Session 6: IV Fluids Flashcards
Give examples of IV fluids
5% dextrose 4% dextrose/0.18% saline 0.9% saline Hartmann’s solution
Explain the function of 5% dextrose.
A differing osmolality but in this case 278 mOsm/kg. Glucose is taken up by the cells rapidly to prevent hyperglycaemia. H2O reduces osmolality of all compartments. This means that the solution goes into intracellular (2/3), interstitial (1/4) and intravascular (1/12)
Are isosmotic solutions always isotonic?
No
Are hyperosmotic solutions always hypertonic?
No
Are hyposmotic solutions always hypotonic?
Yes
Is tonicity the same thing as osmolarity?
No.
Define osmolarity
The concentration solute/volume
Define tonicity
This is a behavioural term. It describes what a solution does to a cell when the cell is placed in the solution. Hypo - swells Hyper - shrinks
Explain the function and distribution of fluid in 0.9% saline
154 mmol Na+ and 154 mmol Cl- with an osmolality of 308 mOsm/kg The Na+ will remain in the ECF so there will be no change in osmolarity meaning it is isosmotic. No fluid goes into ICF. 3/4 goes interstitial ECF. 1/4 goes Intravascular ECF.
Explain the function and distribution of fluid in Hartmann’s.
131 mmol Na+, 111 mmol Cl-, 5 mmol K+, 2 mmol Ca2+, 29 mmol lactate Osmolality of 280 mOsm/kg The majority of the solution is retained in the ECF since the osmolality is maintained with the effective osmoles Na+, K+ and Ca2+ No fluid goes into ICF. 3/4 goes interstitial ECF. 1/4 intravascular ECF.
Explain the function and distribution of fluid in 4% dextrose/0.18% saline.
Has 30 mmol Na+, 30 mmol Cl- and 40 g/l glucose. Osmolality of 284 mOsm/kg Effectively 200 ml 0.9% saline and 800 ml 5% dextrose Reduces osmolality of all compartments. The saline part remains in the ECF. ICF - 2/3 X 800 = 533 ECF interstitial = 1/4 x 800 + 3/4 x 200 = 350 ECF intravascular = 1/12 x 800 + 1/4 x 200 = 117
Is 5% dextrose isosmotic and isotonic?
Yes in a bag they are. It’s isosmotic in the body but not isotonic. 5% dextrose is hypotonic in the body.
Is 0.9% saline isosmotic and isotonic?
Yes
Is Hartmann’s isosmotic and isotonic?
Yes
A 34 yr old man with appendicitis walks in. 80 kg
He needs 30 ml/kg/day of water
He needs 1-2 mmol/kg/day of sodium
He needs 0.5-1 mmol/kg/day of potassium
He needs 1 mmol/kg/day of chloride
He needs 50-100g/day of glucose to avoid starvation acidosis
A
B
D
