This document defines key terms related to asepsis and infection control such as sepsis, asepsis, antisepsis, disinfectants, and sterilization. It describes various methods of sterilization including physical sterilization using dry heat, moist heat and autoclaving. Chemical sterilization using agents like alcohols, aldehydes, chlorhexidine, and iodine is also discussed. Gas sterilization using ethylene oxide and irradiation sterilization techniques are summarized. Principles of surgical asepsis including maintaining a sterile field and proper preparation of surgical personnel and patients are highlighted in brief.

1. Ganga Prasad Yadav
M.V.Sc., 1st Semester
Veterinary Surgery & Radiology

2. Common Definitions
Sepsis: Presence of pathogenic microorganisms,
or their toxic products in the tissues of a patient.
Asepsis: The absence of pathogenic micro-
organisms in living tissues.
Aseptic technique: The clean practice used to
remove or destroy pathogens and to prevent their
spread from one animal/people or place to
another animal/people or place.
Antisepsis: Prevention of sepsis by the destruction
or inhibition of microorganisms using an agent
that may be safely applied to living tissues.

3. Common Definitions
 Antiseptic: A chemical agent that either kills pathogenic
micro-organisms, or inhibits their growth on animate
(living) tissue. Example: Chlorhexidine
 Disinfectant: A germicidal chemical substance that kills
micro-organisms on inanimate objects. Example:
glutaraldehyde.
 Disinfection: Removal of micro-organisms, but not
necessarily their spores and viruses found on non-living
objects.
 Sterilization: complete elimination of microbial
viability, including vegetative forms of bacteria and
spores by physical or chemical means.

4. Transmission of microorganisms
• Microorganisms are transmitted by
Transmission of
microorganisms
Hospital Staffs Environment
Contaminated
Instruments

5. Sources of Contamination
 Sources of Contamination
Surgical personnel
Non-sterile barriers:
 Surgical clothing
 Scrub tops
 Surgical head cover
 Face masks
Sterile barriers:
 Gloves
 Surgical skin scrub

6. Sources of Contamination
 Patient
 Operating theatre
environment
 Surgical
equipments

7. Principles of surgery asepsis
Followings are the principles of surgical
asepsis:
1. Use only sterile items within a sterile field.
2. Scrubbed personnel are gowned and gloved.
3. Sterile personnel operate within a sterile filed
(sterile personnel touch only sterile items or
areas, unsterile personnel touch only
unsterile items or areas.

8. Principles of surgery asepsis
4. Sterile drapes are used to crate a sterile field.
5. All items used in a sterile field must be sterile.
6. All items introduced onto a sterile field should be
opened , dispensed and transferred by methods
that maintain sterility and integrity.
7. A sterile field should be maintained and
monitored constantly.
8. Surgical staff should be trained to recognize when
they have broken technique and should know how
to remedy the situation.

9. Levels of sterility and disinfection
• On the basis of magnitude of the risk of
infection, the use of surgical instruments and
equipments can be classified into three
categories:
Level of Sterility and Disinfection
1. Critical: Surgical
Pack Instruments 2. Semicritical:
Endotracheal tube
3. Noncritical: Face
masks and
Rebreathing Bags

10. Preparation for Surgery
• It involves:
Surgeon’s
preparation:
1. Surgical head cover
2. Mask
3. Surgical shoes
4. Hand scrubbing
5. Hand drying
6. Gowning
7. Gloving
Patient preparation:
1. Hair removal
2. skin preparation
3. Patient draping

11. Scrub Solutions
• Commonly used scrub
solutions are:
1. Chlorhexidine
- Excellent spectrum
- Ocassionally sensitive
to mucous membrane.
2. Povidine iodine
- Excellent spectrum
- Ocassionally skin
sensitive.

