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What are the 3 parts of fluid therapy planning?
- fluid deficit= dehydration
- maintenance= obligatory losses
- ongoing losses= vomiting, diarrhea, panting, salivation
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Define dehydration.
loss of isotonic fluid (water AND salt) (loss of ECF)
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How do you estimate dehydration? (4)
- history (vomiting, diarrhea)
- PE
- bloodwork (PCV/TP, BUN)
- UA (USG)
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What are the 5 physical exam findings associated with dehydration?
- MMs
- skin elasticity (turgor)
- position of the eye in the orbit
- changes in body weight
- volume status
- (thirst mechanism activated in all these circumstances)
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Describe the parameter of MM moistness.
- the amount of saliva and tear film varies with hydration status (dehydration= "tacky membranes")
- qualitative
- influenced by evaporation (panting)
- tear production influences by KCS/ dry eye
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Describe the parameter of skin elasticity.
- pull up over thorax (horse- neck, cow- upper eyelid) into a fold--> watch it return to normal position
- normal: immediate return, dehydration: return to normal position slow or not at all
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What factors might affect skin elasticity, aside from hydration status?
- young- increased
- old- decreased
- obese- increased
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Describe the position of the eye in the orbit parameter.
- sunken eye is associated with reduced volume of the retrobulbar fat
- qualitative
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What factors might affect the position of the eye in the orbit, aside from hydration status? (3)
- obesity/ emaciation
- ocular disease
- breed and conformation
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Describe changes in body weight parameter.
- most sensitive and specific parameter
- PE changes correspond to 10% dehydration
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The thirst centers are triggered by 2 mechanisms:
- Decrease ECF--> triggers ADH release--> triggers RAAS--> triggers thirst centers in brain
- Increase in osmolality of the extracellular space (increased conc of Na+)
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___________ causes significant hypovolemia.
Only severe dehydration (>10%)
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Hypovolemia=
loss of intravascular fluid (dehydration= loss of interstitial fluid)
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Signs of hypovolemia/ shock. (6)
- MM color
- CRT
- HR
- Pulse quality
- Temperature of extremities
- Mental state
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What bloodwork changes will you see with dehydration?
- PCV/TP increase- hemoconcentration
- BUN- increase
- Na+ SHOULD BE NORMAL (due to isotonic loss)
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What fluid do we use to compensate dehydration?
since dehydration is a loss of isotonic fluid, replace with an isotonic crystalloid
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What timeframe do we use to replace dehydration?
b/w 4-24hrs, but usually 8-12hrs
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What are the end points of replacing dehydration?
normalization of hydration parameters, monitor for fluid overload (inc resp rate, crackles)
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What are obligatory losses?
GI, renal, insensible (respiration, sweat, saliva)
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What are maintenance rates for:
Horses
Cows
Dogs
Cats
- Horses: 40mL/kg/day
- Cows: 50mL/kg/day (increase for ongoing losses in lactating cows)
- Dogs: 132 x (BWkg)0.75
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For maintenance fluids, what type of fluids do you use?
- Usually use isotonic, but it probably has too much Na+ and not enough K+ (K+ supplementation)
- By the book, you should use hypotonic crystalloids [Plasmalyte or Normosol] (but it's a hassel; only really done with cardiac and renal patients)
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How do you handle abnormal ongoing losses?
- 1. leave out at first, monitor ongoing losses, and add later to plan (more work/ monitoring)
- 2. When you know the patient will have abnormal ongoing losses, add the predicted losses and monitor to see if you were right (1/2 maintenance or 1x maintenance added)
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How do you monitor ongoing losses? (5)
- re-assess patient every 4-12 hours
- body weight
- fluid balance (input versus output)
- quantitative (urine output by catheter, amount eaten, drunk)
- qualitative (hypersalivation, diarrhea)
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