Treatment of Fluid and Electrolyte Imbalance Flashcards
(51 cards)
When may a patient with fluid overload still be prescribed IV fluids?
e.g. if someone with LV failure has pulmonary oedema → doesn’t mean their TBW is high so may be situations here they need IV fluids
When do you give IV fluids/fluid replacement?
1) Maintenance
2) Replacement
3) Resuscitation
When do you give maintenance fluids?
To maintain euvolaemia when oral intake is reduced e.g. NBM< nausea, vomiting, diarrhoea (not absorbing)
When do you give replacement fluids?
- Previous ongoing or predictable future losses
- e.g. D&V, urine, drains, skin losses, sweat, third spacing, burns, surgery, polyuria
When do you give resuscitation fluids?
- To rapidly restore the intravascular compartment
- e.g. following haemorrhage, marked dehydration, vasodilation, shock
How do you diagnose dehydration>
1) High Hb → blood is haemoconcentrated → less fluid in blood
2) Low body weight → if 3kg less than 3 days ago, loss of water not fat, look at daily weight
3) Urine output → retrospective
4) Hypotension (depends on physiological state of patient) → BP tends to be one of the last things to fall bc of vasoconstriction in young people but in older people might go down quicker
What are the aims of fluid replacement?
1) Maintain normovolaemia
2) Maintain normal electrolyte concentrations
3) Compensate for any extra fluid losses with like for like → esp. with blood
How do you try and replace losses exactly?
1) Previous loss → volume, type of fluid
2) Maintenance requirement → volume (what have they lost and what extra do they need)
3) Expected future loss → volume, type of fluid
What are 5 types of IV fluids?
1) Glucose 5%
2) Sodium chloride 0.18% and glucose 4% (dextrose saline)
3) Saline 0.9%
4) Balanced crystalloids
5) Colloid
What is a feature of all IV fluids?
They are isotonic → same osmolality as plasma
Why is glucose 5% given?
It is used just for water replacement → it makes fluid isotonic but without electrolytes and glucose is broken down rapidly
Describe how glucose 5% acts in the body
1) Fluid stays in circulation for a few minutes and then is distributed into cells (so intracellular)
2) Doesn’t increase blood glucose (maybe just temp)
3) Not nutritional → doesn’t cover calorie intake
What is dextrose saline used for?
Maintenance → it covers sodium and water requriement
What is normal saline used for?
One bag (1L) meets daily sodium need in one dose
What is an example of a balanced crystalloid fluid?
Hartmann’s
What fluid does balanced crystalloid reflect?
ECF (physiological) → basically dextrose saline and potassium + buffer
What can balanced crystalloid not be used for?
Replacing potassium → only has 5mmol so not enough to replace intracellular potassium
When should you not give balanced crystalloids and why?
Hyperkalaemia → might push them over the edge into cardiac arrhythmia
What do colloids contain and therefore where does it stay?
Molecules that don’t cross semi-permeable membranes e.g. proteins → therefore the fluid mainly stays in the plasma volume
What is the ultimate colloid?
Blood
Why can colloids be better to use than balanced crystalloid?
Bc BP stays up longer
What are other colloids?
Albumin, gelatine
What is the difference between treating a healthy euvolaemic patient who is NBM and someone who is susceptible to fluid overload but is also euvolaemic and NBM?
Healthy → better to go slightly over bc otherwise they often lie there thirsty
Susceptible to fluid overload (heart/liver/kidney failure) → don’t do this
What are the principles when giving IV fluids?
1) Assess patients regularly, keeping a careful fluid balance chart
2) Stop IV fluids as soon as not required → much better to drink
3) If on IV fluids for > 3 days use oral/enteral feed or TPN (can be on IV TPN for a long time) if necessary
4) Include fluid given in IV drugs and pumps
