ISE789 End of Semester Review

Course Projects They are being graded. You can stop by my office on Monday to pick them up.

What we have covered Text on Healthcare –Organization and structure –Condition and methods –Position papers Biology for engineers –Disease and causes –Bioengineering Systems Engineering in Healthcare –Queueing models

Continued Engineering for Medical Devices –Requirements –Anatomy –Biomechanics –Bio Inert –Bio active Bactericidal metals and models –Silver and other bactericidal metals –Ions Disinfectants and sterilization –Chapter posted two weeks ago –Methods and application

The Exam Some multiple choice Some short answers Some problems It will take you the entire time.

Sterilization and Disinfection ISE789 Dr. R. A. Wysk

Agenda What are disinfectants? How do we disinfect, sterilize and clean? Why do we disinfect? What are the processes that can be used?

Microorganisms Some good Some not so good Sterilize – no living forms Disinfect – remove certain life forms

Disinfect Disinfectants are antimicrobial agents that are applied to non-living objects to destroy microorganisms, the process of which is known as disinfection.antimicrobial agentsmicroorganisms –Cleaning an article of some or all of the pathogenic organisms which may cause infection A perfect disinfectant would also offer complete and full sterilization, without harming other forms of life, be inexpensive, and non-corrosive. sterilization –There are no perfect disinfectants.

The hows and how tos Cause the minimal amount of disruption to human and physical environment. Long or short life activities –Surgery Alcohol Betadine –Aldehydes

Dry Heat Thermal Method Principle/ Conditions AdvantagesDisadvantagesUses Thermal inactivation: destroys by oxidation Non-corrosive Simple design and principle Less effective than moist heat; requires longer times and/or higher temperatures Materials that are damaged by, or are impenetrable to, moist heat

Hot Air Oven Principle/ Conditions AdvantagesDisadvantagesUses o C for 2-4 hours penetrates water- insoluble materials (e.g., grease and oil) less corrosive to metals and sharp instruments than steam slow diffusion, penetration loading, packing critical to performance not suitable for reusable plastics anhydrous materials, such as oils, greases and powders laboratory glassware, instruments closed containers

Red Heat Flame Method Principle/ Conditions AdvantagesDisadvantagesUses Oxidation to ashes (Burning) Rapidinitial contact with flame can produce a viable aerosol possibility of accidental fire I noculating loops, needles, other disposable medical supplies

Incineration Method Principle/ Conditions AdvantagesDisadvantagesUses Oxidation to ashes (Burning) 1 – 60 minutes at temperatures up to 1000 o C Reduces volume of waste by more than 95% improper use may lead to emission of pathogens in smoke requires transport of infectious waste excess plastic (>20%) content reduces combustibility for decontaminat ion of waste items prior to disposal in landfill

Pasteurization Method Principle/ Conditions AdvantagesDisadvantagesUses Heating to below boiling point (generally 77 o C) for up to 30 minutes can be used on heat sensitive liquids and medical devices low cost Not particularly reliable Milk and dairy products some heat- sensitive medical equipment

Boiling Method Principle/ Conditions AdvantagesDisadvantagesUses Maximum temperature attainable is ~100 o C for minutes Minimal equipment needed Not reliable Cumbersome Small instruments and equipment

Autoclaving Method Principle/ Conditions AdvantagesDisadvantagesUses Steam under pressure 15 – 90 minutes at temperatures up to 120 o C at 5 psi Steam under pressure 4 – 20 minutes at temperatures up to 132 o C at 27 psi Minimal time required The standard for lab use, i.e., most dependable Loading and packing critical to performance Items must be free of dirt and solid adhesions Can damage heat sensitive items Penetration of sterile glassware Decontamination of reusable supplies and equipment Decontamination of infectious wastel

Autoclave A Front Loading Autoclave

Autoclave A Stove-top Autoclave

Ultraviolet Light 260 nm light wave sources (UV lamps) Effective for a variety of pathogens (bacteria, virus and fungus) –Poor penetration (limited to light permeable goods, like water) –Particulate, like dust, decrease the effectiveness –Light source must be cleaned routinely

Other methods Infrared radiation Microwaves Gamma radiation Filtration

Chemical Sterilants and disinfectants Instruments that can not be sterilized using high temperatures may undergo a gas sterilization process such as ethylene oxide or other chemical germicides.

Chloride compounds (liquid bleach) Effective concentrations, contact time AdvantagesDisadvantagesUses 100 – 10,000 ppm (.01- 1%) free chlorine 10 – 60 minutes broad spectrum low cost Widely available Bactericidal at low temps Toxic, corrosive to skin and metals Unstable Inactivated by organic matter Deteriorates under heat and light General disinfectant Waste liquids Surface contamination Instruments

Calcium hypochlorite Effective concentrations, contact time AdvantagesDisadvantagesUses 100 – 10,000 ppm ( %) free chlorine 10 – 60 minutes broad spectrum low cost Widely available Bactericidal at low temps Toxic, corrosive to skin and metals Unstable Inactivated by organic matter Deteriorates under heat and light General disinfectant Waste liquids Surface contamination Instruments

Iodine Preparations Effective concentrations, contact time AdvantagesDisadvantagesUses 30 – 1,000 ppm ( %) free iodine 10 – 30 minutes broad spectrum Non-stinging Less toxic Less irritating Not consistent Some iodophors support the growth of Pseudomonas Germicidal soaps Surface decontamination Instruments

Alcohols Principle/ Conditions AdvantagesDisadvantagesUses 70-80% ethanol 60-90% isopropanol 10 – 30 minutes low toxicity low cost Low residue Non-corrosive Rapid evaporation Flammable Damage to rubber, plastic and shellac Ineffective against spores Skin disinfectant Counter-tops

Phenolic Compounds Principle/ Conditions AdvantagesDisadvantagesUses 400 – 50,000 ppm 10 – 30 minutes Tolerant of organic load Leaves an active residue biogradeable Pungent odor Not sporicidal Leaves a residue Antiseptic some heat- sensitive medical equipment

Hydrogen Peroxide Principle/ Conditions AdvantagesDisadvantagesUses 3 – 30% aqueous solution 10 – 60 minutes 6% for 30 minutes Rapid action No residue Low toxicity low cost Environmentally safe Limited sporicidal Corrosive to some metals Potentially explosive at high concentrations Can be irritating to eyes Surface decontaminati on Instruments and equipment

What to use? When?