Benefits and Limitations of Non-Blood Volume Expanders
Non-Blood Volume Expanders include products such as Hetastarch, Pentastarch, Dextran and Saline/Ringer’s Solution. Some patients inquire about the use of these products as an aid in offsetting blood loss.
- Do these volume expanders raise a person’s blood count?
- Why would a physician restrict the amounts of these volume expanders to be given?
- Are volume expanders ‘blood substitutes’?
To help you understand the answers to the above questions, think of your blood as being something like chicken noodle soup:
Suppose that you were preparing a pot of chicken noodle soup that was going to be used to feed ten people. How much soup would you make? You would prepare ten servings to feed your ten guests. Lets now imagine three emergencies with your soup.
Emergency #1: Suppose that when you went to serve your ten guests you found that you actually had not ten but nine servings of soup? A family member ate a serving of soup without your knowledge! What could you do so as to still serve a bowl of soup to each of your ten guests? You could add a serving of ‘Soup Volume Expander’ otherwise known as water. That water would dilute your pot of soup, expanding its volume, so that you once again had ten servings. This culinary sleight of hand would probably go unnoticed by your guests. Only you would realize that the soup was a bit thinner than you had prepared.
Emergency #2: Imagine the same situation again. You have nine servings of soup and ten guests. Suppose that this time instead of adding one serving of water to your pot of soup you that you instead add six servings of water. Would the resulting much more diluted pot of soup more closely resemble the original pot of soup? No. In fact it would now be significantly different so that many of your guests would notice. You would now have fifteen servings of rather thin soup.
Emergency #3: Again you have ten guests to serve chicken noodle soup. You lift the lid off of your pot and discover that the soup is almost all gone! In fact you have just barely one serving of soup left. Once again you could add enough ‘Soup Volume Expander’ - water to the pot to increase the volume to ten servings. But would the result pass very well as chicken noodle soup? No. You probably would decide that you just could not serve soup to your guests.
How might these situations shed some light upon the benefits and limitations of Non-Blood Volume Expanders?
Each of us has a volume of blood that for us is normal. Basically, the larger we are, the larger our blood volume. Through surgery, trauma or other bleeding we may lose part of our blood volume.
As in Example #1, if the blood loss is relatively modest, non-blood volume expanders can very often be effectively used.
As in Example #2, using non-blood volume expanders in excess does not make a situation better and in fact can make it worse. When people speak of blood count they often are describing measurements of Hemoglobin or Hematocrit. These different measurements are a number that compares the amount of the oxygen carrying capacity of your blood with the total blood volume of your blood. Increasing the blood volume with non-blood volume expanders has the effect of decreasing the amount of oxygen carrying capacity as compared with blood volume. In other words, an infusion of volume expander will have the effect of lowering not raising blood counts. Therefore a doctor will be careful to use enough volume expanders for the desired benefit while also being careful not to overuse them.
As in Example #3, non-blood volume expanders are not a blood substitute. They do not perform and are not intended to perform all of what a person’s own blood accomplishes. They therefore are not a panacea for addressing blood loss.
The above comparison between soup and blood is just that, a comparison. Through a comparison like this it can be seen that non-blood volume expanders have both uses and limitations.