fluids Flashcards
daily fluid requirements
25-30ml/kg/day
what increases fluid requirements
vomiting/diarrhoea high output stoma fistulas burns
what decreases fluid requirements
renal/hepatic impairment cardiac failure head injury
signs of fluid depletion
weight loss low bp rapid/shallow breaths weak pulse reduced urine output dry, less elastic skin thirst
signs of fluid overload
weight gain high/normal bp rapid breaths rapid pulseincreased urine output oedematous skin
what two mechanisms maintain fluid volume homeostasis
anti-diuretic hormonerenin angiotensin system
how does anti-diuretic hormone maintain fluid homeostasis
synthesised in hypothalamus stored and released from posterior pituitary gland on reduced renal water excretion causes thirst
how does the renin angiotensin system maintain fluid homeostasis
activated by dehydration/falling renal perfusion increases aldosterone release causes sodium and water retention
indications for fluid replacement
maintain homeostasis/correct lossesNBMoral intake failure excessive losses special cases - burns/brain injury/children
3 methods of fluid administration
peripheral central subcutaneous
when would you administer fluids peripherally
short - mid term needs replacing every 24 hours
when would you administer fluids centrally
over 10 days use poor peripheral access
when would you administer fluids subcutaneously
prolonged administration off label! not for rapid transfusion
how should fluids be prescribed
reviewed daily - only prescribed 24 hrs at a time
what are the 3 types of fluids
colloid crystalloid blood
what are crystalloid solutions
small molecules in water isotonic
examples of crystalloid fluids
0.9% NaCl - plasma expander (hypernatremia!!)5% glucose - distributes well dextrose saline - glucose+sodium for intravascular volume hartmanns - balanced salt for resus
how is crystalloid fluid distribution determined
sodium content - more sodium = extracellular space - less sodium = evenly distributes around body
advantages of crystalloid fluids
osmotic gradient widely available cheap low ADR risk
what are colloidal fluids
dispersion of large organic molecules in carrier solutionplasma expansion contributes to oncotic pressure
examples of colloidal fluids
albumin - for shock/burns ect dextrans - larger size = longer acting - anaphylaxis gelatin - anaphylaxis
what is oncotic pressure
Osmotic pressure exerted by PROTEINS in BLOOD PLASMA that usually tends to pull WATER into the circulatory system.
what are the advantages to colloidal fluids
smaller volumes get better plasma expansion than crystalloidlonger half life can be given faster
what are the disadvantages of colloidal fluids
max. volume per day ADR risk expensive
