IV fluids Flashcards
What are the fluid compartments of the body?
Intracellular fluid (2/3rds) - 28L
Extracellular fluid (1/3rd) - 14L:
- Interstitial fluid (11L)
- Plasma (3L)
What is the difference between osmolarity and osmolality?
Osmolarity - number of osmoles of solute/litre
Osmolality - number of osmoles of solute/kg
What different fluids comprise our extracellular fluid?
Interstitial fluid
Intravascular fluid
Water in connective tissue
Transcellular fluid
Transcellular fluid - fluid in cavities lined by epithelium (eg CSF, aqueous humor of the eye)
What factors determine osmotic pressure?
number of dissociated particles - n
concentration (g/l) - c
molecular weight - M
temperature (K) - T
Osmotic pressure = n x c(c/M)RT
R (universal gas constant)
What is normal plasma osmolarity?
What calculation determines this?
298 mosm/L
2([na+] + [k+]) + urea + glucose
2( [140] + [4] ) + 5 + 5
When assessing if a patient needs fluid resuscitation - you use an ABCDE approach initially
What are the indications that fluid resuscitation is needed?
Systolic bp < 100 mmHg
HR > 90 bpm
RR > 20
NEWS >/= 5
Cap refill > 2s or peripheries cold to touch
Note - this equally depends on the presentation, history and labratory measurements as well
What comprises ‘maintenance’ fluids?
Maintenance IV fluids are based off daily requirements
25-30 mls/kg/day
1 mmol/kg/day of Na+ and K+
50-100 g/day glucose
What are the daily requirements for:
Sodium Na+
Potassium K+
Glucose
Sodium = 1-2 mmol/kg/day
Potassium = 0.7 mmol/kg/day
Glucose = 2-4 g/kg/day
If you have a solution of 5% glucose - what is the concentration of glucose?
5% glucose = 5g/100ml
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
If you were to place RBCs in a Hypertonic and a hypotonic solution - what would happen and why?
Hypertonic - H20 would move out of the RBCs as there is a higher concentration of restricted particles in the ECF
Hypotonic - theres more trapped stuff inside the cells - so water moves into them and they swell up
Out of K+ and Na+
Which is more concetrated in the ICF and in the ECF?
ECF contains a lot of sodium Na+ (and accompanying anions)
ICF contains a lot more potassium K+ (and macromolecules)
If there are changes in tonicity - the symptoms that arise are largely ________
why is this?
Tonicity changes = neurological symptoms
Hypotonicity:
- cell swelling…
- raised ICP, compromised CBFcerebral blood flow, herniation
Hypertonicity:
- cell dehydration (shrinking)…
- ICHintracerebral haemorrhage, venous sinus thrombosis
Whats the difference between a crystalloid and a colloid?
Give examples of each
Crystalloids = aqueous mixtures with lots of soluble stuff
Colloids = water with insoluble stuff in it
Crystalloids:
- dextrose, saline, Hartmann’s solution, plasmalite etc
Colloids:
- gelatins, starch, albumin, blood products, dextrans
What are the indications for the use of crystalloids or colloids?
Situations for use of CRYSTALLOIDS:
- fluid resuscitation in the presence of hypovolemia, hemorrhage, sepsis, and dehydration…
- ECF expansion
Situations for use of COLLOIDS:
- anaphylaxis
- renal failure
- coagulopathy
- rheology (investigations of how stuff flows)
Should you use 0.9% saline?
What are the problems associated with its use?
No - too much salt
Can cause:
Hypercholaemic acidosis, reduced renal blood flow and reduced GFR
This all exacerbates sodium retention
How do you assess a patients volume status?
1 - history:
- previous limited intake, thirst, abnormal losses of fluid, comorbidities
2 - examination:
- pulse & blood pressure
- cap refill, temperature of peripheries
- JVP
- oedema
- postural hypotension
3 - clinical monitoring:
- NEWS, fluid balance, weight monitoring
4 - laboratory assessments:
- FBC
- U&Es
- creatinine
How much fluid is given for ‘maintenance fluid’?
At what rate is this given?
30ml/kg/24hrs (20-25ml in frail & elderly)
This means it is usually 1200mls - 2400mls per day depending ofc on the weight of the patient
Rate of 50-100 ml/hr. Never go over 100 ml/hr due to risk of hyponatraemia
What fluid is the go-to for maintenance?
In what situations would you give other fluids for maintenance?
0.18% NaCl / 4% glucose / 0.3% KCl
Unless:
- K+ > 5.0 ——– use 0.18% NaCl / 4% glucose
- Na+ < 132.0 ——– use plasmalyte 148
How do you calculate how much ‘replacement’ fluid is needed?
What is the link between replacement fluid and maintenance fluid?
Add up losses in the last 24hrs (or sooner if required) - e.g. bleeding, D & V, drain output, fistulae
Give this volume back to the patient
Replacement fluid is in addition to maintenance fluid
What is the go to fluid for replacement?
Plasmalyte 148
If there are Upper GI losses (no clue) - then use 0.9% NaCl with KCl
How do you assess a patient for fluid resuscitation?
Fluid resucitation indicated for patients with severe dehydration, sepsis or haemorrhage leading to hypovolaemia & hypotension
For a patient who presents with above^:
give fluid challenge of 250-500ml over 5-15 mins and reassess
If adequate response - continue with replacement and maintenance fluids
If no/inadequate response - repeat fluid challenge and reassess
(you can continue to repeat until you reach the daily limit of 2000ml)
What fluid is used for fluid resuscitation?
Plasmalyte 148
Colloid
Blood
not sure what indications are for each
