What is Hemorrhagic Shock?
Shock is a medical condition that happens when the body’s tissues don’t get enough oxygen. This is usually due to a mismatch between how much oxygen your tissues need and how much your body can provide. There are four main types of shock: hypovolemic, cardiogenic, obstructive, and distributive shock.
Hypovolemic shock is a specific type of shock that happens when there’s not enough blood or fluid inside your blood vessels. This could happen because of severe dehydration through various causes or due to significant blood loss. In this article, we’ll mostly focus on hemorrhagic shock, which is a type of hypovolemic shock caused by bleeding, discussing its cause, how it’s diagnosed, and how it’s treated.
What Causes Hemorrhagic Shock?
Hemorrhagic shock is most often associated with physical trauma, but it can actually be caused by a variety of issues affecting many parts of the body. It’s most commonly seen after cases of non-specific or targeted injuries, but can also follow problems in either the upper or lower digestive tract. There have been instances of hemorrhagic shock resulting from issues related to childbirth, the circulatory system, medical treatments, or even the urinary system. Bleeding linked to this condition can be either visible or hidden inside the body.
Hemorrhagic shock happens when a person loses so much blood that their body cannot function properly. This life-threatening amount of blood can be lost from areas such as the chest, stomach, or even the space behind the abdomen. Even a person’s thigh can hold up to one to two liters of blood.
In terms of treating hemorrhagic shock, it’s critical to find and control where the bleeding is coming from. However, discussing how this is done is beyond the scope of this article.
Risk Factors and Frequency for Hemorrhagic Shock
Trauma is one of the top causes of death around the world. Roughly half of these deaths are due to too much bleeding. In 2001, in the United States, trauma was the third most common cause of death and top cause of death for those between the ages of 1 and 44. While anyone can experience trauma, young people are affected more often. About 40% of injuries occur in people between the ages of 20 and 39, particularly those between 20 to 24 years.
- Among those suffering from trauma, many bleed severely. In fact, a trauma center indicated that in one year, 62.2% of heavy blood transfusions were due to trauma.
- The rest of the cases requiring heavy blood transfusion were as a result of heart surgery, critical care, cardiology, childbirth services, and general surgery, with trauma accounting for more than 75% of blood used.
As people age, their bodies’ capabilities decrease, medicine usage such as anticoagulants increase, and they may have more health problems. These factors make it harder for older people to cope with the health stress from heavy bleeding, so their conditions can deteriorate faster.
Signs and Symptoms of Hemorrhagic Shock
It’s crucial to gauge the extent of blood loss by observing a patient’s vital signs and mental state changes. According to the American College of Surgeons Advanced Trauma Life Support (ATLS), different amounts of blood loss can lead to varying physiological reactions in an average 70 kg person. Given that the blood makes up about 7% of the total body weight, this equates to roughly five liters for an average 70 kg male.
- Class 1: This indicates a loss of up to 15% of total blood volume, which is around 750 mL. Heart rate is barely or not at all increased during this stage, and there is generally no variation in blood pressure, pulse pressure, or respiratory rate.
- Class 2: This stage represents a loss between 15% and 30% of total blood volume, ranging from 750 mL to 1500 mL. The heart and respiratory rates increase (100 BPM to 120 BPM, 20 RR to 24 RR), and the pulse pressure starts to reduce. However, the systolic blood pressure may remain constant or decrease slightly.
- Class 3: Here, the loss ranges from 30% to 40% of total blood volume, which equates to 1500 mL to 2000 mL. This stage involves a significant drop in blood pressure and a change in mental state. The heart rate and respiratory rate increase noticeably (more than 120 BPM). The urine output reduces, and the capillary refill time lengthens.
- Class 4: This stage involves a loss of over 40% of total blood volume. It’s characterized by hypotension with a narrow pulse pressure (less than 25 mmHg), accelerated heart rate (more than 120 BPM), and increasingly altered mental status. The urine output is minimal or non-existent, and capillary refill is delayed.
Note that the above classification system is based on a healthy 70 kg individual. Various factors may change how a patient reacts to blood volume reduction. For instance, elderly patients on beta-blockers might not have an increased heart rate as a response to decreased blood volume. Similarly, patients with high baseline blood pressure may experience a functional drop in blood pressure—even to a systolic blood pressure of 110 mmHg.
