Hypovolemia is a medical condition characterised by low levels of blood or water in the body. Hypo means below or less, and volemia means volume. Hence, the term hypovolemia represents the depletion of body fluid volume.
The human brain needs a continuous blood supply for normal functioning.1 When there's a reduction in blood volume, insufficient blood supply to both the heart and brain results in lethargy, dizziness, fatigue, low blood pressure, and fainting in some cases.
Causes of hypovolemia
Hypovolemia occurs when the body loses fluid like blood or water. Some of the following conditions can disturb the normal fluid balance and result in hypovolemia:
- Water deficiency: About 51% of human blood is water, so water deficiency or dehydration reduces the volume of the blood, resulting in hypovolemia
- Excessive Sweating: Physical activity and hot weather conditions cause intense sweating, which results in fluid deficiency. About 99% of the sweat is water; consequently, sweating leads to low blood volume2
- Medical conditions: Some people sweat more than others because of certain medical conditions like hyperactive thyroid glands, which result in a significant loss of salt and water. Diarrhoea and vomiting can also cause you to lose a lot of fluids, making you feel weak, dizzy, and tired
- Small or large intestines obstruction: Occlusion or obstruction within bowel (intestine) cavities leads to swelling, abdominal pain, vomiting, diarrhoea, and colon distension.3 This results in excessive fluid loss, which causes dehydration and volume depletion
- Bleeding: Severe bleeding due to injury or car/motor accident results in a reduced circulating blood volume. The situation eventually leads to hypovolemic shock, in which organs stop functioning due to a lack of blood supply
- Medications: Drugs, such as diuretics, increase urine output, which leads to fluid deficiency and low blood circulation volume. If you are using diuretics regularly, consult your doctor when you experience side effects such as vomiting, diarrhoea, and dehydration4
- Inflammation: It is your body's natural defence against injuries and infections. When harmful bacteria or pathogens invade your body, your immune system reacts and widens the pores of your blood vessels. This causes blood to leak into surrounding areas, reducing the amount of blood in your vessels and causing symptoms of hypovolemia5
Signs and symptoms of hypovolemia
Clinical symptoms consistent with hypovolemia are hypotension (low blood pressure) and increased heart rate. You may also experience the following symptoms:
- Pallor (pale skin)
- Increased thirst
- Decreased urine output
- Impaired consciousness
- Muscle cramps
- Increased heartbeat
- Dry mouth
If the situation progresses to hypovolemic shock, you may experience loss of consciousness6
Management and treatment of hypovolemia
Management of hypovolemia begins with fluid administration, known as fluid resuscitation. Treatment is initiated after diagnosing the root cause.
Clinical practice suggests managing the symptoms of hypovolemic patients with the immediate administration of intravenous (IV) fluids by drip. The following fluids can be administered via the IV route:
Normal Saline: It is a solution consisting of 0.9% salt dissolved in water. It means that 0.9 grams of salt (sodium chloride) is added to 100 ml of water to match the salt concentration in human body fluids. Normal saline is commonly used as a fluid treatment for dehydration or as the initial approach for patients with hypovolemia. Typically, patients receive up to one litre of sodium chloride solution per day. However, if more than one litre per day is necessary, it's vital for healthcare professionals to continuously monitor the patient.7
Dextrose: It is a solution consisting of 5% glucose dissolved in water. Unlike normal saline, it is ineffective in replacing the circulating volume of plasma/blood. Thus, it is not recommended for initial management of hypovolemia. In addition, dextrose is contraindicated in patients with diabetes or increased blood glucose levels.
Ringer Lactate: It is a solution that includes a mixture of different salts dissolved in water. It contains sodium, potassium, chloride, calcium, and lactate. It is administered for patients with severe blood volume loss due to conditions such as sepsis or severe bleeding.
However, patients with heart, kidney, or liver problems are at risk of developing side effects. Therefore, continuous monitoring of those patients receiving ringer lactate by the healthcare team is important.8
After managing the patient with IV fluids, the underlying cause of hypovolemia is treated.
- In cases of blood volume loss caused by sepsis, antimicrobial agents are administered via the IV route
- For patients experiencing fluid deficiency due to injuries or accidents, blood transfusions are given to replace the lost blood cells and platelets9
- In the event of fluid loss due to severe vomiting and diarrhoea, antidiarrheals or antiemetics are recommended after initial fluid management to prevent further fluid loss
- Diuretics are commonly used by patients with heart conditions and hypertension (high blood pressure). However, if a patient starts to exhibit symptoms of hypovolemia, discontinuing diuretics is advisable10
- Patients with inflammatory disorders need a combination of anti-inflammatories and antimicrobials to fight infections
Accurate diagnosis by healthcare providers is critical for recovering from hypovolemia.
