Hypovolemic shock typically refers to a severe drop in blood volume that leads to further complications in a person’s health.
The heart cannot pump blood around the body unless a certain volume of blood is present. Blood volume describes the total amount of blood in the body. If a person’s blood volume drops significantly, then a person can go into hypovolemic shock.
Many health problems can lead to hypovolemic shock. A doctor will diagnose a patient with the issue once an individual loses 20% or more of their blood volume. Hypovolemic shock is a medical emergency that is difficult to diagnose and treat. It can result in organ failure.
In a study, more than 82% of patients who died from hypovolemic shock died within the first 24 hours.
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There are approximately three stages of hypovolemic shock based on the level of blood volume loss. All the stages require fast treatment. The earlier doctors can recognize the stage of shock a person is in, the faster they can give the patient the appropriate treatment.
Mild
During the earliest stage of hypovolemic shock, a person loses less than 20% of their blood volume. This stage can be difficult to diagnose because blood pressure and breathing will still be normal.
The most noticeable symptom at this stage is skin that appears pale. The person may also experience sudden anxiety.
Moderate
In the second stage, the body loses 20-40% of blood. The individual may experience increased heart and breathing rates.
Blood pressure may still be within normal range. However, the diastolic pressure, or bottom number, of their blood pressure may be high. The person may begin sweating, as well as feeling more anxious and restless.
Severe
By stage 3, a person with hypovolemic shock will have lost more than 40% of their blood.
The systolic pressure, or top number, of their blood pressure, will be 100 millimeters of mercury (mm Hg) or lower. Their heart rate will increase to over 120 beats per minute (bpm). They will also have a rapid breathing rate of more than 30 breaths per minute.
They will begin to experience mental distress, including anxiety and agitation. Their skin will be pale and cold, and they will begin sweating. They will have a weak pulse but an extremely rapid heart rate.
Breathing will become be very fast and difficult. Systolic blood pressure will be under 70 mm/Hg. They may experience the following symptoms:
- drifting in and out of consciousness
- sweating heavily
- feeling cool to the touch
- looking extremely pale
A major cause of hypovolemic shock can be acute blood loss. The term hemorrhagic shock refers specifically to this type of hypovolemic shock. This can occur as a result of an acute tissue injury or because of conditions like internal bleeding or illness.
But, hypovolemic shock can also refer to any major loss of bodily fluid that also results in significant blood loss. Blood plasma is the liquid part of blood that holds red blood cells, white blood cells, and blood platelets. Water makes up 92% of plasma. If a person loses a significant volume of fluid, the plasma part of blood will deplete too.
For this reason, many conditions that are not acute blood loss can lead to a critical reduction in blood volume. Severe burns, persistent diarrhea, vomiting, and even excessive sweating could all be potential causes of hypovolemic shock.
Doctors can identify hypovolemic shock more easily when they can see significant blood loss from an external wound. However, hypovolemic shock often develops as a complication of an underlying medical condition. Internal bleeding may not be obvious from observation and is often hard to control without surgery.
Medical professionals and first responders are trained to recognize the signs of blood loss. However, people should educate themselves on its signs so that they can get help for themselves and others as quickly as possible.
Hypovolemic shock usually occurs as a result of either an illness, injury, or other medical condition. As a result, doctors may find it hard to predetermine specific risk factors. Any risk factors would be the risk of getting a condition that can cause the shock, such as the risk of being severely injured in a car crash or having an aneurysm rupture.
When a person is dehydrated, they lose a significant amount of water volume. People who are dehydrated can become hypovolemic if they are also losing salt, which can lead to a loss in blood volume.
For this reason, people who are dehydrated, or at risk of becoming dehydrated, should continue to drink fluids, especially if their illness is causing them to experience vomiting or diarrhea. These can lead to further loss of fluids.
A person may not be able to prevent the injuries or illnesses that cause hypovolemic shock. However, a person may be able to prevent further complications by rehydrating.