Testing for Hemorrhagic Shock
The first step in dealing with severe blood loss, or ‘hemorrhagic shock’ as doctors call it, is to recognize it. Ideally, this should be done before the patient experiences low blood pressure. Doctors closely monitor certain physical reactions to low blood volume such as a rapid heart rate (tachycardia), fast breathing (tachypnea), and a decreasing difference between the systolic and diastolic blood pressure, referred to as ‘narrowing pulse pressure.’ Initial signs can also include cold hands and feet and delayed return of skin color after it’s pressed, which are indicators of reduced blood flow.
In cases of injury or trauma, doctors use a step-by-step method referred to as the primary and secondary surveys, which is recommended by Advanced Trauma Life Support (ATLS). Physical checks and imaging tests such as X-Rays can help pinpoint where the bleeding is coming from. A specific type of ultrasound known as a Focused Assessment with Sonography for Trauma (FAST) is often used during these initial checks. This technique is very accurate at identifying blood in specific areas of the body, with a precision rate of above 99%. However, it’s important to know that a negative ultrasound result doesn’t necessarily mean there’s no injury inside the abdomen.
Treatment Options for Hemorrhagic Shock
Understanding of bleeding in injury situations has improved. Instead of relying only on large blood transfusions, we now have a more comprehensive approach called “damage control resuscitation”. This strategy aims to treat the combination of abnormal blood clotting, acidosis (a harmful excess of acid in your body), and low body temperature that often occur after injury.
The idea of damage control resuscitation includes keeping the blood pressure low on purpose, using blood transfusion to help clotting, and controlling bleeding. The idea of keeping blood pressure low on purpose is only recommended for patients with bleeding shock who haven’t suffered a head injury. The goal is to maintain enough blood flow to the body’s tissues without restarting bleeding from vessels that have just clotted. This technique is all about a purposeful restriction of fluids until the bleeding can be controlled, even if it means the body’s organs aren’t optimally perfused for a while. There are mixed results from studies on this technique, and it has to be used based on the type of injury, possibility of head injury, severity of the injury and proximity to a trauma center.
There’s still ongoing research and debate about how much and what type of fluids to use during resuscitation. The most commonly used fluids are normal saline and lactated ringers. However, normal saline can lead to a type of acidosis due to high chloride content, while lactated ringers can cause metabolic alkalosis as lactate changes into bicarbonate.
More recently, damage control resuscitation emphasizes using blood products earlier and in preference to a lot of crystalloids (fluids like saline). This approach aims to minimize disruptions to metabolism, clotting problems caused by resuscitation, and dilution of blood that occurs with crystalloid resuscitation. What the ultimate goal of resuscitation should be and what ratios of blood products should be used are still subjects of research and debate. One study did not find a significant difference in death rates at 24 hours or 30 days when different ratios of plasma to platelets to red blood cells were used. However, patients who received more balanced ratios were less likely to die from bleeding within 24 hours and more likely to experience clotting.
Some products used in addition to blood products also help to prevent clots from breaking down, known as antifibrinolytics. Several antifibrinolytics have been found to be safe and effective in elective surgery. The CRASH-2 study showed that an antifibrinolytic drug called tranexamic acid was able to reduce overall death rates when given in the first eight hours after an injury. The benefits of tranexamic acid are even greater when the drug is given within the first three hours after surgery.
At the same time as using the damage control resuscitation approach, it’s important to intervene quickly to control the source of the bleeding. The exact approach can depend on how close the patient is to definitive treatment.
What else can Hemorrhagic Shock be?
In trauma patients, although severe bleeding is the most commonly seen cause of shock, other causes should not be overlooked. One such possibility is obstructive shock. This type of shock might happen as a result of specific medical conditions such as tension pneumothorax and cardiac tamponade. In case the patient has head or neck injuries, a condition called neurogenic shock, which is a type of distributive shock, can occur due to a decrease in resistance in the body’s peripheral blood vessels. Evidence of this can be an unexpectedly low heart rate coupled with low blood pressure.
Moreover, heart-related issues like cardiac contusion and heart attacks can lead to another kind of shock, known as cardiogenic shock. Lastly, other possible causes, which are not directly linked with trauma or loss of blood, must also be considered. In patients where the cause of shock isn’t easily identifiable, doctors should also consider septic shock and toxic causes.