Postoperative fever is an abnormally high temperature that follows after a surgical operation. Although it may be due to infection, often the temperature appears to occur in the absence of infection, and is a heightened inflammatory response to the stresses of surgery. Other causes include damage to blood vessels and lung problems, and altogether, the fever is a common occurrence in surgical patients. Commonly, a postoperative fever that is not due to infection resolves itself within two days of the surgery.
Although definitions of postoperative fever may vary according to the health authorities in different areas, a typical example of the definition of a postoperative fever is a temperature of above 100° F (about 38° C) over two days straight. Alternatively, a patient may still have the diagnosis if he or she has a temperature above 102° F (about 39° C) over only one day. The presence of these high temperatures, compared to a normal human temperature of 98.6° F (37° C) indicates that the body is running an inflammatory response orchestrated by the immune system.
Inflammation and high temperature are part of the immune response to microbial infection, and they can also be present when microbes are not invading the body. A postoperative fever is very common after surgery, and does not always pose a serious risk to the patient. Sometimes, though, the cause of the fever may be potentially life-threatening, such as an infection or a blood clot.
Commonly, a fever that occurs after surgery and then disappears within two days is not caused by an infection. Patients with this type of postoperative fever tend to be in the majority. When a patient still has a fever when three days have passed, the doctor then typically looks for more serious causes than the short-term inflammatory response to surgery.
Microbial pathogens can infect the site of the incision made for surgery, or affect sites inside the body that were involved in the surgery. If the person also has to use a catheter, which is a tube inserted into the body, microbes can infect the catheter and the insertion site. If the infection grows and gets into the bloodstream, the patient is under a significant risk of death. If a postoperative fever lasts for three days and continues, the doctor may take samples for microbiological testing to look for infectious pathogens.
Some serious cases of postoperative fever stem not from infections but rather from other forms of damage to the body. Atelactasis is a condition where the areas of the lungs that swap new air for old carbon dioxide collapse, and cannot perform their job anymore. The blood vessels may also break, or the blood may clot abnormally, producing potentially dangerous conditions such as blood clots and hematomas. Fever after surgery is monitored to ensure none of these dangerous causes of high temperature are present.