Fluids Flashcards
(21 cards)
given a patients weight how do you calculate the intravascular, intracellular and extravascular fluid volumes
TBW = 0.6 * body weight
e.g. 70kg man has 42 litres of water
ECF = 1/3 of total fluid (14L) ICF = 2/3 total fluid ((28L)
interstitial fluid = 3/4 of ECF
plasma = 1/4 fluid
transcellular fluid = roughly 500ml
how does total body water content change with weight and age
neonates = 80% water
children = 70%
women and obese men = 50%
what are sensible fluid losses
urinary losses
what are insensible fluid losses
sweat, lung, faeces
what is the minimum urine output for physiologically normal kidneys
0.5ml/kg/hour
what are acceptable maintenance fluid regimes
‘one salty 2 sweet’ - 1x 1L normal saline + 20mmolKCL over 8 hours, 2x1L 5% dextrose + 20mmol KCL over 8 hours for 24 hour cover
NICE: 30mmol/kg/day (adults)
Paeds regime also can be applied - 100ml/kg/day for first 10kg, 50 for next 10 and 25 for each subsequent
what is the minimum requirement of glucose per day
40mmol
what is the minimum requirement of postassium per day
1mmol/kg/day
what is the minimum requirement of sodium per day
2mmol/kg/day
what is the general rule for fluid losses in a patient with pyrexia
10% more fluid requiredq
what does the RAAS do
efferent renal artery constriction, peripheral vasoconstriction, sympathetic activation, release of aldosterone leading to distal Na absorption
also leads to increased cardiac muscle stretch leading to pump failure over time
what are the signs of dehydration
mild: headache, lack of energy, tiredness
moderate: dry mouth, increased alertness, sunken eyes, muscle cramps
severe: confusion, disorientation, tachycardia, tachypnoea, low bp
what metabolic derrangement occurs with excessive vomiting
hypochloremic, hypokalaemic metabolic alkalosis
how do you treat excessive vomiting causing metabolic derrangement
saline IV + 20mmol potassium with review
what metabolic derragements occur in a high volume output pancreatic/ileal/jejunal/bile fistula
metabolic acidosis due to low bicarbonate levels
high potassium even if total potassium is depleted
what metabolic derrangements are caused by diarrhoea
hyperchloraemic metabolic alkalosis + hypokalaemia if profuse
whats the treatment for diarrhoea + metabolic derrangement
oral rehydration therapy
IV fluids if necessary
how should you give fluids with cerebral oedema
2/3 maintenance of an isotonic solution (saline fine)
what metabolic derrangement is seen on acute tubular necrosis
hyperkalaemia, hypermagnesia, hyperphosphataemia, hyponatraemia, hypocalcaemia
metabolic acidosis
what are some essential bloods if you suspect dehydration
FBC, U+E, lactate and glucose
what metabolic derrangement might be extected in a patient with cardiac failure
Patients are at risk of dilutional hyponatraemia in severe CCF due to dietary sodium restriction and the inability to excrete water (RAAS over activation).
Hypokalaemia can result from prolonged
administration of diuretics, or hyperkalaemia can occur in severe heart failure leading to reductions in GFR, particularly if they are on potassium sparing diuretics/ ACEls.