The easiest way for a medical professional to diagnose hypovolemic shock is through observation and examination. A physical exam will show whether the person has low blood pressure, increased heart and breathing rates, and a low body temperature.
Doctors can use blood tests to help support this diagnosis. A blood chemistry test can give some additional clues about the level of salt and electrolytes in the body as well as how the kidneys and liver are functioning. A complete blood count (CBC) can tell how much blood a person has lost.
The following tests or devices can help determine the underlying cause of the hypovolemia or locate a source of internal bleeding:
- a CT scan can give a view of the organs in the body
- an echocardiogram can assess how well the heart fills up with and squeezes blood
- an endoscopy can help find a bleeding source in the gastrointestinal tract
Treating hypovolemic shock means treating the underlying medical cause. Physicians first will try to stop fluid loss and stabilize blood volume levels before more complications develop.
Doctors usually replace lost blood volume with intravenous (IV) fluids called crystalloids. These are liquids with a thin consistency, such as a saline solution. The doctor may also use thicker solutions called colloids.
In the most severe cases, the remaining blood becomes diluted. This can result in low levels of platelets and other blood components that help form clots that stop bleeding. The medical team will replace these components when necessary, especially if the person is still bleeding, through plasma or red blood cell (RBC) transfusions.
After the shock is under control and the blood volume stabilizes, the doctor can treat the underlying illness or injury.
Hypovolemic shock is a life-threatening emergency. A person’s outlook depends heavily on which complications develop while a person is in shock. This can include damage to the kidneys or brain. It is critical that an emergency doctor increases the person’s blood volume quickly to restore blood supply to all organs.
The amount of time it takes to increase the blood volume can depend on:
- the stage of shock
- the rate of blood loss
- the extent of blood loss
- any underlying medical conditions, such as heart disease or taking blood thinners
Hypovolemic shock and older adults
Older adults are particularly at risk of getting hypovolemic shock because they can be more susceptible to dehydration, which can trigger hypovolemia. They also do not tolerate having a low blood volume well.
The risk of complications increases with age, especially if other conditions have already caused organ damage such as kidney failure or a heart attack.
It is especially important that older adults receive prompt treatment as soon as they, or individuals near them, recognize any signs of hypovolemic shock.
Hypovolemic shock is a medical emergency in which blood volume drops to a dangerous level. It occurs when the body loses excessive amounts of water and salt. The condition has four stages. By the fourth stage, a person’s condition becomes critical.
Treatment for this type of shock involves replacing fluids in the body, usually with a saline solution. However, treatment is difficult and the condition usually carries a high risk of death. The best way to stabilize the condition is to spot symptoms as early as possible and to seek prompt medical treatment.
Three goals exist in the emergency department treatment of the patient with hypovolemic shock as follows: (1) maximize oxygen delivery - completed by ensuring adequacy of ventilation, increasing oxygen saturation of the blood, and restoring blood flow, (2) control further blood loss, and (3) fluid resuscitation. Also, the patient's disposition should be rapidly and appropriately determined.
The patient's airway should be assessed immediately upon arrival and stabilized if necessary. The depth and rate of respirations, as well as breath sounds, should be assessed. If pathology (eg, pneumothorax, hemothorax, flail chest) that interferes with breathing is found, it should be addressed immediately. High-flow supplemental oxygen should be administered to all patients, and ventilatory support should be given, if needed. Excessive positive-pressure ventilation can be detrimental for a patient suffering hypovolemic shock and should be avoided.
Two large-bore IV lines should be started. The Poiseuille law states that flow is inversely related to the length of the IV catheter and directly related to its radius to the fourth power. Thus, a short large-caliber IV catheter is ideal; the caliber is much more significant than the length. IV access may be obtained by means of percutaneous access in the antecubital veins, cutdown of saphenous or arm veins, or access in the central veins by using the Seldinger technique. If central lines are obtained, a large-bore single-lumen catheter should be used. Intraosseous access has and continues to be used for hypotensive children younger than 6 years. Intraosseous access has also been used in hypotensive adults. [3] The most important factor in determining the route of access is the practitioner's skill and experience.
