The 5 W's is a mnemonic used to organize the most common causes of postoperative fever, as well as help determine the etiology based on postoperative day.
Day 1 post-operatively, the most common cause of fever is atelectasis. Thus patients should have 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 chest X-ray, and obtain sputum culture in order to treat with antibiotics.
Fever which develops 3-5 days postoperatively can be attributed to UTI from prolonged catheterization. Urinalysis and urine cultures should be done 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 occurring between post-operative days 4-6. PE leads to fever, shortness of breath, tachycardia and hypoxia. It may arise from a DVT which has embolized into the airspace.
On postoperative days 5-7, the development of fever may point to wound involvement. The surgical site must be observed to determine if there is an abscess, gangrene or cellulitis.
"Wonder drugs" refers to fever caused iatrogenically, which typically shows up after the 7th post-operative day. Drugs include serotonergics causing serotonin syndrome or dopaminergic agents causing neuroleptic malignant syndrome. There are reactions to sulfa drugs, or pain drug withdrawal. Furthermore, there can be IV infection and blood transfusion reactions.
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