IV fluids Flashcards
What are the 4 questions we have to ask when prescribing fluid?
1) What is my patient’s fluid status?
2) Do they need IV fluid?
3) How much fluid?
4) What type of fluid?
What do we look at when assessing fluid status?
- Airway e.g. on a ventilator
- Breathing (signs of pulm oedema)
- Circ (signs of fluid overload e.g. raised JVP)
- Disability
- Extremities (skin turgor, temp & mucous membranes)
Also vitals e.g. HR & BP
Urine
Sweat
How do we recognise hypovolaemia?
- Thirsty
- Flat veins
- Cool peripheries
- Not sweating
- Low or postural BP (maybe dizzy)
- Tachycardic
- Concentrate oliguria
What are the signs of hypervolaemia?
- Breathless
- Distended veins
- warm, oedematous extremeties
- Sweating
- High BP & HR
- Dilute polyuria
Be aware”
A patient may have signs of hyper or hypovolaemia for a different reason
E.g. just because a patient has pulm oedema doesn’t mean they’re fluid overloaded
Also a euvolaemic or hypervolaemic patient could have cold fingers as well
What are the different types of fluids in terms of purpose?
Resuscitative (very rapid bolus for shock patients)
Routine maintenance (Saline for patient’s who can’t drink)
Replacement (fluid tailored to replace electrolytes)
How do we determine how much fluid they need?
Work out the water deficit from intake and output:
- Input chart
- Catheters & Drains
- Vomit bowels & sputum pots
- Stool charts & stoma losses
- Estimate insensible losses e.g. sweat, ventilation, wounds, burn an bleeding
What are the different physical types of fluids?
Dextrose
Crystalloids e.g. normal saline or hartmann’s
Plasma expanders
What is dextrose used for?
Chronically dehydrated (need fluid that moves into other compartments) Hypernatraemic patients (can't have crystalloids)
What are crystalloids used for?
Acute dehdyration, AKI & Resus.
It’s good for restoring fluid/blood volume because it remains in the ECF
What do we use plasma expanders for?
Shown to be no better than crystalloids for resus but can be useful with blood for haemorrhage
Difference between diffusion & osmosis?
Diffusion is when solute moves through a permeable membrane from high to low conc.
Osmosis is when water moves through a solute impermeable membrane from high to low conc
Difference between osmolarity and osmolality?
Osmolarity = solute conc per unit volume of solvent
Osmolality = Solute conc per unit mass of solvent
Difference between osmolarity and tonicity?
Osmolarity takes into account all solutes in the solvent including ones that can cross the membrane and so don’t apply osmotic pressure
Tonicity is only a measure of those solutes that can’t cross the SPM so exert osmotic pressure, ergo its a measure of osmotic pressure
