PATIENT SUPPORT - Fluid Therapy Flashcards
What is dehydration?
Dehydration is a deficit in total body water
What is hypovolaemia?
Hypovolaemia is a deficit in intravascular volume
What are the four key clinical signs of hypovolaemia?
Cold extremities
Weak peripheral pulses
Tachycardia
Prolonged capillary refill time (CRT)
What causes cold extremities, weak peripheral pulses, prolonged capillary refill time and tachycardia in hypovolaemic patients?
Hypovolaemia leads to reduced blood pressure and tissue perfusion which results in cold extremities, weak peripheral pulses and prolonged capillary refill time. The heart rate increases to compensate for this
Which clinical sign of hypovolaemia can be seen in cats but not dogs?
Bradycardia
Which clinical sign indicates a fluid deficit of less than 5%?
Undetectable clinical signs
Which clinical signs indicate a fluid deficit of 5-6%?
Tacky mucous membranes
Which clinical signs indicate a fluid deficit of 6-8%?
Mild skin tent
Dry mucous membranes
Which clinical sign indicates a fluid deficit of 8-10%?
Retracted globes within the orbit (eye sinking)
Which clinical signs indicate a fluid deficit of 10-12%?
Persistent marked skin tenting
Some clinical signs of hypovolaemia
Which clinical sign indicates a fluid deficit of over 12%?
Hypovolaemic shock
Death
What is osmolarity?
Osmolarity refers to the concentration of solute particles in a fluid
What is tonicity?
Tonicity refers to the how the solute concentration within a solution influences the movement of water across a semi-permeable membrane
What are the three classifications of tonicity?
Isotonic
Hypotonic
Hypertonic
What are the three main classifications of fluids used for fluid therapy?
Crystalloid fluids
Colloid fluids
Blood products
What are crystalloid fluids?
Crystalloid fluids are fluids primarily consisting of water combined with sodium, chloride and/or glucose. Depending on the type of fluid, it may also contain other electrolytes
What are the three subdivisions of crystalloid solutions?
Isotonic crystalloids
Hypotonic crystalloids
Hypertonic crystalloids
What is the composition of isotonic crystalloid solutions?
Isotonic crystalloid solutions consist of water, sodium and chloride in proportions similar to plasma
Why are isotonic crystalloids often referred to as replacement crystalloids?
Isotonic crystalloids contain have a similar osmolarity and electrolyte composition to plasma, hence they are known as replacement fluids
When is the use of isotonic crystalloids indicated?
Isotonic crystalloids are effective replacement fluids and thus are effective in the treatment of hypovolaemia, dehydration and to replace ongoing losses (e.g. vomiting, diarrhoea, effusions, haemorrhage)
List two examples of isotonic crystalloid solutions
0.9% saline
Hartmann’s solution
Why is Hartmann’s solution often the preferred isotonic crystalloid for fluid replacement?
Hartmann’s solution contains electrolytes such as sodium, chloride, potassium and calcium which are very similar to the composition of plasma, as well as a buffer (lactate) that regulates pH
When would 0.9% saline be a more appropriate isotonic crystalloid for fluid replacement?
0.9% saline would be the preferred isotonic crystalloid in patients with hypercalcaemia or hyperkalaemia or that have livers that are unable to metabolise the lactate in Hartmann’s
When is the use of hypotonic crystalloids indicated?
Hypotonic crystalloids are only indicated when dehydration only is suspected, with no evidence of hypoperfusion
Why are hypotonic crystalloids contraindicated in the treatment of hypovolaemia and shock?
Hypotonic crystalloids have a lower osmolarity than plasma and thus adminstration of hypotonic crystalloids would result in the formation of a osmotic gradient that would draw fluid out of the intravascular space, decreasing the blood volume and exacerbating the hypovolaemia and state of shock
What are hypertonic crystalloids?
Hypertonic crystalloids are solutions with a much greater osmalarity than plasma and thus administration of these fluids into the intravascular space will generate an osmotic gradient which will draw fluid from the interstisial space and even intracellular space into the intravascular space
Give an example of a hypertonic crystalloid solution
7.2% (hypertonic) saline
When are hypertonic crystalloid solutions indicated?
In patients with traumatic brain injury
In patients which require a rapid expansion of intravascular volume
Why are hypertonic crystalloids indicated in patients with traumatic brain injury?
