surgical site infectiob

Question 1

what is it?

Answer 1

Surgical site infection (SSI) is a type of healthcare-associated infection that can occur post-surgery within the area operated upon. The pathogens can originate from the patient’s endogenous flora or the external environment, including healthcare workers and surgical instruments.

Question 2

what are common bacterial causes?

Answer 2

Staphylococcus aureus, coagulase-negative staphylococci and Escherichia coli

Question 3

what are patient-related factors?

Answer 3

Conditions such as diabetes mellitus, obesity, malnutrition, immunosuppression and peripheral vascular disease increase the risk of SSI due to impaired wound healing and host defence mechanisms.

Nicotine has vasoconstrictive effects that impair oxygenation of tissues, thus hindering the healing process and increasing susceptibility to infection.

Elderly patients have a higher risk of SSI due to age-associated changes in skin integrity, immune response and comorbidity burden.

Question 4

what are procedure-related factors?

Answer 4

Poor surgical technique such as inadequate haemostasis or tissue handling can lead to necrosis or haematoma formation providing a medium for bacterial proliferation.

Prolonged surgeries increase exposure time to potential pathogens thereby elevating the risk of SSI.

Clean-contaminated, contaminated or dirty surgeries inherently carry a higher risk of infection compared to clean surgeries.

Question 5

what are postoperative factors?

Answer 5

Poor glycaemic control in the immediate postoperative period has been associated with an increased incidence of SSI due to impairment in neutrophil function.

Improper wound care practices can introduce pathogens into the surgical site leading to infection.

Inappropriate use of antibiotic prophylaxis, either in terms of timing, choice of agent or duration can increase the risk of SSI.

Question 6

what is the pathophysiology?

Answer 6

1. bacterial contamination from endogenous sources such as skin flora or exogenous sources like surgical instruments, operating room air, or healthcare personnel.
2. bacteria adhere to host tissues using specific adhesins. These adhesins recognise and bind to receptors on host cells, enabling colonisation of the wound.
3. some bacteria form biofilms - structured communities embedded in a self-produced matrix. Biofilms protect bacteria from host defences and antibiotic therapy, making them difficult to eradicate.
4. bacteria cause tissue damage through various mechanisms such as toxin production and induction of inflammation. Bacteria also proliferate within the wound environment.
5. Some bacteria have the capacity to invade host tissues directly or disseminate via bloodstream or lymphatics causing systemic infection.

Question 7

what are the classifications?

Answer 7

Superficial Incisional SSI
Deep Incisional SSI
Organ/Space SSI

Question 8

what is Superficial Incisional SSI?

Answer 8

This type of infection occurs within 30 days after surgery. It involves only skin or subcutaneous tissue of the incision.
Patients may present with purulent drainage, localised pain, redness, swelling or heat. Laboratory tests may show elevated white blood cell count.

Question 9

what is Deep Incisional SSI?

Answer 9

This infection also occurs within 30 days after operation if no implant is left in place or within one year if an implant is in place and the infection appears to be related to the surgery.
The deep soft tissues (e.g., fascial and muscle layers) are involved in this type of SSI. Patients often present with fever, tenderness at the surgical site, and possibly an abscess or other evidence of infection involving the deep layers.

Question 10

what is Organ/Space SSI?

Answer 10

This type of infection can occur within 30 days post-surgery if no implant is left in place or within a year if an implant is in place and seems to be related to the surgery.
It involves any part of the anatomy (organs or spaces), other than the incision, which was opened or manipulated during an operation. Symptoms depend on the organ system involved but may include fever, pain, and specific symptoms related to the organ infected.

Question 11

what are localised features?

Answer 11

fever
oedema
pain/tenderness
purulent discharge
dehiscence

Question 12

what are systemic features?

Answer 12

fever
tachycardia
hypotension
altered mental status

Question 13

what are the ix done?

Answer 13

Microbiological Sampling
FBC - raised WCC
CRP, ESR - elevated
serology
USS to identify collections
CT anatomical info about deeper structures
MRI for osteomyelitis

Question 14

what is the mx?

Answer 14

start empirical abc and change based on culutres
surgical debridement of infected tissues
wound care