To determine the primary cause of hypovolemia, your healthcare team will examine your physical symptoms and review laboratory test results.
If you experience weakness, dizziness, fatigue, or loss of consciousness, it may be time to monitor your blood pressure and heart rate. Low blood pressure can sometimes cause dizziness and loss of consciousness in individuals. Moreover, the mouth and nose can also be examined for any abnormal signs. If symptoms such as dry mucous, decreased breathing rate, increased heart rate, low blood pressure, dizziness and pale skin are consistent, laboratory tests are required to confirm the diagnosis further.6
- Sodium blood test: This test includes collecting the blood from the vein to determine the concentration of sodium in the serum
- Sodium urine test: In this test, a urine sample is collected in a bottle to determine the level of sodium in the urine. A low sodium concentration in the urine indicates that hypovolemia does not arise from kidney-related problems. This means that the kidneys are functioning normally, and fluid loss is not due to kidney problems
- Blood urea nitrogen test: This test includes collecting the blood from the vein to measure the amount of urea nitrogen in your blood. It provides important information about kidney performance. Thus, a high blood urea nitrogen level indicates that the hypovolemia is due to a kidney problem, as the kidneys are responsible for removing waste products like urea from your body11
- Hematocrit test: It is a simple test used to measure the percentage of red blood cells in your body. During dehydration, plasma volume decreases and blood density increases, resulting in an abnormally high hematocrit value. However, if hypovolemia is the result of excessive blood loss, the hematocrit value decreases.12 Hence, the underlying cause of hypovolemia can be determined through laboratory tests and reports
How can I prevent hypovolemia?
- The first and foremost recommendation is to stay hydrated by drinking plenty of fluids throughout the day
- Avoid outdoor activities during extreme heat to prevent excessive sweating and dehydration
- Avoid strenuous physical activities in hot weather
- Take precautions to prevent injuries and burns, and seek immediate medical attention if they occur
- Treat infections and illnesses promptly to avoid blood leakage into surrounding areas and the development of hypovolemia
How common is hypovolemia
Hypovolemia is generally more prevalent in people who live in hot climates and engage in intense physical activities. These people are more susceptible to sweating and dehydration.
In addition, people with critical illness are at risk of developing hypovolemia.
Who is at risk of hypovolemia?
People with heart and kidney problems, like cardiac dysfunction (heart malfunctioning) and kidney insufficiency, are more susceptible to hypovolemia. The heart plays a vital role in pumping and maintaining blood volume. When it's pumping efficiency declines, blood accumulates in the heart, causing a shortage of blood volume. Similarly, the kidneys are responsible for returning the necessary amount of water to the bloodstream, with only excess water being excreted as urine. When the kidneys fail to function properly, more water will be lost in the urine.
Moreover, people who encounter sudden injuries or accidents may experience excessive blood loss, making them more susceptible to hypovolemia. Additionally, people undergoing surgery face an elevated risk of developing hypovolemia.
What can I expect if I have hypovolemia?
It depends on the cause and severity of your condition. If symptoms are not treated immediately, the situation can develop into hypovolemic shock.
Hypovolemia requires immediate management with IV fluid, and it is necessary to treat the underlying cause. Failure to do so may result in hypovolemic shock, which may lead to irreversible organ damage.
When should I see a doctor?
The doctor should be immediately consulted during the following emergencies:
- When you experience severe bleeding due to a traumatic injury
- If you notice the development of symptoms of hypovolemic shock. These symptoms include a rapid pulse, fast breathing, dizziness, clammy skin, and possible loss of consciousness
- Persistent vomiting and diarrhoea which can lead to the depletion of fluids and minerals within the body
- While having intense fever as a result of an underlying infection or inflammation
Hypovolemia is a serious medical condition that can progress into hypovolemic shock if left untreated. People with heart or kidney problems, as well as individuals exposed to hot weather, are at a higher risk of developing hypovolemia. Healthcare providers can promptly manage the patients by giving IV fluid via drip, followed by a thorough diagnosis to identify and address the underlying cause.
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- Singh S, Kerndt CC, Davis D. Ringer’s Lactate. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 [cited 2023 Jul 10]. Available from: http://www.ncbi.nlm.nih.gov/books/NBK500033/
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