Fires And Decontamination Flashcards
What enzymatic process differentiates biological oxidation from combustion?
Biological oxidation uses enzymes to regulate slow, low-temperature reactions (e.g., glucose metabolism), while combustion releases energy rapidly at high temperatures without enzymes.
Justify why hypochlorites are recommended for blood spill decontamination despite their limitations.
Hypochlorites have broad-spectrum activity (bacteria, viruses, spores), but must be freshly diluted to avoid corrosion and organic matter inactivation.
How does the density of ether vapour influence fire risks in the OR?
Ether vapour sinks and spreads along floors, creating concentrated, explosive pockets that may ignite via unseen sparks.
Design a protocol to disinfect a ventilator circuit lacking autoclave access.
Disassemble components, clean with detergent, disinfect in a washer at ≥71°C for 3 minutes, dry thoroughly, and replace every 48 hours.
Why are bacterial spores resistant to most disinfectants?
Spores have a keratinized outer layer and metabolic dormancy, requiring prolonged exposure to glutaraldehyde or autoclaving for eradication.
Evaluate the risk of reusing single-use endotracheal tubes after disinfection.
Possible if cleaned meticulously and disinfected with 70% alcohol, but thermal methods risk material damage. Not ideal due to potential micro-cracks.
What is the stoichiometric mixture of diethyl ether in air, and why is it clinically significant?
3.4% ether in air. Mixtures near this ratio burn explosively, necessitating strict OR ventilation to dilute concentrations.
Propose a method to reduce static electricity risks in a low-resource OR.
Use antistatic rubber tubing, ground equipment, avoid synthetic fabrics, and maintain humidity with water containers.
Why is formaldehyde rarely used for sterilisation despite its efficacy?
It is irritant, absorbed by materials, and releases hazardous fumes post-sterilisation, posing long-term health risks.
Compare the flammability risks of ethyl chloride versus modern volatile agents.
Ethyl chloride explodes in air/O₂ at low concentrations (LL 6.5% in air). Modern agents (e.g., sevoflurane) are non-flammable.
Analyze the statement: ‘Alcohol disinfectants require pre-cleaning of equipment.’
True. Organic debris inactivates alcohol; surfaces must be clean for effective microbial reduction.
Develop a training module for OR staff on avoiding compression-induced explosions.
Train to avoid lubricants on oxygen valves, inspect cylinders for leaks, and handle gas regulators carefully to prevent adiabatic heating.
What makes tuberculosis bacteria resistant to standard chemical disinfectants?
Their waxy, lipid-rich cell walls require prolonged exposure to 2% glutaraldehyde or phenolic solutions.
Predict the outcome of using ethylene oxide sterilisation for heat-sensitive equipment.
Effective but requires 2–24 hours, aeration to remove residual gas, and poses toxicity risks if improperly handled.
Explain why boiling water cannot sterilize equipment at sea level.
Boiling (100°C) kills microbes but not bacterial spores; autoclaving (≥121°C under pressure) is required for sterilisation.
Critique the use of open-mask ether anesthesia in modern practice.
High risk due to flammable vapour spread; closed systems (e.g., LMA) and non-flammable agents are safer alternatives.
How does the ‘zone of risk’ concept guide OR layout?
Ignition sources must be kept >25cm from anaesthetic apparatus to avoid sparking explosive gas leaks.
Create a decision tree for selecting disinfection vs. sterilisation based on equipment risk category.
High-risk (sterilise), intermediate-risk (disinfect), low-risk (clean/dry). Consider material compatibility and microbial load.
Why is Cidex (2% glutaraldehyde) unsuitable for plastic endotracheal tubes?
It may be absorbed by plastic, causing irritation, and requires 30-minute immersion, increasing material degradation risk.
Assess the role of heat-moisture exchangers in reducing respiratory circuit contamination.
They trap condensation, reducing microbial growth. Combine with regular circuit changes and drying for optimal safety.
Question
Answer
Which three components are necessary for fires or explosions in the operating room?
Combustible substances, oxygen (or nitrous oxide), and an ignition source.
What is the primary danger of a ‘cool flame’ produced by ether?
It can act as a powerful ignition source if it encounters an explosive mixture, often remaining undetected until too late.
Why is nitrous oxide particularly dangerous in the context of operating room fires?
Nitrous oxide is a strong oxidant that supports combustion as effectively as oxygen, increasing explosion risks.
Under what conditions does diethyl ether become explosive in oxygen?
Between 1.5% and 40% v/v concentration, with maximum detonability at approximately 15% in oxygen.
Evaluate the risk of using diathermy during anesthesia with ether and oxygen.
Diathermy near ether-oxygen mixtures is extremely dangerous due to explosion risks. Oxygen or diathermy must be switched off.
Design a protocol to safely use ether in a resource-limited setting.
Use closed breathing systems (e.g., LMA/intubation), avoid supplemental oxygen near diathermy, ensure ventilation, and store ether in dark, antistatic containers.
What distinguishes high-risk medical equipment from intermediate-risk items?
High-risk items enter sterile body areas (e.g., surgical instruments) and require sterilization. Intermediate-risk items contact mucous membranes (e.g., laryngoscopes) and require disinfection.
Why is boiling at high altitudes less effective for disinfection?
Boiling temperature decreases with altitude (e.g., 86°C at 4000m), requiring extended boiling times (e.g., 20 minutes) to achieve disinfection.
Compare the effectiveness of 70% alcohol vs. 2% glutaraldehyde for disinfecting endotracheal tubes.
70% alcohol is preferred for endotracheal tubes, as glutaraldehyde may be absorbed by plastic and is irritant. Alcohol requires 10-minute immersion.
Propose a decontamination strategy for reusable suction catheters.
Clean thoroughly, disinfect with 70% alcohol for 10 minutes, and allow to dry before reuse.
What is the minimum autoclave temperature and time required for sterilization?
134°C for 3 minutes or 121°C for 15 minutes under pressurized steam.
Why is the azcotropic mixture of halothane and ether considered safer?
It is non-explosive (except at >10% in oxygen) and combines the benefits of both agents while minimizing flammability.
How does the Arrhenius law relate to fire risks in the operating room?
Reaction rate doubles with every 10°C temperature increase, accelerating combustion if heat dissipation is inadequate.
Justify the use of scavenging systems in ether-based anesthesia.
They remove flammable vapors from the operating room, reducing the risk of explosive mixtures accumulating.
Create a checklist for preventing static electricity-induced fires in the OR.
Use antistatic breathing tubes, ensure proper grounding of equipment, maintain humidity, and avoid synthetic materials.
What disinfectant is effective against HIV and HBV, and what exposure time is required?
2% glutaraldehyde (Cidex) inactivates these viruses in 1-2 minutes, but soiled items require 30-minute immersion.
Why should hypochlorites be avoided for metal instrument disinfection?
They are corrosive to metals and degrade in the presence of organic matter.
Analyze the fire risk when using alcohol-soaked drapes near oxygen sources.
Alcohol burns with an invisible flame; soaked drapes can ignite via sparks (e.g., diathermy), especially in oxygen-rich environments.
Evaluate the statement: ‘Sterilization is unnecessary for respiratory equipment.’
True for most cases, as respiratory infections are not spore-related. Cleaning and disinfection (e.g., 71°C for 3 minutes) suffice.
Develop a procedure for decontaminating laryngoscope blades.
Wash after use, then disinfect by soaking in 70% alcohol for 10 minutes or boiling at 100°C for 5 minutes.
