Formulae for determining the correct rate for the infusion of IV fluids can get complicated. No matter how complex the formulae, nurses always check the answer they get against their own logic.

MEDICATION SAFETY

While medications do a lot of good, most of them can cause damage if too high a dose is administered. Because of this nurses typically double-check their calculations when they are giving a new or potentially deadly medication. As a nursing student you will check every doctor’s order with your instructor before the two of you act on the order. For a student to give a medication or change an IV rate without consultation with a professional is not permitted by this School or the clinical agencies. Of course you must act if a client needs a medication or a change to his/ her IV. It is your job to keep your instructor informed that you are in a situation that requires medication calculation and administration or a change to the IV.

IV FLUIDS

The amount of fluids administered intravenously each hour should never be more than you would want to drink in an hour. Most often doctors order only about 4 ounces of IV fluid per hour for their clients. The Metric System is usually used by doctors to order the infusion rate for an IV. There are 30ml in an ounce of fluid. "Infuse 125 ml/ hour" is a common IV order. If the client has a heart or kidney problem, IV fluids might be restricted to 50 – 80ml/ hour. More than that could cause their lungs to fill with fluid, drowning them from the inside. In the following exercises if you get an answer wildly different from these numbers, your logic should tell you that your answer is probably wrong.

BASIC INFORMATION YOU NEED TO KNOW ABOUT AN IV

1. Usually IVs come in clear plastic bags with lines on the side showing how much fluid is left in the bag so a nurse can see how much of the IV has infused.
   
2. The most common size is about a quart which is equal to 1000 ml. 1000 ml is one liter. The total amount is printed on the bag.
   
3. There are many different solutions in these bags, but they all look the same. The name of the solution is printed on the bag. Even though they may be all piled in a heap on a shelf, it is critical that the correct solution be hung for each patient. The wrong solution could kill.
   
4. The tubing that connects the bag to the client comes in different diameters. The wider the tubing, the faster fluid gets into the client. When you look at the box the tubing came in it could give a "Drop Factor" of 10 drops/ ml or 12 or 15 or 20 drops/ ml. When the Drop Factor is between 10 – 20 it is called "macrodrip tubing". A drip rate can’t be figured out unless you know the Drop Factor for the tubing being used.
   
5. Some tubing has a needle built in that limits the size of the drop that can enter the tubing from the IV bag. Pediatric nurses use this kind of tubing because their little patients can only tolerate tiny amounts of IV fluid. It takes 60 of these little drops to equal one ml. When the Drop Factor is 60 the tubing is called "microdrip tubing"
   
6. All IV tubing has a chamber at the end near the IV bag where nurses can see the fluid dripping out of the bag before the fluid enters the tubing. This is where they count the rate of the falling drops using the second hand on their watches. So you can check your answers for logic be aware that if the tubing delivers one ml every 10 drops, a drip rate of 21 will give the patient 125 ml in an hour. If the tubing delivers one ml every 15 drops, a drip rate of 31 will give the patient 125 ml in an hour.
   
7. If the drip rate is less than 10 drops each minute the client’s vein may clot off the IV, meaning s/he might have to get stuck again to start a new IV.
   
8. Just because the IV is no longer in the IV bag a nurse can not assume that it infused into the client. It could have disconnected and be in a puddle on the floor. Nurses always check the client’s infusion site to make sure everything is connected and the client’s arm looks okay.
   

FORMULAE AND PRACTICE

The goal for these exercises is for you to be able to quickly formulate and calculate IV problems.

This is a useful formula to compute the drip rate of an IV. Memorize it. You will need to prove that you can use it in every clinical course before you will be allowed into the clinical area.

= drops/minute

Another way of saying the same thing is:

Example #1

Dr. A. orders your client to receive 125 ml of D5W an hour for the next 8 hours. The nursing unit used tubing with a drop factor of 10. What is the drip rate?

Fill in the formula putting an X for the drip rate because that is what you want to know.

