Disinfection
Cleaning of items is essential before disinfection is undertaken and
the efficiency also depends on:
1. the nature of microorganisms;
2. the load of microorganisms;
3. the duration of exposure to the
agent;
4. the temperature.
Disinfection
with low-temperature steam
Typical conditions include exposure to dry saturated steam at a
temperature of 730C for a period of 20 minutes at a pressure below
atmospheric. This is a useful process for dealing with dirty returns from the
operating theatre or clinics which may be contaminated with protein from bodily
secretions and microorganisms. Following this method of disinfection the
instruments must be cleaned.
Disinfection
with boiling water
This utilises soft water at 1000C at normal pressure for 5
minutes. Instruments must be thoroughly cleaned before being utilised.
Disinfection
with formaldehyde
Formaldehyde gas is a broad-spectrum antimicrobial agent. This process
utilises a cabinet which is airtight and circulates gaseous formaldehyde up to
500C.
Disinfection
with glutaraldehyde
A 2 per cent solution of glutataldehyde is effective against most
bacterial viruses, including hepatitis B and C and HIV, and is particularly
useful for the decontamination of flexible endoscopes.
• Thorough cleansing is essential.
• The degree of decontamination is proportional to the time of
immersion.
• It is a toxic substance and causes irritant, allergic reactions
to the staff, particularly skin reactions, which limits its use.
Safeguards during sterilisation must include:
• appropriate packing for the sterilisation of disinfection
process in order to avoid reduced penetration of the active agent. This is
particularly important in the packing in the autoclave;
• arrangements of articles so that all surfaces are directly
exposed to the agent. This includes opening or unlocking jointed instruments and
disassembling instruments;
• the use of chemical indicators routinely;
• the interval monitoring of sterilisation process with chemical,
thermal and, sometimes, biological indicators;
• the utilisation of flash sterilisation, where a temperature of
1470C is used at a pressure of 40 lb/in.2, is now rare and
should only be considered in an emergency situation;
• a careful maintenance plan for all sterilisation processes.