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# Clinical Calculations: Module 8: Critical Care Intravenous Medications

## Critical Care Intravenous Medications

### Module 8 –Critical Care Intravenous Medications and Fluids

What’s in this module?

This module will focus the care of clients who are critically ill.  Illnesses the nurse will encounter in critical care involve problems with key body functions such as airway, breathing, cardiac function, consciousness, severe pain, and other conditions.  The medications in critical care must be regulated carefully.  Incorrect doses can be very dangerous to the client.  The client often has multiple IV infusions and multiple medications at the same time.

Summary of problem types in this module

1. IV fluids delivered using a microdrip set: how many milliliters per hour (ml/hr) should the nurse set on the micropump?  In this case, the ml/hr will be carried to one decimal place.

2. Multiple IV fluids and fluids with added medication:  how many milliliters per hour (ml/hr) should the nurse set on the pump?  With a micropump, the ml/hr will be carried to one decimal place.

3. IV and PO medication based on body weight: how many mg or mcg (per hour with IV) should you give?

4. Medication with upper and lower limits based on body weight: how many mg or mcg (per dose or per hour with IV) should you give for each limit for a safe dose range?

Equivalents to know

You should now know all your commonly used equivalents.

Rounding rules to know

You will need to know all the rules you have used previously.

You will need to know one new rule for microdrip fluids:

• If you are told in the problem that you have a micropump for the IV fluid infusion, take the math out two (2) places past the decimal point and round to the first place past the decimal point (the tenths position).

You have already encountered all the SF and AU used in this module.

An Introduction to Critical Care

The pump illustrated below is a microdrip pump or micropump.  Notice that this pump allows the nurse to use one decimal place when entering the ml/hr infusion rate and the volume to be infused (VTBI).  This allows more control of the medication delivered to the client.

The pump illustrated below can regulate two IV lines. Notice that the pump on the left shows ml/hour as a whole number. The pump on the right is showing a microdrip rate calculated to one decimal place. The micropump is most often used to deliver medications requiring careful regulation.

https://i.ytimg.com/vi/27Gm4vDscrc/hqdefault.jpg   Retrieved 6/10/19

All critical care medications require close monitoring.  Some of doses will be in mcg instead of mg.  Some are based on the client’s weight in kg.  Make certain that you correctly identify the unit of measurement in the healthcare provider’s order and notice if the medication is weight-based.

https://www.vetrimark.com/MEDICATION-image.pjpg   Retrieved 6/22/19

When a medication is added to IV fluid, the nurse must use a label like the one illustrated above to identify the medication added.  The time, date, and name of the nurse adding the medication are recorded.  The name, strength, and expiration date and time are also recorded.

ecx.images-amazon.com/images/I/41%2BVQbRCPIL._SX342_.jpg   Retrieved 6/20/19

Each IV tube should be labeled with the name of the medication the tube is delivering.  This allows the nurse to trace each tube back to the bag of the medication and forward into the IV pump.  The dose, date and time the tubing was placed into use, and the initials of the nurse starting the use of the tubing set are on the label.  The labels above are examples of labels for IV tubing.

Heparin can be used in IV fluid instead of as an injection.  In the illustration above, heparin is provided in a 250 ml bag of 5% Dextrose IV fluid.  The strength of the medication is 50 USP units per ml.  The flow rate will depend on the healthcare provider’s order.

Heparin is used as a blood thinner to prevent blood clots in a client who is bed-ridden in a hospital or to prevent existing clots from getting larger.  In critical care, the medication is often given IV instead of by an injection.

The chart above is a summary of different types of IV fluid and some of the abbreviations used for that fluid.  The type of fluid to be given to the client will be determined by the healthcare provider and will be in the prescription.  Bags of the different types of fluid will be available on the critical care unit or from the pharmacy.

You saw this illustration in the previous module.  Medication can be delivered as an IV bolus (also called IV push or IVP) using the injection port on the IV tubing set.  This method is used for medication that does not need to be diluted and can be delivered relatively quickly.  The healthcare provider will order IV bolus or IVP in the client’s prescription as the delivery method for the medication.

Problem Type 1:  Microdrip IV Infusions

Your answer for this type of problem will be the ml/hr to which the nurse will adjust the flow of IV fluid. The nurse will use the IV pump to adjust the flow by entering the total quantity to be infused and the correct flow rate into the pump.

