1. IV Flow Rates –BASED ON BODY WEIGHT
To find the IV flow rate based upon weight:
Convert the weight to kg.
Determine the desired dose.
Calculate the amount to administer.
Calculate the flow rate.
Learning Outcome: 19.2 Calculate IV flow rates for medications ordered based on body weight over a specified period of time (e.g. mg/kg/min or mcg/kg/min).
Rule 18-8 can be applied to critical care IV dosage calculation.
Round patient’s weight to the nearest tenth.

2. IV Flow Rates – BASED ON BODY WEIGHT (cont.)
Find the hourly rate for an adult weighing lb.
Ordered: dopamine 5 mcg/kg/min
On hand : dopamine 400 mg/250 mL NS
Step A Convert wt to kg:
1 kg: 2.2 lb = ? : 220 lb
2.2 ? = 220 lb
? = 100 kg
Example
Learning Outcome: 19.2 Calculate IV flow rates for medications ordered based on body weight over a specified period of time (e.g. mg/kg/min or mcg/kg/min).

3. IV Flow Rates – BASED ON BODY WEIGHT (cont.)
Convert mg to mcg: 1000 mcg: 1 mg = ? : 400 mg ? = 400,000 mcg Concentration of dose on hand is 400,000 mcg/250 mL or 1600 mcg / 1 mL
Example
Learning Outcome: 19.2 Calculate IV flow rates for medications ordered based on body weight over a specified period of time (e.g. mg/kg/min or mcg/kg/min).

4. IV Flow Rates – BASED ON BODY WEIGHT (cont.)
Step B Calculate desired dose.
H = 400 mg Q = 250 mL O = 5 mcg/kg/min
5 mcg/kg = D /100 kg
D = 500 mcg/min
Example
Learning Outcome: 19.2 Calculate IV flow rates for medications ordered based on body weight over a specified period of time (e.g. mg/kg/min or mcg/kg/min).
Using formula method

5. IV Flow Rates – BASED ON BODY WEIGHT (cont.)
Calculate amount to administer:
H = mcg Q = 1 mL D = 500 mcg/min
Fill in formula D/H x Q = A
500 mcg/min / 1600 mcg X 1 mL = A
ml /min = A
Find hourly rate: mL /1 min x 60 min/1 h
18.75 mL/h = 18.8 mL/h
Example
Learning Outcome: 19.2 Calculate IV flow rates for medications ordered based on body weight over a specified period of time (e.g. mg/kg/min or mcg/kg/min).
Proportion method or dimensional analysis can also be used to calculate orders based on body weight.
See examples in text.

6. IV Flow Rates – BASED ON BODY WEIGHT (cont.)
Step C Think!...Is It Reasonable? Since the desired dose is approximately 1/3 of dose on hand, and is approximately 1/3 of the dosage unit, that is reasonable. Because there are 60 min/h and 60 x = 18.75, the flow rate is reasonable.
Example
Learning Outcome: 19.2 Calculate IV flow rates for medications ordered based on body weight over a specified period of time (e.g. mg/kg/min or mcg/kg/min).

7. IV Flow Rates – BASED ON BODY WEIGHT (cont.)
Rule 19-3 If you know:
the total amount of medication in the total volume of solution
the volume of solution that the patient has received
Learning Outcome: 19.2 Calculate IV flow rates for medications ordered based on body weight over a specified period of time (e.g. mg/kg/min or mcg/kg/min).

8. IV Flow Rates – BASED ON BODY WEIGHT (cont.)
Rule 19-3 Then you can
use a proportion to calculate the amount of medication the patient has received (dose).
Learning Outcome: 19.2 Calculate IV flow rates for medications ordered based on body weight over a specified period of time (e.g. mg/kg/min or mcg/kg/min).

9. IV Flow Rates – BASED ON BODY WEIGHT (cont.)
Determine the amount of dopamine the patient received after 45 minutes. Using prior example: total amount of medication = 400 mg total volume of solution = 250 mL flow rate = 18.8 mL/h
Example
Learning Outcome: 19.2 Calculate IV flow rates for medications ordered based on body weight over a specified period of time (e.g. mg/kg/min or mcg/kg/min).

10. IV Flow Rates – BASED ON BODY WEIGHT (cont.)
Calculate amount received in 45 min.
18.8 mL:60 min = A : 45 min
60 x A = 18.8 mL x 45
60A/60 = 846 mL/60
A = 14.1 mL
Example
Learning Outcome: 19.2 Calculate IV flow rates for medications ordered based on body weight over a specified period of time (e.g. mg/kg/min or mcg/kg/min).

11. IV Flow Rates – BASED ON BODY WEIGHT (cont.)
total amount of medication = 400 mg
total volume of solution = 250 mL
volume received = 14.1 mL
400 mg/250 mL = x/14.1 mL
250x/250 = 5640 mg/250
In 45 minutes the patient received 22.6 mg of dopamine.
Example
Learning Outcome: 19.2 Calculate IV flow rates for medications ordered based on body weight over a specified period of time (e.g. mg/kg/min or mcg/kg/min).

12. Practice
Determine the amount to administer and flow rate for a patient weighing 175 lb. Ordered: Nitroprusside 0.5 mcg/kg/min IV On hand: Nitroprusside 50mg/ 250 mL D5W Patient’s weight in kg? Desired dose? Flow Rate?
79.5 kg
Learning Outcome: 19.2 Calculate IV flow rates for medications ordered based on body weight over a specified period of time (e.g. mg/kg/min or mcg/kg/min).
Step A – Convert weight.
1 kg: 2.2 lb = x : 175 lb [cancel units – lb]
x = 175 / 2.2lb = 79.5 kg
Step B Calculate desired dose:
0.5 mcg/kg = ?/79.5 kg
x = 0.5 mcg x 79.5 = mcg /min = 39.8 mcg/min
Calculate amount to administer:
A mL/h = 1 mg/1000 mcg x 250 mL/50 mg x 39.8 mcg/1 min x 60 min/1h
[cancel units – mcg, min]
A mL/h = 597,000 mg / 50,000 h
A mL/h = 11.9 mL / h
Step C Dose ordered is approximately 1/5 of dose on hand and 60 x 1/5 = 12, so it is reasonable.
39.8 mcg/min
11.9 mL/h

13. Apply Your Knowledge Complete the formula: Volume of solution received
Total amount of medication = amount of medication received
Total volume of solution ?
Volume of solution received
Learning Outcome: 19.2 Calculate IV flow rates for medications ordered based on body weight over a specified period of time (e.g. mg/kg/min or mcg/kg/min).