Answers
How would you prepare the KCl for peripheral administration and at what rate should it be administered? (3 marks)
To prepare 10mEq/100ml from a 20mEq/50ml stock solution:
- Take out 25ml of stock solution to obtain 10mEq KCl.
- Then dilute with 75ml of water for injection to obtain 10mEq in 100 ml.
Patient requires 40 mEq KCl -> i.e. 4 x 10mEq/100ml
Administer at the max rate 10mEq/100ml/hr for four hours to deliver 40 mEq KCl.
NB. Equivalents is an American term.
What is the total osmolarity (mOsm/L) of the above IV solution if 0.9% NaCl was used as the diluent. (KCl=74.5; NaCl=58.4) (3 marks)
To get the answer in mOsm/L, calculate quantity of KCl and NaCl as if you have 1L of the above soln.
KCl:
- 1mEq K+ = 1mmol K+
- 10mEq/100ml => 100mEq K+ in 1000ml.
- 100mEq = 100 mmol K+
- 1 mol K+Cl- = 2 Osm KCl
- 100mmol KCl= 200 mOsm KCl
NaCl:
- Calculate the number of moles of NaCl in the above soln:
- 25ml of KCl stock is diluted with 75ml 0.9% NaCl to get 10mEq KCl/100ml.
- Therefore in 1000ml of the made up solution there is 750ml of 0.9% NaCl.
- 0.9% NaCl (Normal Saline) means 9g NaCl in 1 L. Therefore in 750ml of NS there is 0.75*9 = 6.75g of NaCl.
- No moles= 6.75/58.4 = 0.1156 mol or 115.6 mmol
- 1 mmol NaCl = 2 mOsm
- 115.6*2 = 231 mOsm NaCl
Total osmolarity of the above solution:
200+231 = 431 mOsm/L
2 comments