A rise in body temperature following surgery, known as post-operative fever, is common. This elevation occurs because the body is reacting to the stress of the operation and tissue trauma. While concerning, a fever is often a temporary and expected response to the healing process. Understanding this reaction helps distinguish between normal temperature fluctuations and a serious underlying complication requiring medical attention.
The Post-Surgery Fever Timeline
The timing of a temperature increase after surgery is the most informative clue for determining its cause. Medical professionals categorize fever based on when it appears, separating it into “early” and “late” onset. This timeline helps determine if the fever is a physiological reaction to the surgery or the result of a developing infection.
An early fever appears within the first 48 hours and is typically due to non-infectious factors. A late fever, developing after the 48-hour mark, raises a stronger suspicion of an underlying infection or complication.
Non-Infectious Reasons for Early Fever
Fevers occurring during the first two days after surgery are frequently non-infectious. The surgical process causes a generalized inflammatory response, the body’s natural defense mechanism. Tissue manipulation and incision trauma trigger the release of chemical messengers, called pyrogens, which signal the brain to raise the core temperature.
A common cause of early post-operative fever is atelectasis, involving the partial collapse of tiny air sacs in the lungs. This is often due to general anesthesia and shallow breathing. Atelectasis is common in immediate recovery and is managed with deep breathing exercises and mobilization.
Reactions to substances used during the procedure can also trigger an early fever. Patients may react temporarily to blood products or various medications, including certain antibiotics. These non-infectious fevers are self-limiting, resolving as the body clears surgical stress hormones and foreign substances.
Recognizing Signs of Infection
A fever developing 48 hours or more after surgery is more likely to signal a developing infection requiring careful evaluation. Potential sources of infection are often categorized using the “W” mnemonic, which links the timing of the fever to the most probable cause.
The “W” Mnemonic for Late Fever
The mnemonic identifies common sources of infection:
- Wound infection often manifests around the fifth to seventh post-operative day. Signs include increasing redness, warmth, swelling, or foul discharge at the incision site. Pain may also worsen instead of gradually improving.
- Water refers to a urinary tract infection (UTI), common between post-operative days three and five, especially if a urinary catheter was used. Symptoms include a burning sensation during urination, frequent urgency, or lower abdominal pain.
- Wind, in the context of a late fever, points toward pneumonia. This is signaled by a new or worsening cough, shortness of breath, and chest pain.
- Walking relates to deep vein thrombosis (DVT), which usually presents after day five. While DVT may cause a low-grade fever, it is accompanied by swelling, pain, and tenderness in one leg.
- Wonder drugs, or drug-induced fevers, can appear at any point and are identified after other infectious causes have been ruled out.
When to Contact Your Medical Team
Knowing when a fever transitions from routine recovery to a warning sign is important for patient safety. Patients should follow the specific post-operative instructions provided by their surgical team.
A sustained temperature above 101.5°F (38.6°C) is a common threshold that warrants calling the medical team for advice. Additionally, a low-grade fever persisting for more than 24 to 48 hours should be reported, especially if it does not respond to fever-reducing medications.
Any fever accompanied by signs of infection should prompt immediate communication with a healthcare provider, regardless of the temperature reading. These red flag symptoms include a noticeable increase in pain, new or excessive drainage from the surgical site, difficulty breathing, or the inability to urinate. Reporting these details helps the medical team quickly assess the situation and determine if an in-person evaluation is necessary.