19-1 © 2012 the mcgraw-hill companies, inc. all rights reserved. chapter 19 critical care iv...

19-1

© 2012 The McGraw-Hill Companies, Inc. All rights reserved.

Chapter 19 Critical Care IV Calculations

PowerPoint® Presentation to accompany:

Math and Dosage Calculations for Healthcare Professionals

Fourth Edition

Booth, Whaley, Sienkiewicz, and Palmunen

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Learning Outcomes

19.1 Calculate the hourly flow rate for IV infusions ordered in dosage per time (e.g. mcg/min, mg/h).

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Learning Outcomes

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).

19.3 Calculate IV flow rates for titrated medications.

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Key Terms Antiarrhythmic

medications

Dry weight

Hemodynamics

Titrate

Vasoactive medications

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Introduction Controlling vital functions in critically ill

patients requires constant intervention.

Constant monitoring is necessary.

Medications are infused by an electronic infusion pump and include: vasoactive medications;

antiarrhythmic medications;

IVs administered at ordered rate.

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Hourly Flow Rates – DOSAGE PER HOUR

Rule 19-1 Rule 19-1 Converting dosage/h to mL/h

Determine the following:

D = rate of desired dose

Q = dosage unit

H = dose on hand

A = amount to administer

Use preferred method to calculate.

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Hourly Flow Rates – DOSAGE PER HOUR (cont.)

Find the hourly flow rate.

Ordered: morphine sulfate 4 mg/h

On hand: morphine sulfate 10 mg/100 mL D5W

Step A No conversion is needed.

ExampleExample

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Step B Calculate

H = 10 mg; Q = 100 mL; D = 4 mg/hr

10 mg: 100 mL = 4 mg/h : A

100 mL x 4/h = 10 x A

400 mL/h/10 = 10A / 10

A = 40 mL/h

ExampleExample

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Step C Dosage strength is 1mg to 10 mL

and 4 mL x 10 is 40 mL, so it is

reasonable.

ExampleExample

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Hourly Flow Rates – DOSAGE PER MINUTE (cont.)

Rule 19-2 Rule 19-2 To convert a per minute order to an hourly rate:

1. Convert the order to mL/min. Determine:

D Q

H A

Calculate using your chosen calculation method.

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Rule 19-2 Rule 19-2 (cont.)

Convert mL/min to mL/h

Proportion and formula methods – multiply by 60

Dimensional analysis use the factor 60/1 as

part of your equation

Hourly flow rate = mL/h

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Find the hourly flow rate.

Ordered: 5000 mg Esmolol in 500 mL D5W at 8 mg/min via infusion pump

Step A Convert mg/min to mg/h.

A conversion factor or 60 min/1 hr is needed.

ExampleExample

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Step B Calculate using dimensional analysis.

H = 5000 mg; Q = 500 mL; D = 8 mg/min

A mL/h = 500 mL/5000 mg x 8 mg/1 min x 60 min/1 h

A mL/h = 2400 mL/50 h

A mL/h = 48 mL/h

ExampleExample

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Step C Think!...Is It Reasonable?

The concentration of

5000 mg/ 500 mL = 10 mg / mL,

8 mg/min x 60 min/h = 480 mg/h and

480 10 = 48 mL It is reasonable.

ExampleExample

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Practice

Ordered: Procainamide 4 mg/min IV

On hand: Procainamide hydrochloride 1 g/ 250 mL D5W

Calculate hourly flow rate:

ANSWER: 60 mL/h

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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.

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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

ExampleExample

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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

ExampleExample

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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

ExampleExample

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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

ExampleExample

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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 and60 x 0.3125 = 18.75, the flow rate is reasonable.

ExampleExample

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Rule 19-3 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

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Rule 19-3 Rule 19-3 Then you can

use a proportion to calculate the amount of medication the patient has received (dose).

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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

ExampleExample

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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

ExampleExample

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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.

ExampleExample

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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

39.8 mcg/min

11.9 mL/h

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IV Flow Rates for Titrated Medications (cont.)

Goal – to administer the least amount of medication to obtain desired effect

Titration is used to adjust rate to the effect on the patient’s hemodynamics. Constant monitoring Frequent adjustment Titration table

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Rule 19-4 Rule 19-4 For safe titration:

1. Calculate starting rate.

2. Calculate minimum allowable rate.

3. Calculate maximum allowable rate.

4. Begin infusion at starting rate.

5. Titrate dosage based on patient response.

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Rule 19-4 Rule 19-4 (cont.)

6. Do not exceed maximal rate.

7. If the patient's response exceeds the prescribed parameters at the minimal dose, discontinue the infusion and notify AP.

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Error Alert

The patient’s weight may fluctuate frequently due to changes in volume status. Base calculations on the patient’s “dry weight” when titrating IV rates.

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ExampleExample Ordered: Dopamine 400

mg/500 mL NS, to infuse at 5 to 20

mcg/kg/min IV to maintain systolic BP

greater than 90 mm Hg. Keep HR less

than 100.

Start at 5 mcg/kg/min and titrate to effect.

Use titration table on next slide.

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ExampleExample Dopamine dosage (mcg/100kg)

IV rate (ml/h) 1600 mcg/1 mL

5 mcg/kg/min 18.8 mL/h



20 mcg/kg/min 75 mL/h

What is minimum rate?

What is maximum rate?

What is starting rate?

18.8 mL/h

75 mL/h

18.8 mL/h

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Practice

Ordered: Xylocaine 1 g in 250 mL D5W; start IV infusion at 2 mg/min and titrate to absence of ventricular dysrhythmia; dosage range 1 mg/min – 4 mg/min.

Calculate the minimum dose.

Calculate the maximum dose.

Calculate the starting dose 30 mL/h

60 mL/h

15 mL/h

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In Summary

In this chapter you have learned to

calculate the hourly flow rate for IV infusions ordered in dosage per time (e.g. mcg/ min, mg/h);

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).

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In Summary

In this chapter you have learned to

calculate IV flow rates for titrated medications.

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Apply Your Knowledge

True or False:

Vasoactive medications regulate the heart rate and rhythm.

Medications can be titrated to achieve a specific effect.

To be administered by electronic infusion pump, IVs must be calculated in mL/min.

F

T

F

They are administered to keep blood pressure within normal range

mL/h

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Apply Your Knowledge

Complete the formula:

Total amount of medication = amount of medication received

Total volume of solution ?

Volume of solution received

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Apply Your KnowledgeDopamine Dosage IV Rate (mL/h)

1000 mcg/1 mL

A 5 mcg/kg/min 11.7 mL/h

B 10 mcg/kg/min 23.4 mL/h

C 15 mcg/kg/min 35.1 mL/h

D 20 mcg/kg/min 46.9 mL/h

If the desired response did not occur by the maximum rate of 46.9 mL/h or it it exceeded parameters at minimum dose.

At which point(s) would you call the AP?

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End of Chapter 19

Great works

are performed

not by strength but

by perseveranc

e.~ Samuel Johnson

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