Hypertonic crystalloids are indicated in patients with traumatic brain injury as they help to reduce intracranial pressure (ICP) through drawing fluid out of the brain tissue into the intravascular space. Hypertonic crystalloids also improve cerebral perfusion by expanding the intravascular volume
When are hypertonic crystalloids contraindicated?
Patients with dehydration
Patients with hypernatraemia
Patients with uncontrolled haemorrhage
Why are hypertonic crystalloids contraindicated in dehydrated patients?
Hypertonic crystalloids increase the osmolarity of the intravascular space and thus draw fluid from the interstitium and intracellular space into the intravascular space, exacerbating dehydration
Why are hypertonic crystalloids contraindicated in hypernatraemic patients?
Hypertonic crystalloids are contraindicated in hypernatraemic patients as they have a large concentration of sodium and thus can worsen hypernatraemia
Why are hypertonic crystalloids contraindicated in patients with uncontrolled haemorrhage?
Hypertonic crystalloids are contraindicated in patients with uncontrolled haemorrhage as they will rapidly expand the intravascular volume by drawing in fluid from the intersitial and intracellular space and just exacerbate the active bleeding. Furthermore, the hypertonic crystalloid will not replace any lost blood components and cause a dilutional coagulopathy
What are synthetic colloids?
Synthetic colloids are large molecules which increase the oncotic pressure of plasma, which holds fluid in the intravascular space for long periods of time. However, this long prevelance in the intravascular space leads to very adverse effects
How to you calculate the total fluid requirement for a patient?
Total fluid requirement = Maintenance fluids + Fluid deficit + Ongoing losses
How do you calculate the maintenance fluid requirement for an animal with no ongoing losses?
Maintenance (ml/day) = Body weight (kg) x 50ml/kg/day
How do you calculate fluid deficits?
Fluid deficit (litres) = Body weight (kg) x (% dehydration ÷ 100)
You divide the dehydration % by 100 to express the value as a decimal
How do you calculate the hourly fluid requirement for a patient based off of the total fluid requirement?
Hourly fluid requirement (ml) = total fluid requirement (ml) ÷ 24
What are the drip rates for an adult and paediatric giving set?
Adult: 20 drops per ml
Paediatric: 60 drops per ml
What is the approximate blood volume of a dog?
90ml/kg
What is the approximate blood volume of a cat?
60 ml/kg
What is the approximate blood volume of a horse?
80 - 100ml/kg
How can you estimate intra-operative blood loss?
Intra-operative blood loss can be estimated by counting the number of blood soaked surgical swabs as a standard surgical swab will hold 5 - 10ml of blood when soaked
Which two methods can be used to quantify intraoperative blood loss?
Weighing the blood soaked surgical swabs
Measure the volume of blood collected in a suction apparatus
For reference when weighing blood soaked surgical swabs to quantify intraoperative blood loss, how many grams is equivalant to 1ml of blood?
1ml of blood weights slightly more than 1g (approx 1.06g)
Why can quantifying intraoperative blood loss based on suction colletion be an unrealiable way to quantify intraoperative blood loss?
Blood collected by suction is often diluted with saline flush
How can you improve the accuracy of quantifying intraoperative blood loss using suction collection?
To increase the accuracy of quantifying intraoperative blood loss using suction collection, you must compare the PCV of the fluid collected to the PCV of the patient and use the follwing calculation:
Blood lost = Suction PCV / Patient PCV x 100 ml
How should you treat intraoperative blood loss if the loss is less than 10% of the blood volume?
Generally losses of less than 10% blood loss are well tolerated and can be treated with crystalloid fluid administration if appropriate
How should you treat intraoperative blood loss if the loss exceeds 10% of the blood volume?
If the loss exceeds 10% of blood volume, colloid fluid administration may be more appropriate
How should you treat intraoperative blood loss if the loss exceeds 15% of the blood volume?
If the loss exceeds 15% of blood volume ,a fluid with oxygen-carrying capacity, such as whole fresh blood, should be considered
Why is it so important for whole fresh blood to be typed and matched before being administered to cats?
A high proportion of cats have naturally occurring red cell antibodies and so a potentially lethal transfusion reaction can occur the first time unmatched blood is administered
