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pathy5 > Wound, bone and joint infections > Flashcards

Wound, bone and joint infections Flashcards

1
Q

What is the epidemiology of surgical site infections?

A

In 2011 , 15.7% of HAI were SSIs

In US $ 600 million spent on knee and hip infections in 2009

Increased length of stay ( THR- 11 days longer)

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2
Q

What are the major surgical site pathogens?

A

Staph.aureus (MSSA and MRSA)
E.coli
Pseudomonas aeruginosa

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3
Q

What is the pathogenesis of surgical site infections?

A

Contamination of wound at operation
Pathogenicity and innoculum of microorganisms
Host immune response

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4
Q

How much bacteria will cause an infection?

A

If surgical site is contaminated with
> 10 5 microorganisms per gram of tissue, risk of SSI is increased.
The dose of contaminating bacteria required to cause infection is much lower if there is foreign material present e.g silk suture

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5
Q

What are the 3 levels of SSI?

A

Superficial incisional- affect skin and subcutaneous tissue

Deep incisional- affect fascial and muscle layers

Organ/space infection- any part of anatomy other than incision

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6
Q

What organism is likely to infection a patient post SAH?

  1. E.coli
  2. Enterobacter
  3. Neisseria meningitides
  4. MRSA
A

MRSA

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7
Q

When can you prevent an SSI?

A

Pre-operative phase

Intra-operative phase

Post-operative phase

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8
Q

Why is age a risk factor?

A

An independent risk factor
A direct linear trend of increasing risk until 65 years of age
A prospective study examining patient undergoing total hip replacement. Age over 75 was found to be a significant risk factor

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9
Q

Should you treat some infections remote to the surgical site pre operatively?

A

Treat all infections remote to the surgical site. May require operation to be postponed.

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10
Q

How does underlying illness affect infections?

A

ASA score of 3 or more
Diabetes – two to three fold increased risk. Association with post-op hyperglycaemia. Control blood glucose. HbA1C < 7
Malnutrition
Low serum albumin
Radiotherapy and steroid use. Taper steroids
Rheumatoid arthiritis. Stop disease modifying agents for 4 weeks before and 8 weeks post-op.

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11
Q

How does obesity impact infection?

A

Adipose tissue is poorly vascularised. Poor oxygenation of tissues and functioning of the immune response increases the risk of SSIs

Risk increased by 2 to 7 in patients with a BMI of 35 or more

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12
Q

How does smoking impact infection?

A

Smoking duration and number of cigarettes smoked
Nicotine delays primary wound healing
Peripheral vascular disease
Encourage tobacco cessation

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13
Q

How does Pre-operative showering impact infection?

A

Microorganisms colonising the skin may contaminate exposed tissues and cause an SSI

There is no difference in SSI incidence when chlorhexidine or detergent/bar soap is used

Patients should be advised to shower or bath using soap on the day of surgery or the day before

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14
Q

How does Hair removal impact infection?

A

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

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15
Q

How does Nasal decontamination impact infection?

A

S.aureus is carried in the nares of 20-30%

A multivariate analysis demonstrated that S.aureus carriage was the most powerful independent risk factor for SSI following cardiothoracic surgery

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16
Q

How does Antibiotic prophylaxis impact infection?

A

Antibiotic prophylaxis should be given at induction of anaesthesia
Bactericidal concentration of the drug should be established in serum and tissues at time of incision.
Additional doses may be necessary if there has been significant blood loss or if the operation has been prolonged

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17
Q

How do you manage infected surgical personnel?

A

Encourage surgical personnel who have symptoms of a transmissible infection to report to occupational health.

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18
Q

How do we control theatre traffic?

A

One person sheds 1 billion skin cells per day ; 10% carry bacteria
Microbial load in theatre is related to the number of people present
Theatre personnel should be kept to a minimum

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19
Q

How can we improve ventilation?

A

Maintain positive pressure ventilation
Maintain around 20 air changes per hour (of which at least 3must be fresh air)
Filter all air
Keep operating room doors closed
Consider laminar flow for orthopaedic implant surgery

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20
Q

Why should we sterilise surgical instruments?

A

Sterilise all surgical instruments
Inadequate sterilisation of surgical instruments has resulted in SSI outbreaks

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21
Q

How should we skin prep?

A

When skin is incised microorganisms may contaminate tissues and cause an SSI

Prepare skin at surgical site using antiseptic preparation: povidine-iodine or chlorhexidine.

Chlorhexidine in 70% alcohol is used

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22
Q

Why should we do aseptic technique?

