Fluid Therapy Flashcards
what are the 3 components of a fluid plan
- volume
- route and rate
- fluid type
isotonic crystalloids
osmolality is similar/equal to the patient’s plasma
- LRS
- plasmalyte
- 0.9% NaCl
- D5W
how should K+ supplementation be used
when fluids are running at 1-3x maintenance rate ONLY
should never be used in a rapid rehydration plan (over 4-6 hours)
- want to add at a slow rate
dehydration
loss of both water AND salt - not pure water loss
how is dehydration evaluated
history, PE, lab data
PE parameters for dehydration
- skin turgor
- MM moisture
- eye position
- body weight
skin turgor
skin elasticity
decreases with dehydration
- normal: returns immediately
- 5% deficit: slow to return
- 12% deficit: remains standing
affected by BCS and age
evaluating MM moisture
gums: tacky
tear film: decreased
evaluating eye position
sunken eyes
late stage dehydration - indicates moderate to severe dehydration
lab data indicating dehydration
- USG > 1.030
- urine output < 1 mL/kg/hr
- PCV/TP: elevated
+/- hypernatremia
what are the categories of dehydration
mild: 5-7%
moderate: 8-10%
severe: 10-12%
equation for calculating fluid deficit
L of deficit = % dehydration x kg BW
route for replacing fluid deficit
SQ or IV
how to calculate rehydration rate for fluid deficit
volume deficit / 4 to 6 hours
larger deficits require faster rehydration
slower rates for cardiac disease or geriatric cats
maintenance rate
accounts for urine production and insensible (respiratory) losses
what is the standard maintenance rate for all mammals
2-4 mL/kg/hr
how should maintenance rate change for neonates
increase to 4-6 mL/kg/hr
dog allometric rate for maintenance
80 x BW^3/4
cat allometric rate for maintenance
70 x BW^3/4
what is the average daily loss of potassium
15-20 meq/L
does NOT get sufficiently replaced in isotonic crystalloids
what is the maximum safe rate of K+ supplementation
0.5 meq/kg/hr
what are considered abnormal losses
vomiting, diarrhea, polyuria, cavitary effusions
vomiting: small volume losses
diarrhea: large volume losses
average K+ loss from GI losses
10-30 meq/L
range of estimating abnormal losses
1/2 to 2x maintenance rate
estimation based on severity and duration of abnormal losses
how to estimate abnormal ongoing losses in severe dehydration
fluid deficit / hours of loss
colloids
high molecular weight substance that largely remains in the intravascular compartment and generates an oncotic pressure
what molecule contributes to oncotic pressure
albumin
do crystalloids have oncotic pressure
NO - only colloids
what are natural colloids
albumin
plasma
what are synthetic colloids
hetastarch
vetstarch
rate of hetastarch supplementation
1 ml/kg/hr added to total fluid need
remove the same amount of crystalloid
indications for colloid therapy
- albumin < 1.5 g/dL
- interstitial edema due to LOW COP and patient requires fluid therapy
how does anesthesia affect patient’s fluid needs
- patient is fasted –> decreased/no fluid intake
- drug side effects –> fluid shifts and hypotension
- breathing dry, cold air –> evaporative fluid loss
- exposed tissue –> evaporative fluid loss
- hemorrhage –> volume loss
- stress response to anesthesia/sx
- degradation of glycocalyx
what are reasons for fluid administration under general anesthesia
- requires placement of IVC
- replaces insensible losses due to extravasation
- meets maintenance requirements
- compensates for losses during procedure
- replaces absolute and relative deficits
goal of fluid administration under general anesthesia
maintain tissue perfusion and O2 pressure
when should anesthesia be avoided in fluid compromised patients
- major fluid deficits
- hypovolemic
- dehydration
do isotonic crystalloids effectively treat anesthesia induced hypotension
NO - poor volume expanders and distributes into tissues (does not remain in blood stream)
what is a sample individualized fluid plan for surgery
- basal requirement: 1 ml/kg/hr
- insensible losses:
- minimal sx: 1-2 ml/kg/hr
- major sx: 3-6 ml/kg/hr - fasting deficit: 1-4 ml/kg/hr in the first hour only
total: 3-10 ml/kg/hr
typically within 3-5 ml/kg/hr
what cardiac parameters does fluid therapy influence
preload
what is the goal of fluid therapy (volume expansion)
optimize/increase stroke volume and cardiac output
do all patients increase stroke volume in response to fluids
NO - only patients on the lower end of the Frank Starling curve will have an increase in stroke volume in response to fluids
how to monitor if a patient will benefit from fluids
arterial BP tracing
if systolic pressure DECREASES during inspiration, the patient will benefit from fluid therapy
