What is Hypovolemic Shock?
Hypovolemic shock is a very serious condition that could be life-threatening if not treated promptly. It happens when the body loses a high amount of blood or fluids, which can lead to a severe drop in blood pressure and a decrease in the amount of oxygen reaching the tissues. Known as tissue hypoperfusion and tissue hypoxia, this can cause serious damage if not corrected. If hypovolemic shock is not treated, it can cause severe damage to vital organs and ultimately lead to failure of multiple organs.
Quickly recognizing and treating this condition can literally save a life. Treatment typically involves replenishing the body’s fluid levels to normal, often referred to as restoring euvolemia. Once doctors figure out what caused the severe fluid or blood loss that led to the hypovolemic shock, they will immediately start fluid replacement therapy, while also trying to control the source of the loss. The speed and type of fluid replacement depends on a few factors, such as the patient’s condition.
What Causes Hypovolemic Shock?
Shock is a condition in which there’s not enough blood flow to the body’s tissues, leading to a lack of oxygen and harm to the cells. There are four main types of shock, but they all result in this same basic problem. These types are distributive shock, hypovolemic shock, cardiogenic shock, and obstructive shock.
Distributive septic shock, which is a severe infection that leads to low blood pressure, is the most common type seen in adults who are brought to the emergency department and intensive care unit. However, in children, especially in developing countries, the most common type is hypovolemic shock. This is usually caused by severe dehydration from diarrhea.
Hypovolemic shock itself can be broken down into two categories: hemorrhagic, which is caused by heavy bleeding, and non-hemorrhagic, which is due to a loss of body fluids. Traumatic injuries are the most common cause of hemorrhagic shock, but it can also be caused by bleeding from the digestive and urinary systems, or after surgery.
On the other hand, non-hemorrhagic hypovolemic shock can be caused by various factors:
Losses from the Digestive System: This is the most common source. The digestive tract secretes around 3-6 liters of fluid a day, but only 100-200 mL of this is typically lost to stool since most gets reabsorbed. When more fluid is lost than is reabsorbed, such as from vomiting, diarrhea, or a blockage in the bowel, it can lead to this type of shock.
Losses from the Kidneys: The kidneys usually release salt and water from the body in an amount that’s equal to what’s being taken in. However, if too much is lost due to diuretic medication, high blood sugar, or certain kidney diseases, it can lead to this type of shock.
Losses from the Skin: If a great deal of fluid is lost through the skin, such as through sweating in a hot and dry climate, or from burns or other skin wounds, it can also result in this type of shock.
Sequestration of Fluid: This refers to fluid being trapped in an area where it can’t be used by the body, resulting in a type of shock. This is common in certain conditions that cause a severe inflammatory response, such as pancreatitis or intestinal obstruction.
Risk Factors and Frequency for Hypovolemic Shock
Hypovolemic shock, which is a condition caused by the severe loss of body fluids, often occurs from non-hemorrhagic sources. However, hemorrhagic shock, which is caused by excessive bleeding, usually results from trauma. In fact, a study found that 62.2% of large blood transfusions at a top-tier trauma center were due to injuries. Of all the blood products used in this study, 75% were linked to traumatic injuries. It’s important to note that older people are more susceptible to hypovolemic shock since they have a lower capacity to compensate for the loss of body fluids.
Signs and Symptoms of Hypovolemic Shock
Hypovolemic shock can often be diagnosed through a patient’s history and a physical examination. A patient with hypovolemic shock may have a history of trauma, severe bleeding, or recent surgeries. In cases of non-bleeding hypovolemic shock, which is due to fluid loss, it’s important to investigate potential causes such as gastrointestinal issues, kidney problems, open wounds, skin conditions, or ‘third-spacing’ – a term which refers to a situation where fluid moves out from the normal blood circulation into other spaces in the body. Symptoms of hypovolemic shock can be related to loss of fluid volume, imbalances in body salts or electrolytes, or issues with the body’s acid-base balance.
Those dealing with fluid volume depletion may experience thirst, muscle cramps, and low blood pressure upon standing up quickly. In severe instances of hypovolemic shock, individuals may also experience intestinal and heart issues leading to abdominal or chest pain. In addition, the brain’s lack of an adequate blood supply can cause agitation, tiredness, or confusion.