A

Maintaining effective haemostasis while preserving adequate blood supply, gently handling tissues, avoiding inadvertent entries into hollow viscus, removing devitilised tissues and eradicating dead space.
Adhere to asepsis when placing intravascular devices or epidural catheters

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23
Q

Why is normothermia important?

A

Mild hypothermia appears to increase the risk of SSIs by causing vasoconstriction, decreased delivery of oxygen to wound space and subsequent impairment of neutrophil function

In theatre suite: Measure patients temperature before inducing anaesthesia. Start forced air warming if temperature is below 36ºC
Warm intravenous fluid. Warm irrigation fluid

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24
Q

Why is oxygenation important?

A

Maintain optimal oxygenation during surgery, to maintain a haemoglobin saturation of more than 95%
Higher inspired oxygen concentrations in peri-operative period reduces SSIs

25
Q

What are the bone and joint infections?

A

Septic arthritis
Vertebral osteomyelitis
Chronic osteomyelitis
Prosthetic joint infection

26
Q

What is the epidemiology of septic arthritis?

A

Incidence is 2-10 cases per 100,000
In patients with RA incidence is 28-38 per 100,000 population.
Mortality is 7-15%
Morbidity is 50%

27
Q

What is the RFs of septic arthritis?

A

Rheumatoid arthritis , osteoarthritis, crystal induced arthritis

Joint prosthesis

Intravenous drug abuse

Diabetes, chronic renal disease, chronic liver disease

Immunosuppression- steroids

Trauma- intra-articular injection, penetrating injury

28
Q

What is the pathophysiology of septic arthritis?

A

Organisms adhere to the synovial membrane, bacterial proliferation in the synovial fluid with generation of host inflammatory response.
Joint damage leads to exposure of host derived proteins such as fibronectin to which bacteria adhere

29
Q

What is the bacterial factors in septic arthritis?

A

Bacterial Factors
S.aureus has receptors such as fibronectin binding protein that recognise selected host proteins.
Kingella kingae synovial adherence is via bacterial pili

Some strains of Staph. aureus produce the cytotoxin PVL ( Panton-Valentine Leucocidin) which have been associated with fulminant infections.

30
Q

What is the host factors in septic arthritis?

A

Leucocyte derived proteases and cytokines can lead to cartilage degradation and bone loss.

Raised intra-articular pressure can hamper capillary blood flow and lead to cartilage and bone ischaemia and necrosis.

Genetic deletion of macrophage –derived cytokines (lymphotoxin α, TNFα, interleukin 1 receptor) reduces host response in S.aureus sepsis in animal models

Absence of interleukin10 in knockout mice increases the severity of staphylococcal joint disease.

Genetic variation in expression of these cytokines may lead to differential susceptibility to septic arthritis.

31
Q

What are the Causative organisms of septic arthritis (with % of how common)?

A

Staph. aureus 46%
- Coagulase negative staphylococci 4%

Streptococci 22%
Streptococcus pyogenes
Streptococcus pneumoniae
Streptococcus agalactiae

Gram negative organisms

  • E.coli
  • Haemophilus influezae
  • Neisseria gonorrhoeae
  • Salmonella

Rare- Lyme, brucellosis, mycobacteria, fungi

32
Q

What are the clinical features of septic arthritis?

A

1-2 week history of red, painful, swollen restricted joint
Monoarticular in 90%
Knee is involved in 50%

Patients with rheumatoid arthritis may show more subtle signs of joint infection

33
Q

What Ix would you do for septic arthritis?

A

Blood culture before antibiotics are given

Synovial fluid aspiration for microscopy and culture
ESR,CRP

-Traditionally a synovial count> 50,000 WBC cells/mm3 used to suggest septic arthritis

(Negative culture result does not exclude septic arthritis)

34
Q

What Imaging would you do for septic arthritis?

A

US- confirm effusion and guide needle aspiration

CT- erosive bone change, periarticular soft tissue extension

MRI- joint effusion, articular cartilage destruction, abscess, contiguous osteomyelitis

35
Q

What Mx would you do for septic arthritis?

A

Antibiotics- No data on optimum duration of treatment (cephalosporin/ flucloxacillin - may need to add vancomycin if at high risk of MRSA)

Upto 6 weeks of antibiotics may be given

OPAT (outpatient parenteral antibiotic team)

Drainage

36
Q

How do you get vertebral osteomyelitis?

A

Acute haematogenous

Exogenous- after disc surgery - implant associated

37
Q

What are the causative organisms of vertebral osteomyelitis?

