Sterilization and Disinfection

Dr. Wasif Haq

Concept & Need to Sterilize instruments

• Pakistan carries one of the world's highest burdens of chronic hepatitis and mortality due to liver failure and hepatocellular carcinomas.

• Contaminated needle use in medical care ,drug abuse, unsafe blood and blood product transfusion .

• 19 million, of Pakistan’s population of 160 million are suffering from hepatitis.

• One out of every 10 Pakistanis suffers from either Hepatitis B or C.

• 40,000 - 45,000 cases of H.I.V./ A.I.D.S. since 1986.

Terms & Definition• Sepsis: Breakdown of living tissue by

action of microorganisms and is usually accompanied by inflammation.

• Asepsis: Avoidance of sepsis.• Antiseptic and disinfectants:

Substances that can prevent the multiplication of organisms capable of causing infection.

• Sterility: Freedom from viable forms of microorganisms.

• Universal Precautions & Personal Protective Equipment.

Universal Precautions

• “All patients and blood contaminated body fluids are treated as infectious”.

• What body fluids can be highly infectious? Semen, vaginal secretions, synovial fluid, cerebrospinal fluid, pleural fluid, peritoneal fluid, pericardial fluid, amniotic fluid.

How to follow Universal precautions?

• Recognition of potential hazards (body fluids)

• Personal protective equipment (P.P.E.): Use of barriers e.g. gloves, lab coat, masks, eye shield, facemask etc.

• Knowledge and application of techniques that reduce the exposure e.g. hand washing, disposal of contaminated needles, disposal of body fluids.

“Success is simple. Do what's right, the right way, at the right time.”

Sterilization; types, advantages & disadvantages.

Sterilization & Types• Sterilization is defined as the process that

destroys all forms of microbial life including bacteria, fungi, viruses as well as bacterial spores.

• Types of sterilization

Physical Chemical

(Dry heat, moist heat, autoclave, (Ethylene Oxide radiation) Aldehydes,Ozone)

Physical Methods of Sterilization

• Heat: Protein denaturation, coagulation, oxidative damage to cells.

• Moist heat superior to dry heat; quick and lower temperature.

• Steam pressure sterilization (Autoclaving): Utilizes steam under increased pressure. Uses 121 0 C at 15 Ibs Pressure for 15 minutes or 134 0 C at 30 Ibs pressure for 4 minutes.

• Irradiation: Gamma rays or accelerated electrons used.

Chemical Methods• Ethylene Oxide: Rapidly destroys spores.• Highly flammable, hence mixed with CO2 or

Nitrogen to make it safer.• Gas concentration: 200 -800 mg/l,

Temperature: 30-60 0 C, Humidity: 45-85%, Time: 3 hours.

• Aldehydes (Formaldehyde, Gluteraldehyde & Phthalaldehyde) : Formaldehyde slower action, 2% Gluteraldehyde requires 3 hours immersion, 0.55% solution Phthalaldehyde better and quicker action than Gluteraldehyde and effective against Gluteraldehyde resistant spores.

Choosing the best technique

Technique Advantages Disadvantages Comments

Autoclave Rapid, effective for dental instruments, surgical packs & towels packs.

Items sensitive to heat e.g. carbon steel instruments, carbide and diamond burs corrode.

121 0 C 15 Ibs 15 mins134 0 C, 30 Ibs 4 mins

Dry heat Items sensitive to heat e.g. carbon steel instruments, carbide and diamond burs can be sterilized.

Rubber, plastic instruments cannot be sterilized.Maximum sterilization failures.

160 0 C 60 minutes, 170 0 C 40 minutes, 180 0 C 20 minutes.Don’t open until temperature falls below 60 0 C

Ethylene Oxide Heat & moisture sensitive articles, electrical equipment.

Toxic, flammable, carcinogenic.

Gas:200 -800 mg/l, Temperature: 30-60 0 C, Humidity: 45-85%, Time: 3 hours.

Irradiation Syringes, gloves, plastic dishes, glassware, antibiotics

Poor penetrative power and costly.

Sterilizing dose: 25 K Gy in few seconds.

Aldehydes. Heat sensitive instruments.

Irritant, carcionogenic, inactivated by proteins.

Variable time :10 mins to 3 hours.

How to check quality of sterilization?

Sterilization Check

• Sterilization bags and tapes change color upon exposure to heat and sterilization chemicals.

• If used alone, reliability is questionable.

• Commercially available bacterial spores.

• Bacillus strarothermophilus; evaluation of heat sterilization.

Other Measures

• Do not store gloves in sunlight to prevent oxidation; store in tightly closed plastic bags.

• Remove watches, jewelry, rings before treatment.

• Wash hands when changing gloves.• Chlorhexidine hand cleaners preferred.• Head rest, light handle, tray table can be

covered with disposable cover/sheets.• If several patients waiting, treat the non-

infectious patients first.

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