What is the most common cause of fever within the first 48 hours postoperatively?

The most common cause of fever within the first 48 hours postoperatively is atelectasis. This is a condition where part or all of a lung collapses, often due to shallow breathing or poor ventilation following surgery. After an operation, patients may have reduced mobility and may not take deep breaths sufficiently, leading to the accumulation of secretions in the lungs and subsequent lung collapse. This process can trigger an inflammatory response, resulting in fever.

Atelectasis is particularly prevalent in the early postoperative period because it can develop swiftly, often within hours after surgery, particularly in patients who are less active or have received general anesthesia. Therefore, the body may respond to this condition by producing a fever as part of the inflammatory process.

While other causes of postoperative fever, such as infections, dehydration, and thrombosis, can occur, they are generally less likely to present within the first 48 hours. Infections typically need more time to develop and manifest, while dehydration often leads to different symptoms. Thrombosis concerns related to fever usually arise later and can be less common in the immediate postoperative setting.