A

S.aureus- 48.3%
CNS- 6.7%
Gram Negative Rods- 23.1%
Strep- 43.1%

38
Q

Where do you get vertebral osteomyelitis?

A

cervical- 10.6%
cervico-thoraco- 0.4%
lumbar 43.1%

39
Q

What are the symptoms of vertebral osteomyelitis?

A

Back pain- 86%

Fever- 60%

Neurological impairment 34%

40
Q

How do you diagnose vertebral osteomyeltitis?

A

MRI: 90% sensitive
Blood cultures
CT/ open biopsy

41
Q

How do you treat vertebral osteomyeltitis?

A

Six weeks of treatment
Longer treatment if undrained abscesses/implant associated

42
Q

What is the S/S of chronic osteomyelitis?

A

Pain
Brodies abscess
Sinus tract

43
Q

What is the diagnosis of chronic osteomyelitis?

A

MRI
Bone biopsy for culture and histology

44
Q

What is the treatment of chronic osteomyelitis?

A

Radical debridement down to living bone
remove sequestra, and remove infected bone and soft tissue

45
Q

What is the Modified Lautenbach technique?

A

Debridement and collection of multiple samples for culture and histology

All internal fixation devices removed and double-ended reaming was performed

Osteoscopy was used to ensure that healthy bleeding could be seen and any sequestra found was removed. Pulse lavage.

Double lumen suction irrigation system was introduced through a subcutaneous tunnel.

Post-op suction is applied for 30 mins
Antibiotics are instilled through the central lumen followed by 1ml of streptokinase. The suction system was clamped for the next 3.5 hrs.
Antibiotic instilled depended on culture results.
Every week 1l of Hartmanns solution was infused through each drain . Suction fluid was sent for culture
Irrigation was continued for 3 weeks usually
Oral antibiotics were continued for 6 weeks after discharge
After follow up for 101 months, 26 out of 35 patients had no signs of infection

46
Q

What is the Papineau technique?

A

Initially described by Papineau in 1973
Complete excision of infected tissue and necrotic bone
Open cancellous bone grafting of the osseous defect.
Split skin grafting for wound closure
Papineau reported a 93 % success rate after treating 180 patients
Panda et al reported a 89% success rate.

47
Q

What are the signs and symptoms of PJI?

A

Pain
Patient complains that the joint was ‘never right’
Early failure
Sinus tract

48
Q

What is the causative organisms of PJI?

A

Gram positive cocci
-coagulase negative staphylococci
-staphylococus aureus
Streptococci sp
Enterococci sp

Aerobic gram negative bacilli
Enterobacteriaceae
Pseudomonas aeruginosa

Anaerobes
Polymicrobial
Culture negative
Fungi

49
Q

What is the diagnosis of PJI?

A

Radiology- loosening
If CRP>13.5 for prosthetic knee joint infection
CRP> 5 for prosthetic hip joint infection

Joint aspiration
If >1700/ml of WCC correlates with knee PJI
If > 4200/ml of WCC correlates with hip PJI

May only get planktonic bacteria in joint fluid, may need to sample bacteria where infection is most likely

50
Q

What is intraoperative microbiological sampling?

A

Tissue specimens from at least 5 sites around the implant
Histopathology – infection defined as >5 neutrophils per high power field.
If 3 or more specimens yield identical organisms, this is highly predictive of infection (sensitivity 65%, specificity 99%)

51
Q

What is a single stage revision?

A

Remove all foreign material and dead bone

Change gloves, drapes etc

Re-implant new prosthesis with antibiotic impregnated cement and give iv antibiotics

52
Q

What is the endo Klinik single stage revision?

A

Aspirate joint to identify pathogen
Excision of infected tissue , synovectomy
Add antibiotics to bone cement according to culture results
Implantation of a cemented hip or knee prosthesis using antibiotic loaded cement
Give 7-10 days of iv antibiotics
Culture drain tips
Success rate is 89% in 2002

53
Q

What’s a two stage revision?

A

Remove prosthesis
Take samples for microbiology and histology
Period of iv antibiotics (6weeks). Stop antibiotics for 2 weeks
Re-debride and sample at second stage
Re-implantation with antibiotic impregnated cement
No further antibiotics if samples clear
OPAT

54
Q

How do you diagnose brucella?

A

Brucella IgG

Brucella DNA in tissue

55
Q

How do you treat brucella?

A

Rifampicin, ciprofloxacin, flucloxacillin

56
Q

What is this?

A

Brucella granuloma

57
Q

What is this?

A

Chronic osteomyelitis (child)

58
Q

What is this?

A

Prosthetic Joint Infection (PJI)

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