When you lose blood or other fluids from your body, the amount of blood left circulating, known as your blood volume, is less. Hypovolemic shock happens when a sudden and significant loss of blood or body fluids drops your blood volume.
It's always considered a life-threatening emergency. Blood helps to hold your body temperature steady, forms blood clots, and moves oxygen and nutrients to all of your body's cells. If your blood volume gets too low, your organs won't be able to keep working.
Hypovolemic shock is most often the result of blood loss after a major blood vessel bursts or from a serious injury. This is called hemorrhagic shock. You can also get it from heavy bleeding related to pregnancy, from burns, or even from severe vomiting and diarrhea.
Injuries from a deep cut or hard impact as well as illnesses could lead to hypovolemic shock. These include:
- Broken bones around your hips
- Cuts on your head
- Damage to organs in your belly, including your spleen, liver, and kidneys, because of a car accident, bad fall, or other trauma
- A tear in your heart or a large blood vessel, or a weakened spot in a large blood vessel that could burst
- Problems with your digestive tract, such as ulcers
During labor, delivery, or within the following 24 hours, a woman may bleed heavily. It can also happen if the placenta peels away from the wall of the uterus before a baby is born, or if a cyst ruptures.
Ectopic pregnancies are also dangerous. When an embryo outside of the uterus gets too large, it can damage organs and cause heavy internal bleeding.
Extensive burns can damage blood vessels and lead to fluid loss.
One of the most serious complications of dehydration is hypovolemic shock. Severe diarrhea and vomiting can cause it, especially in small children or older adults. It's also possible from having a high fever or extreme sweating.
What hypovolemic shock looks and feels like can vary greatly depending on:
- Your age
- Your past medical care and general health
- The cause of the shock or the source of the injury
- How quickly you lost the blood or fluids
- How much your blood volume has dropped
With an injury, the most obvious symptom of hypovolemic shock is a lot of bleeding. But you won't see blood loss when the bleeding is internal, perhaps from an aortic aneurysm, organ damage, or ectopic pregnancy.
Other signs of hypovolemic shock include:
How Much Blood Loss Is Too Much?
You may lose up to 15% of your total blood volume -- roughly a little less than a quart for an adult -- and likely won't have any serious symptoms.
Once you've lost more than that, though, your remaining blood starts getting pulled away from your skin, muscles, and guts and sent to vital organs including your heart and brain. Your heart will beat faster, trying to keep the blood moving. You may have a weak pulse and pale, cool, clammy skin.
When you lose between 30% and 40% of your blood volume -- around a half-gallon -- your blood pressure will drop, you'll breathe fast, and you may get confused or flustered.
When you've lost more than 40% of your blood volume, your organs will stop working properly. You likely won't have any pee. Your other symptoms will get worse, and you may pass out. If your blood volume isn't restored quickly, you could die.
A nurse or doctor will check your temperature, pulse, breathing, and blood pressure. They'll check the color and feel of your skin. If you're awake and alert, they'll ask you about your past medical issues and questions to find out more about what's going on.
Although you'll get your blood pressure taken, it's not always a reliable way to tell if you're in shock. Most people won't have a lower top number of their blood pressure until they've lost more than 30% of their total blood volume.
If a woman could be in shock because of an ectopic pregnancy or something else related to her reproductive parts, the health care workers will also run a pregnancy test and find out about her last menstrual period and any recent vaginal bleeding.
The first step is to get you to the emergency room as quickly as possible. Along the way, someone should try to stop any visible bleeding.
In the emergency room or hospital, the goals are to:
- Get as much oxygen as possible to all parts of your body
- Stop, or at least control, blood loss
- Replace blood and other fluids
Everyone in hypovolemic shock gets fluids through an IV, a bag of liquid attached to a needle that goes directly into a vein. Most people who lose more than 30% of their blood volume will also need a blood transfusion. Many will need some kind of surgery, too, especially if they have internal or gynecological bleeding.
The outcome depends on how serious your condition is when you start treatment, how quickly blood and fluids are replaced, and whether you have any other issues or complications.