The 5 W's are a mnemonic used to remember the most common causes of postoperative fever, as well as help determine the etiology based on postoperative day.
On day 1 post-operatively, the most common cause of fever is atelectasis; thus, patients should have a chest X-ray and incentive spirometry done.
Within postoperative days 1-3, pneumonia is usually the next diagnosis if atelectasis does not resolve after treatment. In order to diagnose pneumonia, we look for infiltration on a chest X-ray and obtain a sputum culture in order to treat it with antibiotics.
Fever that develops 3-5 days postoperatively can be attributed to UTI from prolonged catheterization. Urinalysis and urine cultures should be taken before moving on to treatment with antibiotics and catheter replacement.
DVT, or deep vein thrombosis, occurs from the causes in Virchow's triad (hypercoagulability, stasis, and endothelial injury). Post-operative patients are typically bed-ridden, and DVT formation may arise from lack of ambulatory activity, hence the W-word "Walking."
Pulmonary embolism (PE) is another cause of fever that occurs between postoperative days 4-6. PE leads to fever, shortness of breath, tachycardia, and hypoxia. It may arise from a DVT that has embolized into the airspace.
On postoperative days 5-7, the development of fever may indicate wound involvement. The surgical site must be examined to determine if there is an abscess, gangrene, or cellulitis.
"Wonder drugs" refers to fever caused iatrogenically, which typically arises after the 7th post-operative day. Drugs include serotonergics causing serotonin syndrome, or drugs with dopamine blocking effects (e.g. antipsychotics or antiemetics) causing neuroleptic malignant syndrome. There are also reactions to sulfa drugs, or pain drug withdrawal. Furthermore, there can be IV infection and blood transfusion reactions.
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