Wound Bone And Joint Infections Flashcards
What is the pathogenesis?
Contamination of the wound
Pathogenicity and innoculum of microorganisms
Host immune response
Group a strep more virulent than coagualse staph
What increases the risk of SSI?
Surgical site is contaminated with more than more than 10 to the 5 microorganisms per gram of tissue, risk of SSI increases
Dose requires of bacteria to cause infection is lower if foreign material is present eg silk suture
What are the 3 levels of SSI?
Superficial incisional- affect skin and subcutaneous tissue
Deep incisional- affect fascial and muscle layers
Organ/space infection- any part of any anatomy other than incision
What can mrsa be treated with?
Linezolid
What phases can SSI be prevented?
Pre operative phase
Intra operative
Post op
What is involved in the pre op phase?
Optimising patient
Age is independent, Over 75 major risk factor
Treat infections at other sites, postpone operation
ASA score of 3 or more
Diabetes, 2/3 fold increased risk. Control glucose, hba1c, less than 7
Malnutrition
Low serum albumin
Taper steroid use, radiotherapy
Stop DMARDS for RA 4 weeks before and 8 weeks after
Obesity- poor oxygenation of adipose tissue and functioning of immune system. Increase from 2 to 7 with Bmi of 35 or more
How can smoking increase risk of SSI?
Nicotine delays primary wound healing
Why is pre op showering recommended before surgery?
Microorganisms colonising the skin, contaminate exposed tissue and cause an SSI
no difference in using chlorhexidine and detergent bar soap
Shower on the day or day before
How should hair be removed before surgery?
Micro abrasions can lead to multiplication of bacteria
Use electric clippers with single use head
Try to avoid removing hair
How can nasal contamination affect SSI risk?
S aureus in the nose of 20-30% of people
Multi variate analysis demonstrated that s aureus was most powerful independent risk factor for SSI following cardio thoracic surgery
How should abx prophylaxis occur?
Given at induction of anaesthesia
Bactericidal concentration of the drug should be established in serum and tissues at time of incision
Additional dose may be necessary if there has been significant blood loss or if the operation has been prolonged
What should surgical personnel do to decrease risk of SSI?
If they have symptoms of transmissible infection report to occupational health
How can theatre traffic affect risk of SSI?
1 person sheds 1 billion skin cells per day, 10% carry bacteria
Microbial load is related to number of ppl present in theatre
Theatre personnel should be kept to a minimum
Why is ventilation important?
Maintain positive pressure ventilation Maintain 20 air changes per hour of which at least 3 must be fresh air Filter all air Keep operating room doors closed Consider laminar flow for ortho surgery Reduces bacterial load
What must be done to surgical instrument?
Sterilise them
How can skin be prepared?
At surgical site, use antiseptic preparation, povidine iodine, chlorhexidine in 70% alcohol use
How can surgical technique help reduce SSI?
Maintain effective haemostasis while preserving adequate blood supply
Gently handling tissue
Avoid inadvertent entries into hollow viscus
Remove devitilzed tissue and eradicating dead space
Adhere to asepsis when placing intravascular devices or epidural catheters
How can temperature affect risk of SSI?
Mild hypothermia can increase risk, vasoconstriction, decreased delivery of oxygen to wound space, and subsequent impairment of neutrophil function
Measure patients temp before inducing anaesthesia. Start forced warming if temp is below 36
Warm IV fluid, warm irrigation fluid
How can oxygen levels affect SSI risk?
Maintain optimal oxygenation during surgery to maintain a Hb sat of more than 95
Higher inspired oxygen concentration in peri operative period reduces SSI
How does RA effect septic arthritis risk?.
Increases incidence from 2-10 per 100000 to 28-38
Mortality is 7-15%, morbidity is 50%
What are the risk factors for septic arthritis?
RA, osetoarthritis, crystal induced arthritis
Joint prosthesis, IVDU, diabetes, chronic renal disease, chronic liver disease
Immunosuppresion
A trauma- intra articular injury and penetrating injury
What is the pathophysiology of septic arthritis?
Organisms Adhere to synovial membrane, bacterial proliferation, generation of host inflammatory response
Joint damage leads to exposure of host derived proteins such as fibronectin to which bacteria adhere
What bacterial factors are involved in pathogenesis of septic arthritis
S aureus has receptors such as fibronectin binding protein
Kingella kingae synovial adherence is via bacterial pilli
Some strains of staph aureus produces cytokine pvl- Panton Valentine leucocidin, associated with fulminant infections
What are the host factors involved in pathogenesis of septic arthritis?
Leucocyte derived proteases and cytokines can lead to cartilage degradation and bone loss
Raised ICP can hamper capillary blood flow and lead to cartilage and bone ischaemia and necrosis
Genetic deletion of macrophage derived cytokines (lymphotoxin alpha, tnf alpha, interleukin 1 receptor) reduces host response in s aureus sepsis
Absence of il 10 in Ko mouse, increase severity of staph disease