Placement of an arterial line should be considered for patients with severe hemorrhage. For these patients, the arterial line will provide continuous blood pressure monitoring and also ease arterial blood gas testing.
Once IV access is obtained, initial fluid resuscitation is performed with an isotonic crystalloid, such as lactated Ringer solution or normal saline. An initial bolus of 1-2 L is given in an adult (20 mL/kg in a pediatric patient), and the patient's response is assessed.
If vital signs return to normal, the patient may be monitored to ensure stability, and blood should be sent for typed and cross-matched. If vital signs transiently improve, crystalloid infusion should continue and type-specific blood obtained. If little or no improvement is seen, crystalloid infusion should continue, and type O blood should be given (type O Rh-negative blood should be given to female patients of childbearing age to prevent sensitization and future complications).
If a patient is moribund and markedly hypotensive (class IV shock), both crystalloid and type O blood should be started initially. These guidelines for crystalloid and blood infusion are not rules; therapy should be based on the condition of the patient.
In a double-blind randomized clinical trial involving 294 severe trauma patients, investigators found that 3% hypertonic saline solution (HSS) was safe and effective in the resuscitation of patients with hypovolemic shock. Results showed that 3% and 7.5% HSSs quickly restored mean arterial pressure and led to the need for an approximately 50% lower total fluid volume compared with the lactated Ringer’s solution (LRS) group (P < 0.001). [4]
The position of the patient can be used to improve circulation; one example is raising the hypotensive patient's legs while fluid is being given. Another example of useful positioning is rolling a hypotensive gravid patient with trauma onto her left side, which displaces the fetus from the inferior vena cava and increases circulation. The Trendelenburg position is no longer recommended for hypotensive patients, as the patient is predisposed to aspiration. In addition, the Trendelenburg position does not improve cardiopulmonary performance and may worsen gas exchange.
Autotransfusion may be a possibility in some patients with trauma. Several devices that allow for the sterile collection, anticoagulation, filtration, and retransfusion of blood are available. In the trauma setting, this blood almost always is from a hemothorax collected by means of tube thoracostomy.
Control of further hemorrhage depends on the source of bleeding and often requires surgical intervention. In the patient with trauma, external bleeding should be controlled with direct pressure; internal bleeding requires surgical intervention. Long-bone fractures should be treated with traction to decrease blood loss.
In the patient whose pulse is lost in the ED or just prior to arrival, an emergency thoracotomy with cross-clamping of the aorta may be indicated to preserve blood flow to the brain. This procedure is palliative at best and requires immediate transfer to the operating room.
In the patient with GI bleeding, intravenous vasopressin and H2 blockers have been used. Vasopressin commonly is associated with adverse reactions, such as hypertension, arrhythmias, gangrene, and myocardial or splanchnic ischemia. Therefore, it should be considered secondary to more definitive measures. H2 blockers are relatively safe but have no proven benefit.
Somatostatin and octreotide infusions have been shown to reduce gastrointestinal bleeding from varices and peptic ulcer disease. These agents possess the advantages of vasopressin without the significant side effects.
In patients with variceal bleeding, use of a Sengstaken-Blakemore tube can be considered. These devices have a gastric balloon and an esophageal balloon. The gastric one is inflated first, and then the esophageal one is inflated if bleeding continues. The use of this tube has been associated with severe adverse reactions, such as esophageal rupture, asphyxiation, aspiration and mucosal ulceration. For this reason, its use should be considered only as a temporary measure in extreme circumstances.
Virtually all causes of acute gynecological bleeding that cause hypovolemia (eg, ectopic pregnancy, placenta previa, abruptio placenta, ruptured cyst, miscarriage) require surgical intervention.
Early consultation and definitive care are the keys. The goal in the ED is to stabilize the hypovolemic patient, determine the cause of bleeding, and provide definitive care as quickly as possible. If transfer to another hospital is necessary, resources should be mobilized early.
