Advanced Calculations

Nursing 201Ms. Frasier

Summer 2014

Dimensional Analysis Simple technique with a fancy name Allows manipulation of units Also referred as factor label

method or the unit factor method

Less errors The advantage of dimensional analysis

is only one equation is needed

Review

ml/hr gtt/min

Infusion of IV fluids with an IV pump Solve for mL/h

The formula: x mL/h = Total volume in milliliters Total time in hours

On the left side of the equation, place what you are solving for. X

On the right side of the equation, place the available information related to the measurement that was placed on the left side of the equation. 1000ml

8h Answer 125mL/hr

Drops per minute (gtt/min) Knowing the drop factor is the first step The drop factor always appears on the IV package Macrodrops are large and deliver 10, 15, 20 gtt/mL Microdrops are small and deliver 60 gtt/mL Drop factor = gtt/mL

Example: order: D5W to infuse at 100ml/hr. drop factor 10gtt/mL. at what rate in gtt/min should the IV be regulated?

1. You are calculating for gtt/min, so write gtt/min to the left of the equation, (that is what you are looking for)

2. Extract the information that contains gtt/min from the problem; drop factor is 10gtt/mL. add this factor into the equation. X gtt = 10gtt

min mL

The next fraction is written so that the denominator matches the previous fraction (what you are looking for). Looking back at problem we are to infuse 100mL in 1 hr. enter the 1hr as 60min since we are looking for gtt/min.

Order: An IV medication of 50mL NS in 20 min. drop factor (60gtt/mL). At what rate in gtt/min should the IV be regulated?

You are calculating gtt/min, so write gtt/min to the left of the equation, followed by equals sign, label x, since that is what you are looking for: extract the information that contains gtt from the problem. Drop factor 60gtts/mL. numerators match up

₌

Practice ProblemsCalculate the flow rate in mL/hr using dimensional analysis

1. 1,800 mL of D5W in 24 hr by infusion pump _____________

2. 2,000 mL D5W in 24 hr by infusion pump _______________

3. 500 mL RL in 12 hr by infusion pump __________________

4. 100 mL 0.45% NS in 45 min by infusion pump ___________

5. 1,500 mL D5LR in 24 hr by infusion pump _______________

6. 750mL D5W in 16 hr by infusion pump ________________

7. 30 mL of Ancef in 0.9% NS in 20min by infusion pump _____

Answers1.

2.

3. 133mL/hr

4. 63mL/hr

5.

Practice ProblemsCalculate the flow rate in gtt / min using dimensional analysis

1. Administer D5LR at 75mL/hr. the drop factor is 10gtt/mL

2. Administer D5NS at 30mL/hr. the drop factor is a microdrop

3. Administer RL at 125mL/hr. the drop factor is 15gtt/mL

4. Administer 1000 mL D5NS in 6 hrs. the drop factor is 15gtt/mL

5. An IV medication in 60mL of NS is to be given in 45 min. the drop factor is a microdrop

6. 1000 mL of LR is to infuse in 16 hr. the drop factor is 15gtt/mL

7. Infuse 150mL of D5W in 2hr. The drop factor is 20gtt/mL

Answers1.

2.

3.

4. = step 1: calculate mL/hr

5.

6.

Critical Care Calculations Critically ill clients receive medications that are potent and

require close monitoring

Titrated medications are added to a specific volume of fluid and rate adjusted to desired effect; when a solution is titrated, the lowest dosage of the med is set first and ↑ or ↓ as necessary

The drugs that are titrated are potent antiarrhythmics, vasopressor, and vasodilator medications

Infusion pumps are used for titration

Critical Care Calculations

• Volume• mL / hr

• Dosage• mg / min• mg / hr• mcg / min• mcg / hr• mcg / kg / min• mg / kg / min• mcg / kg / hr• mg / kg / hr

• mg / min• mg / hrA client is receiving Pronestyl 60mL/hr. the solution available is pronestyl 2g in 500mL D5W . Calculate the mg/hr and the mg/min the client will receive.

x 4 mg/min

mcg / min mcg / hrOrder: a patient with heart failure has nitroglycerin infusing at 3mL/h. the nitroglycerin concentration is 100mg in 500 mL of D5W. At what rate, in micrograms per minute, is the nitroglycerin infusing?

