Intravenous fluids are fluids which are intended to be administered to a patient intravenously, directly through the circulatory system. These fluids must be sterile to protect patients from injury, and there are a number of different types available for use. Many companies manufacture packaged intravenous fluids, as well as products which can be mixed with sterile water to prepare a solution for intravenous administration.
Fluids are given when someone's fluid volume falls. There are a number of things which can cause a drop in fluid volume. Vomiting and diarrhea are a classic example, which is why people are encouraged to drink fluids when they are sick, to keep their fluid volume stable. Another cause is blood loss, which causes problems both because people lose blood products, and because they experience a loss in fluid volume. Electrolyte levels in the blood can also become unstable as a result of rapid changes in fluid volume, in which case IV fluids can be used to restore the balance.
Intravenous fluids can be broken into two broad groups. Crystalloids such as saline solutions contain a solution of molecules which can dissolve in water. When crystalloids are administered, they tend to create low osmotic pressure, allowing fluid to move across the blood vessels, and this can be linked with edema. Colloids contain particles which are not soluble in water, and they create high osmotic pressure, attracting fluid into the blood vessels. Blood is an example of a commonly administered intravenous colloid.
Changes in fluid volume can cause changes in blood pressure, and a series of cascading reactions in the body. However, IV fluids are not always the solution. If the wrong fluid is administered, too many fluids are given, or a patient is not monitored, giving fluids can actually make the situation worse. For example, a patient may develop severe edema which can take some time to resolve as the body tries to express the excess water.
Intravenous fluids can also be used as a route of medication administration. If a doctor wants to deliver a small amount of medication over an extended period of time, it can be dissolved in a bag of intravenous fluids and set on an infusion pump which delivers the medicated fluid directly into the blood. They are also commonly used to assist with surgical recovery; people who receive fluids after surgery tend to experience better recovery than people who do not.