In patients with trauma, if the emergency medical services personnel indicate potential serious injury, the surgeon (or trauma team) should be notified prior to the patient's arrival. In a 55-year-old patient with abdominal pain, for example, emergency ultrasonography of the abdomen may be necessary to identify an abdominal aortic aneurysm before the vascular surgeon is notified. Every patient should be individually evaluated, because delaying definitive care can increase morbidity and mortality.
Whether crystalloids or colloids are best for resuscitation continues to be a matter for discussion and research. Many fluids have been studied for use in resuscitation; these include isotonic sodium chloride solution, lactated Ringer solution, [5] hypertonic saline, albumin, purified protein fraction, fresh frozen plasma, hetastarch, pentastarch, and dextran 70.
Proponents of colloid resuscitation argue that the increased oncotic pressure produced with these substances decreases pulmonary edema. However, the pulmonary vasculature allows considerable flow of material, including proteins, between the intravascular space and interstitium. Maintenance of the pulmonary hydrostatic pressure at less than 15 mm Hg appears to be a more important factor in preventing pulmonary edema.
Another argument is that less colloid is needed to increase the intravascular volume. Studies have shown this to be true. However, they still have not demonstrated any difference in outcome with colloids compared with crystalloids.
Synthetic colloid solutions, such as hetastarch, pentastarch, and dextran 70, have some advantages compared with natural colloids such as purified protein fraction, fresh frozen plasma, and albumin. They have the same volume-expanding properties, but because of their structures and high molecular weights, they remain mostly in the intravascular space, reducing the occurrence of interstitial edema. Although theoretic advantages exist, studies have failed to show a difference in ventilatory parameters, pulmonary function test results, days using a ventilator, total hospital days, or survival.
The European Society of Intensive Care Medicine (ESICM) advises against the use of colloids-hydroxyethyl starches (HES) in patients with severe sepsis or risk of acute kidney injury. Physicians should also avoid using colloids in patients with head injury and refrain from administering gelatins and HES in organ donors. [6]
The combination of hypertonic saline and dextran also has been studied because of previous evidence that it may improve cardiac contractility and circulation. Studies in the US and Japan have failed to show any difference when this combination was compared with isotonic sodium chloride solution or lactated Ringer solution. Thus, despite the many available resuscitation fluids, current recommendations still advocate the use of normal saline or lactated Ringer solution. In the US, one reason for the predominant use of crystalloids over the other resuscitative fluids is cost.
Recent literature suggests that the early administration of FFP and platelets improves survival and decreases overall PRBC need in patients undergoing a massive transfusion. [7]
During World War I, Cannon observed and characterized patients in clinical shock. He later suggested a model of permissive hypotension in the treatment of torso wounds, with the intent of minimizing further bleeding.
Findings from early studies showed that animals that were bled had increased survival if they received fluid resuscitation. However, in these studies, bleeding was well controlled with ligation after the animals were bled.
During the Korean and Vietnam wars, much more aggressive fluid resuscitation, as well as rapid access to definitive care, was emphasized. It was noted that patients who were aggressively resuscitated tended to have better outcomes, and in the 1970s, these principles were widely adopted in civilian patients.
Since then, many studies have been conducted to determine if these principles are valid in patients with uncontrolled hemorrhage. Most of these studies revealed increased survival in the permissive hypotension or delayed treatment arms. The theory is that increased pressure causes more bleeding and disrupts initial clots, whereas extreme hypotension may increase the risk of cerebral perfusion.
The questions that have not been answered adequately are as follows: Which mechanisms and injury patterns are more amenable to the restoration of circulating blood volume? What BP is adequate but not excessive?
Although some data indicate that a systolic BP of 80-90 mm Hg may be adequate in penetrating truncal trauma without head injury, further studies are needed.
Current recommendations are for aggressive fluid resuscitation with lactated Ringer solution or normal saline in all patients with signs and symptoms of shock, regardless of underlying cause.