Question

A pharmacist prepares an isotonic saline solution for intravenous infusion. Instead of preparing a \(0.15 \mathrm{M}\) solution, a \(1.5 \mathrm{M}\) solution is prepared. What would happen to the red blood cells if this erroneously prepared solution is infused?

Short answer

Answer: The potential effect on red blood cells with the administration of an incorrect saline concentration of 1.5 M would be shrinkage and potential damage or destruction due to its hypertonic nature, which causes water to leave the cells through osmosis. This could result in severe consequences for the patient receiving the infusion.

Step-by-step solution

Understand isotonic, hypertonic, and hypotonic solutions

An isotonic solution has the same concentration of solutes as the cell it surrounds. This means there is no net movement of water across the cell membrane, and the cell remains stable. A hypertonic solution has a higher concentration of solutes than the cell, causing water to move out of the cell through osmosis; this results in the cell shrinking. A hypotonic solution has a lower concentration of solutes than the cell, causing water to move into the cell through osmosis; this results in the cell swelling and potentially bursting.

Identify the correct and incorrect solutions

The correct isotonic saline solution should have a concentration of \(0.15 \mathrm{M}\). The incorrect solution has a much higher concentration of \(1.5 \mathrm{M}\).

Determine the effect of the incorrect solution on red blood cells

Since the incorrect solution has a higher concentration than the correct one (\(1.5 \mathrm{M}\) vs. \(0.15 \mathrm{M}\)), it is considered hypertonic compared to the cells. In this case, water would move out of the red blood cells through osmosis, causing them to shrink, which could result in impairment of their function and/or destruction.

Conclusion

If the erroneously prepared \(1.5 \mathrm{M}\) solution were infused intravenously, the hypertonic nature of this solution would cause water to leave the red blood cells, resulting in their shrinkage and potential damage or destruction. This could have severe consequences for the patient receiving the infusion.

Key concepts

Hypertonic Solution

When we talk about a 'hypertonic solution', we're referring to a liquid that contains more dissolved substances—what scientists call solutes—than are found within the cells it comes into contact with. Think of it as a very salty soup compared to a less salty one. The body is a finely tuned machine that maintains specific solute levels in its cells, and when the balance is disrupted, water moves to where the solutes are most concentrated, trying to dilute it.

In the exercise, the pharmacist accidentally creates a hypertonic solution by dissolving too much salt in the water. This means there's a higher concentration of salt outside the red blood cells than inside. As a result, osmosis—a process we'll discuss in a bit—causes water to leave the cell, trying to balance out the saltiness on both sides of the cell's membrane. Unfortunately, this leads to the cells shrinking, known medically as crenation, which can impair their ability to transport oxygen effectively.

Hypotonic Solution

In contrast to a hypertonic solution, a 'hypotonic solution' has fewer solutes in comparison to the cells it encounters. Imagine having a glass of lightly salted water next to a saltier one—the lightly salted one is closer to what we call hypotonic. Cells immersed in a hypotonic solution experience an influx of water, as the liquid moves from an area of low solute concentration (outside the cells) to a higher concentration (inside the cells) through osmosis.

In our bloodstream, a hypotonic solution causes red blood cells to swell up like balloons filling with air, because water rushes into them. If the disparity is large enough, the cells can burst, an effect known as hemolysis. Therefore, when preparing intravenous solutions, it's crucial to match the solute concentration to that of the blood to prevent damaging our red blood cells and maintain proper cell function.

Osmosis

Osmosis is the star of the show when it comes to understanding how substances move across cell membranes. It's a type of diffusion specifically for water, where water moves across a semipermeable membrane from an area with fewer solutes (particles like salts or sugars dissolved in water) to an area with more solutes. This balancing act is crucial for cells to function correctly.

Osmosis can be easily demonstrated with a simple experiment: Place a raisin in a cup of water and watch what happens overnight. The next day, you'll notice that the raisin has puffed up because water has moved into it to balance the concentration of the substances inside and outside the raisin. In the same way, but in reverse, the red blood cells in our exercise lose water due to osmosis, as they are placed in a hypertonic solution—a scenario that can be harmful in medical situations.

Red Blood Cells

Red blood cells, or 'erythrocytes,' are the transportation heroes of the human body, delivering oxygen from the lungs to tissues and organs. They are shaped like tiny donuts without holes, which allows them to be flexible and travel through the tiniest blood vessels. Inside these cells is hemoglobin, a protein that binds oxygen and gives blood its red color.

As we've learned, the health and function of red blood cells are closely linked to the solutions they come in contact with. If placed in a hypertonic solution, as with the pharmacist's error, these cells will shrink and may even die. Conversely, in a hypotonic solution, they can swell and burst. This delicate balance is why medical professionals are careful in preparing solutions that match the body's natural osmotic conditions, generally aiming for an isotonic environment where red blood cells can thrive and do their job effectively.