a) Dilution and rate of administration
A 55 year old (62kg) is prescribed one dose of 40 mEq KCl to be administered to correct his hypokalemia. Your pharmacy stocks 10 ml vials of KCl 2mEq/mL. The manufacturer recommends the maximum concentration for administration is 10mEq/100ml and the max rate of administration is 0.5 mEq/kg/hr
i) How much diluent would you need to prepare the patient’s dose? (1 mark)
Pharmacy stock: 10 ml vials of 2 mEq/ml KCl => 20 mEq/10ml
Patient requires 40 mEq => 2 vials = 40 mEq/20ml
Max concentration allowed is 10 mEq/100ml => 40 mEq/400ml
380ml diluent is required to convert 40 mEq/20 ml to 40 mEq/400ml.
ii) From the solution you prepared for this patient, what specific rate of administration would you inform the nurse to give the medication? (2 mark)
Max administration rate is 0.5 mEq/kg/hr
Patient weighs 62 kg
0.5 x 62 = 31 mEq/hr
You need to calculate how many mls of 40 mEq/400ml will give you 31 mEq.
400ml x (31/40) = 310 ml
Max rate of administration 310ml/hour (or 5.17 ml per min, or round down to 5 ml per min if the machine is not able to be that accurate).
iii) How long would you anticipate the infusion time to be? (1 mark)
Infusion rate is 310 ml for one hour. After one hour 90 ml of the 400 mEq/400ml solution will be left.
90/310 = 0.3 hr
in total 1.3 hours.