Fluids Flashcards
What is hypovolaemia?
When fluid is lost rapidly from the intravascular space (in vessels)
What is dehydration?
Fluid is lost slowly from the extravascular compartment (cells)
Redistribution means loss from all compartments
What are the physiological consequences of hypovolaemia?
Reduces preload Reduces stroke volume Reduced CO Vasoconstriction Tachycardia
How do you assess intravascular volume?
HR
MM colour
CRT
BP
What is normal CRT?
<2 secs
How do you assess extravascular volume?
Moistness of MM
Skin turgor/tenting
Weight
Eye globe position
What are the physical exam findings of <5% dehydration?
No signs
What are the physical exam findings of 5-6% dehydration?
Tacky mucous membranes
Mild skin tent delay
What are the physical exam findings of 6-8% dehydration?
Dry mucous membranes
Mild increase in CRT ~2 secs
Mild/moderate skin tent delay
Maybe sunken eyes
What are the physical exam findings of 10-12% dehydration?
Dry mucous membranes CRT >2-3 seconds Signs of shock Marked skin tent Sunken eyes
What are the physical exam findings of >15% dehydration?
Death
What can affect assessment of dehydration?
Hypersalivation
Subcut fat
Skin folds
How should you correct dehydration?
Slowly
How should you correct hypovolaemia?
Rapidly
What is the best type of fluid available for hypovolaemia treatment?
Isotonic crystalloids
What are crystalloids?
Solutions containing solutes eg. electrolytes
What are the two types of isotonic crystalloids?
0-9% NaCl and Hartmann’s
Why are isotonic solutions the best?
Dont shift water from intracellular to extracellular compartments
What does Hartmann’s contain that 0.9% NaCl doesnt?
Potassium and chloride - more balanced
Lactate - treat acidosis
When should you not use Hartmann’s?
Do not mix with blood products or sodium bicarbonate - risk of clotting/precipitation
When should you not use 0.9% NaCl?
When there is acidosis - can exacerbate
When are hypotonic crystalloids used?
Rarely - maybe severe hypernatremia
When are hypertonic crystalloids used?
Commonly in large animals - need less fluid
Used for hyponatremia and intracranial hypertension
What are colloids?
Large molecules that cant cross semipermeable membranes
What effect do colloids have on the body?
Increase the osmotic pressure so need less fluid to resuscitate
When are colloids used?
Rarely - hypovolaemia
Have lots of risks
What are some risks of colloids?
Coagulopathy
Allergic reactions/anaphylaxis
(also expensive)
What are some complications of fluid therapy?
Heart disease/failure
Renal disease
Resp disease
Volume overload
What are some signs of volume overload?
Pulmonary oedema
Venous engorgement - jugular distension
Peripheral oedema - conjunctiva, ocular discharge
What is the formula for fluid requirement?
Extravascular fluid deficit + maintenance requirements + ongoing loss
How do you work out the extravascular fluid deficit?
Estimate the % dehydration
% dehydration x body weight x 10
What is the formula for the maintenance requirement?
2ml/kg/hr
How do you work out the ongoing loss?
Depends on amount lost in vomiting, diarrhoea etc.
What is shock?
An imbalance between oxygen delivery and consumption by the tissues
= Not enough oxygen to tissues
Causes cellular/tissue hypoxia
What is shock most commonly caused by?
Hypoperfusion
What are the 4 types of circulatory shock?
Hypovolaemic
Cardiogenic
Obstructive
Distributive
What is hypovolaemic shock?
Shock due to decreased blood volume - haemorrhagic or non-haemorrhagic
What is cardiogenic shock?
Forward/pump failure causing reduced cardiac output
What are some examples of causes of cardiogenic shock?
Systolic dysfunction
Diastolic dysfunction
Bradyarrhythmias
Tachyarrhythmias
What is obstructive shock?
Due to physical obstructions in blood flow to or from the heart/major blood vessels
What are some examples of causes of obstructive shock?
Gastric dilatation-volvulus (GDV)
Pulmonary thromboembolism
What is distributive shock?
Due to maldistribution of blood flow - usually widespread inappropriate vasodilation
What are some examples of causes of distributive shock?
Anaphylaxis
Sepsis
Burns/trauma
What is the physiological response to hypovolaemic shock?
Adrenaline release
Renin-angiotensin-aldosterone system activation
ADH release
Splenic contraction
Why is adrenaline released during hypovolaemic shock?
Increases HR
Increases peripheral vasoconstriction
Why is the renin-angiotensin-aldosterone system released during hypovolaemic shock?
Increases sodium and water retention and peripheral vasoconstriction
Why is ADH released during hypovolaemic shock?
Increases water retention
Why does splenic contraction occur during hypovolaemic shock?
Releases more RBCs into circulation
How is hypovolaemic shock classified?
Compensated - body is successfully maintaining tissue perfusion
Decompensated - Body is failing and patient is in danger
What are the common features of hypovolaemic shock in cats?
Bradycardia
Hypothermia
Cats are much less predictable
How do you treat hypovolaemic shock?
