A major effect of traumatic injuries and blood loss is hypovolemic shock. “Shock, or hypoperfusion, is the decreased effective circulation causing inadequate delivery of oxygen to the tissues” (WV EMTT, 2001).
There are many different causes and types of shock that fall under three general categories: hypovolemic, distributive, and cardiogenic. While the causes, and treatments, vary the end result, hypoperfusion, remains the same. When the body cannot push oxygen-rich blood to the organs because of any reason, tissue starts to die. For the purpose of this article, we're going to focus exclusively on hypovolemic (low volume) shock, which is what we typically encounter in traumatic injuries.
Hypovolemic shock is the most common form of shock that an operator will encounter in the field. Remember, shock cannot be defined by any one parameter, so it is important that the operator be able to identify the signs and symptoms. Also, remember that hypovolemic shock (a lack of fluids in the body), doesn’t only occur in major bleeding, but in burns and long bouts of vomiting and diarrhea.
Classes of Shock
Hypovolemic shock has been categorized into four classes by the American Academy of Orthopedic Surgeons.
Class 1- Blood loss of < 750mL (15%) This is a slight increase in heart rate and no change in blood pressure. The person may become irritable or anxious.
Class 2- Blood loss of 750 – 1,500mL (15-30%) The respirations and heart rate begin to speed up; there is a rise in diastolic blood pressure and the person becomes anxious and possibly hostile.
Class 3- Blood loss of 1,500 – 2,000 mL (30-40%) The heart rate increases and starts to get weak, the systolic blood pressure begins to drop and the person has a significant altered mental status.
Class 4- Blood loss of >2,000mL (>40%) Severe tachycardia (increased heart rate); significant drop in systolic blood pressure; severely altered mental status or unconsciousness; pale cool skin.
You and your partner are on the shoulder of a freeway after stopping a sedan for speeding 20mph over the limit on an icy winter night. The man looks nervous as you look over his license and insurance paperwork. Your partner moves the rear of the vehicle to assess the backseat when you hear the ominous screeching of tires sliding. An SUV impacts the rear of the vehicle, causing it to spin and strike your partner on his right flank. He screams as his liver lacerates from blunt force trauma, instantly causing massive non-compressible hemorrhage. He is the only person injured, with trauma to an organ that circulates 1,500mL of blood per minute.
Initially, his body is able to make up for 15% of the circulating blood volume, and your partner is in a state of compensated or non-progressive shock (AAOS, 2010). There may be no change in vital signs initially except for a slight increase in heart rate. The body begins to release epinephrine and norepinephrine to cause vasoconstriction, attempting to raise and control the blood pressure. This causes the casualty to become anxious and slightly pale and clammy. Your partner writhes in pain as you call for a medical unit. You know that because of your location and the weather it may take longer than usual. As the loss of blood continues, the casualty progresses into stage two and the effects of shock become more apparent. The body attempts to compensate for the blood loss by increasing the heart rate to try to get the remaining blood circulating and keeping major organs alive. The body falls into a state of acidosis as a chemoreceptor senses the pH level in the body dropping and tells the respiratory drive to increase depth and rate of respirations to blow off CO2 and increase oxygen (Surgeons, 2009). The casualty has delayed capillary refill times ( >2 sec) and tachycardia. Blood glucose levels rise, providing substrate for cellular metabolism. The byproduct of metabolizing this substrate will leave the body more acidic. It has been about five minutes since the impact and your partner is shivering and starts to get irate and keeps asking where the ambulance is. You decide to look at his abdomen and see that it is distended and rigid and a circular bruise around his umbilicus. Soon he reaches 25-30% of blood loss, the body falls into decompensated shock. The casualty may be unable to maintain a blood pressure and has a very delayed capillary refill time. As the shock progresses, the precapillary sphincters begin to relax as the postcapillary sphincters stay closed, resulting in stagnant blood in the capillary beds of non-vital organs (rouleaux formation). The stagnant blood may clot. Your partner soon stops shaking from the cold. His body temperature continues to drop, interfering with his clotting processes. This leads to more acidosis, which decreases heart efficiency, making it even harder for the body to maintain temperature and deliver oxygen. As the body continues to lose more blood and passes stage 3 and 4, the precapillary sphincters open, pushing all those microclots into the body, plugging up vital organs. Pulse pressures become narrow (systolic and diastolic become closer) and the heart no longer has the oxygen and nutrients it needs to beat fast. A slow heart rate is hallmark of irreversible shock. It is critical to intervene early in order to make a difference.