12. Wrapping Instrument Packs

13. Folding and Wrapping Surgical Gown

14. Unwrapping of Sterile Packs

15. Hand Scrubbing Technique

16. Steps in Surgical Gloving
1 2 3
654
Figures: 1- 6 showing steps in surgical gloving

17. Sterilization and Disinfection
Destruction of all the microorganisms (bacteria,
viruses, spores) from objects (instruments, drapes,
catheters, needles, blades) that come in contact
with tissue or enter into the vascular space.
Disinfection: Process of destroying
microorganisms except viruses and spores found
in inanimate objects.
Methods of sterilization:
1. Physical sterilization 2. Chemical sterilization
3. Gas sterilization 4. Irradiation

18. Physical Sterilization
 most commonly used sterilization method.
 used dry or moist heat.
1.1 Dry Heat:
 Mechanism of Action: Denaturation or
destruction of cellular proteins.
a. Flaming:
 Used to sterilized the instruments like
blade, needles passing over the flame of gas
burner till red hot, destroys bacteria.

19. Physical Sterilization
b. Hot air oven:
- Most common and effective method
of sterilization of metal instruments and
glassware.
- A temperature of 120⁰C for 8 hours,
140⁰C for 2.5 hours, 160⁰C for 1 hour and
180⁰C for 20-30 minutes is usually sufficient.

20. Physical Sterilization
1.2 Moist heat:
 Mechanism of action: Denaturation of major cell
constituents.
a. Boiling:
 Most effective method of sterilization.
 2% sodium carbonate added to boiling water to
make alkalinity , that helps in destruction of
microbial spore.
 Uses temperature of 100⁰C for at least 15 minutes
to sterilize syringes and needles.

21. Physical Sterilization.
b. Autoclaving:
 Moist heat in the form of
saturated steam under
pressure.
 A temperature of 121⁰C
under 15 pounds pressure
for 15 minutes.
 Sharp instruments like
scissors, needles and other
routine instruments of a
surgical pack, excluding
sharp blade. Fig.: Autoclave

22. Physical Sterilization
• Flashing : when unwrapped instruments is
autoclaved for shorter period of time. Done
for critical instruments. A temperature of
131⁰C under 30 pounds pressure per square
inch for 4-7 minutes.
• In field condition, large pressure cooker is
used to sterilized surgical instruments and
packs under maintained pressure for 45
minutes.

23. Chemical or cold sterilization
 Refers to immersion of instruments in tray
containing disinfectant solutions such as
Phenol, Alcohol (ethyl or isopropyle alcohol),
Glutaraldehyde, Betapropiolactone, aldehydes
(formalin), Chlorhexidine that destroys the
pathogenic microorganisms on inanimate
objects.
 Destroy all bacteria except tubercle bacillus.

24. Chemical or cold sterilization
 Used for sharp edged instruments like scalpel
blades and hypodermic needles.
 Spores and Viruses may not be destroyed so not
used for critical instruments.
1. Alcohols:
 Mechanism of action: by Protein denaturation,
metabolic interruption and cell lysis.
 Isopropyl alcohol (50-70%) and ethyl alcohol
(70%) used for spot cleaning and injection site
preparation.

25. Chemical or cold sterilization
It is corrosive to stainless steel and volatile.
At lower concentration, acts as bacteriostatic
rather than bactericidal.
2. Aldehyde:
Mechanism of action: By protein and nucleic
acid alkylation.

26. Chemical or cold sterilization
a. Formaldehyde:
 It is in the form of formalin, 37-40%
solution of formaldehyde and water.
 Capable of killing all bacteria, viruses and
spores.
 Extremely pungent smell, irritating to skin
and mucous membranes and has limited
application as a cold sterilization agent.

27. Chemical or cold sterilization
 40% Formalin is used
in fumigator at
minimum relative
humidity of 70%,
temperature 30-40°C to
sterilize operation
theatre.
180 ml of 40%
formalin is used for
1000 cu ft. size of
room.

28. Chemical or cold sterilization
Uses:
 Disinfection of organic wastes, hospital floors, walls.
 Disinfection of membranes in dialysis equipment etc.
b. Glutaraldehyde:
 2% solution of glutaraldehyde is used for
disinfection of lenses, dental equipments, delicate
instruments or anesthetic accessories.
 It is also irritating to skin and mucous membrane
and odor, so well rinsed before use.