To solve these problems, you will need the amount of fluid and the time for infusion of the fluid.  The problem will specify microdrip or micropump.

The SF for these problems is 1 hour.  The AU is mL.  The answer in mL/hour will be carried to two decimal places then rounded to one decimal place.

What if your pump is not working correctly or no pump is available?  A microdrip can be run by gravity in these cases, even though it is not the best method to use.  These problems will also ask you to calculate the gtts/min for a gravity drip. The drop factor for the tubing is 60 gtts per mL.

Example 1:

Your client has a prescription for 500 mL of NS containing an antibiotic over 4 hours by microdrip.  Find the mL/hr to enter into the pump.  Also find the gtts/min for a gravity infusion.

Microdrip infusion

SF = 1 hour

AU = mL

Equivalents:

500 mL = 4 hr

Equation:

Gravity Infusion

SF = 1 min

AU = gtts

Equivalents:

500 mL = 4 hr

1 hr = 60 min

1 mL = 60 gtts

Equation:

Notice that the two answers are the same for a drop factor of 60 gtts/mL.  Rounding differences will make the answers different if the mL/hr for the microdrip is not a whole number.  Remember to carry your answer to two decimal places and round to one decimal place for a microdrip pump.  Your answer for the gravity infusion must be rounded to a whole number.  Also notice that for the gravity infusion, the 60 in the numerator and the denominator can cancel each other.

Example 2:

Your client has a prescription for 750 mL of LR containing a medication over 7 hours using a micropump.  Find the mL/hr to enter into the pump.  Also, find the gtts/min for a gravity infusion.

Microdrip infusion

SF = 1 hour

AU = mL

Equivalents:

750 mL = 7 hr

Equation:

Gravity Infusion

SF = 1 min

AU = gtts

Equivalents:

750 mL = 7 hr

1 hr = 60 min

1 mL = 60 gtts

Equation:

Problem Type 2: Multiple IV Fluids and Fluids with Added Medications

The client may have two types of IV fluid running on a pump that can handle multiple lines.  One fluid, usually a 1000 mL bag, will be continuous until the prescription is changed.  This fluid will probably be delivered by macrodrip pump.  The flow rate in mL/hr for this type of pump will be rounded to a whole number.

Another fluid, a smaller quantity, will deliver a medication by micropump.  Remember that adding medication to either fluid will not change the quantity of the fluid to be infused in your calculations.  This infusion will be called a secondary infusion or IV piggyback (IVPB).  The micropump infusion will have a flow rate in mL/hr calculated to two decimal places then rounded back to one decimal place.

Example 1:

Your client has a prescription for NS IV continuously by macrodrip.  Each 1000 mL is to be infused over 8 hours.

Your client also has a prescription for ciprofloxacin 400 mg every 12 hours in 500 mL D5W to run over 3 hours.

What are the flow rates for your IV pumps?

Microdrip infusion

SF = 1 hour

AU = ml

Equivalents:

500 ml = 3 hr

Equation:

The addition of the medication does not change the quantity to be infused enough to change the amount to infuse.  The prescription is for every 12 hours, so this microdrip will be given twice daily.

Macrodrip infusion

SF = 1 hour

AU = mL

Equivalents:

1000 mL = 8 hr

Equation:

Remember that the flow rate for a macrodrip infusion will be a whole number to set on the pump.  The fluid is to run over 8 hours, so a new bag of fluid will be started three times daily.

Example 2:

Your client has a prescription for LR IV continuously by macrodrip.  Each 1000 mL is to be infused over 11 hours.

Your client also has a prescription for rifampin 300 mg every 8 hours in 750 mL NS to run over 4 hours.

What are the flow rates for your IV pumps?

Microdrip infusion

SF = 1 hour

AU = mL

Equivalents:

750 mL = 4 hr

Equation:

This dose of medication is to be given every 8 hours.

Macrodrip infusion

SF = 1 hour

AU = mL

Equivalents:

1000 mL = 11 hr

Equation:

Remember that the flow rate for a macrodrip infusion will be a whole number to set on the pump.  The fluid is to run over 11 hours, so a new bag of fluid will be started when the previous bag is empty.

