This patient most likely has inflammation of tissues near the wound. Inflammation consists of five classical signs: pain (dolor), swelling (tumor), heat (calor), redness (rubor), and loss of function (functio laesa). The damaging of tissue cells causes the release of vasoactive amines (histamine and serotonin). The main function of histamine and serotonin in the peripheral tissues is the dilation of vessels and increased permeability of blood vessels. This causes plasma to move from vessels into the extracellular space in tissue. Increasing the amount of fluid in the extracellular space causes edema (swelling). During inflammation there are other mediators which have their specific function: for example, bradykinin increases the sensitivity to pain. Acetylcholine, dopamine, and heparin do not take part in the common inflammation process.