Post-operative fever is a temperature of ≥38°C for 2 consecutive days after surgery that can be caused by an inflammatory response or infection. The pathophysiology involves cytokine release triggering heat production in the hypothalamus. Causes include infections like surgical site infections or pneumonia, and non-infectious factors like medications, DVT, or atelectasis. Differential diagnosis depends on fever onset—immediate, acute within a week, subacute 1-4 weeks, or delayed after a month. Evaluation involves examining the surgical site, labs, imaging, and treating any identified infections.

1. POST OPERATIVE FEVER
DR JUNAID HASSAN

2. WHAT IS POST OPERATIVE FEVER ?
•Any fever i.e., temperature of ≥
38 degree Celsius for 2
consecutive days after surgery
caused by inflammatory
response related to the surgery
that occurs from the time of
surgery to more than one month.

3. PATHOPHYSIOLOGY OF POST-OP
FEVER
Manifestation of cytokine release/response
By monocyte, macrophages, endothelial cells
i.e; IL-1, IL-6, TNF-alpha
Act on the hypothalamic endothelium
Stimulate production of PGE2 & cAMP release
cAMP acts as neurotransmitter & raises the
“set-point” => heat conservation & production

4. CAUSES OF POST-OP FEVER
• INFECTIOUS CAUSES
Surgical site infections
 Pneumonia
 UTI
 Catheter infection
 Sinusitis
 Meningitis
 Parotitis
Foreign body
• NON-IFECTIOUS CAUSES
Stress of surgery
 Medications
 Malignant
hyperthermia
 Deep vein
thrombosis
 Fat embolism
 Transfusion
reactions
 Atelectasis

5. DIFFERENTIAL DIAGNOSIS OF POST-
OPERATIVE FEVER
•Immediate Fever --- during surgery &
within hrs.
•Acute Fever -------- within first
week.
•Subacute Fever ----- 1- 4 weeks after
surgery.
•Delayed Fever ------ 1 month after

6. Onset in operating suite or within
hours after surgery
Medication reactions:
antibiotics, blood products,
malignant hyperthermia.
Necrotizing infection:
Clostridium, Group A β-hemo
strep.
Treatment: ABC, resuscitate,

7. ACUTE FEVER
Onset within 1st week after surgery
necrotizing infection (within 48hrs)
anastomotic leak (classically POD# 3 to 5)
Pulmonary embolism
MI
Pneumonia
Aspiration
UTI
Surgical site infection (SSI)
Other: acute gout, pancreatitis

8. Onset from 1 to 4 weeks after surgery
Surgical site infection
UTI
Line infection
Antibiotic-associated diarrhea
Febrile drug reactions
Thrombophlebitis
Sinusitis

9. Onset >1 month after surgery
Infection
Viral infections from blood
products
Surgical site infections

10. THE FIVE “W”
The Five “W” & timing of each
Wind (POD#1) atelectasis,
pneumonia
Water (POD#3) UTI, anastomotic
leak
Wound (POD#5) wound infection,
abscess
Walking (POD#7) DVT / PE
Wonder-drug or What did we do?
Many drugs cause fever, blood transfusions,
central lines we put in (line sepsis)

12. ABCs
Resuscitate
Anesthesia record, operative note,
nursing report, flowchart
Physical examination:
Complete exam
Look at wounds - take off dressings
Look at drain output
Check IV sites, CV line, Foley, tubes

13. INVESTIGATIONS
If infection is suspected, following Lab tests should
be done order if concerned for infection:
CBC, sputum culture, urine complete,
Imaging:
CXR (for pneumonia)
Lower extremity venous duplex (for DVT)
CT scan (for abscess, leak, pancreatitis, PE)

14. Remove/replace sources of infection
Foley catheter, central lines, or
peripheral IV’s
Surgical debridement: Open, debride,
and drain infected wounds
If suspect pneumonia, bacteremia, UTI,
sepsis – start broad spectrum antibiotics,
piperacillin/tazocin and clindamycin.
Anticoagulation for DVT/PE
CT guided drainage of abscess

15. The 5 W’s
Think the worst and rule it out!
Necrotizing fasciitis must be
identified and treated aggressively