Postoperative Fever

Immediate Fever

Fever occurs immediately after surgery or within hours on postoperative days (POD) 0 or 1.

• Malignant hyperthermia: high-grade fever (greater than 40 C), occurs shortly after inhalational anesthetics or muscle relaxant (e.g., halothane or succinylcholine), may have a family history of death after anesthesia. Laboratory studies will reveal with metabolic acidosis and hypercalcemia. If not readily recognized, it can cause cardiac arrest. The treatment is intravenous dantrolene, 100% oxygen, correction of acidosis, cooling blankets, and watching for myoglobinuria.
• Bacteremia: High-grade fever (greater than 40 C) occurring 30 to 40 minutes after the beginning of the procedure (e.g., Urinary tract instrumentation in the presence of infected urine). Management includes blood cultures three times and starting empiric antibiotics.
• Gas gangrene of the wound: High-grade fever (greater than 40 C) occurring after gastrointestinal (GI) surgery due to contamination with Clostridium perfringens; severe wound pain; treat with surgical debridement and antibiotics.
• Febrile non-hemolytic transfusion reaction: Fevers, chills, and malaise 1 to 6 hours after surgery (without hemolysis). Management: Stop transfusion (rule out hemolytic transfusion reaction) and give antipyretics (avoid aspirin in the thrombocytopenic patient).

Acute Fever

Fever occurs in the first week (1 to 7 POD).

• POD 1 to 3: atelectasis: After prolonged intubation, the presence of upper abdominal incision, inadequate postoperative pain control, lying supine. Should be prevented by incentive spirometry, semi-recumbent position, adequate pain control, early ambulation. Clinically may be asymptomatic or with increased work of breathing, respiratory alkalosis, chest x-ray with volume loss. Treatment includes spirometry, chest physiotherapy, semi-recumbent position (improves expansion of alveoli by preventing pressure from intra-abdominal organs on the diaphragm and hence improving functional residual capacity)
• POD 3: Unresolved atelectasis resulting in pneumonia (respiratory symptoms, Chest x-ray with infiltrates or consolidation, sputum culture, empiric antibiotics and modify according to culture result and sensitivity), or development of urinary tract infection (urine analysis and culture, treat with empiric antibiotics and modify according to culture result and sensitivity)
• POD 5: Thrombophlebitis (may be asymptomatic or symptomatic, diagnose with Doppler ultrasound of deep leg and pelvic veins and treat with heparin)
• POD 7: Pulmonary embolism (tachycardia, tachypnea, pleuritic chest pain, ECG with right heart strain pattern (a low central venous pressure goes against diagnosis), arterial blood gas with hypoxemia and hypocapnia, confirm the diagnosis with CT angiogram, and treat with heparin if recurrent pulmonary embolism while anticoagulated with therapeutic INR, Inferior vena cava filter placement is the next step
• POD 7 (5 to 10): Wound infection: Risk increases if the patient is immunocompromised (e.g., diabetic), abdominal wound, duration of surgery greater than 2 hours, or contamination during surgery. Signs include erythema, warmth, tenderness, discharge. Rule out abscess by physical exam plus ultrasound if needed. If an abscess is present, drainage and antibiotics are needed. Prevention is by careful surgical technique and prophylactic antibiotics (e.g., intravenous cefazolin at the time of induction of anesthesia as well as postoperatively if needed)

Subacute Fever

Fever occurs between postoperative weeks 1 and 4.

• POD 10: Deep infection (pelvic or abdominal abscess and if abdominal abscess could be sub-hepatic or sub-phrenic). A digital rectal exam to rule out the pelvic abscess and CT scan to localize intra-abdominal abscess. Treatment includes re-exploration vs. radiological guided percutaneous drainage.
• Drugs: Diagnosis of exclusion includes rash and peripheral eosinophilia

Delayed Fever

Fever after more than 4 weeks.

• Skin and soft tissue infections (SSTI)
• Viral infections

The above differential diagnosis is for causes that are categorized based on timing. However, there are many other causes that may have specific signs on physical exam and occur after specific surgery that are not included in the above differential.

