Medication administration - Intravenous: Nursing pharmacology

The intravenous, or IV, route is a common route for the administration of medications and solutions. Some common ones are antibiotics, electrolytes, and fat emulsions. 

IV medications can be administered through a peripheral intravenous catheter, or PIV, or a central venous catheter, or CVC. PIV catheters are typically inserted into veins on the hand or lower arms and are used for less than 1 week.  

On the other hand, CVCs are used for patients who need long-term infusions. They can be inserted at sites such as the internal jugular vein, subclavian vein, or femoral vein; and terminate at the junction of the superior or inferior vena cava and right atrium. If a central line is inserted peripherally, like in the basilic or brachial vein, it's called a peripherally inserted central catheter, or PICC.  

Now, medications can be administered in 3 different ways: direct injection, continuous infusion, or intermittent infusion. 

First, medications given by direct injection are often referred to as IV push. This route uses the patient’s intravenous line to administer a small volume of medication directly into the bloodstream.  

When administering medications via direct injection, first, ensure the patency and status of the IV site by flushing with saline before use and assessing for redness, swelling, or pain at the site. Be sure to note the medication’s push rate, or the time spent administering the medication through the IV, since some medications should be pushed slowly, like furosemide, while other medications should be pushed quickly, like adenosine. Finally, if your patient is receiving multiple medications through their IV, ensure the medications and any fluids are compatible.  

As the nurse, you’ll perform calculations to ensure the correct dose of an IV medication is administered.  

To calculate a dose using the Dimensional Analysis, or DA, method, the three components you need are D, for the Desired dose, or dose ordered by the health care provider; H, for Have, or the dosage you have available; and V, for Vehicle or the form and amount in which the medication comes, like tablets or liquid.      Let’s calculate the dosage of an IV push medication. 

First, you’ll read the order, which is: furosemide 40 mg IV push one time.  

Then, check the medication label: 

Since the medication comes in 100 mg per 10 mL, you’ll calculate how many mLs you should administer to achieve the Desired dose. To do this, first identify your components, Desired, Have, and Vehicle. 

In this case, D is 40 mg, which was obtained from the health care provider’s order. H is 100 mg, which was obtained from the medication label. And V, is 10 mL, which was also obtained from the label.  

Next, you’ll determine if a conversion factor is required. To determine this, compare the units of D with the units of H, and if they’re the same, no conversion factor is needed. Because both D and H are in milligrams, no conversion factor is needed.  

Now, set up the equation, where X is the dose you’ll administer in milliliters, written out like this: 

X volume of milliliters equals Vehicle over Have multiplied by Desired. 
 Now, plug in the values for the components to get X equals 10 milliliters multiplied by 40 milligrams divided by 100 milligrams. 

Remember, you can cross out any duplicate units of measurement because they cancel out. 

Now you’ll multiply 10 by 40 to get 400 divided by 100. 

The answer is 4 mL, meaning you'll administer 4 mL of furosemide to achieve the ordered dose of 40 mg. To verify the rate at which to push this dose, you can refer to the package insert or your facility policy. Typically, this medication is administered at a rate of 1 mL per minute, so you'll administer 4 mL of furosemide over 4 minutes.  

Now, when medications are prescribed intravenously over a period of time, they can be given either intermittently or continuously.  

Intermittent infusions can be given at various intervals, from multiple times per day, per week, or per month, and infused for a specific amount of time from minutes to several hours. On the other hand, continuous infusions are given without breaks between infusions and require the patient to be attached to the IV infusion until the infusion is complete.  

Now, both types of infusions can be administered by gravity or with the use of an IV pump. An IV pump should be used whenever available, because they infuse the medications at an accurate rate and have special safety functions to help prevent medication errors.

Let’s look at how to calculate a continuous medication infusion that will be administered through an IV pump. 

First, you’ll read the order, which is: nicardipine 5 mg per hour continuous IV infusion.  

Then, check the medication label: 

Since the medication is available in a concentration of 20 mg in 200 mL, you’ll calculate how many milliliters per hour to infuse. To do this, first identify your components, Desired, Have, and Vehicle.   

In this case, D is 5 mg per hour, which was obtained from the health care provider’s order. H is 20 mg, which was obtained from the medication label. And V is 200 mL, which was also obtained from the label.  

Next, you’ll determine if a conversion factor is required. To do this, compare the units of D with the units of H. Because both D and H are in milligrams, no conversion factor is needed.   

Now, set up the equation, where X is the dose you’ll administer, written out like this: 

X number of milliliters per hour equals Vehicle over Have multiplied by Desired. And since there’s a time component, we also have T, for Time.