SURGICAL SITE INFECTION

Introduction

• Devastating surgical complication.• Although reduced now• CHALENGING PROBLEM• Costly – patient & health care system.

Historical Aspects

• Pringle 1750 – “Antiseptic”• Isaac Benedict Prevost 1807 – first proof of

microorganisms as the causation of sepsis.• Louis Paster 1863 – Putrifaction is caused by

microbes from air.• Joseph Lister – used antiseptic soln to prevent

putrifaction & demonstrated that pus is a disaster rather than a sign of healing.

• Lister’s technique of sterilization, skin preparation and washing became –

Foundation of “Antiseptic Surgery”.• First step in development of “Asepsis in surgery”.• Introduction of antibiotics 1940 –

Streptococcal hospital infection disappeared.• 1950s World wide epidemic of nosocomial

infection by Virulent resistant Staphylococcus.

Nosocomial Infection

• Develops during hospitalization• Neither present nor incubating at the time of

patients admission.• 50% involve surgical site infection.

National Nosocomial Infection Surveillance (NNIS)

• Current version for SSI risk index scores each operation by counting the risk factors:

1. Type of wound2. ASA score of 3,4 or5 (Host defense)3. Duration of surgery – lasting more than T-hours

Surgical site infection

• Postoperative wound developing signs of inflammation or serous discharge is labeled as “possibly infected”.

• Cruse et al 1977 classified wounds – 4 categories

1. Clean wound:• No infection, no break in aseptic technique & no

hollow muscular organ opened.

2. Clean contaminated wound: Hollow muscular organ opened with minimal

organ spillage.

3. Contaminated wound: Hollow organ opened with gross spillage, acute

inflammation without pus, traumatic wounds within 4 hours and major break in aseptic technique.

4. Dirty wound: Perforated viscus, pus, traumatic wound more than 4

hours old.

• INFECTION RATE

1.5

7.7

15.2

40

0

5

10

15

20

25

30

35

40

1st Qtr

Clean

Clean contaminated

Contaminated

Dirty

• Infection in clean wounds – Surveillance & research.– < 1% Ideal.– 1-2% can be acceptable.– > 2% cause of concern.

• Monthly announcement– Everyone aware of SSI– Can reduce by 38% by appropriate feedback.

Rate of infection

• Purely a statistic for the surgeon.• Total DISASTER for the patient.• Sir Watson Jones 1962 – “Infection of one

clean case in a thousand is a disaster of the first magnitude”.

• Even slight delay in healing, redness of skin, or any other sign of wound infection – evidence of failure.

Orthopaedic clean wound

• Too many variables– Surgery of soft tissues alone or of bones– With or without implants– Emergency trauma or planned trauma cases– Timing of surgery in trauma– Reaming of medullary canal, primary plating.– Stable and unstable fixation.

Post Operative infection?

• Primary or secondary?• Possible to predict?• High risk patients?• Possible to prevent in best possible operative

conditions?

• All operative wounds get contaminated during surgery – does not mean infection.

• Sources of contamination:1. Surgeon & his team2. Air in OT3. Skin of patient & all OT personnel.• Conversion of this contamination to

infection is to be avoided.

Depends upon:

• Virulence of the organisms• Degree of contamination• Presence of dead & devitalized tissue,

implants & suture material.• Site of operation i.e. bone• Duration of surgery• HOST RESPONSE – Immunological status

SSI

• Story of germination of a seed in soil.• 95% of bacteria reach – Via air by direct

sedimentation into the wound or the instruments.

• Highest conc. – within the circle of surgical team directly over the wound.

• No of bacteria directly proportional to the increase in activity and number of the team – max. at the time of induction, positioning and extubation/ Closure.

• Staphylococcus aureus carrier – 30-50% of general population.

• Every person sheds ~55,000 skin scales/min. – 10-20% contain live bacteria.

• Increase in shedding:– Loose cotton scrub suits– Higher temperature & humidity.

Gloves

• In a study of 1209 cases – 141 gloves were found punctured.

• 18,000 Staph aureus can pass a single puncture in 20min.

• 3-5 min hand scrub with antiseptic soln. is essential.

• Double gloves – additional security.• New cut resistant gloves.

Airborne bacteria

• Air handling systems of OT.• Type of scrub suits worn.• Air bacterial count in ordinary OT varies from

50 – 500 colony meter cube• “A Sterile air operating room” & Concept of “Rapid Unimpeded Down flow of

Filtered Air and Exhaust Ventilated Whole Body Suit” – Sir John Charnley

Microbiological facts:

1. Airborne bacterial contamination is directly related to number & activity of people in OR.

2. Inversely related to the effectiveness of personnel garment barrier & no. of air exchange / hour.

3. Air borne bacteria are agglomerated on inanimate particles size from 2-10 microns.

4. Almost always gram positive corresponding to skin flora.

Methods of cleaning air

1. Laminar air flow – clean, filtered air with frequent whole air exchange.

2. Ultraviolet light system3. Vacuum body exhaust system4. Garment barrier.5. HEPA (High Efficacy Particle Air filter) –

removing 99.9% particles larger than 0.3 microns. (Bacteria - .5-10.5)

Laminar flow

• Super-high air turn over (400-600) in a laminar flow room – “Air broom” action.

• Flow – Horizontal or Vertical.• Conventional OR – 12-25 air exchanges each

hour – Federal standards.• “Unobstructed” – If not – positive pressure is generated• Doors kept closed.

• Air temperature – 21.1 to 24.4 C– Lower temperatures are preferred.

