IV Fluids Flashcards
What 4 questions should you ask yourself when prescribing fluid?
- Is the patient hypovolaemic, euvolaemic or hypervolaemic
- Does the patient need IV/SC fluids
- How much
- Which fluid
What are the two spaces where fluid can be
What are the three compartments of the body
Intracellular fluid
Extracellular fluid
Intracellular fluid- 28L
Interstitial fluid-11L
Plasma- 3L
What is normal plasma osmolarity
298mosm/l
What is involved in extracellular fluid
ISF
Intravascualr fluid
Water in connective tissues
Trancellular fluid
How do you calculate osmotic pressure
NxC(C/M) RxT
Where N=number or dissociated particles C= concentration (G/L) M=Molecular weight R= universal gas constant T= Absolute temperature (K)
What is osmolality
Number of osmoles in a solute/KG
What is osmolarity
Number of osmoles of a solute/litre
What is the Osmolar gap
Difference between calculated and actual osmolarity. That’s due to other things in plasma, affecting osmolarity
What is tonicity
Effective osmolality
Only particles restricted to one of the compartments will determine water distribution
Particles which move freely will not influence water distribution
ECF—> Na (and accompanying anions)
ICE—> K and macromolecules
What happens if you give a patient a hypotonic solution
Cell swelling
Rasied ICP, Compromised CBF and herniation
What happens if you give hypertonic solution
Cellular dehydration
ICH venous sinuous thrombosis
Where do fluids go in the body
Glucose- mostly intracellular and interstitial
Sodium Chloride 0.18%, glucose 4%- pretty even split between intracellular and interstitial
Saline 0.9%- interstitial
Balanced crystalloids- 820ml interstitial 180 plasma
Colloid- Plasma
What are some examples of colloids
gelatins, starches, dextrans, albumin, blood products
What are some examples of cystalloids
5% dextrose 0.9% saline Hartmannn's splution Plasma-lyte 0.18% normal saline in 4% dextrose
What are the pros/cons of colloids
Anaphlaxis
Coagulopathy
renal failure
Rheology
What are the pros/cons of crsytalloids
Cheap, non-allergenic
ECF expansion
odema/ increased vascular pressure
What happens to free water in the body
What happens to isotonic solutions in the fluids
Water- goes everywhere, no holding back. Bad for the brain
Isotonic- stays in extracellular compartment
What are the normal daily fluid and electrolyte requirement
25-30 ml/kg/d water
1 mol/kg/day sodium, potassium, chloride
50-100g/day glucose (e.g. glucose 5% contains 5g/100ml)
Discuss 0.9% NACL
Very little scientific basis for use, contains 154 mmol/L sodium. 154mmol/L chloride
Causes hypercholaemic acidosis
Reduces renal blood flow
Reduces GFR
Exacerbates sodium retention
How do you measure body fluid
Very difficult,
Ask how warm they are, are they thirsty, skin turgour, cap refill
How do you use ABCDE to prescribe fluids
Systolic BP<100mmHg Heart rate>90bpom Cap refill>2s Cold peripheries Resp rr>20
How can you assess the patients likely fluid and electrolyte needs
History- previous limited intake, thirst, abnormal losses, co-morbidities
Clinical examination- pulse, BP, cap refill, JVP, oedema, postural hypotension
Clinical monitering- NEWS, Fluid balance charts, weight
Lab assessments, FBC, Urea, Creatnine, electrolytes
What are the reasons for using a fluid chart
24hr chart that needs patient weight
Guidance in chart- structured framework, 4 questions, traffic light for fluids, rationalise fluid availability
- Assess patient- fluid sate
2- why give fluid - How much
- What kind
How much maintenance fluid should be given
30ML/KG/24 hours (20-25ml in frail and elderly)
