What are the common etiologies of postoperative fever on postoperative day (POD) 1-2?

Postoperative fever within the first two days after surgery is most frequently attributed to atelectasis and pneumonia. This early onset fever can occur due to several factors related to the surgical procedure and the patient's postoperative state.

Atelectasis, or the collapse of part of the lung, can frequently develop after surgery, particularly in patients who have undergone abdominal or thoracic procedures. Factors such as reduced mobility and inadequate ventilation can exacerbate this condition, leading to inflammation and fever. Similarly, pneumonia can arise as patients may have poor coughing reflexes or secretions collected in the lungs due to anesthesia and postoperative factors, which increases the risk of respiratory infections.

Other conditions, such as urinary tract infections or deep vein thrombosis, tend to manifest later and are less common causes of fever in the immediate postoperative period. Wound infections typically present at a later stage post-surgery, beyond POD 2, as they often require time to develop after the surgical incision. Understanding the timeline and typical causal factors is crucial for effectively diagnosing and managing postoperative complications.