Rapid administration of fluids - isotonic crystalloids
Blood transfusion - severe or if anaemic
Check still not losing fluids
What size bolus do you give a dog for hypovolaemic shock?
10-20ml/kg
What size bolus do you give a cat for hypovolaemic shock?
5-10ml/kg
What is the shock dose?
Equates to the total blood volume of the patient - dont give full shock dose!
What is the shock dose in dogs?
80-90ml.kg
What is the shock dose in cats?
50-55ml/kg
What is the target urine output for determining efficacy of treatment?
> 0.5ml/kg/hr
How much hypertonic fluid should be administered if used once?
4ml/kg
What lab tests are used in fluid therapy?
Packed cell volume
Total solids
What does both increases PCV and TS indicate?
Dehydration - slow so time for RBCs to increase
What does both decreased PCV and TS indicate?
Haemorrhage
Anaemia
What does decreased PCV but normal TS indicate?
Haemolytic anaemia
What does normal PCV but decreased TS mean?
Acute haemorrhage
Or hypoproteinaemia
How can a urea dipstick help with fluid therapy?
Increase in urea can indicate dehydration - pre-renal
What is the name of the group of tests used to support assessment of sick patients needing fluid therapy?
The minimum database
What diseases might need a blood transfusion?
Hypovolaemic anaemia
IMHA
Coagulopathies
Thrombocytopaenia
When should you give a blood transfusion to an anaemic patient?
If there are clinical signs of anaemia - not just based on PCV alone
What are the 4 different types of blood products available?
Whole blood
Packed RBCs
Fresh frozen plasma and frozen plasma
Cryoprecipitate
What animals is blood transfusion available for?
Dogs
No blood banks for cats but can obtain locally
How do you get packed RBCs/plasma?
Hard spin centrifugation of whole blood - separates them out
What counts as fresh whole blood compared to stored whole blood?
Fresh whole blood - <6 hrs after collection
Stored - >8 hrs after
What is found in fresh whole blood that isnt found in stored whole blood?
Some functional platelets
Clotting factors
(Both have RBCs)
What is the PCV of packed RBCs?
70-80%
What does fresh frozen plasma contain?
All coagulation factors
Albumin/proteins
How is fresh frozen plasma stored?
Stored at -20 to -40 degrees for less than a year
What is frozen plasma?
Plasma that has been stored for >1 year
Or that has been thawed and refrozen
What does frozen plasma not contain that fresh frozen plasma does?
Labile factors are lost - VIII and vWF
How long can frozen plasma be stored for?
Up to 5 years
What is found in both fresh frozen plasma and frozen plasma?
Stable coagulation factors
How is cryoprecipitate made?
By slowly partially thawing fresh frozen plasma and then centrifuge it again
What is cryoprecipitate rich in?
Fibrinogen, VIII and vWF
When is cryoprecipitate used?
In von Willebrands disease and haemophilia A
Not used very commonly
What disease is fresh whole blood the ideal option for?
Blood loss anaemia
What disease is fresh frozen plasma the ideal option for?
Unknown coagulopathy
What disease is frozen plasma the ideal option for?
Rodenticide toxicity
What disease is packed red blood cells the ideal option for?
Euvolaemic anaemia - normal blood volume but loss of RBCs
How many different blood types are there in dogs?
6
Which is the only dog erythrocyte antigen that be we can type for in clinical practice?
DEA 1.1 - can be positive or negative
What blood should DEA1.1 negative dogs recieve?
Only DEA 1.1 negative blood
What blood should DEA1.1 positive dogs recieve?
Either DEA 1.1 positive or negative blood
What blood type should be given in an emergency in dogs?
DEA1.1 negative blood
What does the blood of a sensitised DEA1.1 negative dog contain?
RBC doesnt have a DEA1.1 antigen
But its plasma contains anti-DEA1.1 antibodies
What causes a transfusion reaction to DEA1.1?
If a DEA1.1 negative dog is given DEA1.1 positive blood twice
Anti-DEA1.1 antibodies developed the first time will kill the second lot of DEA1.1 positive blood
Do dogs and cats get naturally occurring alloantibodies?
Dogs dont
Cats do - born with antibodies against other blood types so dont need sensitisation for a transfusion reaction
What are the 3 blood types in cats?
A, B and AB
Which cat blood type is the most reactive?
Type B - has lots of anti-A antibodies
Which blood type should be given to a type AB patient?
Type AB
If not available then give type A
What is a major crossmatch?
Testing the recipients serum with donor RBCs
What is a minor crossmatch?
Testing the donor serum with recipient RBCs
When should crossmatching occur?
When the recipient has received a transfusion more than 4 days ago
What is the difference between open and closed donation?
Open - more than one site of potential contamination
Only one exposure
Over what time period do you give a blood transfusion?
4-6 hours
How do you begin administering a blood transfusion?
1ml/kg/hr for 20 mins - slow to allow early recognition of transfusion reactions
How often should you monitor transfusions?
Every 15-30 mins during
1, 12 and 24 hrs after
