6. Fluid therapy SDLs Flashcards
You attend a Farm to assess a calf with severe diarrhoea, the calf is still bright but has a prolonged skin tent and tacky membranes. The patients heart rate and pulses are normal. The Farmer is not happy to let you remove the calf from the farm for treatment and doesn’t want anything ‘complicated’. You agree to provide an oral fluid plan to the farmer. Which fluid type would be most appropriate?
isotonic
Isotonic is the most appropriate method for oral rehydration, there are no deleterious effects on the GI tract itself and importantly you are unlikely to negatively affect the patients electrolyte levels - particularly when leaving an owner in charge or administration where they may give it quicker than you advise for convenience.
You are treating a horse for uncomplicated dehydration via an intravenous route. The patient has a mild metabolic acidosis on blood gas analysis. Which of the following solutions would be most appropriate.
isotonic hartmanns
The patient is stable so we don’t need to be aggressive by using hypertonic saline. Hartmanns is a balanced solution and appropriate for the mild acidosis, whereas saline may make the acidosis worse. Dextrose 5% saline is too hypotonic and may alter electrolytes.
During a bitch spay major haemorrhage occurred and the patients blood pressure dropped significantly to dangerous levels. There is no blood available in the practice to administer and the patients blood was suctioned into a non-sterile container so auto-transfusion is not possible. The haemorrhage has been controlled. Which of the following fluid types could be used to restore circulating volume rapidly?
hypertonic saline
Hypertonic saline would be an appropriate choice in this patient because it is not dehydrated and only hypovolaemic, rapid intravascular expansion should therefore be possible and it should be followed with an isotonic solution.
A collapsed Labrador Retriever presents to you, the owner reports it has had profuse watery diarrhoea for 24 hours and has started vomiting. Your initial triage reveals a prolonged skin tent, dry mucous membranes, weak pulses and a marked tachycardia. Which of the following fluid types would be the most appropriate to start at this point?
isotonic hartmanns
This patient is both dehydrated and hypovolaemic, therefore, hypertonic saline would be contraindicated. The most likely outcome of hypovolaemia and dehydration will be a metabolic acidosis secondary to poor perfusion and anaerobic respiration, so isotonic hartmanns would be the best choice at an aggressive rate.
A beagle presents to you having been kicked in the head by a horse. The patient’s mentation is subdued and the owner reports it had a short seizure in the car on the way to you. Which of the following fluid types would be beneficial to this patient.
hypertonic saline
This presentation is classical for a raised intracranial pressure following head trauma, as such hypertonic saline would be the treatment of choice to osmotically remove fluid from the cerbral space and relieve the pressure build up.
through which ways does the body lose fluid
- urine (most significant)
- feces/diarrhea (also Na, K, Cl and HCO3 in diarrhea)
- vomit
- blood loss
- third space loss
- inflammatory exudate
- insensible losses (sweat)
- redistribution
what is meant by fluid loss through third space loss
- the third space means body cavities (thorax/abdo)
- fluid can be transudate, modified transudate or exudate depending on disease causing it
- the loss of fluid +/- protein are the major concerns, both will reduce the blood volume -> poor oxygen supply to tissues -> anaerobic respiration -> lactic acid formation -> acidosis
what is transudate
low protein, low cell count fluid
a thin, watery fluid with low protein and cell content that passes through membranes or squeezes into tissue
what is modified transudate
high protein low cell count
what is exudate
high protein, high cell count (esp albumin)
what is meant by fluid loss through inflammatory exudate
- this is loss of fluid due to inflammation (burns are good example)
- burns lead to marked fluid and protein loss from the site
- depending on the extent of the burn that fluid and protein loss can be significant
what is meant by insensible fluid losses
- losses that are almost impossible to quantify so have to be guessed to a certain extent
- examples are sweating and breathing, through both fluid is lost but usually only to a small degree. can be significant in some cases (sweating horses)
what is meant by fluid loss through redistribution
- no loss of volume per se
- increase in blood vessels to fill
- rekates to hypovolaemia and distributive shock
- in distributive disease (sepsis) blood vessels dilate around the body
- blood volume hasnt changed but there are more pipes to fill up now so whilst you havent lost any fluid you need more fluid to fill those blood vessels back up
- peripheral vasodilation causes a relative hypovolemia due to change in capacitance
where is fluid stored
- intracellular
- extracellular divided into:
- interstitium
- intravascular space
where is most of the blood stored in the body
intracellular and interstitial compartments
< 10% body weight in intravascular component
define dehydration
loss of fluid from the intracellular and interstitial compartments
a patient who has had diarrhea for several days compensates by ……… and becomes………
compensates by removing fluid from the interstitial space into the intravascular spaces and becomes dehydrated
define hypovolemia
loss of fluid from the intravascular space
what clinical signs indicate hypovolemia
- poor pulse quality
- pale mucous membranes
- slow CRT
- low BP
- high HR
- hypothermia
- high lactate, PCT and TP (lactate = poor o2 supply to tissues, PCV = concentrated blood)
