Wound, Bone and Joint Infections Flashcards
What are the 3 major pathogens in surgical site infection?
Staph.aureus (MSSA + MRSA)
E.coli
Pseudomonas aeruginosa
What is the pathogenesis of a surgical site infection?
- Contamination of wound at operation
- Pathogenicity + innoculum of microorganisms
- Host immune response
If surgical site is contaminated with > 10^5 microorganisms per gram of tissue, risk of SSI is increased.
Dose of contaminating bacteria required to cause infection is much lower if foreign material is present e.g silk suture.
What are the three levels of surgical site infection?
Superficial incisional: Affect skin + subcutaneous tissue.
Deep incisional: Affect fascial + muscle layers.
Organ/ space infection: Any part of anatomy other than incision.
A patient is admitted, with a SAH + subdural haemorrhage after a fall.
Decompressive craniectomy.
In April, they had a cranioplasty with titanium plate.
Pt was readmitted in Oct with large subdural collection with midline shift + had a subsequent abscess evacuation.
Titanium plates removed.
Underneath there was severe infection with 1-1.5cm thick pus.
What is the likely organism? What drug should be commenced?
MRSA
IV Linezolid
What are three different phases where surgical site infections can be prevented?
Pre-operative phase
Intra-operative phase
Post-operative phase
What is the relationship between age and developing a surgical site infection?
Independent RF.
Direct linear trend of increasing risk until 65y
Age >75 was found to be a significant RF.
List 6 underlying illnesses are risk factors for a surgical site infection
ASA score of >,3
Diabetes: 2-3 fold increased risk. A/W post-op hyperglycaemia. Control blood glucose. HbA1C < 7.
Malnutrition
Low serum albumin
Radiotherapy + steroid use: Taper steroids.
Rheumatoid arthiritis: Stop disease modifying agents for 4w pre + 8w post-op.
Why is obesity a risk factor for surgical site infections?
Adipose tissue is poorly vascularised.
Poor oxygenation of tissues + functioning of immune response increases risk of SSIs.
Risk increased by 2-7 in patients with a BMI of >,35
How is smoking a risk factor for surgical site infections?
Smoking duration + no. of cigarettes smoked.
Nicotine delays primary wound healing.
Causes Peripheral vascular disease.
Vasocontrictive effect of nicotine reduces oxygen-carrying capacity of blood.
Encourage tobacco cessation pre-op
How can pre-operative showering affect the risk of surgical site infections?
Microorganisms colonising the skin may contaminate exposed tissues + cause an SSI.
No difference in SSI incidence when chlorhexidine or detergent/ bar soap is used.
Pts should be advised to shower or bath using soap on day of surgery/ day before.
How can hair removal affect the risk of surgical site infections?
Micro-abrasions caused by shaving with a razor may lead to multiplication of bacteria.
Use electric clippers on the day of surgery with single-use head.
Hair should not be removed unless it will interfere with the operation.
How can nasal decontamination affect the risk of surgical site infections?
S.aureus is carried in the nares of 20-30%.
An analysis demonstrated that S.aureus carriage was the most powerful independent RF for SSI following cardiothoracic surgery.
Nasal de-colonisation should be performed
How can antibiotic prophylaxis affect the risk of surgical site infections?
Abx prophylaxis should be given at induction of anaesthesia.
Bactericidal conc. of the drug should be established in serum + tissues at time of incision.
Additional doses may be necessary if significant blood loss or if operation prolonged.
How can ventilation affect the risk of surgical site infections?
Maintain positive pressure ventilation.
Maintain ~20 air changes per hour (>,3 must be fresh air).
Filter all air.
Keep operating room doors closed.
Consider laminar flow for orthopaedic implant surgery.
How can sterilisation affect the risk of surgical site infections?
Sterilise all surgical instruments.
Inadequate sterilisation of surgical instruments has resulted in SSI outbreaks.
How should skin be prepared to reduce the risk of surgical site infections?
When skin is incised microorganisms may contaminate tissues + cause an SSI.
Prepare skin at surgical site using antiseptic preparation using Chlorhexidine in 70% alcohol
What is an aseptic surgical technique?
Maintaining effective haemostasis while preserving adequate blood supply, gently handling tissues, avoiding inadvertent entries into hollow viscus, removing devitilised tissues + eradicating dead space.
Adhere to asepsis when placing intravascular devices or epidural catheters.
How does hypothermia affect the risk of surgical site infections?
Mild hypothermia: increase risk of SSIs by causing vasoconstriction, decreased delivery of O2 to wound space + subsequent impairment of neutrophil function.
In theatre suite: Measure pt temp before inducing anaesthesia. Start forced air warming if temp is <36ºC.
Warm IV fluid.
Warm irrigation fluid.
How does adequate oxygenation affect the risk of surgical site infections?
Maintain optimal oxygenation during surgery, to maintain a haemoglobin saturation > 95%.
Higher inspired O2 conc. in peri-operative period reduces SSIs.
What are three common bone and joint infections?
Septic arthritis
Chronic osteomyelitis
Prosthetic joint infection
What is the epidemiology and prognosis of septic arthritis?
Incidence: 2-10/ 100,000.
In pts with RA incidence: 28-38/ 100,000
Mortality: 7-15%.
Morbidity: 50%.