• Humidity: 50%– Prevent static electricity and – Decrease perspiration– Decreased viability of bacteria

Garment Barrier

• AORN recommends:– Pant suit or one piece suit with ankle closure &

shoe covers.– All hair covered by cap or hood– Face mask – high microbial filtration efficacy.

• Micro porous textile – disposable/reusable – use in gown & drape barrier systems.

• Standard cotton scrub suit or drapes – – pore size 100 microns– Sheds more bacteria “Cheese grater” effect.– “Bellows” action– Wet

• Microporous material is superior as:– Resistance to blood & water– Abrasion resistant– Lint free– Memory free– High degree of drapability.

• e.g Polypropylene nonwoven gown.

Host defense mechanism

• Skin test score• Serum albumin level• Age of the patient– Prediction regarding susceptibility to infection

• Other factors– Diabetes, Old age, Obesity, Rh Arthritis,– Major implant surgery– AIDS

• Protein calorie malnutrition – most imp. factor.• Clean wound infection rate in– Diabetics – 10.5%– With obesity – 13.5%– With malnutrition 16.5%

• Polytrauma patients.• These compromised situations - decision

regarding early operative intervention has to weigh against possibility of infection.

Organisms

• 60% of SSI – Gram +ve bacteria esp. Staph aureus and epidermidis.

• 20% - Gram –ve bacteria like E.Coli, Pseudomonas, Klebsiella etc.

• Precise bacteriological diagnosis– 6 aerobic and anaerobic cultures.– Enriched media for at least 2 weeks.

• 90% of implant surgeries result from intraoperative contamination.

• 50% of these become clinically evident 3 months after surgery

• Many of these caused by low virulence organisms like Staph epidermidis and other anaerobes.

• Steady increase in G –ve bacteria – more difficult to treat as is resistant Staph aureus.

• 2-8 million inoculums of Staph aureus injected develop infection.

• Only 100 organisms in presence of foreign body.

• Main reservoir – human body.• Nasal carriers – 30-50% of general population.• Glycocalyx biofilms:– Bacteria get adhered to implant surface.

Susceptibility of bone to infection

• Limited soft tissue space• Blood supply favoring necrosis• Inadequate mechanism to reabsorb necrotic

bone• Increased duration of surgery

Role of prophylactic antibiotics

• Tengve et al reported– 16.9% rate of infection with no antibiotics.– 1.8% with prophylactic antibiotics.

• Antibiotics given before bacterial inoculation– Inhibit growth of bacteria

• After inoculation– Prevent overt clinical signs of infection, but

bacteria can always be isolated from the wound.

Pathophysiology

• As a response to operative trauma – Maximum exudation occurs in the first 6 hrs and– Contamination occurs at the time of surgery

• Antibiotic must be present in the circulation & into hematoma throughout the operation in sufficient concentration – to kill these bacteria.

Prophylactic antibiotic

• Started just before surgery• Ideal conc. in serum during surgery should be

4% of MIC in a healthy individual. 8% in a compromised patient.• No extra advantage of continuing for 5 or

more days over limited therapy. (Stone et al)

Topical antibiotics

• Willson et al 1991 – Topical triple antibiotic soln.- Neuromycin, polymyxin and bacitracin.

• Bacitracin – allergic rxn so stopped.• Simple good wash with NS or RL is very

effective.

Clinical presentation of postoperative infection

• 3 types of presentation:1. Early – within 8 weeks2. Delayed – 8 weeks – 1 year.3. Late – after 1 year.

• Early further 4 types (Mukhopadaya)i. Imminent within 48 hrsii. 3-9 days i.e. before suture removaliii. 10-21st day andiv. 3-8 weeks.

Classical presentation

• Disproportionate pain• Fever >102 F• Wound – signs of local cellulitis• Mild to moderate serosanguineous discharge.

Seen only when antibiotics and anti inflammatory are not given.

Common presentation

• Severe pain• Fever not responding to high doses of drugs• Frank purulent discharge• Wound already partially opened up due to cut

through sutures.

Late infection

• Go home with apparently normal wound healing

• Return with chronic discharging sinus• Persistent tachycardia• Pain not presenting complaint.

Diagnosis of infection

• Fever and Leukocytosis – not always helpful.• Thrombotic index• “Leukergy” – based on the phenomenon– WBCs agglomerate in the peripheral blood of

patients with inflammatory disease.– Percentage of agglomerated cells correlate with

the severity of infection.– Rapid and inexpensive.

• Persistent elevation of ESR – – Suggests infection– Neither very sensitive nor specific.

• ESR with CRP• Results better but still unreliable.• Bone scan – more accurate.

Treatment

• Immediate action.• Discharging fluid to be sent for – – Gram staining, – Culture & sensitivity.

• Broad spectrum antibiotic along with aminoglycoside started – no relief in 24 hrs –

• Open and debride thoroughly.• Always better to debride than wait for

antibiotics to act.

• Wound always closed by loose intermittent sutures or by secondary suturing later.

• A well fixed implant can be left as such.• Loose implant – removal or refixation or

Exfixation.• Implants once infected needs removal• Well fixed implant left in place till fracture

unites.

• Plate fixation – Early diagnosis and removal – extensive cortical necrosis.

• Non union is not due to infection but inadequate fixation.

• Sir John Charnley 1982 “Because of the tragic seriousness of post

operative infection, I regard it as our duty to continue in the future to study to eliminate post operative infection by any means or combination of means, whatever, I say eliminate deliberately because I have not yet abandoned the hope that some way we’ll achieve this target”

Thank You!