Problem Type 3:  IV Medication Based on Body Weight

In this problem type, there are two parts:

1. Finding the correct dose for the client: The SF for a problem based on body weight will be the weight of the client.  Pay attention to the unit of weight.  A conversion between pounds and kilograms within the problem may be necessary.  The AU will be the dose in units or mg or mcg.
2. Finding the mL per hour to set on the micropump: Since we are looking at IV medication on a pump, the SF will be 1 hour.  The  AU will be mL carried to two decimal places then rounded to one decimal place.

Example 1:

Your client has a prescription for Heparin 0.4 units/kg/min.  You have on hand Heparin 12,500 units in 250 mL D5W.  The client weighs 90 kg.  Find the units per minute to give the client and find the mL per hour to set on the micropump.

Units per Minute

SF = 90 kg

AU = units

Equivalents:

1 kg = 0.4 units per minute

Equation:

Milliliters per Hour:

SF = 1 hr

AU = mL

Equivalents:

12,500 units = 250 mL

36 units = 1 min

60 min = 1 hour

Equation:

Example 2:

Your client has a prescription for remifentanil 0.75 mcg/kg/min IV.  The pharmacy has provided a bag of 15 mg remifentanil in 750 mL NS for you to use in administering the medication.  The client weighs 185 lb.  Find the mcg per minute to give the client and find the mL per hour to set on the micropump.

Mcg per Minute

SF = 185 lb

AU = mcg

Equivalents:

1 kg = 2.2 lb

1 kg = 0.75 mcg/min

Equation:

Milliliters per Hour

SF = 1 hr

AU = mL

Equivalents:

15 mg = 750 mL

1 mg = 1000 mcg

63.1 mcg = 1 min

60 min = 1 hour

Equation:

Problem Type 4:  Medication with Upper and Lower Limits

Critical care medications must be controlled carefully.   Many of the medications in use will have a safe dose range: an upper limit and a lower limit for the dose of the medication.  Medication should not be prescribed above the upper dose limit because the client may be at a higher risk for harmful adverse effects of the medication.  The effectiveness of the medication may not be greater while the client is at higher risk.  Medication prescribed at a dose below the lower limit will generally not be effective for the intended purpose.

In working this type of problem, both the upper and lower limits for doses of the medication must be calculated.  The healthcare provider’s prescription for the client will be compared to the limits to make certain that it is safe but effective.  The prescribed dose must fall between the upper and lower limits established by the manufacturer.

Once the dose has been determined to be safe, the amount to give the client can be determined.  The medication in question may be oral, parenteral, or IV.  Make certain that you determine how the medication is supplied before working the last part of the problem.  Also, be aware of any divided doses in the prescription.

Example 1:

Your client has a new prescription for sodium bicarbonate 50,000 mg per day orally in four divided doses.  The client weighs 215 pounds.

Information about the medication:  sodium bicarbonate has a safe dose range of 420-840 mg/kg/day orally divided into four doses.  The medication on hand is provided as a powder with a concentration of 2616 mg/0.5 tsp.  Please convert the tsp to give mL for accuracy.  The powder is to be mixed in water before use.

Upper dose limit:   Your upper dose limit is 840 mg/kg/day.

SF = 215 lb

AU = mg

Equivalents:

1 kg = 2.2 lb

840 mg = 1 kg

Equation for upper dosing level:

Lower dose limit:  Your lower dose limit is 420 mg/kg/day.

SF = 215 lb

AU = mg

Equivalents:

1 kg = 2.2 lb

420 mg = 1 kg

Equation for lower dosing level:

Within the safe dose range?  Yes, the prescription falls between the upper and lower limits for dosing.

Amount to give

SF = 50,000 mg

AU = mL per dose

Equivalents:

0.5 tsp = 2616 mg

5 mL = 1 tsp

4 doses

Equation for the amount to give in mL:

Don’t forget: avoid rounding until the very end of the problem (the calculation of the amount per dose).

Example 2:

Your client has a prescription for vancomycin 1500 mg IV over 3 hours for 5 days using a micropump. The client weighs 180 pounds.

Information about the medication:  vancomycin has a safe dose range of 15-20 mg/kg/day  The medication on hand is provided as 1 g in 200 mL of solution.

Please calculate the upper and lower dose ranges per day, determine if the prescription is safe, and determine the mL/hour to set on the IV pump.

Upper dose limit

SF = 180 lb

AU = mg

Equivalents:

1 kg = 2.2 lb

20 mg = 1 kg

Equation:

Lower dose limit

SF = 180 lb

AU = mg

Equivalents:

1 kg = 2.2 lb

15 mg = 1 kg

Equation for lower dosing level:

Within the safe dose range?  Yes, the prescription falls between the upper and lower limits for dosing.

