Fluids Flashcards
What is the definition of osmolality?
The number of osmoles in a kilogram of a solvent
What is osmolarity?
The number of osmoles in a litre of a solvent
How much of our body is water?
60%
Of this 60%, how much is in ECF and ICF?
- Intracellular fluid is inside of the cells and comprises of 2/3’s of the 60%
- extracellular fluid is outside of the cells and is 1/3 of the 60%
The ECF is comprised of two components, namely:
- plasma(fluid in circulation) 20%
2. interstitial fluid(fluid between cells) 80%
What is normal plasma osmolality?
275-295mmOsm/kg
What is the plasma osmolality equation?
- 2[NA] plus urea plus glucose
What is pulsus paradoxus?
What causes pulsus paradoxus?
- negative pressure intrathoracically on ispiration which causes pooling in the lungs
- decreased filling of the left heart and decreased stroke volume
What do we use for maintenance?
crystalloid
What do we use for bolus?
colloid
What are the static parameters?
- HR
- BP
- CVP
- urine output
What are the dynamic parameters?
- stroke volume variation
- pulse pressure variation
- passive leg raise test
What is tonicity?
It is the difference in osmotic activity between two compartments
What is the mechanism for low plasma osmolarity?
This means that there is increased water in the plasma and so the water will diffuse intracellularly where there is less water
High plasma osmolarity >195 means?
That there is not enough water extracellularly and so the water will travel from the inside of the cell extracellularly
What does the hydrostatic pressure consist of?
It is at the arteriolar end of the capillary and forces the blood outside of the capillary
What does the osmotic pressure consist of?
It is in the venous side and forces the blood back into the capillary
What will cause tissue oedema?
- increased hydrostatic pressure
- decreased oncotic colloid pressure
- endothelial damage of the capillary
What are some mechanisms of the renal system to cope with fluid loss?
With the renin, angiotensin. aldosterone system which subsequently increases aldosterone which will cause reabsorption of water and sodium at the distal tubule
What is the cause of a patient presenting with fluid deficit?
- vomiting
- perspiration
- diarrhea
What are crystalloids?
- hypotonic-maintenance 5 and 10% maintelyte
2. isotonic- replacement fluids-ringers lacate,0,9% Na chloride
Why are colloids great as fluid replacements?
- They do not contain infective agents
- They are cheaper
- They are good volume replacers
What must you do pre-operatively if there’s a fluid deficit?
If the patient is fluid deficit, then give isotonic balanced solutions that will be sufficient to maintain HR, ventricullar filling pressure, and mean arterial pressure
Does administering anaesthesia cause vasoconstriction or vasodilation?
- vasodilation and can cause a decrease in preloading of the heart
What amount of fluid do you give prior to elective surgery?
2 ml.kg/hour nil per mouth
What amount of fluid do you give to patients that could require more fluid?
6ml.kg of a balanced salt solution prior to anaesthetic induction
When is blood loss enough for a blood transfusion?
When it is more than 20%
What is the urine output we expect post-operatively?
0,4-0,5ml.kg
Which fluid has the risk of causing metabolic acidosis?
-0,9% saline
Intra-operative fluids is broken up into 3 categories:
- Rehydration
- Maintenance
- Replacement of ongoing losses
How do you replace blood loss intra-operatively?
- start with isotonic crystalloids
- then move tocolloids if more than 1 L is lost, then start replacing with blood
