CAL - fluid therapy

Question 1

Fluids appropriate for volume resuscitation in severe/ decompensated hypovolaemic chock

Answer 1

• Hypertonic (7%) saline
• Synthetic colloid
• ** (FIRST CHOICE) Hartmann’s solution (Lactated Ringer’s solution or Compound Sodium Lactate) **
• Gelofusin
• 0.9% saline.

Question 2

Why is hartmann’s usually preferable to saline?

Answer 2

it is slightly more physiological and less likely to contribute to acid-base abnormalities (e..g hyperchloraemic metabolic acidosis)

Question 3

An hour after isotonic crystalloid fluid, how much fluid will remain in intravascular space?

Answer 3

only 25% (the rest will be in the interstitium)

Question 4

How does body try and recover lost blood?

Answer 4

• splenic contraction
• movement of extravascular fluid into intravascular space
• release of ADH (retention of fluid and Na)
• other homeostatic mechanisms

Question 5

What happens if fluids are given slowly?

Answer 5

• they won’t increase intravascular volume but will replace lost extravascular fluid (i.e. how to address dehydration)

Question 6

Bolus rate of fluids for hypovolaemia

Answer 6

a 10, 20 or 30 ml/kg bolus over 15 minutes and then reassess.

Question 7

Rate of insensible losses

Answer 7

1-3ml/kg/hr depending on size (less for larger dogs). Affected by if V/D, panting etc

Question 8

When do you stop fluid therapy?

Answer 8

once eating or drinking

Question 9

How to assess a patient for dehydration

Answer 9

• complete PE (especially indicators of interstitial hydration))

Question 10

Laboratory finding ssuggestive of dehydration

Answer 10

• haemoconcentration findings (increased haematocrit)
• increased TP
• but in isolation cannot establish hydration status - look at PE

Question 11

CS dehydration status

Answer 11

No CS detectable

Question 12

Dehydration of what severity may manifest with signs of hypovolaemia?

Answer 12

severe dehydration (>12%)

Question 13

CS - dehydration of 5-6%

Answer 13

subtle loss of skin elasticity

Question 14

CS - dehydration of 6-8%

Answer 14

• definite prolongation in return of skin to normal position
• slight CRT prolongation
• possible dry MM
• eyes possibly sunked inorbits

Question 15

CS - dehydration of 8-10%

Answer 15

• tented skin stands in place
• dry MM
• eyes sunken into orbits

Question 16

CS - dehydration of >10%

Answer 16

• may manifest signs of shock (more common in cats)

- prolonged CRT

Question 17

Appropriate fluids - dehydration

Answer 17

any balanced crystalloid:

• 0.9% saline
• Hartmann’s (LRS or CSL)

Question 18

Tx - dehydration

Answer 18

• 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

Question 19

How much fluids SC do cats tolerate?

Answer 19

no more than 100-120ml/tx as painful/uncomfortable

Question 20

Equation for calculating fluid deficit

Answer 20

Fluid deficit = dehydration deficits + maintenance + on-going losses

Question 21

Dose - maintenance fluid requirement

Answer 21

50-80ml/kg/day

Question 22

Define sensible losses

Answer 22

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.

Question 23

Define insensible fluid losses

Answer 23

faecal, cutaneous and respiratory losses. Ranges from 10-20ml/kg/day, higher in dogs with excessive panting

Question 24

Findings suggestive of over-hydration

Answer 24

Chemosis, Gelatinous skin, Jugular venous distension, Weight gain, Tachypnoea/dyspnoea, Serous nasal discharge

Question 25

Differentiate dehydration and hypovolaemia

Answer 25

• HYPOVOLAEMIA: decease in circulating blood volume which requires immediate tx
• DEHYDRATION: loss of interstitial fluid volume without change in intravascular volume

Question 26

CS - hypovolaemia

Answer 26

• Increased heart rate,
• Decreased pulse pressure
• Reduced jugular filling
• Increased respiratory rate
• Cold extremities
• Decreased urine output

Question 27

CS - dehydration

Answer 27

• Prolonged skin tent
• Tacky mucous membranes
• Sunken eyes (rarely seen in adult horses)

Question 28

Is it common for dehydration and hypovolaemia to co-exist?

Answer 28

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.

Question 29

Laboratory findings supportive of hypovolaemia and dehydration

Answer 29

• 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)

Question 30

What size catheter would you use in a horse for dehydration/hypovolaemia?

Answer 30

• 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

Question 31

How to expand intravascular volume rapidly in horses?

Answer 31

you can bolus 1-2L of hypertonic saline first (2-4ml/kg), followed by the balanced electrolyte solution.