What occurs during extravasation?

During extravasation, fluid escapes from the vein into the surrounding tissue. This phenomenon typically occurs when intravenous fluid administration or injections fail to remain within the vascular system, often due to a breach in the vessel wall or when the needle is not properly placed within the vein. As a result, fluid, which may include medications, blood, or other substances, leaks into the surrounding interstitial space. This can lead to swelling, discomfort, and in some cases, tissue damage depending on the nature of the extravasated material.

In contrast, the other options describe different processes that do not accurately reflect what happens during extravasation. For instance, fluid entering the vein after injection pertains to the normal function of a correctly administered intravenous injection, while fluid building up in a blood vessel could refer to conditions such as thrombosis rather than extravasation. Lastly, fluid being absorbed directly by muscles does not depict the mechanism of fluid escaping from a vascular space, as it implies a direct absorption process rather than leakage.