Sterilization of surgical materials and instruments ⋆ AgVetnepal

Table of Contents

Physical sterilization

Steam sterilization is the most commonly employed method of sterilization of instruments and equipment.
Different types of autoclaves are
- pressure steam sterilizer
- steam pressure sterilizer
- vacuum steam sterilizer
- dressing sterilizer
- gravity displacement sterilizer

Points to be considered

Instrument packs are positioned vertically (on edge ) and longitudinally in autoclave
A 13 minutes sterilizing cycle (exposure to saturated stem at 1210C) is a safe minimum required
Large linen packs require 30 minutes at 1210C
Once sterilized, sterile packs should be stored in closed cabinets. All packs should be dated.
Sharp instruments ¾ scissors, needles; surgical instruments can be sterilized by this method.

Dry heat destroys microorganisms primarily by oxidation process.
It is used to sterilize those materials for which moist heat cannot be used either due to deleterious effects on the material or material being impermeable to steam e.g: oils, powders, glass surgicals etc.
Slow process and long exposure time at a high temperature is required as spores are relatively resistance to dry heat.

Direct exposure of instruments to flame – not reliable.
Hot air oven – most common method.
An exposure to dry heat at a temperature of 1600C for 60 min will achieve sterilization equal to that of moist heat at 1210C for 15 min, at 151 lbs pressure.
Temperature time combinations for dry heat sterilization
- 1200c for 8.0 hours
- 1400c for 2.5 hours
- 1600c for 60 minutes
- 1700c for 40 minutes
Exposure time relates to the time after specific temperature has been achieved and don’t include heating lags.
Clean gowns, paper wrapped material, swabs, Petridis – 1200c for 8 hours
Stainless steel lens and glass ware – 1600c for 60 min

Filtration is used in air conditioning system to remove particles as small as 0.3 μm in diameter and also used to filter-sterilize heat labile solutions.

Ultraviolet light is used for surface sterilization.
Ionizing radiations, Beta and cathode rays are used to sterilize heat sensitive prepackaged surgical materials.
Example: Surgical mask – to produce two fold effect. CHEMICAL AGENT
An ideal chemical agent should have following properties
- kill all pathogenic microorganism
- work effectively in short period of time
- exert residual action
- not corrode, dry or stain
- be stable, odorless, non toxic
- be effective in presence of organic matter
- not be inactivated by other concurrently used chemicals

Ethylene oxide acts by inactivating the DNA molecules in the microbial cells thus preventing cell reproduction. Temperature – 120 to 140^oF
Eg: ethylene oxide, formal dehyde and beta propiolatone (generally used)
Sharp edged instruments – Scalpel blades, hypodermic needles.

Ethyl alcohol (70%), Isopropyl alcohol (90%) are commonly used
Presence of water easily denatures the protein.
- 70% alcohol is more qermicidal than absolute alcohol.
- Isoprophyl alcohol is more bacterial than ethyl alcohol
Sterilization can be done by immensities continuously. Eg: Needles.