•mcg/kg/min•mcg/kg/hrOrder: 400 mg of dopamine is added to 250ml. Of 0.9% NS. The order is to begin the infusion at 2mcg/kg/min. the patient’s weight is 150lb. The nurse needs to calculate the rate, in milliliters per hours, at which to set the IV pump.

1. Convert client’s weight to kilograms: 150lb 2.2

2. Now that you have the client’s weight in kg, determine the dosage per min.

68.2kg x 2mcg/kg/min 136.4mcg/min

x

Practice Problems1. A client weighing 50kg is to receive a Dobutrex solution of

250mg in 500ml D5W ordered to titrate between 2.5 and 5 mcg/kg/min.

a. Determine the flow rate setting for a volumetric pump. b. If the IV flow rate is being maintained at 25mL/hr after

several titrations, what is the dosage infusing per minute?

2. Order: Epinephrine at 30mL/hr. The solution available is 2mg of epinephrine in 250mL D5W. Calculate the following: c. mg/hrd. mcg/hre. mcg/min

3. Aminophylline 0.25g is added to 500mL D5W to infuse at 20mL/hr. Calculate the following: a. mg/hr

4. Order: 3mcg/kg/min of Nipride:Available: 50mg of Nipride in 250mL D5W . Client’s weight is 60 kg. b. Calculate the flow rate in mL/hr that will deliver this dosage.

5. A nitroglycerin drip is infusing at 3mL/hr. The solution available is 50mg of nitroglycerin in 250mL D5W. Calculate the following: c. mcg/hrd. mcg/min

Heparin IV• HIGH ALERT MEDICATION

• Heparin is a potent anticoagulant that prevents clot formation and blood coagulation

• Expressed in units (no “U” abbreviation) • The therapeutic range for heparin is determined individually

by monitoring the client’s blood clotting value (APTT – activated partial thromboplastin time)

• Heparin is considered to be more therapeutic when based on weight in kg.

• May be given SQ or IV. Never IM.• Should always be on a pump…will be ordered either ml/hr or

units/hr• Remember heparin comes in many different strengths. Make

sure you have the correct one.

Examples• mL/hr – units/hr

Order: 15 units/hour. On hand you have 40units in 250ml of NS. How many ml/hr will you administer?

ml/hr

Order: D5W 1000ml containing 20,000 units of heparin to infuse at 30mL/hr. calculate the dosage of heparin the client is to receive per hour.

600 units per hour

Calculating heparin dosages based on weight

A client weighs 165 lb.Order: heparin 25,000 units in 1000ml 0.9% sodium chloride. Bolus with heparin at 80units/kg, then initiate drip at 18units/kg/hr. calculate the initial bolus dosage, then calculate the infusion rate at ml/hr.

x bolus

54ml/hr

Or

A client weighs 176 lb. Heparin infusion 20,000 units in 1000mL 0.9% sodium chloride. Order: bolus with heparin sodium at 80units/kg, then initiate drip at 18units/kg/hr. Calculate the following: a. ___________ bolus dosageb. ___________ infusion rate (initial)c. ___________ mL/hrAnswers: 6400 units, 1440units/hr, 72mL/hr

46. pg.519 Order: Heparin drip at 18units/kg.Available: 25,000units of heparin in 1,000mL of D5W. The client weighs 80 kg. At what rate will you set the infusion pump?

First determine units/kg the client should receive.

18x80 = 1440units then mL/hrAnswer: 58 mL/hr

47. Pg 519 A client weighs 200 lb.

Order: Administer a bolus of heparin sodium IV at 80units/kg. how many units will you administer:

48. pg. 520 A client weight 210 lb.

Order: Heparin IV infusion: heparin sodium 25,000 units in 1,000 mL of 0.9% NS. Order is give a bolus with heparin sodium 80units/kg, then initiate drip at 18units/kg/hr.

Calculate the following: a. Heparin bolus dosage ____________________b. Infusion rate for the IV (initial) _____________c. At what rate will you set the infusion pump? ___________

• Practice! Practice! Practice!

• Review Heparin Weight Based Protocol