Fluids Flashcards
How much water content is in an infant?
70-80%
What is intracellular fluid?
2/3 of fluid inside cells
Low in Na
High in K
What is extracellular fluid?
1/3 of fluids is outside the cells
Plasma (intravascular)
Between cells (interstitial and lymph) - edema
High in Na
Low in K
What is transcellular fluid?
CSF, GI tract and pleural, synovial and peritoneal spaces
A “third space” syndrome can develop when increase in transcellular fluid occurs at expense of fluid in other compartments
How does water move between intravascular and interstitial and in/out of cells?
Fluid moves between intravascular & interstitial compartments by filtration
Water moves in/out of cells by osmosis
Forces of fluid balance
hydrostatic pressure
osmotic pressure
diffusion
active transport
vesicular transport
What is the major protein that maintains oncotic pressure?
albumin
What are the forces that favor filtration from the capillary?
capillary hydrostatic pressure and interstitial oncotic pressure
What are the forces that oppose filtration?
capillary oncotic pressure and interstitial hydrostatic pressure
In fetus and preterm, where is the largest proportion of water in the body?
45-50% TBW at birth
30% TBW at 2 years
20% TBW at maturity
Differences in infants
highest % of body weight being water at birth
higher ECF
larger body surface area
higher resp and metabolic rate
high daily fluid requirement with little volume reserve
immature kidneys (dilute and concentrate urine, adjust to changes in electrolytes and sodium)
What is the cause of dehydration?
sodium!!! but also glucose and protein in certain conditions
What are the types of dehydration?
Isotonic dehydration
Hypotonic dehydration
Hypertonic dehyrdation
What is isotonic dehydration?
Electrolyte and water deficits are in balanced proportions
Most common
Major loss from ECF (hypovolemic shock)
No osmotic force is present to cause redistribution
What is hypotonic dehydration?
Electrolyte deficit exceeds water deficit
Water transfers from ECF to ICF, brain cells swell
Na < 130 mEq/L
Little losses show severe signs
Sodium normal value
130-140 mEq/L
What is Hypertonic Dehydration?
Water loss in excess of electrolyte loss
Most dangerous (requires specific fluid therapy)
Fluid shifts from ICF to ECF
Na >150 mEq/L
shock less apparent
Seizure more likely, cerebral changes
What are the cerebral changes in hypertonic dehydration?
disturbances of consciousness
poor ability to focus attention
lethargy
increased muscle tone with hyperreflexia
hyperirritability to stimuli (tactile, auditory, bright light)
Causes of hyponatremia
Gain more H20 than Na (D5W, enema)
Loss of more Na than H20 (D + V with H20 replacement)
Na < 130 mmol/L
Decreased osmolality of blood
Why is D5W act as a hypotonic solution?
dextrose is quickly metabolized
S&S of hyponatremia
anorexia, headache, muscle weakness, decreased deep tendon reflexes, lethargy, confusion, coma
Seizures
Tx of hyponatremia
restricted water intake (allows kidneys to rebalance)
hypertonic saline
Causes of hypernatremia
loss of more H20 tha Na (diabetes, D + V, sweating, high solute intake)
Gain of more Na than H2O (no access to water)
Hypernatremia = >150 mmol/L
Increased osmolality (body fluids too concentrated)