While a physical exam may not be entirely specific or sensitive, it can still indicate possible hypovolemic shock. Some physical signs of volume depletion might include dry mouth and throat, saggy skin, and low jugular vein distention. Additional cues may include rapid heartbeat, low blood pressure, and decreased urine output. Shocked patients may look cold, with a pale or bluish skin tone and a clammy feel to the skin. Despite experiencing shock, blood pressure may initially appear normal or elevated. But as the effective circulating blood volume decreases, low blood pressure and rapid heart rate can ensue, accompanied by a reduction in venous blood pressure in the chest, an increase in vascular resistance, and a decrease in the amount of blood the heart pumps.
Testing for Hypovolemic Shock
When a patient suffers from hypovolemic shock, which is a condition where the body loses more than 20% of its blood or fluid supply, certain laboratory values can be abnormal. Some things that can change include increased BUN (a waste product created by your kidneys) and serum creatinine levels which may indicate kidneys not functioning as they should. The patient may have high or low levels of sodium and potassium in the blood, conditions known as hypernatremia or hyponatremia, and hyperkalemia or hypokalemia respectively.
Lactic acidosis, a condition caused by a build-up of lactic acid in the body, is another abnormality that could be detected. However, depending on the specific situation, patients could either become more alkalotic (higher pH level, less acidity) or more acidic. For example, in cases of severe blood loss (called hemorrhagic shock), the patient’s hematocrit (the proportion of red cells to total blood volume) and hemoglobin levels (a protein responsible for carrying oxygen in the blood) can be critically low. But, ironically, these levels can also be higher due to hemoconcentration, a condition where your blood has a higher concentration of cells and proteins because of lost fluid.
Hypovolemic patients typically have low urinary sodium because their kidneys try to hold onto as much sodium and water as possible to maintain body’s fluid balance. However, this might also be seen in patients with heart failure, liver cirrhosis, or nephrotic syndrome (a kidney disorder that causes your body to excrete too much protein). An elevated urine osmolality (a measure of urine concentration) can also suggest hypovolemia but this can also be a result of the kidney’s impaired ability to concentrate urine.
Central venous pressure (CVP), a measurement of the blood pressure in the vena cava (the large vein that carries blood from the body back to the heart), is often used to check a patient’s fluid status. However, its reliability has recently been questioned as factors like the position of the central venous catheter (a tube placed into a patient’s large vein), ventilator settings, chest wall’s ability to stretch and recoil, and right-sided heart failure can all affect its accuracy.
Other measurements, like the variation in pulse pressure or respiratory variation in inferior vena cava diameter, are sometimes used, but their effectiveness is variable and subject to certain limitations. For example, these measurements are only accurate for patients without spontaneous breaths or irregular heartbeats. Also, certain conditions like right heart failure, decreased lung or chest wall compliance, and high respiratory rates can compromise their accuracy. An effect of passive leg raises on heart’s pumping ability as measured by an echocardiogram (an ultrasound of the heart) seems to be the most reliable measurement of fluid status, but it too has limitations.
Treatment Options for Hypovolemic Shock
Before starting treatment for shock, it’s essential to identify what type of shock the patient is experiencing. Sometimes, identifying the specific shock type can be challenging and is referred to as undifferentiated shock. For patients experiencing shock due to low blood volume (hypovolemic shock), it’s vital to determine whether it’s due to blood loss (hemorrhagic) or other causes (non-hemorrhagic) as this dictates the treatment approach.
For patients with hemorrhagic hypovolemic shock, immediate steps need to be taken to control bleeding and replenish blood volume. This could involve an endoscopic or surgical procedure, or frequently, a procedure conducted by an interventional radiologist who uses imaging equipment to guide treatments. Studies have shown that replacing blood loss with blood products rather than alternative solutions improves patient outcomes. The process might also include anti-fibrinolytic medicine given to patients with severe bleeding within three hours of a traumatic injury to decrease major bleeding.
Research is currently going on for finding oxygen-carrying substitutes as an alternative to red blood cells. However, these blood substitutes haven’t been used in the United States yet.
In case of non-hemorrhagic hypovolemic shock, it’s important to start treating the patient by restoring the blood volume as soon as possible. Sometimes it’s hard to determine the exact type of fluid lost, so it’s smart to start with a warm isotonic crystalloid solution (a solution with the same concentration as the body’s cell contents). This solution can be given quickly to restore tissue function. And based on the patient’s response, this could be repeated.
