Blood pressure and edema, a type of swelling that occurs when fluid leaks into the interstitial spaces of the body, are closely linked. Both high and low blood pressure can contribute to edema, as well as being associated with it, and treatment of edema can involve controlling blood pressure. People can limit their risks of developing edema by keeping their blood pressure in a healthy range. People at risk for edema, such as pregnant women and people with heart failure, should be alert for the signs so they can receive treatment as quickly as possible.
There are a number of reasons why fluid may leak out of the blood vessels and into the interstitial space. Vessels can become weakened, forcing fluid out, and an imbalance of salts in the body can cause fluid to be pulled out of the vessels as the body attempts to return to an isotonic state, where the balance of salts on both sides of the blood vessels is the same. High and low blood pressure are both linked with damage to the blood vessels and the development of imbalances in the composition of bodily fluids.
In the case of high blood pressure and edema, the high blood pressure causes the blood vessels to leak, leading to localized edema. The fluid loss causes the kidneys to retain more fluid as they work to maintain the needed balance of salts in the body fluids. This makes the edema worse, as the excess fluid will continue leaking out of the damaged vessels and more fluid will be retained to replace it. People with high blood pressure, also known as hypertension, can develop edema anywhere in the body and are at risk of a dangerous form called pulmonary edema.
Low blood pressure can also be linked with edema. People with certain chronic conditions exposing them to the risk of edema can also have low blood pressure. Circulatory conditions can lead to edema by allowing blood and fluids to pool in the extremities, and low blood pressure makes it hard for the body to circulate blood effectively to clear the fluid. In pregnancy, edema often appears in the legs due to reduced blood pressure in the blood vessels in the legs caused by pressure on the blood vessels from the swelling uterus.
Edema is sometimes the first sign of an underlying medical condition. People with high blood pressure and edema may be prescribed medications to reduce their blood pressure and can take other steps to moderate their blood pressure as well. Compression garments can be used in the treatment of the edema. Individuals with low blood pressure and edema will need treatment for the underlying cause of the low blood pressure.