Amount to give

SF = 1 hr

AU = mL

Equivalents:

1500 mg = 3 hrs

1 g = 1000 mg

1 g = 200 mL

Equation:

## Practice Problems

### Module 8 Practice Problems

Microdrip IV Infusions

1. A nurse working on a hospital critical care unit has a client on IV fluids.  The healthcare provider has written a new prescription for amiodarone 360 mg over six hours on a microdrip pump.  Amiodarone 360 mg is contained in 500 mL NS.  The drop factor for the IV tubing is 60 gtts/mL.  What flow rate in mL/hr will the nurse set on the IV pump?  What flow rate in gtts/min would the nurse use for a gravity infusion?

1.  A hospitalized client has a new prescription for 750 mL D5W IV via microdrip pump over 8 hours.  The D5W contains isoproterenol 480 mcg.  What flow rate in mL/hr will the nurse set on the IV pump?  The drop factor for the IV tubing is 60 gtts/mL.  What flow rate in gtts/min would the nurse use for a gravity infusion?

1. Your client has a prescription for norepinephrine 360 mcg in 250 mL LR over 3 hours using a micropump. What flow rate in mL/hr will you set on the IV pump?  The drop factor for the IV tubing is 60 gtts/mL.  What flow rate in gtts/min would you use for a gravity infusion?

1.  Your client has a prescription for vasopressin 14.4 units IV in 750 mL NS over 6 hours using a micropump.  What flow rate in mL/hr will you set on the IV pump?  The drop factor for the tubing is 60 gtts/mL.  What flow rate in gtts/min would you use for a gravity infusion?

1. A hospitalized client on the critical care unit has a new prescription for sotalol 150 mg IV in 500 mL D5W over 4.5 hours by micropump.  What flow rate in mL/hr will the nurse set on the IV pump?  The drop factor of the IV tubing is 60 gtts/mL.  What flow rate in gtts/min would you use for a gravity infusion?

Multiple IV Fluids and Fluids with Added Medications

1.  A nurse is working with a client on an intensive care unit.  The healthcare provider has written a new prescription for nicardipine 25 mg to be delivered in 500 mL NS IV over 5 hours by micropump.  The client has another order for continuous infusion of LR 1000 mL IV over 8 hours. What flow rates in mL/hr will the nurse set on the IV pumps?

1. Your client has a new prescription for 1/2NS 1000 mL IV to infuse over 9 hours.  Your client has another new prescription for norepinephrine 10 mcg/min to be given in 750 mL NS over 6 hours by micropump.  You are to add 360 mcg of norepinephrine to the 750 mL of NS.  What flow rates in mL/hr will the nurse set on the IV pumps?

1. You are starting a new bag of D5W 1000 mL IV to run over 8 hours.  The client receiving D5W has a new prescription for fentanyl 75 mcg X 1 IV in 250 mL NS to run over 1.5 hours by micropump.  What flow rates in mL/hr will the nurse set on the IV pumps?

1. A client has a prescription for a Lactated Ringers IV continuous infusion.  Remaining in the bag is 800 mL to be given over 7 hours.  The client also has a prescription for vasopressin 0.03 units/minute in 500 mL NS.  You will add 5.4 units of vasopressin to the NS and run it by micropump over 3 hours.  What flow rates in mL/hr will you set on the IV pumps?

1. A client has a prescription for D5 ½ NS 1000 mL by continuous infusion over 10 hours.  Three hours have elapsed.   Remaining in the bag are 900 mL. The client also has a prescription for neosynephrine 0.5 mg IV every 10 minutes, with a maximum dose of 5 mg.  You will add neosynephrine 5 mg to 250 mL LR and deliver the medication by micropump over 110 minutes.  What flow rates in mL/hr will you set on the IV pumps?

IV Medication Based on Body Weight

For the following five problems, calculate 1) the dose per minute and 2) the flow rate to set on a micropump in mL/hr.

1. A client has a prescription for pentobarbital 2 mg/kg/hour IV.  You have available 1,500 mg of pentobarbital in 125 mL NS.  The client’s weight is 180 lbs.

