5. Fluid Replacement Therapy Flashcards
What is toxicity?
Measure of the effective osmotic pressure gradient of two solutions separated by a semipermeable membrane
What is the TBW of a newborn baby?
75%
What is the TBW in the elderly?
45%
What s the major extracellular cation?
Sodium
Where does sodium move between?
Between intracellular fluid, interstitial fluid and intravascular fluid
Where does potassium move between?
From interstitial fluid to intracellular fluid
What happens when a 5% dextrose solution is administered?
Intravascular glucose moves into interstitial fluid then gets taken up by cells and draws water with it by osmosis
Used to maintain fluid
What happens when 0.9% saline is administered?
Contains Na+ and Cl-
All remains in interstitial fluid or intravascular fluid
What happens when Hartman’s solution is administered?
Majority retained in ECF as osmolarity maintained with effective osmoles of sodium, potassium and calcium
What happens when 1000ml 4% dextrose/0.18% saline solution is administered?
800ml H2O reduces osmolarity of all compartments
200ml 0.9% saline remains in ECF
Used to maintain hydration
Why do patients need fluids?
Nil by mouth Malfunctioning GI tract Dehydration Fluid losses Abnormal electrolytes
How do you know which fluids to give?
What does the patients need as maintenance? (give if unable to take orally)
Has patient lost any additional fluids? What are they losing? (Replace as close to that as possible)
What are the non-osmotic stimuli of increased ADH secretion?
Drugs (morphine)
Pain
Nausea
Low effective circulating volume
Why can hospitalised patients require fluid?
Increased ADH
Generally do not sweat excessively
Stress response - RAAS, catecholamines
Reduced caloric expenditure