Vasopressors (medications that narrow blood vessels) shouldn’t be used for hypovolemic shock because they can make tissue perfusion (the process of delivering blood to the body’s tissues) worse. However, in the initial phase of treatment, they can be used to help restore the blood volume.
When treating severe loss of body fluids not due to bleeding, it’s preferred to use crystalloid fluids (like saline or lactated Ringer’s solution) over colloid solutions (like albumin or starch). Depending on the patient’s needs, the type of crystalloid used can be chosen based on their lab results, the estimated fluid required for resuscitation, their acid/base balance, and the physician’s preferences.
An important note is that if large amounts of normal saline are used, it can lead to a type of metabolic acidosis (an imbalance in the body’s acid/base balance). So, fluids with lower chloride concentrations, like lactated Ringer’s solution, might be chosen. These solutions are known as buffered or balanced crystalloids. Some studies suggest that patients who need a lot of fluid might have less kidney damage if they’re given balanced crystalloids.
While albumin solutions were once used for resuscitation, studies haven’t shown an improvement in patient outcomes. And, they’ve shown that starch solutions could actually lead to increased death rates and kidney failure.
What else can Hypovolemic Shock be?
Distributive shock is a type of medical condition where the blood vessels become too dilated (vasodilatory), causing issues with blood flow. It’s often seen in patients with septic shock, which is the most common type of shock. It generally can be differentiated from hypovolemic shock (shock due to blood loss) because it doesn’t cause a decrease in the resistance of peripheral blood vessels. Neurogenic shock, usually seen after a high spinal injury, is another form of distributive shock. The main difference between distributive shock and hypovolemic shock is that the latter shows an increase in peripheral vascular resistance.
Obstructive shock happens when something physically gets in the way of the heart’s output. This could be due to conditions like cardiac tamponade (pressure on the heart due to fluid buildup) or tension pneumothorax (pressure on the lungs due to air buildup). Determining if it’s obstructive shock or hemorrhagic shock (shock due to excessive bleeding) in trauma patients can be difficult because often, they occur together. For doctors, if they find a high Central Venous Pressure (CVP), it’s usually an indicator of obstructive shock.
Cardiogenic shock results when the heart itself fails to pump efficiently, often as a result of a heart attack or blunt injury to the heart. Unlike in hypovolemic shock, here we see an increased CVP along with increased resistance in peripheral blood vessels.
In certain cases, the type of shock is not immediately clear to doctors. This is referred to as undifferentiated shock. It could potentially involve a mixture of all of the above shock types.
What to expect with Hypovolemic Shock
The chances of getting better from hypovolemic shock, a condition characterized by severe loss of blood or fluids, heavily depend on its cause and seriousness. Swift control of the bleeding source and immediate fluid replacement have led to better results for those suffering from bleeding-related hypovolemic shock.
However, if patients with this condition progress into a state of Multiple Organ Failure (MOF) – where several major organs stop working properly – their situation may deteriorate, and the risk of death increases. Older individuals or those with pre-existing health conditions generally have poorer outcomes.
Possible Complications When Diagnosed with Hypovolemic Shock
The main concern with hypovolemic shock, a condition caused by a rapid loss of blood or body fluids, is circulatory failure. This means the heart can’t pump enough blood to the body, which can lead to Multiple Organ Failure (MOF) and even death. There are other complications, too, but these mainly result from the treatments used. For example, an excess of fluids in the bloodstream (circulatory overload), increased pressure in the abdomen, and reactions related to the transfusion of blood or blood products can happen. On top of that, there can also be complications arising from surgical procedures and radiology interventions.
Potential Complications:
- Circulatory failure leading to MOF and death
- Complications from treatment procedures like circulatory overload
- Increased pressure in the abdomen
- Reactions related to blood transfusion
- Complications resulting from surgeries and radiological procedures
Preventing Hypovolemic Shock
Hypovolemic shock is a condition that happens when a person loses a dangerous amount of blood or fluids. This is serious because if the affected person doesn’t receive treatment soon enough, there may be less oxygen carried to vital cells and organs in the body. If this happens, organs can fail, and in worst-case scenarios, it might cause death.
