6. Fluid therapy SDLs

Question 1

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?

Answer 1

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.

Question 2

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.

Answer 2

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.

Question 3

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?

Answer 3

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.

Question 4

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?

Answer 4

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.

Question 5

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.

Answer 5

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.

Question 6

through which ways does the body lose fluid

Answer 6

• 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

Question 7

what is meant by fluid loss through third space loss

Answer 7

• 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

Question 8

what is transudate

Answer 8

low protein, low cell count fluid
a thin, watery fluid with low protein and cell content that passes through membranes or squeezes into tissue

Question 9

what is modified transudate

Answer 9

high protein low cell count

Question 10

what is exudate

Answer 10

high protein, high cell count (esp albumin)

Question 11

what is meant by fluid loss through inflammatory exudate

Answer 11

• 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

Question 12

what is meant by insensible fluid losses

Answer 12

• 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)

Question 13

what is meant by fluid loss through redistribution

Answer 13

• 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

Question 14

where is fluid stored

Answer 14

• intracellular
• extracellular divided into:
• interstitium
• intravascular space

Question 15

where is most of the blood stored in the body

Answer 15

intracellular and interstitial compartments
< 10% body weight in intravascular component

Question 16

define dehydration

Answer 16

loss of fluid from the intracellular and interstitial compartments

Question 17

a patient who has had diarrhea for several days compensates by ……… and becomes………

Answer 17

compensates by removing fluid from the interstitial space into the intravascular spaces and becomes dehydrated

Question 18

define hypovolemia

Answer 18

loss of fluid from the intravascular space

Question 19

what clinical signs indicate hypovolemia

Answer 19

• 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)

Question 20

what clinical signs indicate dehydration

Answer 20

• skin tent
• tacky dry mucous membranes
• sunken and dull eyes
• poor mentation
• weight loss

Question 21

define shock

Answer 21

tissue hypoxia which can be due to
- reduced oxygen delivery to tissues
- excessive oxygen demand/usage by tissues
- inadequate utilisation of oxygen by tissues

Question 22

list groups of shocks

Answer 22

• hypovolemic
• distributive
• cardiogenic
• obstructive

Question 23

why is hypovolemic shock

Answer 23

hemorrhagic = blood pressure drops = reduced perfusion of tissues with blood

Question 24

what is distributive shock

Answer 24

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

Question 25

what is cardiogenic shock

Answer 25

secondary to heart disease = pump no longer working effectively = blood pressure falls = reduced perfusion of blood into tissues

Question 26

what is obstructive shock

Answer 26

something is blocking a blood vessel (thrombus or clot) or compressing a blood vessle meaning blood cannot reach the tissues

Question 27

how can we recognize shock

Answer 27

- 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

Question 28

what are the 3 types of fluids we can provide a patient

Answer 28

- crystalloids - colloids - transfusion products

Question 29

list examples of isotonic fluids

Answer 29

- hartmanns - 0.9% NaCl - dextrose

Question 30

what are isotonic fluids used for

Answer 30

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)

Question 31

what is hartmanns fluid

Answer 31

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)

Question 32

what is the challenge with giving dextrose as a fluid

Answer 32

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

Question 33

what is a hypertonic solution and when is it used

Answer 33

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

Question 34

what is an example of a hypotonic fluid and what is it used for

Answer 34

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

Question 35

what are colloids and when are they used/why not

Answer 35

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

Question 36

list transfuison products and indications for their use

Answer 36

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)

Question 37

list routes of fluid administration

Answer 37

- 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

Question 38

how do you decide how quickly fluid needs to be administered

Answer 38

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)

Question 39

what are some classical shock rates for hypovolemia

Answer 39

dogs: 90ml/kg/hr cats: 60ml/kg/hr equine/cattle: 80ml/kg/hr

Question 40

what are some shock rate boluses

Answer 40

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

Question 41

how do you calculate fluid rates for dehydration

Answer 41