Operation Theatre Surveillance Air sampling or Conventional Methods
Operation Theatre Surveillance:
Air sampling or Conventional Methods
Surgical site infections (SSIs) are second to third most common site
of health care associated infections. These complications of surgical
procedures cause considerable morbidity, and mortality. If these occur
deep at the site of the procedure, can carry mortality as high as 77 % .
There is considerable evidence available to indicate that the surgical site
infections are a significant health risk to hospital patients. Sources of
infection may be either endogenous (from the patient himself) or
exogenous from the theatre environment. A large body of information is
available which indicates that prevention of post operative infection is
dependent on several factors including effective theatre design,
sterilization and disinfection procedures, good surgical technique,
bacterial contamination of theatre air, discipline which includes restricting
the movement of staff . Many of debates are extended over on this topic
including the frequency of microbiological surveillance for operation
Key words: Air sampling, three bucket system, slit sampler,
colony forming units
INTRODUCTION & SITUATION ANALYSIS
Even today most of the surgeons are worrying about the OT
associated infections with anaerobes like clostridium tetani in most of the
instances. Infections with Cl. tetani are associated with very bad surgical
procedures which includes the over jealous manipulations of the tissues of
surgical site and leaving the dead tissue in the surgical site at the end of
the procedure and also heavy dust in the operation theatre environment.
Surveillance for clostridial spores is an age old concept of OT surveillance
and lost its importance with the available and applicable OT sterilization
and disinfection awareness Programme and practices. Today we rarely
encounter a infection with C.tetani
Routine testing for clostridial spores is not mandatory except
during certain situations like new constructions or structural alterations
are made to the theatre. But pyogenic infections mostly with S.aureus
and S.epidermidis are possible even with technically qualitative surgical
procedures . Healthy carriers have been found to shed staphylococci
which is responsible for inevitable airborne contamination. While there is
evidence to indicate that most outbreaks are caused by heavy dispersers
, every attempt should be made to minimize airborne transmission
within operating theatres. Studies in a number of operating theatres have
suggested that there is a general relationship between total air count and
risk of infection. Counts in the range of 700-1800/m 3 were related to
significant risk of infection and when they were under 180/m 3 the risk
was slight .
So prevention of airborne microbial contamination will prevent
the surgical site infections. To achieve this basic strategy we should
follow the certain guidelines. Which would include, proper and continuing
education to staff to prevent shedding of microbes and restrict the
unnecessary movements of OT staff within and outside the OT
MEASURES TO REDUCE MICROBIAL LOAD IN OT:
Fumigation or other newer methods of sterilization of
Operation Theater alone cannot sterilize or make the OT environment
safe. Failure to provide adequate operation theatre ventilation is
associated with risk of postoperative infections. Theatre ventilation has
been found to be a critical factor in prosthetic and joint surgery . While
maintaining the proper ventilation, we have to be careful about the
microbial load in the OT environment .Filtration of OT air by fitting the
HEPA filters are mandatory to fulfill the above criteria. Since the operation
theater environments are the dynamic, good equipment and
arrangements are only not safe since it becomes unsafe because of
human activities. Culture swabs from unnecessary surfaces of OT
environment (roof, upper parts of wall) may causes confusion during the
interpretation of the results . Dust should be removed with cloth wetted
with clean water Chemical and disinfectants should not be used as habit.
Chemical agents or disinfectants or detergents should be used when OT
floor and surfaces are contaminated with blood and body fluids. Swabbing
the surfaces with suitable commercially available disinfectant Bacillocid
(Mixture of dihydroxy formaldehyde, glutaraldehyde and bezalkonium
chloride) by using the three bucket system will remove the majority of
1st Bucket with water: Dirty mop is rinsed
2nd Bucket with fresh water for rinsing: Mop rinsed again in this
3rdBucket with suitable disinfectant: Mop is immersed in the solution
Should be mopped liberally. Wash the used mop with
disinfectant after use and dry.
STANDARD GUIDELINES AND PLANNING FOR AIR
There are no Universally agreed standards for any country or
place regarding when to undertake microbiological sampling in the
operating theatre and on the interpretation of sampling results .
However, there is sufficient evidence to support the undertaking of
microbiological air sampling in the operation theatre as part of the
vigilance & safety of an operating theatre, after any major structural
replacements (not including High Efficiency Particulate (HEPA) filter
changes and as deemed necessary by the hospital infection control
committee. Health care workers should follow certain guidelines before air
sampling. Prior to air sampling, obtain the suitable air sampling
equipment from a laboratory, establish laboratory time-lines for sample
collection, processing and provision of results and should not ignore to
consult the hospital microbiologist or infection control unit.
HOW TO DO THE AIR SAMPLING?
Bacterial counts in operation theaters are influenced by the
number of individuals present, ventilation and air flow methods. Air
sampling should be done after the all new or replacement work has
completed. The ventilation system should run continuously for 24 hours
before sampling and the theatre surfaces and fixed equipment, ducting
and air diffuser plates have to be cleaned.
Settle plate method by using blood agar, It is being practiced in
basic hospitals to detect pathogenic bacteria major isolate being
Staphylococcus aureus bacteria in hospital air. Settle plate method with
blood agar where the plates have to be kept at 2 ½ feet height on the
four corners of room and results are obtained based on the mean colony
number on the all culture plates after a prescribed time. Because of
recent advances in certain surgical procedures and bacterial counts settle
plate method is replaced with Slit sampler and Air centrifuge
equipment through which we can calculate the safe levels of colony
counts. There are several different types of air samplers available and the
manufacturer’s instructions for use must be followed. If affordable, the
preferred method is to use a sampler with timer and remote control.
RECOMMENDED METHOD FOR AIR SAMPLING
A single sample should be collected from each operating theatre.
The air sampler should be checked for cleanliness before use by
following the manufacturer’s instructions.
The theatre being sampled should have been left vacant for a
minimum of 15 minutes, preferably one hour. To avoid false-positive
results the theatre doors must be kept closed prior to and during the
Staff should wear theatre attire and a surgical mask, with proper
hands wash and surgical gloves.
Place the agar strips or plate into the sampler under aseptic
precautions and set up the equipment.
The air sampler should be placed in the middle of the theatre table
at the height of 2.5 feet and to be secured on a trolley.
The air sampler should then be switched on either by remote control
or manually, before leaving the room.
The sampling equipment will determine the volume of air sampled.
Sampling volume needs to be more than 0.25 m3 (250 L) and optimally
around 1m3 (1000 L).
Once sampling is completed, remove the test strips/agar plate
aseptically and label it clearly and send it the processing environment.
RESULTS AND INTERPRETATION:
Culture plates should be incubated under optimum conditions
in the microbiology laboratory. Early culture reports hardly available until
after 24 hours of incubation. Aerobic cultures on non-selective medium
(preferably Blood agar) should not exceed 35 colony – forming units of
bacteria and fungi per cubic meter of air for a conventional theatre and
1cfu for an ultra clean theatre to perform joint replacement and cardiac
surgeries . These counts are not rigid standards and are intended as a
guideline only. Even though the swabs are taken for OT surveillance to
isolate and identify the clostridial spores, air sampling is must to measure
the safer load of microbes. In some of the hospitals OT sampling is done
by swabbing and plating on the blood agar and results are being
announced after 24-48 hours of aerobic incubation. By the above
mentioned method quantitative estimation of the microbial load is not
possible. Literature which is supporting for this kind of practice is not
available from various sources. Moreover, this type of cultures on nonselective medium will create unnecessary confusion while detecting OT
sterilization status and which should be abandoned.
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