Week 4 Principles of Sterilisation and Disinfection

Question 1

Three classifications of medical items

Answer 1

Non-critical items, semi-critical items and critical items

Question 2

Definition of non-critical item

Answer 2

They come into contact with intact skin. The require regular cleaning and low level disinfection to remove transient infectious agents

Question 3

Semi-critical items

Answer 3

Come into contact with non intact skin or mucus membranes. They must be disinfected, single use or sterilised prior to use for patient safety

Question 4

Critical items

Answer 4

Come into contact with sterile tissues and body cavities and must be sterile at the time of use

Question 5

Cleaning

Answer 5

Removal of organic material that may support the growth and persistence of infectious agents in the healthcare environment. This process is used for non-critical items

Question 6

Disinfection

Answer 6

The destruction and removal of infectious agents resulting in a reduction in the number of living infectious agents to an acceptable level

Question 7

Sterilisation

Answer 7

The process of sterilisation results in the complete destruction of ALL living infectious agents

Question 8

Contact between chemical agent and infectious agent is only effective…

Answer 8

If the surface of the medical item is free from organic material

Question 9

Exposure time between the chemical agent and infectious agent is important why

Answer 9

The chemical agent must be in contact with the infectious agent long enough to ensure an effective biocides time-course as indicated by the kill-curve

Question 10

What does adequate concentration mean

Answer 10

There must be an adequate number molecules of the chemical agent to equal the number of infectious cells present.

Question 11

How is choice of agent determined

Answer 11

By the risk of transmission of infectious agents to susceptible hosts the composition of the item to be treated and the structure of the agent

Question 12

Physical control methods

Answer 12

Temperature extremes 
Filtration
Pressure (commonly combined with temperature) 
Filtration 
Irradiation

Question 13

Temperature extremes

Answer 13

High (>100°C) and low (<4°C) temperatures can be used to kill and/or control the growth of the infectious agents

Question 14

Pressure

Answer 14

Autoclaving is the most commonly used sterilisation method .

Question 15

Filtration

Answer 15

Filtration sifts infectious agents out of solutions that will be administered to people including intravenous fluids and medications

Question 16

Irradiation

Answer 16

Non-ionising radiation - does not remove electrons, it has low penetrance and is therefore not appropriate for sterilisation of dense materials

Ionising radiation - gamma rays are high energy forms of radiation that effectively sterilise dense materials by removing electrons from atoms and molecules - used on syringes

Question 17

Chemical control methods

Answer 17

Alcohols 
Halogens 
Quaternary ammonium compounds 
Phenolics
Hydrogen peroxide 
Aldehydes

Question 18

Alcohols

Answer 18

Ethanol and/or isopropanol at concentrations of 60-90% are highly effective surface disinfectants and antiseptics if allowed to air dry

Question 19

Halogens

Answer 19

Such as sodium hypochlorite (bleach), iodine and chlorhxidine are broad spectrum and effectively disinfect drinking water, mouth wash, contaminated surfaces and skin

They are inactivated by organic material and are corrosive

Question 20

Quaternary ammonium compounds

Answer 20

Catatonic agents used for surface disinfection and include hospital grade disinfectants

Question 21

Phenolics

Answer 21

Are toxic hard surface disinfectants (not very commonly used)

Question 22

Hydrogen peroxide

Answer 22

is a broad spectrum disinfecting agent that remains active in the presence of high levels of organic contamination

Question 23

Aldehydes

Answer 23

Broad spectrum disinfectants work in the presence of organic material and are sporicidal

Question 24

How are chemical control methods impacted

Answer 24

Organic material
Temperature 
Water hardness 
pH 
Relative humidity

Question 25

Biofilms

Answer 25

Can form on any surface iPad the interface between liquid and a solid. Commonly found in healthcare environments. They create a physical barrier between the infectious agents and the chemical agent as well as sheering forces protection

Question 26

You’re required to re-process a re-usable medical item at the completion of treatment of a non-infectious patient in the clinic.

• medical grade stainless steel
• appears to be contaminated with small amount of flesh blood and tissue

Answer 26

The item must be debunked to reduce interference of organic material with the re-processing procedure
Detergent should be used to remove organic material
The item requires sterilisation prior to re-use
Item can safely be treated with steam under pressure