CAL - fluid therapy Flashcards
Fluids appropriate for volume resuscitation in severe/ decompensated hypovolaemic chock
- Hypertonic (7%) saline
- Synthetic colloid
- ** (FIRST CHOICE) Hartmann’s solution (Lactated Ringer’s solution or Compound Sodium Lactate) **
- Gelofusin
- 0.9% saline.
Why is hartmann’s usually preferable to saline?
it is slightly more physiological and less likely to contribute to acid-base abnormalities (e..g hyperchloraemic metabolic acidosis)
An hour after isotonic crystalloid fluid, how much fluid will remain in intravascular space?
only 25% (the rest will be in the interstitium)
How does body try and recover lost blood?
- splenic contraction
- movement of extravascular fluid into intravascular space
- release of ADH (retention of fluid and Na)
- other homeostatic mechanisms
What happens if fluids are given slowly?
- they won’t increase intravascular volume but will replace lost extravascular fluid (i.e. how to address dehydration)
Bolus rate of fluids for hypovolaemia
a 10, 20 or 30 ml/kg bolus over 15 minutes and then reassess.
Rate of insensible losses
1-3ml/kg/hr depending on size (less for larger dogs). Affected by if V/D, panting etc
When do you stop fluid therapy?
once eating or drinking
How to assess a patient for dehydration
- complete PE (especially indicators of interstitial hydration))
Laboratory finding ssuggestive of dehydration
- haemoconcentration findings (increased haematocrit)
- increased TP
- but in isolation cannot establish hydration status - look at PE
CS dehydration status
No CS detectable
Dehydration of what severity may manifest with signs of hypovolaemia?
severe dehydration (>12%)
CS - dehydration of 5-6%
subtle loss of skin elasticity
CS - dehydration of 6-8%
- definite prolongation in return of skin to normal position
- slight CRT prolongation
- possible dry MM
- eyes possibly sunked inorbits
CS - dehydration of 8-10%
- tented skin stands in place
- dry MM
- eyes sunken into orbits
CS - dehydration of >10%
- may manifest signs of shock (more common in cats)
- prolonged CRT
Appropriate fluids - dehydration
any balanced crystalloid:
- 0.9% saline
- Hartmann’s (LRS or CSL)
Tx - dehydration
- rehydrate over 24-48 hours
- only if concurrent hypovolaemia (i.e. dehydration >10%) should you give a fluid bolus
- otherwise CRI
- if eating/drinking normally, no additional fluids
- fluids SC is an option but not in one tx
How much fluids SC do cats tolerate?
no more than 100-120ml/tx as painful/uncomfortable
Equation for calculating fluid deficit
Fluid deficit = dehydration deficits + maintenance + on-going losses
Dose - maintenance fluid requirement
50-80ml/kg/day
Define sensible losses
a measured amount of fluid loss (e.g. urine output). Can range from 27-40ml/kg/day. Can be quite high for animals with severe PU. Potentially fluid losses via vomiting can also be estimated.
Define insensible fluid losses
faecal, cutaneous and respiratory losses. Ranges from 10-20ml/kg/day, higher in dogs with excessive panting
Findings suggestive of over-hydration
Chemosis, Gelatinous skin, Jugular venous distension, Weight gain, Tachypnoea/dyspnoea, Serous nasal discharge
Differentiate dehydration and hypovolaemia
- HYPOVOLAEMIA: decease in circulating blood volume which requires immediate tx
- DEHYDRATION: loss of interstitial fluid volume without change in intravascular volume
CS - hypovolaemia
- Increased heart rate,
- Decreased pulse pressure
- Reduced jugular filling
- Increased respiratory rate
- Cold extremities
- Decreased urine output
CS - dehydration
- Prolonged skin tent
- Tacky mucous membranes
- Sunken eyes (rarely seen in adult horses)
Is it common for dehydration and hypovolaemia to co-exist?
Yes - in horses but not in small animals. They will co-exist in horses as the intersititial volume will be quickly moblised to replenish the intravascular volume.
Laboratory findings supportive of hypovolaemia and dehydration
- Haemoconcentration (increased PCV, TP) can support the assessment of dehydration, however, it cannot be used solely to determine hydration status. Animals that lose a great deal of interstitial fluid will invariably have haemoconcentration.
- The dehydration masks in this case a pre-existing hypoproteinaemia.
- Increased serum creatinine and BUN (decreased renal perfusion; pre-renal azotaemia)
- Increased USG
- Increased plasma lactate (decreased peripheral perfusion → decreased oxygen delivery to peripheral tissues → anaerobic glycolysis → increased lactate production)
What size catheter would you use in a horse for dehydration/hypovolaemia?
- a 10G or 12G over-the needle catheter. Aim = high flow rate (only possible if you minimise resistance to fluid flow - by increasing catheter radius)
- alternatively two 14-G catheters, one in R and L jugular veins
How to expand intravascular volume rapidly in horses?
you can bolus 1-2L of hypertonic saline first (2-4ml/kg), followed by the balanced electrolyte solution.
