Fluids Flashcards
Fluid Admin goals
- Maintain intravascular volume
- Augment CO
- Maintain tissue perfusion & O2 delivery
- Maintain electrolyte balance
- Enhance microcirculatory flow
- Facilitate delivery of nutrients & clearance of waste
Total Body Water
Adult: 60% of lean body mass
Neonates: 75-85%
1 y/o: 65%
ICV
40% of body weight
2/3 of TBW
cation: K+
anion: Phos
ECV
20% of body weight
1/3 of TBW
cation: Na++
anion: Cl-
ECV divisions
plasma - 1/4
interstitial fluid in tissue spaces - 3/4
Starling Forces (4)
Interstitial hydrostatic pressure
interstitial oncotic pressure
capillary hydrostatic pressure
plasma oncotic pressure
Positive Net Filtration
= fluid into tissues
supported by:
- capillary hydrostatic pressure
- interstitial oncotic pressure
overall balance of filtration
slightly positive
~2ml/min into tissues - uptaken by lymphatics back into intravascular
percentage of daily losses in urine
60%
Pediatric losses considerations
SA:weight rate is ~ 3x that of an adult
= more insensible losses
= more heat loss
= more sodium loss
ECV & ICV in pediatrics
ECV in infants is 40% & decreases with age
ICV is 20% in premature & 30% by adolescents
Neurohormonal Mechanisms for Fluid Balance
- RAAS
- ADH
- ANP
RAAS
In response to hypotension & sympathetic stim:
renin from kidneys cleaves angiotensinogen from liver = ANG I + ACE (in lungs) = ANG II = water & Na ++ reabsorption
also = aldosterone release = water & Na++ reabsorption
ADH
released from posterior pituitary in response to increase serum osmolality…
= increased water & sodium reabsorption
= increased urine concentration
= arterial vasoconstriction
ANP
released due to stretch on atrial walls from increased preload or hypervolemia…
= increased sodium & water EXCRETION
= inhibitor of ADH & RAAS
Evaluating Volume Status
BP HR turgor/fontanelles UOP perfusion CO
s/s of volume loss
5%: poor turgor/sunken fontanelles
10%: tachycardia, oliguria, cold up to knees
15%: hypotension, sunken eyes, extremities cold
20%: unconscious
Crystalloids
- Resuscitation of dehydration
- Lack of allergenic potential
- ease of metabolism & clearance
o Beneficial for restoring immediate vascular volume, preserving microcirculatory flow, reducing hormone mediated vasoconstriction & correcting plasma hyper-viscosity seen with acute hemorrhage - Isotonic crystalloids distribute evenly throughout the ECV
= Limited ability to expand plasma
= Hemodilution plasma proteins
= Loss of capillary oncotic pressure
filtration of 75-80% of admin volume goes into interstitial spaces
NS
Na = Cl in the solution but in plasma Na > Cl
= risk for acid/base imbalances - hyperchloremic metabolic acidosis
may also impair renal function and reduce GFR
NS compared to plasmalyte
associated with increased incidence of kidney failure, acidosis, blood transfusions (acidotic effect on coagulation) & post-op wound infections
Colloids
suspension of high molecular weight molecules in electrolyte solutions
- good volume expanders
- albumin is the only naturally occurring
Cortisol Effect
released from HPA axis activation
- increased production & release of plasma proteins
- maintains intravascular volume
- inhibits inflammatory mediators
Release of Cytokines
mediated amounts = promotes local hemostasis & migrates neutrophils
large amounts = vasodilation, endothelial damage, increased filtration, tissue edema, intravascular loss, hypotension & decreased organ perfusion
Maintenance Fluids 4-2-1
- first 10kg = 4ml/kg/hr
- second 10kg = 2ml/kg/hr
- additional kg = 1ml/kg/hr
ex: 54kg = 40 + 20 + 4 = 64ml/kg/hr
NPO deficit
maintenance x NPO hours
hour 1: 50% + maint.
hour 2: 25% + maint.
hour 3: 25% + maint.
should be given pre-operatively
Blood Replacement
3: 1 with crystalloid
1: 1 with colloid
Third Spacing Losses due to Trauma
minimal: 0-2ml/kg/hg
moderate: 2-4ml/kg/hr
max: 4-12ml/kg/hr
Allowable Blood lose
EBV x (HCT-25)/HCT
or
EBV x (HGBinitial - HGB acceptable)/ HGB initial
HCT
o Premature infant: 40-45 - Transfuse: 35 o Newborn: 45-65 - Transfuse: 30-35 o 3 Months: 30-42 - Transfuse: 25 o 1 y/o: 34-43 - Transfuse: 20-25 o Adult: 38-46 - Transfuse: 20-30
