Fluid Therapy Flashcards
What are the sources of water gain and loss?
Gain: Drinking, eating, metabolic water
Loss: Insensible (i.e. body cannot control)- respiration and skin. Sensible (i.e. body can control) - urine, faeces
What are the normal ranges for insensible and sensible losses?
Insensible - Approx 10-20mls/kg/day
Sensible - Approx 30-40mls/kg/day
What is the maintenance fluid rate?
50mls/kg/day
What are electrolytes?
Minerals that are dissolved in bodily fluids. They are ions within a solution
Define osmosis
The movement of water across a semi-permeable membrane from an area of lower concentrated solution to an area of higher concentrated solution => in order to equalise the concentrations
Describe the movement of fluid between capillaries and cells
High pressure capillary. Due to high pressure, fluid leaks out into the ISF and is then drawn into the cells to balance concentrations. The cells then push fluid and waste out of the cell into ISF and, as the capillary now has a higher concentration (as fluid was previously lost), the fluid is drawn back into the capillaries. Any leftover fluid is collected by the lymphatic system
What could cause oedema?
Decreased plasma proteins (prevents the capillaries from having osmotic draw to get fluid back into them)
or
Ineffective lymphatic drainage
What 3 mechanisms are in place for when an animal becomes dehydrated (i.e. plasma osmolarity increases)
- Osmoreceptors in hypothalamus detect changes and stimulate thirst
- Posterior pituitary gland activated and releases ADH which acts on the permeability of the DCT and causes reabsorption of water in the kidneys
- RAA system - drop in blood pressure causes kidney to release Renin which converts A-A1- (ACE) - A2. A2 then causes vasoconstriction increasing blood pressure, and also causes the adrenal gland to release aldosterone which causes salt retention in kidney (water follows) therefore increasing blood pressure
What signs would you see in a mild-moderately dehydrated patient?
dry MM decrease in skin elasticity decreased urine output mild tachycardia slightly prolonged CRT
What signs would you see in a severely dehydrated patient?
Skin tenting Sunken eyes 3rd eyelid protrusion Oliguria/anuria Weak pulse Long CRT Then collapse, shock etc
What is the normal urine output?
1-2mls/kg/hr
What are the normal specific gravity values for dogs and cats?
Dog: 1.015-1.045
Cat: 1.020-1.060
What is the normal PCV values for dogs and cats?
Dog: 37-55%
Cat: 24-45%
What is the normal body pH?
7.4 approx
What pulmonary regulation takes place if the blood becomes too acidic?
Detected by arterial chemoreceptors which increases tidal volume (deeper) or respiration rate (faster).
Combine H+ ions with bicarb which is then breathed out as CO2 and water.
What renal regulation takes place if the blood becomes too acidic?
Adjusts H+ and bicarbonate to form ammonium and excretes this in the urine to get rid of the excess H+ ions and bring blood pH back up
Which is quicker? Pulmonary or renal regulation of blood pH?
Pulmonary
What is metabolic acidosis?
Where an acid state in the body occurs due to altered metabolism. I.e. unable to excrete acid or losing excess alkali
When would metabolic acidosis occur?
- Vomiting/diarrhoea (in normal vomiting lose more alkaline bile than stomach acid)
- Renal failure (aren’t excreting acid as efficiently)
- Shock ( not enough blood reaching kidneys to be filtered)
What is metabolic alkalosis?
Where an alkaline state in the body occurs due to altered metabolism
When would metabolic alkalosis occur?
- Vomiting stomach contents only (e.g. pyloric obstruction)
2. Over-administration of bicarbonate
What is respiratory acidosis?
Where an acid state in the body occurs when the respiratory system cannot excrete acid
When would respiratory acidosis occur?
- Respiratory obstruction ( prevents exit of H+)
- Acute respiratory failure (reduces RR, build up acid)
- Hypoventilation
- Anaesthetic problems
What is respiratory alkalosis?
An alkaline state in the body that occurs when the respiratory system loses excess acid
When would respiratory alkalosis occur?
- Hyperventilation
- Pain/ stress (increases RR)
- Hyperthermia/ Heat stroke (panting)
- Excessive IPPV
When would a patient be short of water only?
Unable to drink
Unable to concentrate urine (DI)
When would a patient lose water and electrolytes?
V/d
Metabolic Disorders
What kind of loss is blood loss (in terms of tonicity)?
Isotonic
In what scenario would a patient lose plasma?
Burns
What must we consider before administering IVFT?
