaemia?
poor Pulse quality
pale Mucous membrane
long CRT
high Heart rate
low rectal temp
Blood parameters
What are the clinical signs of dehydration?
Prolonged skin tent
Tacky or dry mucous membranes
Sunken and dull eyes
Weight loss
what is shock?
Tissue hypoxia (low oxygen) due to:
- reduced O2 delivery
- excessive O2 demand/usage
- inadequate utilisation of O2
What are the 4 types of shock causing reduced delivery?
Hypovolaemic:
- e.g. haemorrhagic
- BP drops => reduced perfusion of tissues
Distributive:
- vasodilation => reduced ability of blood to fill vessels => reduced BP => reduced perfusion of tissues
Cardiogenic:
- ‘pump’ no longer working effectively => reduced BP => reduced perfusion of tissue
Obstructive:
- BV blocked or compressed so blood cannot reach tissues
How can you diagnose hypovolaemic shock?
same as hypovolaemia:
poor Pulse quality
pale Mucous membrane
long CRT
high Heart rate
low rectal temp
Blood parameters
How can distributive shock be diagnosed?
Dark pink/red mucous membranes
Quick capillary time
Normal or high temp
Reduced BP:
- weak pulse
Why does dehydration cause sunken eyes
Loss of fluid and cells from fat pad behind eyes
What are the 3 types of fluids?
Crystalloids - isotonic, hypertonic, hypotonic
Colloids
Transfusion products
Explain isotonic fluid uses
Used for fluid resuscitation for hypovolaemia and dehydration
Equilibrate across membranes to restore both intra and extra vascular spaces => intravascular volume expansion can be short lived
Give examples of isotonic fluids
Hartmann’s:
- Contains Na, Cl, Ca, lactate, Mg
- Especially useful in metabolic acidosis
Sodium chloride:
- less balanced in terms of electrolytes
- quite acidifying
Dextrose solutions:
- glucose in it is rapidly metabolised leaving NaCl
- really a hypotonic fluid
Explain the use of hypertonic fluids
Saline solutions (7.2%):
- IV
- draws fluid into intravascular space from interstitial space (do not use in dehydration)
- useful for hypovolaemic shock
- draws fluid from brain so useful in head trauma
- always follow with isotonic solutions
Explain hypotonic fluid use
Saline solutions (0.45%):
- rarely used
- used in hypernatraemia (high Na in blood) to dilute it down
- if drop blood Na too fast => creates osmotic gradient into brain => floods brain => cerebral oedema
Describe the use of colloid fluids
contain macromolecules which mimic albumin (protein) in the blood to provide oncotic pressure
Provide a constant buff to intravascular volume by helping to retain fluids
Have been shown to increase risk of death and acute kidney injury
Describe the use of transfusion products
Used to replace what’s been lost
Whole blood for haemorrhage
Packed RBCs for anaemia
Fresh frozen plasma for loss of clotting factors
Risk of transfusion reaction so administer slowly
What are the routes of fluid administration?
Intravenous:
- rapid and continuous
- useful for hypovolaemia and dehydration
Intraosseous:
- isotonic fluids only
Subcutaneous:
- relies of subcut blood supply to redistribute fluid
- only appropriate in mild dehydration
Oral:
- relies of functioning GIT
Rectal:
- for dehydration rather than hypovolaemia
Intraperitoneal:
- dependent on good peritoneal blood supply
How do you calculate the rate to administer fluids in dehydration?
deficit + maintenance + ongoing losses
What is front loading and conservative fluid rates?
Front loading - replace 1/2 deficit in 1-4 hrs, remainder over 24 hrs
Conservative - replace over 24 hrs
what rates should be used for transfusions?
Slow initially - 0.25-0.5 ml/kg/hr for 30 mins
If no signs of reaction => 3-6ml/kg/hr for 3-4hrs
What methods are there for setting rate of fluid therapy?
Burette:
- relies of gravity
Mechanical:
- drip pump
- syringe driver
- pressure bags
how do we monitor fluid therapy?
Weight gain
blood pressure increase
Lactate reduces
Clinical signs cease
Urine output increases
what are the signs of fluid overload
Weight increase in excess of target weight
Hypertension
Peripheral oedema
Effusions
Pulmonary oedema
