Post-Op Pyrexia Flashcards
What is pyrexia?
Pyrexia (fever) refers to a raised body temperature, typically greater than 37.5c.
Give examples of causes of post-operative pyrexia
- Infection
- Iatrogenic
- Which may include a drug-induced reaction (e.g. antibiotics or anaesthetic agents) or from a transfusion reaction.
- Venous thromboembolism
- Secondary to prosthetic implantation
- With any foreign body, for example after an AAA repair, a low-grade fever may be evident
- Pyrexia of Unknown Origin
Briefly describe the pathophysiology of infection leading to post-op pyrexia
The most common cause of pyrexia in the post-operative patient is infection. The specific post-operative day on which the fever develops may indicate the source of the infection:
- Day 1-2 – consider a respiratory source
- Day 3-5 – consider a urinary tract source
- Day 5-7 – consider a surgical site infection or abscess/collection formation
- Any day post-operatively – consider infected IV lines or central lines as a source
The investigation of the infection source should also be tailored to the patient. For example, in a patient who has undergone a bowel resection, post-anastomotic leak is an important differential to be considered and should be investigated as a matter of urgency.
What is Pyrexia Of Unknown Origin? And what may cause this?
Pyrexia of Unknown Origin (PUO) is defined as a recurrent fever (>38oc) persisting for >3wks without an obvious cause, despite >1wk of inpatient investigation.
Causes of PUO include infection of unknown source (30%), malignancy (classically B-symptoms from lymphoma, 30%), connective tissue diseases or vasculitis (30%) and drug reactions.
What are the clinical features of post-op pyrexia?
The underlying source of the pyrexia will largely determine the clinical presentation of the patient. Importantly, if the patient appears unwell and needs urgent resuscitation and management, start an A to E approach as necessary and only attempt to identify the source of infection once the patient is stable.
If no obvious source is apparent, enquire about specific systems symptoms, such as urinary frequency, urgency, or dysuria, productive cough or dyspnoea, haemoptysis, chest or calf pain, or wound or IV line tenderness or discharge.
On initial examination, examine for signs of pulmonary infection, IV line infections, wound infections, and calf tenderness. If post-operative, also examine for specific complications from the operation (e.g. signs of peritonism in anastomotic leak).
What investigations should be ordered for post-op pyrexia?
A septic screen is essential in investigating the surgical patient with pyrexia. In most cases, the source is obvious and your screen can be tailored accordingly, yet in a less clear presentation a wider screen is indicated. It can include:
- Blood tests
- FBC, CRP and U&Es
- Urine dipstick
- Cultures
- Blood, urine, sputum and wound swab
- Imaging
- Chest X-ray
If the source cannot be identified through the septic screen, more detailed investigations may be required, such as a CT scan for any suspected anastomotic leak or Doppler US for suspected DVT.
Briefly describe the management of post-op pyrexia
Any identified infection should be treated empirically with antibiotics, pending sensitivity results. Empirical antibiotic regimes will vary depending on local sensitivities – therefore follow your local hospital guidance.
If no infectious cause can be identified, do not start empirical antibiotics. First look for non-infectious causes and consult a senior colleague and a microbiologist for further advice.
Additional support can be provided via anti-pyrexials and analgesia. It is important to ensure the patient remains hydrated; observations should be increased and a fluid balance started
A low threshold of suspicion should be present for suspected sepsis. Any new rise in temperature whilst on antibiotics should prompt repeating the septic screen (and investigating other potential causes than infection). Any concerns should warrant an early senior review.
What is the empirical antibiotic regime for a lower respiratory tract infection?
Co-Amoxiclav 625mg PO TDS for 5 days.
What is the empirical antibiotic regime for a lower urinary tract infection?
Trimethoprim 200mg PO BD for 3 days.
What is the empirical antibiotic regime for upper urinary tract infection?
Co-Amoxiclav 625mg PO TDS for 14 days.
What is the empirical antibiotic regime for surgical site infection or cellulitis?
Flucloxacillin 500mg PO QDS for 5 days.
What is the empirical antibiotic regime for IV or central line infections?
Flucloxacillin 500mg PO QDS for 5 days
(Vancomycin, levels requires close monitoring, follow local guidelines for dosing).
What is the empirical antibiotic regime for intra-abdominal infection?
Cefuroxime 1.5g IV TDS + Metronidazole 500mg TDS IV.
What is the empirical antibiotic regime for septic arthritis?
Flucloxacillin 2g IV QDS.
What is the empirical antibiotic regime for infection from an unknown source?
Cefuroxime 1.5g IV TDS + Metronidazole 500mg TDS IV + Gentamycin 5mg/kg STAT.
