Dextrose Solutions Comparison: What, When, and Why
Dextrose solutions can be confusing to nursing students because they don’t act like other IV fluids. Normal Saline is isotonic, 3% Saline is hypertonic, and 0.45% Saline is hypotonic. And they all behave in the body exactly as you would expect those types of fluids to act.
But Dextrose Solutions…don’t. They act differently in the body than you would expect based on their classifications. Let’s discover why!
What is Dextrose?
For nursing school purposes, Dextrose is simply another name for glucose. It’s sugar!
If you want a little more detail, glucose is what we call sugar in our blood stream. It’s what our cells require for energy, and it’s commonly found in nature. In fact, our body is able to break down most of the food we eat into glucose.
Dextrose is chemically identical to glucose, but it is made from corn. Your body can use it the same way that it would use glucose. In fact, if you’re reading a nutrition label on your packaged food and see “dextrose” listed as an ingredient, then you know that there’s added sugar in that food.
What are Examples of Dextrose Solutions?
Some examples of dextrose solutions that you might come across include:
- 5% Dextrose in Water (D5W)
- 5% Dextrose in Normal Saline (D5NS)
- 5% Dextrose in 0.225% Saline (D51/4NS)
- 5% Dextrose in 0.45% Saline (D5 1/2 NS)
- 5% Dextrose in Lactated Ringer’s (D5LR)
- 10% Dextrose in Water (D10W)
- 50% Dextrose (D50)
Are Dextrose Solutions Isotonic, Hypotonic, or Hypertonic?
It’s not as straightforward as it is for the more commonly used IV fluids. For the most part, Dextrose IV solutions are either hypertonic or isotonic. However, once the dextrose has been quickly absorbed by the body, the remaining fluid has a different tonicity.
One way to think about it is like this: whatever tonicity the dextrose solution is when it’s in the IV bag, it will “go down a level” once it has been administered and the dextrose has been used by the body.
For example, D5W and 5% Dextrose in 0.225% Saline are both isotonic in the bag. However, once administered and the dextrose is absorbed, the remaining fluids are 1) water (for D5W) or 2) 1/4 Normal Saline (for Dextrose in 0.225% Saline). In either case, the remaining fluids are hypotonic and would begin acting that way in the intravascular space.
On the other hand, most of the other dextrose solutions are considered hypertonic while in the IV bag. However, once the dextrose has been used up, the remaining fluid may have a different effect. For example, after administering a hypertonic 5% Dextrose in Normal Saline, the dextrose will be used and only the isotonic Normal Saline will remain in the intravascular space.
So what’s a nursing student to do? How should you categorize each of these Dextrose solutions? Some experienced nurses suggest it doesn’t matter so much what they’re categorized as, so long as you understand what they will do to your patient once they’re in the body. I tend to agree with this approach, as it focuses on the physiology behind what is happening, rather than relying on rote memorization.
When do we use Dextrose Solutions?
There are many specialized situations where you might use a dextrose solution. Here’s a few examples.
The most obvious situation to use a Dextrose solution for is severe hypoglycemia, especially if the blood volume and electrolytes are otherwise normal. 5% Dextrose in Normal Saline might be a good choice in this situation because the dextrose will quickly reverse the hypoglycemia, and the patient will be left with the isotonic normal saline that won’t significantly impact blood volume one way or another.
Hypernatremia or Hyperkalemia
If you want to dilute the sodium or potassium in the bloodstream, then choosing a dextrose solution that becomes hypotonic, such as D5W, might be an option. Although this provides the patient with sugar, which they may not actually need, the remaining hypotonic water will want to stay in the blood stream to dilute the excess amount of electrolytes.
Remember that Diabetes Insipidus is NOT related to Diabetes Mellitus, so it doesn’t have anything to do with your blood sugar. As a refresher, Diabetes Insipidus is an endocrine disorder that causes your body to create too much urine, while leaving behind the electrolytes in the blood. Can you see how it might be useful to use a D5W solution again to replace the lost water without adding any electrolytes?
During Surgery and Post-Op
The body is under a lot of stress during surgery and immediately after, which means metabolic needs can increase! That’s why dextrose solutions can sometimes be given in the operating room or shortly post-op in order to help support the body’s energy needs before they are ready to eat normally.
And of course, in ALL of these situations you’d want to closely monitor blood sugars during administration of dextrose to make sure that the patient doesn’t end up with severe hyperglycemia instead! Especially if they are diabetic.
In addition, dextrose solutions are typical recommended for short term use only. So maybe 1-2 days, max. If a patient needs dextrose longer than that for energy, then they will likely be switched to Total Parenteral Nutrition (TPN) to ensure that all nutritional needs are met, not just glucose.
Why can’t we infuse Plain Water (or plain Dextrose)?
It would be DANGEROUS to our patient!!
Plain water and plain dextrose are both outside the safe range of tonicity that we can administer to patients. Plain water is too low, and pure dextrose is too high.
If we infused plain water via IV, that low of a hypotonic fluid would irritate the tissue. In addition, the red blood cells would be extremely likely to be damaged as osmosis kicks in! Water would begin moving into the red blood cells, swelling them like a water balloon (and likely popping them like a balloon as well).
Using pure dextrose would have the exact opposite effect. We would be infusing an extremely hypertonic fluid into the veins, which is also likely to cause irritation and tissue damage. And if you don’t already know what happens to red blood cells when their exposed to hypertonic fluids, then you need to review my Osmosis Experiment where I use an egg to show you exactly what the red blood cells would begin to look like. Spoiler alert: It’s not pretty, and it’s not very good for the patient.
Bottom Line: What You REALLY Need To Know About Dextrose Solutions for Nursing School and NCLEX
You will never see most of these solutions in nursing school because they are most often used in acute or specialized situations. And that also means that you don’t need to become a dextrose expert to be a safe, effective, beginning nurse.
So this is one of those topics where I recommend that you DON’T stress about memorizing every single detail! Just focus on understanding the general concept of how hypotonic, hypertonic, and isotonic solutions work inside the body. That way, if you are faced with an NCLEX question about dextrose, you will be well prepared to combine that knowledge with your critical thinking skills to come up with an well thought out answer.