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