Prescribing IV Infusions CWFS

Problem areas •Calculating infusion rates •Completing the form •Awareness of appropriate volumes and dose •Compatibilities and the BNF

Prescribing infusions •Prescribe on correct chart Once only section of prescription chart for injections (loading doses / IV bolus doses) Drug kardex for multiple boluses IV chart for infusions •Infusion fluid and strength No abbreviations What is in the bag before you add anything?

Volume Number of mls before you add anything N.B. for continuous infusion max 2-3L per day •Additive and dose The drug you are adding and the total number of mg or units to add to the bag •Rate in ml/hour

Injections/infusions •IV = fast injection/bolus Usually just a few millilitres •Slow IV = over 5-10 minutes Usually <10ml unless by syringe driver •Infusion = >100ml over at least 20 minutes Rate has to be monitored

Compatibilities •BNF Appendix 6: Intravenous additives Not exhaustive Ask Pharmacy •Check appendix carefully as not all drugs are compatible with sodium chloride 0.9%

Practice 1 •Mr.Ben is a 37 year old man admitted with a paracetamol overdose. His plasma-paracetamol concentration (mmol/litre) indicates that he requires acetylcysteine. He weighs 67kg. Prescribe on an intravenous prescribing sheet the acetylcysteine regimen that he requires so that it can be administered •BNF Acetylcysteine Adult and Child, initially 150mg/kg over 15 minutes, then 50mg/kg over 4 hours then 100mg/kg over 16 hours. Dilute requisite dose in glucose 5% as follows: Initially 200ml given over 15 minutes, then 500ml over 4 hours, then 1 litre over 16 hours

Practice 1 -Answer •Step 1–calculate the dose over the period of time you require (weight 67kg) 150mg/kg over 15 minutes = 10050mg 50mg/kg over 4 hours = 3350mg 100mg/kg over 16 hours = 6700mg •Step 2–follow BNF instruction for dilution initially 200ml given over 15 minutes then 500ml over 4 hours then 1 litre over 16 hours

Practice 1 -Answer •Step 3–calculate the rate Rate = Volume / Time •10050mg in 200ml dextrose 5% over 15 min •3350mg in 500ml dextrose 5%over 4 hours Rate = 500ml/4hours = 125ml/hour •6700mg in 1 litre dextrose 5%over 16 hours 1l = 1000ml Rate = 1000ml/16hours = 62.5ml/hour

IV practice 2 •Mrs.Smith is a 28 year old epileptic who you wish to initiate on sodium valproate. She is 50kg and currently unable to swallow. •BNF No. 53: Sodium valproate 􀂃Initiation of valproate therapy, by intravenous injection (over 3–5 minutes), 400-800mg (up to 10mg/kg) followed by a continuous intravenous infusion up to max. 2.5g daily. •You wish to give her an initial loading dose of 4mg/kg followed by an intravenous infusion of 1.6g over 24 hours •Prescribe the required loading dose and intravenous infusion that she requires

IV practice 2 -answer •Step 1–calculate the initiation dose 4mg/kg = 4x50 = 200mg over 5 minutes Step 2 –What infusion fluid and volume do you require? BNF: Glucose 5% or sodium chloride 0.9%, any suitable volume. Pick one: Sodium chloride 0.9% 500ml

•Step 3–Convert to ml/hour 500ml over 24 hours = 20.8ml/hour 5.Prescribe it Sodium chloride 0.9% 500ml Sodium valproate 1.6g Rate 20.8ml/hr

IV practice 3 •Mr. Taylor is a 45 year old man requiring inotropic support after infarction. He weighs 60 kg. •The consultant says he needs to be prescribed dobutamine 2.5microgram/kg/min at a concentration of 500micrograms/ml and give it in glucose 5% 500ml. •Prescribe the IV prescription that he requires

IV practice 3 -answer •Step 1 –calculate total amount of dobutamine in bag 500ml at 500mcg/ml = 250000micrograms =250mg •Step 2 -calculate the dose over the period of time you require 2.5mcg/kg/min 60kg 2.5x60x60 = 9000mcg/hour = 9mg/hour

IV practice 3 -answer Step 3 –calculate the rate 9mg/hour 500mcg/ml = 18ml/hour

4.Prescribe it Glucose 5% 500ml Dobutamine 250mg Rate 18ml/hr

Self-check for IV prescriptions •Correct chart? •Correct drug? •Amount of drug in infusion? •Volume and name of diluent? •Rate and/or duration of administration? •Route of administration? •Dated and signed?

Calculations •Read the question carefully •Extract all information from question Which information is given? What are you asked to calculate? •Get as much info as possible from BNF (dosage, administration, etc.) Appendix 6: Intravenous additives Express question as an equation

Safety Check Consider asking somebody else to check your work, especially if tired / stressed