1.  A client has a prescription for Solu-Medrol (methylprednisolone sodium succinate) 0.75 mg/kg IV over 40 minutes in 250 mL of ½ NS, to repeat every 6 hours.  The client’s weight is 155 lbs. Solu-Medrol is supplied as 400 mg per vial.  Each vial measures 4 mL after reconstitution.  Inject the entire vial into the 250 mL of ½ NS.

1. Your client has a prescription for dobutamine 2 mcg/kg/min IV.  The client weighs 130 lbs.  The pharmacy has sent you dobutamine 100,000 mcg in 250 mL of  D5W.

1.  Your client has a prescription for tranexamic acid 2 mg/kg/hour IV.  The client weighs 250 lbs.  You have on hand tranexamic acid 5,000 mg in 250 mL LR.

1.  Your client has a prescription for propofol 5 mcg/kg/min IV.  The client weighs 170 lbs.  You have on hand propofol 1,000 mg in 250 mL D5W.

Medication with Upper and Lower Limits

For the following five problems, calculate 1) the upper limit for dosing, 2) the lower limit for dosing, 3) if the prescribed dose is safe, and 4) the amount of medication to give the client per dose (in ml, tabs, ml/hr or other appropriate measurement unit).

1.  A nurse is administering voriconazole to a client who weighs 130 lbs.  The prescription is voriconazole 200 mg IV in 250 mL NS over 2 hours; repeat every 12 hours.  Drug information: safe dose range 3-4 mg/kg IV every 12 hours.

1.  A client who weighs 115 lbs has a new prescription for cidofovir.  The prescription is cidofovir 250 mg IV in 500 mL D5W over 4 hours.  Repeat in one week.  Drug information: safe dose range 4-5 mg/kg IV every week for 2 weeks.

1.  Your client has a prescription for trimethoprim 900 mg orally daily in 3 divided doses for 21 days.  The client’s weight is 140 lbs.  Drug information: 10-15 mg/kg/day orally in 3 divided doses for 21 days.   Tablets of 200 mg each are on hand.  The tablets can be split.

1.  Your client has a prescription for minocycline hydrochloride ER tablets 135 mg PO daily for 12 weeks.  Your client weighs 115 lb.  Drug information: safe dose range is 1-2 mg/kg for ER tab PO daily for 12 weeks. Do not split, chew or crush these tablets.  You have on hand minocycline HCl ER tabs in 50, 60 and 75 mg.

1.  Your client has a prescription for prednisone 25 mg PO daily for 10 days.  The client’s weight is 75 kg.   Drug information:  safe dose 0.4-0.5 mg/kg/day PO X 5-10 days.  Tablets are available in 1, 2.5, 5, 10 and 20 mg.  The tablets can be split.

### Answers to Module 8 Practice Problems

Microdrip IV Infusions

1. A nurse working on a hospital critical care unit has a client on IV fluids.  The healthcare provider has written a new order for amiodarone 360 mg over six hours on a microdrip pump.  Amiodarone 360 mg is contained in 500 mL NS.  The drop factor for the IV tubing is 60 gtts/mL.  What flow rate in mL/hr will the nurse set on the IV pump?  What flow rate in gtts/min would the nurse use for a gravity infusion?

Flow rate for microdrip pump:

SF = 1 hr

AU = mL

Equivalents:

500 mL = 6 hrs

Equation:

Flow rate for gravity infusion:

SF = 1 min

AU = gtts

Equivalents:

500 mL = 6 hrs

60 gtts = 1 mL

1 hr = 60 mins

Equation:

1.  A hospitalized client has a new prescription for 750 mL D5W IV via microdrip pump over 8 hours.  The D5W contains isoproterenol 480 mcg.  What flow rate in mL/hr will the nurse set on the IV pump?  The drop factor for the IV tubing is 60 gtts/mL.  What flow rate in gtts/min would the nurse use for a gravity infusion?

Flow rate for microdrip pump:

SF = 1 hr

AU = mL

Equivalents:

750 mL = 8 hrs

Equation:

Flow rate for gravity infusion:

SF = 1 min

AU = gtts

Equivalents:

750 mL = 8 hrs

60 gtts = 1 mL

1 hr = 60 mins

Equation:

1. Your client has a prescription for norepinephrine 360 mcg in 250 mL LR over 3 hours using a micropump. What flow rate in mL/hr will you set on the IV pump?  The drop factor for the IV tubing is 60 gtts/mL.  What flow rate in gtts/min would you use for a gravity infusion?