- Amount of fluid required
- Type of fluid required
- Type of dehydration ( hyper-, hypo-, iso-)
- pH of body ( does it need rectified?)
What is the equation for calculating fluid volume required?
Volume = Maintenance + Deficit + Ongoing Losses
What is the maintenance volume and how is it calculated?
The amount of fluid needed to combat normal losses
= 50mls/kg/day
What is the deficit volume and how is it calculated?
The amount that the fluid volume is reduced from normal - once repaid can be left out.
= 10mls/kg/1% dehydration or 1% PCV increase
What is the ongoing losses volume and how is it calculated?
Any predicted continued losses e.g. vomiting.
= 4mls/kg/ how many times it has had vomiting or diarrhoea OR % burns
How can we convert the volume required for a patient per day into a drip rate?
Volume per day /24 = volume per hour.
Divide by 60 to get volume per minute
Multiply the volume per minute by the drops/ml drip rate = drops per minute
Can then divide 60 by the drops per minute = 1 drop every ____ seconds
What is the drip rate of most administration sets?
20 drops/ml
Describe the 3 categories of fluid
- Crystalloids
- solution containing water and electrolytes - Colloids
- solution containing large molecules: plasma expanders - Blood/ blood products
What are crystalloid fluids for?
- rectify fluid and electrolyte loss
- balance abnormal body pH
What are colloid fluids used for?
- reverse shock and rapidly bulk up blood volume
- restores pressure and perfusion
- rapidly expand plasma volume ( dilutes existing RBCs so should consider concurrent O2 therapy)
What conditions are colloid fluids thought to be contraindicated in?
Kidney disease/ damage
What colloid fluid does have an 02 carrying capacity?
Oxyglobin - bumps up blood volume and adds o2!!
What should you consider for diagnosis if a patient is on oxyglobin?
Can cause free-floating Hb which then causes brown staining. Affects blood tests and turns MM and urine brown
Describe 4 blood products
- Whole blood
- Plasma (frozen/fresh frozen)
- Packed red cells (for anaemia)
- Cryo-precipitate ( the bit where all the clotting factors are)
What problem will you face when trying to catheterise a very shocked patient?
Peripheral vessels will be very constricted, hard to place IV. Use jugular
Reasons for not using SC fluids?
- believed to be uncomfortable
- slow absorption
- not good for shocked patients as no circulating blood in periphery for fluid to get absorbed
What cautions with IP fluids?
Risk of damaging organs
Risk of infection
Need to warm fluids
Why would you use IO route for fluids?
- great blood supply means fluids absorbed rapidly
- can give large volumes
How often should an IV catheter be changed?
Every 48-72 hours
What should you use to flush IV catheters?
Heparinised saline - the heparin helps reduce micro-clots that may form in the cannula as its foreign.
What should you check in a patient on IVFT?
- check correct type of fluid, check fluid level, in date and clear.
- Check administration site for bruising, heat, pain, perivascular fluid
- Check line for kinks, blockages and interference
How can you monitor the patient on IVFT in terms of if its working?
- Clinical signs of hydration
- Monitor TPR and MM
- Record urine output and USG
- Monitor PCV
- Monitor any other ongoing losses
- Central venous pressure (using a 3 way tap to move blood up a scale to get BP) (Normal 2-4cm)
What would the signs be if a patient was over-hydrated?
Soft, moist cough Dyspnoea, tachypnoea Tachycardia Lethargy Runny Nose Decreased PCV Abnormally increased Urine output Rapid (overnight) increase in bodyweight
What is No 1 fluid used for (NaCl 0.9%) ?
Sodium Chloride 0.9%
- used for rehydration (after excessive water and sodium loss)
- correcting electrolyte imbalance
- Treating metabolic alkalosis
When is sodium chloride and glucose fluids used?
- maintenance fluids once fluid balance is restored
- treatment of water ONLY deprivation/dehydration
- Addisonian crisis (Na will balance K)
What is Hartmann’s (or lactated ringers)(No11) used for?
- extracellular dehydration
- metabolic acidosis (bicarb balances acid)
- treatment/prevention of hypovolaemia and haemorrhage shock
What is Ringers solution used for (No9)?
- has H20, Na, K, Ca, Cl
- Dehydration with salt depletion (where K has been lost)
- Severe vomiting
- Potassium loss
What is hypertonic saline used for?
- supplementary treatment for circulatory shock
- draws fluid into bloodstream
- short-term, rapid restoration of blood volume
What have you got to be careful with when administering potassium?
If given too fast, can create bradycardia or even a heart attack