what clinical signs indicate dehydration
- skin tent
- tacky dry mucous membranes
- sunken and dull eyes
- poor mentation
- weight loss
define shock
tissue hypoxia which can be due to
- reduced oxygen delivery to tissues
- excessive oxygen demand/usage by tissues
- inadequate utilisation of oxygen by tissues
list groups of shocks
- hypovolemic
- distributive
- cardiogenic
- obstructive
why is hypovolemic shock
hemorrhagic = blood pressure drops = reduced perfusion of tissues with blood
what is distributive shock
relative loss
- septic
- anaphylactic
- neurogenic
vasodilation has reduced the ability of blood to fill the vessels = blood pressure drops = reduced perfusion of blood into tissues
what is cardiogenic shock
secondary to heart disease = pump no longer working effectively = blood pressure falls = reduced perfusion of blood into tissues
what is obstructive shock
something is blocking a blood vessel (thrombus or clot) or compressing a blood vessle meaning blood cannot reach the tissues
how can we recognize shock
- all forms of shock mean a reduced oxygen supply to the tissues so in most cases these animals will be mentally subdued (brain lacking o2)
- distributive shock = curveball. all the blood vessels have opened up so this will be the opposite of hypovolemia in terms of appearance except for blood pressure. will see dark pink/red mucous membranes that refill quickly (< 1s) on CRT and a normal or high temp (could be pyrexic with sepsis) BUT BP is reduced so pulses will be poor or bounding but not strong
- cardiogenic looks similar to hypovolaemia but significant cardiac disease is present as well
- obstructive can be difficult to diagnose as it depends on where the obstruction is
what are the 3 types of fluids we can provide a patient
- crystalloids
- colloids
- transfusion products
list examples of isotonic fluids
- hartmanns
- 0.9% NaCl
- dextrose
what are isotonic fluids used for
fluid resuscitation both for hypovolemia and dehydration. they equilibrate across membranes rapidly to restore both intravascular and extravascular spaces.
HOWEVER this equilibration does mean the effect on the intravascualr volume expansion can be short lived (30-60 mins)
what is hartmanns fluid
lactated ringers
contains Na, Cl, K, Ca and lactate +/- magnesium
useful in most patients especially metabolic acidocis (as lactate is metabolised by kidneys into bicarb)
what is the challenge with giving dextrose as a fluid
contains 5% glucose.
- dangerous fluid type! the glucose is rapidly metabolised leaving the 0.18% NaCl solution with is basically water. therefore meaning it becomes a hypotonic solution which can throw electrolyte concentrations out of balance
DO NOT USE
what is a hypertonic solution and when is it used
7.2% NaCl
- markedly hypertonic so draws fluid into the intravascular space (only use IV)
- fluid is drawn from the interstitial space so NEVER USE IN DEHYDRATED PTs
- works rapidly - so useful in hypovolemic shock
- low volumes required so especially useful in large animals (used prior to colic sx in horses)
- draws fluid from the brain so useful in head trauma or other raised intracranial pressure cases
- BUT sodium can be dangerous so can only be used once or twice per 24 hours and ALWAYS needs to be followed with isotonic fluids
what is an example of a hypotonic fluid and what is it used for
0.45% NaCl
- rarely used in first opinion practice
- main indication would by hypernatraemia (high blood Na) in order to dilute it down
- BUT have to be careful how quickly you reduce hypernatraemia. if you drop blood Na too quickly you create an osmotic gradient into the brain so brain gets flooded causing cerebral oedema
what are colloids and when are they used/why not
controversial
contain macromolecules which mimic albumin in the blood to provide oncotic pressure
therefore they should provide a constant buff to intravascular volume by helping to retain fluid
shown to increase risk of death and acute kidney injury as molecules dont stay in the vessles
list transfuison products and indications for their use
whole blood - haemorrhage (when we need to replace blood volume)
packed RBCs = anaemia (have to use whole blood in cats and Large animals)
fresh frozen plasma = when we have loss of clotting factors (rat poison or liver disease)
albumin = loss of albumin (protein losing enteropathy)
list routes of fluid administration
- intravenous = rapid and continuous so useful for both hypovolemia and dehydration
- intraosseous = almost as fast as IV but more difficult to place and can get complications. isotonic fluids only
- subcutaneous = reliant on good subcutaneous blood supply to redistribute the fluid so only appropriate in mild dehydration
- oral = relies on functioning GIT. often used in large animals. use isotonic fluids
- rectal = dehydration not hypovolaemia. not in diarrhea. shown to be effective in horses
- intraperitoneal = similar to SQ in that it is dependent on good peritoneal blood supply. can be painful. most often used in small furries and neonates
how do you decide how quickly fluid needs to be administered
recognize the underlying problem
hypovolemia = volume status critical to perfusion so correction should be rapid
dehydration = less critical but over time cellular dysfunction will occur so can be corrected at a slower rate
combination = treat the critical problem first (hypovolemia)
what are some classical shock rates for hypovolemia
dogs: 90ml/kg/hr
cats: 60ml/kg/hr
equine/cattle: 80ml/kg/hr
what are some shock rate boluses
dogs: 10-15 ml/kg in 10-15 min
cats: 5-10 ml/kg over 10-15 min
foals/calves: 10-15ml/kg over 10-15 mins
horses/cattle: realistically as fast as can be administered
how do you calculate fluid rates for dehydration
