Post-op fever

Question 1

discuss differential diagnoses in post-operative fever

Answer 1

“THE BIG FIVE”

• Surgical site
• IV sites
• UTI
• Pneumonia
• DVT

Question 2

consider the significance of time and pattern in post-operative fever

Answer 2

Timing
1. Immediate: often benign & mild (transfusion reaction, med Rx, infection prior to surgery, trauma) or malignant hyperthermia (rare)

2. First week (Acute): 
–Hospital acquired pneumonia/ aspiration pneumonia
–IV site infection with bacteraemia
–Urinary tract infection
–Surgical sites

3. > 1 week (subacute):
   –Surgical sites
   –IV sites
   –DVT
   –Drug reactions (antibiotics, phenytoin, others)
   –Other nosocomial infections, esp if in ICU
4. > 1 month (delayed)
   –Surgical site
   –Viruses and transfusion (CMV)

Pattern:

• Spiking temperature (up and down): abscess
• high persistent fever

Question 3

What do you ask in Hx & exam to DDx post op fever?

Answer 3

Hx:
•Symptoms of fever
•Pain in the hip, duration, movement, restricted, analgesic requirements
•Shortness of breath, cough, sputum production, pleuritic chest pain
•Urinary catheter-in-situ, dysuria, frequency
•Pain in the calves, peripheral IV sites

Exam:
•Vital signs- eg. BP, pulse, respiratory rate (tachypnoea), O2 saturation, temperature
•Surgical wound
•IV sites/Spinal site
•Chest
•Legs
•Skin (rash)

Question 4

What are the risk factors for post-operative fever?

Answer 4

General risk factors:

• immunocompromised
• inappropriate/debilitating pain

Risk factors for:
1. surgical site infection:
•Host factors: age, obesity, malnutrition, diabetes, steroids, smoking, infection at another site, skin carriage of Staph aureus
•Type of surgery, wound class, surgical technique, operation duration, hair removal, skin prep used, hypothermia
•Inadequate surgical antibiotic prophylaxis- antibiotic choice, timing
•Theatre traffic

2. IV sites:
   - prolonged use of cannula
   - non sterile technique
3. UTI
   - prolonged use of catheter
4. Pneumonia
   - prolonged sitting & no deep inspiration
   - pain
5. DVT
   - inappropriate/no use of thromboprophylaxis
   - other pro-coagulable states

Question 5

How can you prevent post-operative complications?

Answer 5

–Avoid excessive sedation but also pain
–Mobilise, sit out of bed
–Avoid H2 blockers, PPIs unless ulcer risk
–Regular check/change of drain tubes, cannulas, catheters, dressings on surgical site
–Emphasise sterile techniques

Question 6

How do you exam the surgical site?

Answer 6

• Inspection- erythema, haematoma, wound breakdown, discharge
• Palpate- tenderness, fluctuance, crepitus
• +/- imaging

Question 7

How do you exam IV & other invasive sites?

Answer 7

• IV, arterial line, central line, drain site- inspect all sites, note date inserted, when they were changed
• Drains sites may get infected or be an indicator of deep infection- purulent fluid
• Central line-associated bloodstream infections usually have no localising signs

Question 8

How do you assess the urinary tract for post op fever?

Answer 8

• Was a catheter used or still in situ- is it blocked? What colour is the urine?
• (Bacteruria very common in catheterised patients, but often asymptomatic and not requiring treatment)

Question 9

How do you assess the lungs for post op fever?

Answer 9

• Chest signs- crepitations, dullness to percussion: ? consolidation, ? effusion
• Pulmonary infection versus pulmonary embolus
• NB other non infectious causes of chest signs: ARDS, left ventricular failure/fluid overload

Question 10

How do you assess legs for post op fever?

Answer 10

• DVT- swelling, tender calf, or no signs but high risk
• Check thromboprophylaxis- eg. TEDS, Clexane, Pneumatic calf compressors
• Investigate- Doppler US

Question 11

If a surgical site wound is suspected, what Ix would you order & how do you Rx it?

Answer 11

Ix:
•FBE for WCC & Neutrophils
•XR (depending on the site)
•Wound swab for M/C/S

Rx: antibiotics & surgery (wash & debride if necessary)

Question 12

Describe MRSA

Answer 12

• 15-20% of all S.aureus infections
• Hospital strains on the decline
• Community strains increasing

Question 13

Describe hospital acquired pneumonia. What are the common causative organisms?

Answer 13

•Occurs 48 hours or more after admission (not incubating on admission)
–Most occur outside ICUs, but risk esp in ventilated patients
•Ventilator-associated pneumonia (VAP) develops more than 48 hours after intubation
•Causes more deaths than any other hospital-acquired infection

–Most commonly aerobic gram negative bacilli; eg E.coli, Klebsiella, Enterobacter, Pseudomonas
–Then Staph. aureus, including MRSA
–Resistant pathogens more likely in VAP, ICU patients; c.f wards, longer hospital stay; previous antibiotics, immunosuppression

Question 14

How do you Rx hospital acquired pneumonia?

Answer 14

–Requires a knowledge of the likely bacteria in the particular hospital or ICU in recent months; including resistance patterns

In Melbourne, currently:
–ceftriaxone for HAP in wards
–piperacillin/tazobactan ± azithromycin for VAP

Question 15

How can you prevent hospital acquired pneumonia?

Answer 15

–Avoid excessive sedation
–Mobilise, sit out of bed
–Avoid H2 blockers, PPIs unless ulcer risk