Flow rate for microdrip pump:

SF = 1 hr

AU = mL

Equivalents:

250 mL = 3 hrs

Equation:

Flow rate for gravity infusion:

SF = 1 min

AU = gtts

Equivalents:

250 mL = 3 hrs

60 gtts = 1 mL

1 hr = 60 mins

Equation:

1.  Your client has a prescription for vasopressin 14.4 units IV in 750 mL NS over 6 hours using a micropump.  What flow rate in mL/hr will you set on the IV pump?  The drop factor for the tubing is 60 gtts/mL.  What flow rate in gtts/min would you use for a gravity infusion?

Flow rate for microdrip pump:

SF = 1 hr

AU = mL

Equivalents:

750 mL = 6 hrs

Equation:

Flow rate for gravity infusion:

SF = 1 min

AU = gtts

Equivalents:

750 mL = 6 hrs

60 gtts = 1 mL

1 hr = 60 mins

Equation:

1. A hospitalized client on the critical care unit has a new prescription for sotalol 150 mg IV in 500 mL D5W over 4.5 hours by micropump.  What flow rate in mL/hr will the nurse set on the IV pump?  The drop factor of the IV tubing is 60 gtts/mL.  What flow rate in gtts/min would you use for a gravity infusion?

Flow rate for microdrip pump:

SF = 1 hr

AU = mL

Equivalents:

500 mL = 4.5 hrs

Equation:

Flow rate for gravity infusion:

SF = 1 min

AU = gtts

Equivalents:

500 mL = 4.5 hrs

60 gtts = 1 mL

1 hr = 60 mins

Equation:

Multiple IV Fluids and Fluids with Added Medications

1.  A nurse is working with a client on an intensive care unit.  The healthcare provider has written a new prescription for nicardipine 5 mg/hr to be delivered in 500 mL NS IV over 5 hours by micropump.  The client has another order for continuous infusion of LR 1000 mL IV over 8 hours. What flow rates in mL/hr will the nurse set on the IV pumps?

Flow rate for microdrip infusion:

SF = 1 hr

AU = mL

Equivalents:

500 mL = 5 hrs

Equation:

Flow rate for macrodrip infusion:

SF = 1 hr

AU = mL

Equivalents:

1000 mL = 8 hrs

Equation:

1. Your client has a new prescription for 1/2NS 1000 mL IV to infuse over 9 hours.  Your client has another new prescription for norepinephrine 10 mcg/min to be given in 750 mL NS over 6 hours by micropump.  You are to add 360 mcg of norepinephrine to the 750 mL of NS.  What flow rates in mL/hr will the nurse set on the IV pumps?

Flow rate for microdrip infusion:

SF = 1 hr

AU = mL

Equivalents:

750 mL = 6 hrs

Equation:

Flow rate for macrodrip infusion:

SF = 1 hr

AU = mL

Equivalents:

1000 mL = 9 hrs

Equation:

1. You are starting a new bag of D5W 1000 mL IV to run over 8 hours.  The client receiving D5W has a new prescription for fentanyl 75 mcg X 1 IV in 250 mL NS to run over 1.5 hours by micropump.  What flow rates in mL/hr will the nurse set on the IV pumps?

Flow rate for microdrip infusion:

SF = 1 hr

AU = mL

Equivalents:

250 mL = 1.5 hrs

Equation:

Flow rate for macrodrip infusion:

SF = 1 hr

AU = mL

Equivalents:

1000 mL = 8 hrs

Equation:

1. A client has a prescription for a LR IV continuous infusion.  Remaining in the bag is 800 mL to be given over 7 hours.  The client also has a prescription for vasopressin 0.03 units/minute in 500 mL NS.  You will add 5.4 units of vasopressin to the NS and run it by micropump over 3 hours.  What flow rates in mL/hr will you set on the IV pumps?

Flow rate for microdrip infusion:

SF = 1 hr

AU = mL

Equivalents:

500 mL = 3 hrs

Equation:

Flow rate for macrodrip infusion:

SF = 1 hr

AU = mL

Equivalents:

800 mL = 7 hrs

Equation:

1. A client has a prescription for D5 ½ NS 1000 mL by continuous infusion over 10 hours.  Three hours have elapsed.   Remaining in the bag are 900 mL. The client also has a prescription for neosynephrine 0.5 mg IV every 10 minutes, with a maximum dose of 5 mg.  You will add neosynephrine 5 mg to 250 mL LR and deliver the medication by micropump over 110 minutes.  What flow rates in mL/hr will you set on the IV pumps?

