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how are fluids gained
drinking, food, metabolic sources
how are fluids lost
urination, salivation, evaporation, fecal, vomiting, diarrhea, exudates
how do we know what to give and how much?
maintenance requirements
correction of fluid deficits
consideration of ongoing losses
how are maintenance requirements generally described
approximate RER
not linear, equations often vary
define fluid maintinence for dogs under 25kg
60ml/kg/day
define fluid maintenance for dogs >25kg
40ml/kg/day
describe fluid maintenance for cats
50 ml/kg/day
what are the parameters for fluid deficit
hydration status
caridovascular status
volume status
pt presents with serous nasal discharge, chemosis, pitting edema, jugular distention, and increased RR. Describe hydration and hypoperfusion
overhydration, no hypoperfusion pt
pt presents with no detectable abnormalities. Described hydration and perfusion
<5% dehydration, hypoperfusion unlikely
pt presents with mild decrease in skin elasticity (<2 sec) and tacky MM. Describe hydration and perfusuon
6-8% dehydrated, hypoperfusion unlikely
pt presents with mild lethargy, decreased skin elasticity (>3 seconds), tacky MM, eyes appear slighly sunken, and slight prolongation of CRT. Describe hydration and perfusion
8-10% dehydrated
pt presents with marked lethargy, loss of skin elasticity, dry or cold MM, eyes appear to be sunken in orbits, prolongation of CRT. Describe hydration and perfusion
10-12% dehydration, hypoperfusion likely
pt presents recumbent/moribund, prolonged or absent CRT, loss of skin elasticity, dry and cold MM, eyes sunken. Describe dehydration and perfusion
>12% dehydration, hypoperfusion definite
how do you calculate fluid deficit
BW x dehydration (decimal) = deficit in L
1kg= 1L
how are crystalloids generally defined
fluids containing small molecular solutes only
electrolutes comprise the majority of solute
other small solutes (dextrose/glucose, lactate) are readily metabolized, no lasting osmotic effect from these solules
what are the clinical considerations for crystalloids
electrolytes equilibrate throughout extracellular compartment in about 30 minutes
short lived osmotic effects
only 25% volume remains intravascular after 30-60 mins
fluid effects dependent on tonicity
what are the general complications of crystalloids
volume overload in peripheral tissue and organ edema
inappropriate fluid shifts
induced electrolyte and acid base derangement
exacerbation of hemorrhage
dilutional coagulopathy
what is the normal plasma osmolality of dogs
290-310
what is the normal plasma osmolality of cats
311-322
generally describe isotonic crystalloids
osmolality similar to plasma
minimal fluid shift between extra and intracellular compartments, tonicities between thm are unchanged
what are the uses of isotonic crystalloids
dehydration from most common fluid losses (interstitial dehydration)
rapid volume expansion- hypovolemic shock
most electrolyte imbalances
what are examples of isotonic crystalloids
0.9%NaCl
plasma-lyte A/Normasol-R/ Vetivex
Lactated ringers
what are the advantages of isotonic crystalloids
low cost
readily available
appropriate in most patients
what are the disadvantages of isotonic crystalloids
quickly redistribute so large volumes are required for fluid resuscitation
hemodilution
ppotential for volume overload
what are the specific complications of isotonic crystalloids
induced electrolyte imbalances
induction or exacerbation of acidosis
some drug compatibilities
what is the general rule of fluid choice?
should be compared to the chemical composition of what it is replacing, plasma in most cases
what are the acid base effects of fluids
many are acidic, however, effect on acid base balance is marginal due to lack of free H+
buffered fluids preferred for acidotic patients
alkalotic patients benefit from non-buffered
what is a colloid
large hydrophilic molecules that do not pass freely across membranes
increased colloid oncotic pressure, persistent intravascular volume expansion
what affects the effectiveness of colloids
number of molecules present
limited to intravascular compartmet
do not redistribute
what are synthetic colloids
Hydroxyethyl starches (HES)
dextrans and gelatins in europe
what are natural colloids
plasma
whole blood
albumin
what are hydroxyethyl starches
derived from corn or potato starches
larged, branched glucose polymer chains
hydroxylated to prevent rapid degradation
broken down by a-amylase
excreted by the kidneys in small molecules
what are the indications for hydroxyethyl starches
rapid volume expansion (hypovolemia)
pt in which lower resuscitation volumes may be beneficial such as trauma
hypoalbuminemia (low oncotic pressure)
patients unresponsive to crystalloids
some with vasculitis
what are the advantages of hydroxyethyl starches
small volumes required- volume expanded by up to 1.5x volume administered
long duration of effects
increased colloid oncotic pressure
what are the disadvantages of hydroxyethyl starches
higher cost
higher risk of volume overload
tissue accumulation within cells
long half life
interference with refractometer readings for TP
adverse reactions
what are specific complications possible with hydroxyethyl starches
acute kidney injury (osmotic nephrosis)
impaired platelet function
impaired coag - vWF, factor VIII
delayed onsert refractory pruritus, allergic reactions
how can body size affect the risk of adverse effects of hydroxyethyl starches
smaller weight preparations are bettwr
in what cases are hydroxyethyl starches contraindicated
renal disease
sepsis
coagulopathy
hypertension