Flashcards in Fluid therapy Deck (55)
List ways in which healthy animals lose body water
- Water vapour during breathing
List abnormal ways in which water can be lost from the body
- Third space oss
What is third space loss and give an example?
- Fluid accumulates in body cavity but lost from circulation i.e. effusions, internal haemorrhages, peritonitis, obstructions etc
- e.g. ascites
What are the kinds of fluid losses that can occur in an animal?
- Primary water loss
- Mixed water and electrolyte loss
How does primary water loss occur?
- Water intake decreased, only losing water
- Hypotonic loss
- When patient unable to increase intake sufficiently
- Occurs from ECF, ICF to ECF translocation to compensate
Why do the clinical signs of primary water loss take time to develop?
- Water moves from ICF to ECF to compensate
- ICF is a large reserve
What are the important factors to consider when estimating water loss?
- Duration of illness
- Vomiting/diarrhoea? frequency and volume
- Water intake (quantify, unusual habits)
- Source of loss e.g. open wounds, asscites ec
- What kind of fluid loss has occured
How does mixed water and electrolyte loss occur?
- Vomiting or diarrhoea
- Haemorrhage and effusion
What are the important features of mixed electrolyte and water loss?
- Osmolarity does not change, no movement from ICF
- Loss borne by ECF alone
- Clinical signs develop quickly
What should be included in patient assessment when considering fluid loss?
- Pulse quality (peripheral, changes sooner)
- Heart rate
- Skin tenting
- Regular blood pressure (can change with stress, may no be accurate)
- Tackiness of mucus membranes
- Eye position
What may happen to eye position in severe dehydration?
- May sink into socket
- Third eyellid (nictitating membrane) may move over the top
How can the degree of hypovolaemia be assessed?
- Using approximate ranges for heart rate, pulse quality, mucous memrbane colour, CRT, mentation and extremity temperature
What does loss of a distal pulse indicate?
What is the difference between cats and dogs as hypovolaemia progresses?
- Cats more likely to show bradycardia
- Dogs more likely to show tachycardia
How can fluid deficit be estimated?
- Comparison of clinical signs usually show when at a particular % fluid deficit
- Multiply by animal's weight to get volume of deficit i.e. 20kg dog with 10% dehydration = 2 litre deficit
What is the approximate maintenance fluid requirement for a dog?
- or 1.5-4ml/kg/hour
List the main therapeutic fluids
- Crystalloids (hypotonic, isotonic, hypertonic)
- Blood products
- Haemoglobin based oxygen carrying solutions (HBOCS)
What are the main aims of fluid therapy?
- Improvement of organ function (need adequate perfusion)
- Correction of electrolyte disturbances
- Correction of hypovolaemia
- Correction of acid base disturbances
- Total or partial parenteral nutrition (usually PPN)
What is Lactated Ringer solution?
Isotonic crystalloid solution
What is contained in LRS?
- Na+: 130mEq/l
- Cl-: 109mEq/l
- Lactate as a bicarbonate precursor (so is buffered)
- Tiny amounts of potassium
Why is LRS buffered?
- Controlled alkalinisation
- Avoids dilutional acidosis
Why is LRS not suitable for long term administration?
What is LRS used for?
- Can add other things e.g. glucose
What are the disadvantages of LRS?
- Contains calcium, cannot use if hypercalcaemic
- Only 1/4 will remain in vascular space, rest is excreted, not efficiet in bringing up and maintaining fluid levels
Describe hypotonicc crystalloid fluids
- 0.18% NaCl, or 0.18% NaCl and 5% glucose
- Very few indications - Like giving pure water
- Useless, causes dilution, likely to make patient sicker
What is the effect of administration of hypertonic crystalloid fluid?
- Draws water from interstitial space
- Causes pulmonary-vagal reflex (vasoconstriction, bypass pulmonary circulation)
- Transient effect (10-15 min)
When is use of hypertonic crystalloid fluid indicated?
- Usually large animals e.g. prior to colic surgery
- Low volume resus (life threatening hypovolaemia and raised ICP)
When is use of hypertonic crystalloid fluid contraindicated?
- Fall in BP
- Repeat use
When is use of colloid fluids indicated?
- Support of circulating blood volume is needed
- Severe hypovolaemia
- Systemic inflammatory response syndrome
What types of colloid fluids are available?
- Artificial: oxypolygelatins, dextrans, starches, HBOCs
- Natural: albumin, plasma etc
Describe gelatin colloids
- Plasma half life 2-4 hours
- No need for concurrent crystalloid but often do give both
- Produces osmotic diuresis
- No direct coagulation effects
Describe starch colloids
- Plasma half life 25 hours due to molar substitution
- Initial elimination by tissue uptake
- Excretion by metabolism
- Volume expanded by volume given
- Reversal of microvascular permeability
- Direct coagulation effects
How do starch colloids reverse microvascular permeability?
How do starch colloids have a direct coagulation effect?
Increase APT in dogs
- Factor VIII precipitation
What are the indications for use of blood colloids?
- Clotting disorders
Outline how hypertonic saline can be used for emergency fluid resuscitation in clinical practice
- Life threatening hypovolaemia and raised intra-cranial pressure (ICP)
- Draws water from interstitial space
- Causes pulmonary vagal reflec
- Expands blood palsma for short period of time
Give an example of haemoglobin replacement products in fluid therapy
- Haemoglobin based oxygen carrying HBOC
When are haemoglobin replacement products commonly used and why?
- Hypoxaemic crisis where there has been massive blood loss
- Artifically carries oxygen
What are the limitations to using haemoglobin replacement products?
- Very expensive
- Many practices do not stock so difficult to get hold of in crisis
- Exerts high osmotic pressure, need to infuse slowly and carefully
List the ways in which fluids can be administered
What veins can be used for intravenous administration of fluids?
- Lateral thoracic
What complications can occur in fluid administration?
- Emboli (incl. catheter emboli)
What may cause an unexplained tachycardia following fluid therapy be indicative of?
What should a fluid plan consist of?
- Replace what is already lost, maintain, and counteract ongoing losses
- Sum of deficit, mainteance amount and ongoing losses
What are the advantages of oral administration of fluids?
- More physiological
- Non-invasive (lower risk of infection)
What are the disadvantages of oral administration of fluids?
- Too slow
- May be impossible due to clinical presentation (vomiting, unconscious, unable to swallow)
What are the advantages of IV administration of fluids?
- Large volume can be administered faster
- Precise (know how much is going in)
What are the disadvantages of IV administration of fluid?
- Can overload
- Large volume too fast, come out of veins causing oedema
- Invasive = risk of infection, thrombi and emboli
What are the advantages of subcut administration of fluids?
- Useful if can't find vein
- Can train owner to do this
What are the disadvantages of subcut administration of fluids?
- Risk of infection
- Can be painful (large pocket of fluid under skin)
What are the advantages of intraosseus administration of fluids?
- No veins found
- Small animals e.g. puppies, kittens, rabbits, birds
- veins in birds very fragile (prone to haematoma)
What are the disadvantages of intraosseus administration of fluids?
- Cannot be done in humerus or femur of birds
Why can intraosseus administration of fluids not be done in the humerus or femur of birds?
- Pneumatic bones with air sacs
- Would drown bird
What are the sites for intraosseus administration of fluids in dog or cat?