Introduction
Surgical site infections (SSIs)
are the second most common cause of hospital acquired (Nosocomial) infections.
These complications of surgical procedures cause considerable morbidity and,
when these occur deep at the site of the procedure, can lead to mortality as
high as 77%. The source of SSIs may be endogenous (normal flora of the patient’s
skin, mucous membranes, or viscera) or exogenous, which includes surgical
personnel (especially members of the surgical team), the surgical room environment
(including air, floor & wall), and tools, instruments, and materials
brought to the sterile field during surgery. By maintaining sterile environment
in surgical theater we can control major part of exogenous infections.
Formaldehyde fumigation has
long been an accepted method of sterilization for areas where microbiological
cleanliness is required. Fumigation with formaldehyde vapor is the recognized
and most commonly used method because of its cost effective procedure
(Alternative: vaporized hydrogen peroxide; expensive).
Fumigation
Procedure
Formaldehyde vapor is an
extremely effective biocidal agent. It acts as an alkylating agent,
inactivating micro-organisms by reacting with carboxyl, amino, hydroxyl and
sulphydral groups of proteins as well as amino groups of nucleic acid bases. Fumigation
is effective at above the temperature of 20ºC and relative humidity of 65%.
Formalin is commercially
available as 40% solution of formaldehyde in water. When formalin is heated
formaldehyde vapor is generated. Formaldehyde is a Schedule 1 chemical under
the COSHH (Control of Substances Hazardous to Health) Regulations and has a
Maximum Exposure Limit (MEL) of 2 ppm. But, concentrations encountered during
fumigation is many hundred times higher than this, so fumigation procedure must
be carried out only by trained personnel under strictly defined conditions. All
workers using formaldehyde must be aware of safe handling procedures.
Under certain conditions
formaldehyde can react with hydrochloric acid and chlorine containing
disinfectants such as hypochlorites to form chlormethyl ether, a potent lung
carcinogen. So hydrochloric acid and chlorine-containing disinfectants must be
removed from the room before fumigation.
Step 1:
Preparation
- Thoroughly
clean windows, doors, floor, walls, surgery table and all washable
equipments with soap and water.
- Close
windows and ventilators tightly. If any openings found seal it with
cellophane tape or other material to avoid the leak of fume.
- Switch
off all lights, A/C and other electrical & electronical items.
- Calculate
the room size (surgical theater only) in cubic feet (L×B×H) and calculate
the required amount of formaldehyde as given in step 3.
Step 2:
Precaution
- Adequate
care must be taken by wearing cap, mask, foot cover, spectacle etc.,
- Formaldehyde
is irritant to eye & nose; and it has also been recognized as a potential
carcinogen.
- So the
fumigating person must be provided with the personal protective equipments
(PPE).
- Paste
a warning notice on the front door indicating fumigation is in progress.
Step 3:
Fumigation
- Electric Boiler Fumigation Method
(Recommended): For Each 1000 cubic feet, 500 ml of formaldehyde (40%
solution) added in 1000 ml of distilled water (if not available use tap
water) in an electric boiler. Switch on the boiler, leave the room and
seal the door. After 45 minutes (variable depending to volume present in
the boils apparatus/its heating proficiency) switch off the boiler without
entering in to the room (Switch off the main from outside).
or
- Potassium Permanganate Method: Here
the heat generation is induced by an oxidizer - Potassium permanganate
(KMnO4), which results in auto boiling and generates fume from
formaldehyde. Take 500 ml of
formaldehyde (40% solution) in 1000 ml of distilled water (if not
available use tap water) in a heat resistant bowel, preferably in a steel
bucket and then add 450gm of
KMnO4 for 1000 cubic feet of theater volume. Repeat the same in
separate bucket for every another 1000 cubic feet until it reaches the
complete theater volume. It is important to add KMnO4 to all
buckets simultaneously to reduce the exposure to fume (i.e., need 3 or 4 persons at
different location).
- After
the initiation of formaldehyde vapor, immediately leave the room and seal
it for at least 12 to 24 hours.
Step 4: Neutralization
- Before
neutralization, formaldehyde fumigation system should be taken out from
the surgical theater. Then the toxicity of formaldehyde vapor should be
neutralized with ammonia solution.
- Place
a cotton ball and pour 300 ml of 10% ammonia (for each 500 ml of formaldehyde used) on the floor of surgical
theater, at least 4 hours before (07 a.m.) the “Sterility Test”.
- Formaldehyde
gas reacts with ammonia gas and produce hexamine (synonym
hexamethylenetetramine) which is considered a harmless substance.
- Switch
on the A/C, at least 2 hours before (09 a.m.) the “Sterility Test”.
Example:
Surgical Theater Volume = L×B×H = 20 × 15 × 10 = 3000 cubic feet
Note: Make it into nearest 1000, if the volume is in
fractions
Formaldehyde required for fumigation = 500 ml for
1000 cubic feet
= So, 1500 ml of formaldehyde required (to be diluted in 3000 ml of
distilled water)
Ammonia required for
neutralization = 300 ml of 10% ammonia for 500 ml of formaldehyde
= So 900 ml of 10%
ammonia required
Guidelines to be adhered
for Surgical Theater Sterility:
1.
A record (log
book) should be kept and properly maintained for all fumigations with
following details, date & time of fumigation, date & time of
neutralization, personnel involved, and the dates of “sterility test visits”
& their results.
2.
Construction layout
plan of the surgical theater with measurement details should be attached
with the log book.
3.
The construction must have, a. Separate dressing room
for medical officer and staff nurses, b. Patient waiting room, c. Surgical
room, d. Veranda
4.
Construction, carpentry, plumbing, electrical, cleaning
and other works should be completed before the initiation of fumigation
procedure.
5.
Room allotted for surgery (as shown in the plan) should
not be used for any other purposes.
6. Entire
block should be thoroughly cleaned before fumigation. All apparatus such as
suction, table, focus lights, A/C units, etc.,
should be cleaned according to manufacturer instructions.
7. Surroundings
should be clean and free from garbage, open drainage, bushes, shrubs, wastes, etc.,
8. Warning
notice should be pasted on the front door indicating fumigation is in progress.
9. Entry
should be restricted to authorized persons (Label must be pasted on the main
door).
10. Separate
footwear should be kept at the entrance (inside) of surgical theater.
11. Theater
dress (includes head cap, mask, apron, footwear, etc.,) should be made available for all persons who are entering
into the surgical theater (surgeons, anesthetist, microbiologist team, nurses,
theater assistants & helper).
12. Surgical
theater should be cleaned and fumigated periodically depending upon the case
load.
