Help with Dosage!

[uwa2012]

Ok all you dosage wizards out there I need your help for a few problems!! I use the formula method. So any help would be greatly appreciated!!

1). The order is to infuse Aminophylline 1g in 1000ml od D5W at 0.7mg/kg/hr. The client weighs 95lbs. Calculate the dosage in mg/hr, mg/min, and ml/hr.

2). Cardizem 175mg in 250ml of NS to infuse at 10mg/hr. Calculate the flow rate in ml/hr.

3). Dopamine is running at 28ml/hr. The order is for Dopamine 400mg in 500ml of D5 to infuse at 4-12mcg/kg/min. The dopamine was started at 10mcg/kg/min. The patient weighs 130lbs. Is the correct rate set on the pump?

4). Dobutamine 110mcg/min is ordered. Available is dobutamine 250mg in 250ml D5W. The pump is infusing at 12ml/hr. Calculate the mg/hr, ml/hr, and is the pump rate correct?

[notgivingup1 RN]

unit conversion

mass:

mcg → mg → g → kg ( ÷ by 1,000 )

mcg ← mg ← g ← kg ( x by 1,000 )

lb → kg ( ÷ by 2.2 )

lb ← kg ( x by 2.2 )

volume:

mcl → ml → l → kl ( ÷ by 1,000 )

mcl ← ml ← l ← kl ( x by 1,000 )

time:

min → hr ( ÷ by 60 )

min ← hr ( x by 60 )

example: convert 5,000 mcg to mg.

mcg → mg → g → kg ( ÷ by 1,000 )

5,000 mcg ÷ 1,000 = 5 mg

example: convert 44 lb to kg.

lb → kg ( ÷ by 2.2 )

44 lb ÷ 2.2 = 20 kg

example: convert 0.003 l to mcl.

mcl ← ml ← l ← kl ( x by 1,000 )

0.003 l x 1,000 = 3 ml

3 ml x 1,000 = 3,000 mcl

example: convert 5 hours to minutes.

min ← hr ( x by 60 )

5 hr x 60 = 300 min

mass for mass questions

given an amount of mass per tablet, how many tablets do you require?

formula:

ordered

have

= y (tablets required)

example: metroprolol (lopressor), 25 mg po, is ordered. metropolol is available as 50 mg tablets. how many tablets would the nurse administer?

ordered

have

= y (tablets required)

25 mg

50 mg

= 0.5 tablets

example: potassium chloride is available as 10 mg per tablet. potassium chloride (k-dur), 40 mg, is ordered. how many tablets would the nurse administer?

ordered

have

= y (tablets required)

40 mg

10 mg

= 4 tablets

mass/liquid for liquid questions

given an amount of mass per liquid, how much liquid do you require?

formula:

ordered

have

x volume per have

= y (liquid required)

example: phenytoin (dilantin), 0.1 g po, is ordered to be given through a nasogastric tube. phenytoin is available as 30 mg / 5 ml. how much would the nurse administer?

ordered

have

x volume per have

= y (liquid required)

convert 0.1 g to mg.

mcg ← mg ← g ← kg ( x by 1,000 )

0.1 g x 1,000 = 100 mg

100 mg

30 mg

x 5 ml

= 16.7 ml

example: ordered lasix 40 mg iv push now. available: 80 mg in 1 ml. how much will the nurse draw up?

ordered

have

x volume per have

= y (liquid required)

40 mg

80 mg

x 1 ml

= 0.5 ml

amount in iv fluid questions

given a volume of iv fluid and a dosage expressed in percent, what is the mass of a particular dosage?

formula:

concentration %

100

x volume (ml) = y (dosage amount in g)

example: calculate the amount of dextrose in 1000 ml d5w.

concentration %

100

x volume (ml) = y (dosage amount in g)

5%

100

x 1000 ml = 50 g

example: calculate the amount of sodium chloride in 2000 ml ns.

recall ns is 0.9% nacl (sodium chloride)

concentration %

100

x volume (ml) = y (dosage amount in g)

0.9%

100

x 2000 ml = 18 g

volume/time - iv ml rate questions

given a certain amount of liquid and a time period, what is the necessary iv flow rate in ml/hr? measurement used when iv regulated electronically by infusion pump.

formula:

volume (ml)

time (hr)

= y (flow rate in ml/hr)

example: infuse 250 ml over the next 120 minutes by infusion pump.

volume (ml)

time (hr)

= y (flow rate in ml/hr)

convert 120 minutes to hours.

min → hr ( ÷ by 60 )

120 min ÷ 60 = 2 hr

250 ml

2 hr

= 125 ml/hr

example: ordered 1000 ml d5w iv to infuse in 10 hours by infusion pump.

volume (ml)

time (hr)

= y (flow rate in ml/hr)

1000 ml

10 hr

= 100 ml/hr

volume/time - iv drop rate questions

given a certain amount of liquid, a time period, and a drop factor (gtts/ml), what is the necessary iv flow rate in gtts/min? measurement used when iv is regulated manually. because it is not possible to give a patient a fraction of a drop, it is typical to round answers for these problems up or down to the nearest whole number.

formula:

volume (ml)

time (min)

x drop factor (gtts/ml) = y (flow rate in gtts/min)

example: calculate the iv flow rate for 1200 ml of ns to be infused in 6 hours. the infusion set is calibrated for a drop factor of 15 gtts/ml.

