Hemorrhagic hypotension

 

by Justin Schwartz, GCSOM, MBS 2019
Mentor: Dr. David Averill, PhD

We all understand that bleeding isn’t necessarily a good thing, but when does bleeding go from bad to worse?

According to the American College of Surgeons Advanced Trauma Life Support Program, the answer lies in the percentage of systemic blood that an individual loses and how that corresponds with different classifications of shock. Shock is defined as the inability of your tissues to get the oxygen and nutrients from blood that they need to maintain normal functioning.

I know you’re probably extraordinarily interested in the classification systems, but today we’re here to talk about the treatment aspect in order to restore the blood flow and consequently get oxygen and nutrients back to your tissues so that they don’t die!

When a patient loses 15-30% of their systemic blood volume, they are classified as being in class II Hemorrhagic shock, a stage of shock that is considered to be compensatory. What this means is that your body is utilizing many internal mechanisms in an effort to help restore the flow of and amount of blood inside the vasculature back to normal. At this point, it is important for treatment to center around increasing the amount of fluid in the vasculature as well, without worrying about other properties such as oxygen carrying capacity. Two different solutions that are often used for this treatment are crystalloids and colloids. You may be wondering if it were your life on the line, which would you rather have? Well current research shows that you will be given the cheaper option; don’t worry though, in this case cheaper isn’t necessarily a bad thing! Current research shows that both crystalloids and colloids are equally as effective in restoring intravascular fluid volume, but crystalloids are cheaper so are typically the preferred option.

You may be asking yourself, what if the patient is losing more than 30% of their systemic blood volume? Well, you read my mind and we’ll answer that question now. The classification for 31-40% of systemic blood loss is Class III Hemorrhagic Shock. What exactly does this mean? This means those compensatory mechanisms we spoke briefly about earlier that your body does to help restore intravascular volume no longer occur. Well this just naturally seems like a bad thing, so lets see how treatment differs at this stage. Fluid replacement in the decompensated phase still relies on the use of crystalloids and colloids to help restore the amount of fluid volume inside the vasculature, but we must add some different treatments into the mix to help restore the oxygen carrying capacity of the blood as well. At this point the patient has lost so much blood that not only is normal flow affected, but the reduction in hemoglobin actually means that the blood remaining is just not going to be as effective at transporting oxygen to the tissues. This is when the patient would receive packed red blood cells. In an ideal situation, the patient’s blood would be cross-matched to make sure that the blood that they are getting is a match with the blood that they are receiving, however in a fast paced traumatic environment the medical team may elect to just utilize Type O- blood, the universal donor, which will ensure that the patient does not have an adverse reaction to the blood transfusion they are receiving. Fresh Frozen Plasma is another option that can be utilized at this stage in an attempt to restore clotting factors, which will help your body form clots to stop the bleeding.

Being the problem solver that you are, I understand that your next question probably centers around the fact that since blood banks are often scarce and we don’t always have the time to cross-match the patients blood in an emergent situation to determine what type is appropriate to give them, why is there not some blood substitute we can utilize? Well, that is an excellent question, and the answer is that scientists are currently working on blood substitutes to help restore oxygen carrying capacity called Hemoglobin Based Oxygen Carriers and Perfluorocarbon Based Oxygen Carriers. Although these methods, as well as other novel blood-substitutions that may be discovered can certainly play a huge role in fluid resuscitation in the future, currently the United States Food and Drug Administration do not approve them for use on humans.