Notice that the fact that the information about 8 hours was not needed to figure out the drip rate.

Example #2

Dr. B. orders a liter of D5W to run this 8-hour shift. The drop factor is 15. Put this information in the formula with the X in the spot for the drip rate.

Example #3

Dr. C. wants your client to have 50 ml of a pre-mixed antibiotic. The Pharmacy writes, "infuse in 30 minutes". The tubing box says drop factor = 15.

SUBMITTING YOUR ANSWERS:

Writing equations in text format can be difficult. It is therefore very important to follow certain conventions when submitting equations as answers.

• Use the symbols 'x' and '/' for multiply and divide.
• Use upper case to denote variables. ('X' and 'Y')
• It is usually helpful to put parenthesis around each expression, so that there can be no confusion regarding the order in which to process the equation.

For example 2, above, the correct textual representation of the equation would be:

(1000 x 15) / (8 x 60) = X

Note that the following would be incorrect:

1000 x 15 / 8 x 60 = X

Why? Because this equation works out to:

1000 x (15 / 8) x 60 = X

 

ASSIGNMENT 1:

Now that you know where the information goes in the formula, go back and solve the 3 problems for the drip rate. Note: Always cancel out rather than multiply large numbers. It reduces the chance of error. You can’t count a part of a drop. It the answer comes out with a fraction round up if it is a half or larger. Don’t round up if it is smaller than a half.

E-mail the following answers as Part I of the E-mail assignment due before Class 5:

GRADING FOR PART 1:

3 correct answers = 10 % 2 correct = 5% 1 correct = 0%

OPTIONS FOR ASSIGNMENT 2:

You can do this Part II separately or in groups of 2 or 3. If you choose to work together be sure to include the names of everyone in the group in your E-mail submission.

Everyone in this group gets the same grade so you may want to set some ground rules on participation, time limits, attitude or any other perimeters you feel are important.

You/ your group will be submitting problems in 4 categories:

1. Problems and solutions to the problems - solving for the drip rate.
2. A problem and solution to the problem - solving for the time needed to infuse
3. A problem and solution to the problem - solving for the drop factor
4. A problem and solution to the problem - solving for the amount to be infused

ASSIGNMENT 2:

1. For every person in the group make up a problem like those above, and use the formula to solve it for the drip rate. (A group of 2 makes up 2 problems. A group of 3 makes up 3 problems.) Show how you placed the information in the formula and show your math.

Alter the IV Rate Formula to solve for the other components in that formula besides drip rate : amount to be infused, drop factor, or time the infusion will run.

Example #1

The order stipulates that 2 liters of D5W are to infuse at 30 drops / min. The drop factor is 15. How long will this take?

1. 
   
2. Cross multiply: 30,000 = 30X
   
3. Cancel: 1000 = X min
   
4. An answer of 1000 minutes is not too useful. Change it to hours and minutes:
   1000 minutes divided by 60 min / hour = 16.6 hours
   
5. What does .6 mean? Change that to minutes:
   .6 of an hour times 60 minutes = 36 minutes
   
6. Check the answer for logic:
   Running 2 bags at 30 drops / min for about two shifts will finish the infusion – This makes sense

2. Make up a problem that asks for the time needed for the infusion. Solve it. Give the answer in hours and minutes. Show how you placed the information in the formula and show your math. Comment on the logic of your answer.

3. Make up a problem that asks for the tubing’s drop factor. Solve it. Give your answer in drops/ ml. Show how you placed the information in the formula and show your math. Comment on the logic of your answer.

4. Make up a problem that asks for the amount of fluid to be infused. Solve it. Give your answer in ml. Show how you placed the information in the formula and show your math. Comment on the logic of your answer.

GRADING FOR PART 2:

• Well expressed logical problem statement 5 % x 4 categories = 20%
• Correct placement of information in the formula 10% x 4 categories = 40%
• Correct math 5 % x 4 categories = 20 %
• Assignment submitted by students named in the E-mail prior to Class 5 = 10%