Fluids Flashcards
Normal requirement of H2O?
- 5 ml/kg/h
2. 5L/day
Normal requirement of Na+?
1-2mmol/kg/24h
70-140mmol
Normal requirement of K+?
0.5-1mmol/kg/24h
35-70mmol
Normal urine output?
> 0.5ml/kg/hr
35ml/h
Contents of sodium chloride (0.9%)
Na+ - 154
Cl- - 154
Contents of Hartmann’s solution?
Na - 131
Cl - 111
K - 5
HCO3 - 29
Contents of 5% dextrose?
50g glucose
What is Hartmann’s solution good for?
Most physiological so is good for replacing plasma loss.
Not good for maintenance fluids as would give too much sodium and not enough potassium
What is normal saline good for?
More physiological than dextrose but not as physiological as Hartmann’s.
Too much sodium places massive load on kidneys. Can cause hypercholaraemic acidosis.
What is 5% dextrose for?
Good for maintenance fluids (no electrolytes, glucose maintains initial osmolarity)
What concentrations of potassium are in pre-made versions of saline and dextrose?
20mmol
40mmol
When should you give maintenance fluids?
When patient can’t drink enough
Oral/NG tube fluids are safer as much less likely to cause overload, electrolyte disturbance and don’t require a cannula
Contents of dextrose-saline 4%/0.18%?
Na - 30
Cl - 30
Glucose - 40g
What is dextrose-saline good for?
Good for maintenance fluids because given at the correct rate, contains approximately correct requirements of sodium.
Becoming preferred for maintenance because delivers daily sodium requirement over the course of the regime rather than all in one bag.
What is the traditional maintenance fluid regime?
1 salty + 2 sweet
1L saline 0.9% + 20mmol potassium chloride (8 hours)
1L dextrose 5% + 20mmol potassium chloride (8 hours)
1L dextrose 5% + 20mmol potassium chloride (8 hours)
What should you do before prescribing any fluids?
Check U+Es and adjust regime as necessary to correct any electrolyte abnormalities
What are the two components of replacing fluid loss?
- Pre-existing fluid (replaced STAT)
2. Ongoing losses (replace future losses as they occur)
What should you replace extracellular fluid with? (D+V, NG aspirates, stomas, burns, pancreatitis)
Fluid similar to EC fluid/plasma - Hartmann’s or saline.
If patient needs a lot of sodium-rich fluid resus, Hartmann’s preferred as it contains less chloride (avoid acidosis)
What should you replace normal dehydration with (pyrexia, poor intake)?
Normal maintenance fluids (dextrose-saline)
What should you replace blood with?
Blood - if patient continues to bleed they may also need other products (FFP, platelets) to stop the bleeding rather than replace the lost red cells.
Classes of shock, how much fluid lost and signs?
1 - 0.75L - minimal, mild tachy
2 - 0.75-1.5L - moderate tachy are hypoT
3 - 1.5-2L - severe tachy and hypoT, confusion
4 - >2L - critical tachy and hypoT
Fluids post-op?
K+ is intracellular and can decrease due to cell lysis during surgery.
If K+ is over 4.5, omit for 24 hours.
Fluids in sepsis?
Sepsis causes intravascular depletion due to plasma loss due to leaky capillaries/vasodilation.
Replace with crystalloid, but avoid too much sodium and chloride.
Fluids in heart failure?
No more than 2L/24 hours. If overload develops –> fluid restriction, furosemide, low sodium diet and daily weights.
Causes of low SBP/low urine output in HF?
Must examine because two opposite causes.
- Dehydration - fluid depleted (give fluids)
- LVF and overload - (furosemide - will improve LVF and increase SBP and urine output)
Fluids in liver failure?
Excess Na+ may cause ascites so ONLY use 5% dextrose
Fluids in AKI?
Avoid K+
Fluids in chronic renal disease?
Avoid excess fluids, sodium and potassium (kidneys can’t excrete). Avoid Hartmann’s as contains lactate.
Fluids in extravasation of plasma (e.g. sepsis)?
Fluids that will maintain intravascular volume (e.g. Hartmann’s solution or colloids) - may need inotropic support
Fluids in alcoholics?
MUST given parbinex before giving any 5% dextrose (even if hypoglycaemic). Can precipitate Korsakoff syndrome
Fluids in brain haemorrhage?
Avoid dextrose (causes osmotic haematoma swelling) - “dextrose destroys the brain if there’s a bleed”
Saline best
Fluids in risk of re-feeding syndrome?
Avoid dextrose as it can precipitate
