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.

IV Flow Rates – BASED ON BODY WEIGHT (cont.) Find the hourly rate for an adult weighing 220 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).

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).

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

IV Flow Rates – BASED ON BODY WEIGHT (cont.) Calculate amount to administer: H = 1600 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 0.3125 ml /min = A Find hourly rate: 0.3125 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.

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 0.3125 is approximately 1/3 of the dosage unit, that is reasonable. Because there are 60 min/h and 60 x 0.3125 = 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).

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).

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).

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).

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).

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).

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 = 39.75 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

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).