Flow rate for microdrip infusion:

SF = 1 hr

AU = mL

Equivalents:

250 mL = 110 mins

1 hr = 60 mins

Equation:

Flow rate for macrodrip infusion:

SF = 1 hr

AU = mL

Equivalents:

900 mL = 7 hrs

Equation:

IV Medication Based on Body Weight

For the following five problems, calculate 1) the dose per minute and 2) the flow rate to set on a micropump in mL/hr.

1. A client has a prescription for pentobarbital 2 mg/kg/hour IV.  You have available 1,500 mg of pentobarbital in 125 mL NS.  The client’s weight is 180 lbs.

Dose per minute

SF = 180 lbs

AU = mg

Equivalents:

2 mg = 1 kg

1 kg = 2.2 lbs

1 hr = 60 mins

Equation:

NOTE: Since you were asked the question of how many milligrams the client should receive each minute, you rounded at the end of the problem. You will now use that answer to determine the flow rate to set on the IV pump. If you had only been asked to determine the flow rate to set on the pump, you would leave the milligrams per minute as 2.727 until you complete your calculation for the flow rate. This prevents you from double rounding the flow rate.

Flow rate for the micropump

SF = 1 hr

AU = mL

Equivalents:

2.7 mg = 1 min

15,000 mg = 125 mL

1 hr = 60 mins

Equation:

Note: Had you been asked just to solve for the flow rate, you would have used 2.727 in the equation above. That would have resulted in an answer of 13.63 which rounds to 13.6 mL/hr. If you were using a macropump, both equations would have worked out to 14 ml/hr. With medications that need a micropump, double rounding can make a difference in the flow rate you set on the pump.

1.  A client has a prescription for Solu-Medrol (methylprednisolone sodium succinate) 0.75 mg/kg IV over 40 minutes in 250 mL of ½ NS, to repeat every 6 hours.  The client’s weight is 155 lbs. Solu-Medrol is supplied as 400 mg per vial.  Each vial measures 4 mL after reconstitution.  Inject the entire vial into the 250 mL of ½ NS.

Dose per minute

SF = 155 lbs

AU = mg

Equivalents:

0.75 mg = 1 kg

1 kg = 2.2 lbs

40 minutes

Equation:

Note: When you solve the equation, you get 52.840 milligrams per hour. Since the final number is a 0, you do not include it when you write down the number of milligrams.

Flow rate for the micropump

SF = 1 hr

AU = mL

Equivalents:

1.3 mg = 1 min

400 mg = 250 mL

1 hr = 60 mins

Equation:

1. Your client has a prescription for dobutamine 2 mcg/kg/min IV.  The client weighs 130 lbs.  The pharmacy has sent you dobutamine 100,000 mcg in 250 mL of  D5W.

Dose per minute

SF = 130 lbs

AU = mcg

Equivalents:

2 mcg = 1 kg

1 kg = 2.2 lbs

Equation:

Flow rate for the micropump

SF = 1 hr

AU = mL

Equivalents:

118.2 mcg = 1 min

100,000 mcg = 250 mL

1 hr = 60 mins

Equation:

1.  Your client has a prescription for tranexamic acid 2 mg/kg/hour IV.  The client weighs 250 lbs.  You have on hand tranexamic acid 5,000 mg in 250 mL LR.

Dose per minute

SF = 250 lbs

AU = mg

Equivalents:

2 mg = 1 kg

1 kg = 2.2 lbs

1 hr = 60 mins

Equation:

Flow rate for the micropump

SF = 1 hr

AU = mL

Equivalents:

3.8 mg = 1 min

5000 mg = 250 mL

1 hr = 60 mins

Equation:

1.  Your client has a prescription for propofol 5 mcg/kg/min IV.  The client weighs 170 lbs.  You have on hand propofol 1,000 mg in 250 mL D5W.