Initial assessment includes general appearance, GCS, and vital signs to determine how sick the patient is.[5][6]

• Airway, Breathing, Circulatory, Disability, Exposure (quick assessment to identify and simultaneously provide appropriate management)
• Check patient notes (the type of procedure, timing of the procedure, intraoperative complications, anesthesia records, patient comorbidities, last ward rounds)
• Check patient Intake and Output (including the type of stools, if the patient with type 7 stools rule out Clostridium difficile enterocolitis)
• Check patient orders (is the patient being treated with antibiotics or not, receiving deep vein thrombosis prophylaxis or not)
• System based assessment (pulmonary, cardiac, gastrointestinal, urinary)
• Sites of infection that are visible (i.e., skin for bedsores, cellulitis, vascular access sites)
• Besides tests, vital signs should be monitored. If the patient is hypotensive, venous blood gas is needed to measure serum lactate. It will guide fluid resuscitation; if the patient is tachycardic, bedside ECG might be important to confirm their rhythm, might rule out myocardial infarction; oxygen saturation 96% to 98% in patients with healthy lungs or 89% to 92% in carbon dioxide retaining patients, for example, COPD patients; monitor blood glucose levels because high blood glucose levels point towards septic response; urinalysis to rule out urinary tract infection
• Blood tests: WBC, CRP especially if trending upward might point towards a septic response, hemoglobin level would point toward the oxygen-carrying capacity of the blood, liver function tests to rule out liver injury, coagulation parameters, and platelets to rule out disseminated intravascular coagulation, renal function to rule out kidney injury or electrolyte abnormalities
• Microbiology: Cultures (blood, urine, wound, and sputum if producing it), if suspecting line sepsis (blood culture from the line, remove the line and send the tip to the lab)
• Imaging: Chest x-ray (prove or rule out pneumonic process), abdominal imaging (ultrasound, CT scan to rule out collections)
• Venous doppler of the legs to rule out deep vein thrombosis

Treatment can include oxygen, fluid balance, intravenous fluids, and a urinary catheter, or antibiotics.

• Drugs: antibiotics, analgesia, antiemetics
• Incentive Spirometry
• Venous thromboembolism prophylaxis (low molecular weight heparin and wearing pneumatic stocking)
• Escalation (relay information to a senior health professional and ask for further advice from  infectious disease physician)

As discussed earlier, the differentials are based on the timing of the fever, among other factors. Some of the important differentials are listed below.

• Pneumonia
• Pulmonary embolus
• Wound infection
• Urinary tract infection
• Transfusion reaction
• Sinusitis

In most patients, postoperative fever is due to a benign cause and resolves spontaneously. Patients who have atelectasis recover quickly once they are started on incentive spirometry and/or chest physical therapy. Patients with deep vein thrombosis and pulmonary embolism usually have a low-grade fever that resolves within a few days of treatment. The prognosis is worse for patients who have anastomotic leaks or bowel obstruction.

Failure to diagnose the cause of fever or identify the severity of it can lead the patient into SIRS, sepsis, severe sepsis, or septic shock. This can lead to prolonged hospitalization and even increase the mortality rate.

• Physician
• Infectious disease

Patients who undergo general anesthesia should be advised to use incentive spirometry to prevent atelectasis, which is a common cause of postoperative fever. Early mobilization should also be encouraged in postoperative patients where allowed.

Postoperative fever is a common occurrence on all surgical floors. Because there are so many causes of fever, the problem is usually managed by an interprofessional team of healthcare professionals. The nurse is probably the first person who monitors the patient and discovers the fever. In order to know the cause, the nurse should first check the wound site, auscultate the lungs, and assess for deep vein thrombosis. Other causes of postoperative fever may be a urinary tract infection, an intravenous line (thrombophlebitis), or sepsis. Once the fever has been noted, the health care provider should be notified, and the workup depends on patient presentation and the day of the fever. If atelectasis is suspected, a chest x-ray may be ordered, blood and urine culture for sepsis, and a urinary tract infection and duplex ultrasound if a deep vein thrombus is suspected. The key is to examine the patient as it may provide a clue to the cause. [7][8](Level V)