29. Chemical or cold sterilization
3. Chlorhexidine:
 An antiseptic agent available in detergent,
tincture and aqueous formulations.
0.75-1% solution used for scrubbing.
 Widely used for preparation of surgical patients
and for surgical hand scrubs due to nonirritating
property to skin.
 Effective against gram negative and gram
positive organisms, repeated use increases its
effectiveness.

30. Chemical or cold sterilization
4. Quaternary ammonium compounds: It is
also used in fumigation/fogging of
operation theatre for 45 minutes.
 Example: Microgen D-125 (a commercial
product).
 It is bactericidal, virucidal and fungicidal
disinfectant.
 15 ml of concentrate Microgen D-
125mixed in 1 litre of water for
disinfection every 1000 cu. Ft room in
high risk areas like operation theatre,
ICU, Pathology laboratory etc.

31. Chemical or cold sterilization
5. Iodine compounds
Mechanism of action: released free iodine
from carrier molecules and acts as disinfectant.
1. Povidine Iodine (Betadine):
 Bactericidal, virucidal, fungicidal but poor
sporicidal activity.
 Used for cleaning of wounds, scrubbing of
hands.
2. Iodophors (7.5%): Used as scrub solution for
cleaning dark colored floors and countertops.

32. Chemical or cold sterilization
6. Chlorine compounds
Mechanism of action: by chlorination and
oxidation of essential molecules.
1. Hypochlorite:
 2.5% sodium hypochlorite solution is used.
 Used for cleaning floor and countertops.
 Inactivated by organic debris and corrosive to
metal.

33. Chemical or cold sterilization
7. Phenol and its derivative:
a. Phenol:
 2% solution used for disinfection.
 Acts by disrupting the cell membranes and
precipitate cellular proteins.
 Bactericidal but do not affect viruses and
spores.
 Commonly used as cold sterilint in combination
with detergents or soaps to increase the spectrum
of their activity.

34. Chemical or cold sterilization
b. Crysol: 0.5 – 1% of Crysol used as
intestinal antiseptic.
c. Lysol: used for disinfection of non-living
objects. Examples: Disinfection of floor,
Bathrooms, Washbasins, organic wastes
such as faeces and urine etc.
d. Chloroxylenol (dettol): 2% solution of
dettol used for antiseptic for intact skin.

35. Gas sterilization
1. Ethylene oxide gas:
Effective against all types of
microorganisms.
Kill microorganisms by
altering their normal cellular
metabolism and replication
through alkylation of protein,
ribonucleic acids and
deoxyribonucleic acid.
Moisture and heat sensitive
equipments can be sterilized .

36. Gas sterilization
• The effectiveness of ethylene oxide gas as a
sterilizing agent depends on:
a. Gas concentration: 450 – 1500 mg/L.
b. Temperature: usually 21- 60⁰C.
c. Exposure time: 48 minutes to several hours.
d. Humidity: 40%, necessary for lethal action of
ethylene oxide.

37. Gas sterilization
Used to sterilize
 Endocope
 Gloves
 Catheters
 Items sealed in plastic etc.

38. Irradiation
 Radiation used for sterilization is of two types: Ionising and
Non-ionising radiation.
 Ionising Radiation: Uses shorter wavelengh, high intensity and
high penetrating radiation to destroy microorganisms. For
example: Gamma rays, X-rays.
 Gamma rays have shorter wavelength with deeper penetration .
Used to sterilize pre-packed items:
 Surgical blades, Swabs, Catheters, Syringes
 Gowns
 Drapes
 Table covers etc.
 Non-ionising radiation: Uses longer wavelengh having lower
energy and penetration. For example: UV rays
 UV rays (300-400nm wavelength) produced by mercury vapor
lamp used to sterilize table surfaces, room.

39. References
1. Small Animal Surgery, 4th Edition by Theresa
Welch Fossum.
2. Text Book of Small Animal Surgery, 3rd Edition
by Douglas Slatter.
3. Ruminant Surgery by RPS Tyagi and Jit Singh.
4. Fundamentals of General Veterinary Surgery by
Md. Moin Ansari.
5. Veterinary Surgery Small Animal by Karen M.
Tobias and Spencer A. Johnston.