Dose per minute

SF = 170 lbs

AU = mcg

Equivalents:

5 mcg = 1 kg

1 kg = 2.2 lbs

Equation:

Flow rate for the micropump

SF = 1 hr

AU = mL

Equivalents:

386.4 mcg = 1 min

1000 mg = 250 mL

1 mg = 1,000 mcg

1 hr = 60 mins

Equation:

Medication with Upper and Lower Limits

For the following five problems, calculate 1) the upper limit for dosing, 2) the lower limit for dosing, 3) if the prescribed dose is safe, and 4) the amount of medication to give the client per dose (in ml, tabs, ml/hr or other appropriate measurement unit).

1.  A nurse is administering voriconazole to a client who weighs 130 lbs.  The prescription is voriconazole 200 mg IV in 250 mL NS over 2 hours; repeat every 12 hours.  Drug information: safe dose range 3-4 mg/kg IV every 12 hours.

Upper limit

SF = 130 lbs

AU = mg

Equivalents:

4 mg = 1 kg

1 kg = 2.2 lbs

Equation:

Lower limit

SF = 130 lbs

AU = mg

Equivalents:

3 mg = 1 kg

1 kg = 2.2 lbs

Equation:

Safe to Give?     Yes

Flow rate for the pump

SF = 1 hr

AU = mL

Equivalents:

250 mL = 2 hrs

Equation:

Note: Since there was no mention of a micropump in the problem, you are determining the flow rate for a macropump. Since the medication is dissolved in the 250 mL IV bag and the bag is to infuse over 2 hours, you do not use the amount of medication as part of the equation.

1.  A client who weighs 115 lbs has a new prescription for cidofovir.  The prescription is cidofovir 250 mg IV in 500 mL D5W over 4 hours.  Repeat in one week.  Drug information: safe dose range 4-5 mg/kg IV every week for 2 weeks.

Upper limit

SF = 115 lbs

AU = mg

Equivalents:

5 mg = 1 kg

1 kg = 2.2 lbs

Equation:

Lower limit

SF = 115 lbs

AU = mg

Equivalents:

4 mg = 1 kg

1 kg = 2.2 lbs

Equation:

Safe to give?     Yes

Flow rate for the pump

SF = 1 hr

AU = mL

Equivalents:

500 mL = 4 hrs

Equation:

1.  Your client has a prescription for trimethoprim 900 mg orally daily in 3 divided doses for 21 days.  The client’s weight is 140 lbs.  Drug information: 10-15 mg/kg/day orally in 3 divided doses for 21 days.   Tablets of 200 mg each are on hand.  The tablets can be split.

Upper limit

SF = 140 lbs

AU = mg

Equivalents:

15 mg = 1 kg

1 kg = 2.2 lbs

Equation:

Lower limit

SF = 140 lbs

AU = mg

Equivalents:

10 mg = 1 kg

1 kg = 2.2 lbs

Equation:

Safe to give?   Yes

Tablets per dose

SF = 900 mg

AU = tabs

Equivalents:

1 tab = 200 mg

3 doses

Equation:

1.  Your client has a prescription for minocycline hydrochloride ER tablets 135 mg PO daily for 12 weeks.  Your client weighs 115 lb.  Drug information: safe dose range is 1-2 mg/kg for ER tab PO daily for 12 weeks. Do not split, chew or crush these tablets.  You have on hand minocycline HCl ER tabs in 50, 60 and 75 mg.

Upper limit

SF = 115 lbs

AU = mg

Equivalents:

2 mg = 1 kg

1 kg = 2.2 lbs

Equation:

Lower limit

SF = 115 lbs

AU = mg

Equivalents:

1 mg = 1 kg

1 kg = 2.2 lbs

Equation:

Safe to give?     No. The dose is too high (higher than the upper limit of the safe dose range). Do not give the prescription as it is written. Call the healthcare provider at once.

Too high a dose places the client at higher risk for potentially serious adverse reactions to the medication. A higher dose will not necessarily be more effective in treating the client's illness.

1.  Your client has a prescription for prednisone 25 mg PO daily for 10 days.  The client’s weight is 75 kg.   Drug information:  safe dose 0.4-0.5 mg/kg/day PO X 5-10 days.  Tablets are available in 1, 2.5, 5, 10 and 20 mg.  The tablets can be split.

Upper limit

SF = 75 kg

AU = mg

Equivalents:

0.5 mg = 1 kg

Equation:

Lower limit

SF = 75 kg

AU = mg

Equivalents:

0.4 mg = 1 kg

Equation:

Safe to give?     No. The dose is too low (below the lower limit) and may not be effective. Do not give the prescription as it is written. Call the healthcare provider at once.

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