volume (ml)

time (min)

x drop factor (gtts/ml) = y (flow rate in gtts/min)

convert 6 hours to minutes.

min ← hr ( x by 60 )

6 hr x 60 = 360 min

1200 ml

360 min

x 15 gtts/ml = 50 gtts/min

example: calculate the iv flow rate for 200 ml of 0.9% nacl iv over 120 minutes. infusion set has drop factor of 20 gtts/ml.

volume (ml)

time (min)

x drop factor (gtts/ml) = y (flow rate in gtts/min)

200 ml

120 min

x 20 gtts/ml = 33 gtts/min

fluid maintenance requirement questions

given the weight of a child or infant, calculate the necessary amount of fluid per day. different hospitals may have different policies, but for learning how to perform these pediatric dosage calculations, the following commonly used table of fluid requirements may be used.

weight range

required daily fluid

0-10 kg

100 ml per kg

10-20 kg

1,000 ml + 50 ml per each kg above 10 kg

20-70 kg

1,500 ml + 20 ml per each kg above 20 kg

over 70 kg

2,500 ml (adult requirement)

example: an infant weighs 4 kg. what is the required amount of fluid per day in ml?

0-10 kg

100 ml per kg

4 kg x 100 ml/kg = 400 ml

example: an infant weighs 30.8 lb. what is the required iv flow rate in ml/hr to maintain proper fluid levels?

convert 30.8 lb to kg.

lb → kg ( ÷ by 2.2 )

30.8 lb ÷ 2.2 = 14 kg

10-20 kg

1,000 ml + 50 ml per each kg above 10kg

14 kg - 10 kg = 4 kg (there are 4 kg over 10 kg).

1,000 ml + (50 ml/kg x 4 kg) = 1,200 ml/day

this is now an ordinary iv flow rate - ml rate question. the required volume is 1,200 ml and the time is one day.

volume (ml)

time (hr)

= y (flow rate in ml/hr)

there are 24 hours in one day.

1 day x 24 = 24 hr

1,200 ml

24 hr

= 50 ml/hr

dosage by weight questions

given the weight of a patient and a dosage specified in terms of weight, calculate the necessary dosage. these problems are a type of pediatric dosage calculations.

formula:

weight in kg * dosage per kg

= y (required dosage)

example: a doctor orders 200 mg of rocephin to be taken by a 15.4 lb infant every 8 hours. the medication label shows that 75-150 mg/kg per day is the appropriate dosage range. is this doctor's order within the desired range?

weight in kg * dosage per kg

= y (required dosage)

convert 15.4 lb to kg.

lb → kg ( ÷ by 2.2 )

15.4 lb ÷ 2.2 = 7 kg

7 kg * 75 mg/kg

= 525 mg (minimum desired dosage)

7 kg * 150 mg/kg

= 1,050 mg (maximum desired dosage)

24 hours in one day and the medication is ordered every 8 hours.

24 hrs / 8 hrs = 3 times per day doctor ordered medication

200 * 3 = 600 mg ordered per day

600 mg is within the desired range of 525-1,050 mg

yes doctor has ordered a dosage within the desired range.

example: solumedrol 1.5 mg/kg is ordered for a child weighing 74.8 lb. solumedrol is available as 125 mg / 2ml. how many ml must the nurse administer?

weight in kg * dosage per kg

= y (required dosage)

convert 74.8 lb to kg.

lb → kg ( ÷ by 2.2 )

74.8 lb ÷ 2.2 = 34 kg

34 kg * 1.5 mg/kg

= 51 mg

this is now an ordinary mass/liquid for liquid question. 51 mg is ordered and the medication is available as 125 mg / 2 ml.

ordered

have

x volume per have

= y (liquid required)

51 mg

125 mg

x 2 ml

= 0.82 ml

mass/time - iv ml rate questions

give an order in quantity of mass per time, determine the necessary iv flow rate in ml/hr based on the given mass per volume. these types of problems are often used in critical care nursing.

formula:

ordered per hour

have

x volume (ml)

= y (flow rate in ml/hr)

example: give patient 500 mg of dopamine in 250 ml of d5w to infuse at 20 mg/hr. calculate the flow rate in ml/hr.

ordered per hour

have

x volume (ml)

= y (flow rate in ml/hr)

20 mg/hr

500 mg

x 250 ml

= 10 ml/hr

example: aggrastat at 12.5 mg in 250 ml is prescribed to be infused at a rate of 6 mcg/kg/hr in a patient who weighs 100 kg. at what flow rate in ml/hr will you set the pump?

ordered per hour

have

x volume (ml)

= y (flow rate in ml/hr)

the first step is to convert the order per time to the amount required for this particular patient. this is a dosage by weight question. 100 kg is the weight in kg and 6 mcg/kg/hr is a dosage in terms of kg.

weight in kg * dosage per kg

= y (required dosage)

100 kg * 6 mcg/kg/hr

= 600 mcg/hr

convert 600 mcg/hr to mg/hr.

mcg → mg → g → kg ( ÷ by 1,000 )

600 ÷ 1,000 = 0.6 mg/hr

0.6 mg/hr

12.5 mg

x 250 ml

= 12 ml/hr

[VickyRN, MSN, DNP, RN]

Thank you for the information shared in this thread. Please remember to debate the poster (when needed), but avoid personal attacks.

Since the OP's original question has been answered satisfactorily, this thread is now closed.