Isolated fever in well patient in first 24 hours following surgery? Think physiological reaction to operation

An isolated fever in a patient with no other symptoms is likely to be a physiological systemic inflammatory reaction to the operation. Post-operatively, there is massive production of pro-inflammatory cytokines that can induce a systemic inflammatory immune response

fevers presenting within less than 48 hours of surgery are unlikely to be of a new infectious aetiology

Early causes of post-op pyrexia (0-5 days) include:

• Blood transfusion
• Cellulitis
• Urinary tract infection
• Physiological systemic inflammatory reaction (usually within a day following the operation)
• Pulmonary atelectasis - this if often listed but the evidence base to support this link is limited

Late causes (>5 days) include:

• Venous thromboembolism
• Pneumonia
• Wound infection
• Anastomotic leak

When considering causes of post-op pyrexia, it is helpful to consider the memory aid of 'the 4 W's' (wind, water, wound, what did we do? (iatrogenic).