Treating for shock as a first responder is very important and must be done quickly to avoid more irreversible stages.
Once you have identified the casualty as being in hypovolemic shock, you need to apply EEL-ROT.
E- Elevate the wounded extremity. This will help gravity pull blood back down towards the body. The scenario had a casualty with internal bleeding. If there is no wounded extremity skip to the legs.
E- Elevate the legs to a height above the casualty’s head. Allow gravity to pull the blood from the legs back down to the torso where it is needed to perfuse major organs. Do not elevate an unsplinted leg. Remember you can elevate the entire stretcher, not just the legs. Consider head injuries before elevation (SMCT, 2002).
L- Loosen clothing. Body armor and boots may become a barrier to circulation and perfusion. Loosen boots, belts, gloves, armor or anything that may restrict blood flow. Keep armor on if in a hostile environment.
R- Regulate temperature. Hypothermia compounds other ill effects on the body. The casualty will lose the ability to regulate his/her temperature, causing hypothermia. Hypothermia causes a change in clotting factors, and will cause an increase strain on the body that can lead to death very easily. I cannot stress how important treating for hypothermia is. I have seen body temperatures drop in hypovolemic casualties up to rates of one degree every three minutes. Shield the patient from the ground, as the body will lose heat through conduction as well.
O- Oxygenate. If possible apply 12-15 liters/min of oxygen via non-rebreather mask. This will help counter the acidosis and provide vital oxygen to the cells.
T- Transport. A casualty in shock needs to be admitted into the emergency department as soon as possible.
Again, shock cannot be defined by one parameter. Not only is the amount of blood lost a factor, but the time it is lost in. The body can compensate for 500mL lost in a blood drive over 15 minutes, but may cause exaggerated effects if lost over 30 seconds. Law Enforcement Officers may be able to compensate longer than the average civilian, as athletes have a greater fluid and cardiac capacity. Pregnant women have 50% more blood but will shunt the blood from the baby to perfuse the mother. People in poor health or the elderly may not tolerate blood loss well or may be taking medications like blood thinners.
In the next article I will detail fluid resuscitation protocols that can be used to stabilize perfusion in hypovolemic patients. Remember, as the casualty progresses into shock, vascular collapse will ensue. It is important to gain vascular access early, even if the casualty seems fine. Establish a saline/heparin lock or hang the first bag of fluids TKO (to keep open) if the casualty does not need them yet.
Regardless, always remember of the details of treating shock, remember: it is critical that you stop the life threatening hemorrhage before you start treating for shock.
AAOS. (2010) 68W Advanced Field Craft. Combat Medic Skills. Massachusetts: Jones and Bartlett.
West Virginia EMS (2010). EMT Paramedic Treatment Protocol 4108. Retrieved from http://www.wvuh.com/medcom/Protocols/ALS/Trauma/4108%20Shock.pdf
Soldiers Manual Of Common Tasks. Perform First Aid to Prevent or Control Shock. Retrieved from http://www.medtrng.com/cls/lesson_8.htm
Surgeons (2009). Shock. Surgeons Net Focusing on Surgeon Education. Retrieved from http://www.surgeons.org.uk/advanced-trauma-life-support/shock.html
About Hank V.
Hank is a 6-year veteran currently serving in the U.S. Army Special Operations Forces as a Combat Medic. He has deployed to East Asia and the Middle East.