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- Cleaning = physical process that removes contamination but not necessarily microorganisms
- Disinfection = process that eliminates microorganisms EXCEPT bacterial spores and viruses (e.g., chlorhexidine, iodine, alcohol)
- Sterilization = destroys ALL microbial life
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- Heat - Autoclave (steam sterilization) at 121°C, 15 PSI for 30 minutes
- Radiation - gamma radiation
- Chemical - ethylene oxide, glutaraldehyde for heat-sensitive equipment (e.g., scopes)
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- Decontamination/cleaning - wash with water and detergent
- Packaging
- Sterilization - high or low temperature
- Storage
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- Using "Bowie Dick Tape"
- Color-changing indicator of tape is usually lead carbonate based, which decomposes to lead(II) oxide.
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- Mechanical indicators - time, pressure, temperature
- Chemical indicators - heat or chemical-sensitive ink stickers (autoclave tape)
- Biological indicators - testing commercially prepared bacterial spores to verify they are killed by the process
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- MRC (Medical Research Council) prospective RCT by Lidwell et al. 1982 found that vertical flow was more effective than horizontal flow in joint replacements. Multicenter study of 8,052 joint replacements
- Other factors include antibiotic-loaded cement, systemic antibiotics, ultra-clean air, plastic isolators, and body exhaust suits
TOURNIQUET
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- Length = 1.5 x the circumference to overlap 3-6 inches (excessive overlap creates too much pressure)
- Width = "as large as possible but not touching the surgical site"
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- Principle is = Use lowest possible cuff pressure for as short duration as possible
- No absolute pressure, but consider patient age, skin condition, and underlying PVD
- Usually it is 50mmHg higher than systemic pressure for upper limb and twice the SBP for lower limb.
- More accurate method: calculate limb occlusion pressure using 67 + (circumference of limb/0.06 x width of tourniquet)
- Per this equation, larger limb circumference requires higher pressure, while larger width of tourniquet allows lower pressure
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- Severe crush injuries, Sickle cell disease, PVD
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- By Elevation or Expression.
- Avoid expression (e.g., Esmarch) in cases of infection or cancer.
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- Release after 2 hours for lower limb, 1.5 hours for upper limb
- Deflate for at least 20 minutes
- After this, it can remain inflated for up to 60 minutes.
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- Skin pressure sores, swelling, compartment syndrome from reperfusion, DVT
- Post-tourniquet Syndrome - caused by ischemia and reactive hyperperfusion, resulting in edema, stiffness, and pallor, with weakness without paralysis
- Tourniquet Paralysis Syndrome - flaccid motor paralysis with sensory disturbance due to compression of nerves. Patients with diabetes mellitus or peripheral neuropathy may have increased susceptibility.
SUTURES
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- Absorbable
- Synthetic - Vicryl (polygactin), Monocryl, PDS (polydioxanone)
- Natural - collagen, gut
- Non-Absorbable
- Synthetic - Nylon (Ethilon), Prolene
- Natural - silk
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- They have a higher friction coefficient, improving knot security compared to monofilament sutures
- However, the increased friction causes more tissue trauma and raises infection risk
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- Monocryl - provides wound support for 20 days, resorbs in 3 months
- Vicryl - provides wound support for 30 days, resorbs in 2 months
- PDS - provides wound support for 60 days, resorbs in 6 months
DIATHERMY
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- Electrosurgery - uses alternating current that passes through tissue
- Electrocautery - uses direct current to heat a probe that is placed on tissue. No current passes through the tissue (typically small and battery-operated)
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- A form of electrosurgery that uses high-frequency ALTERNATING current passing between an active electrode and an indifferent electrode or pad
- The active electrode has a much smaller surface area, resulting in higher current density and higher temperature
- The pad has a larger surface area (70cm²), preventing tissue damage when current passes through
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- Coagulation - interrupted pulses producing a square waveform
- Cutting - continuous current producing a sine waveform, vaporizing cell water
- Blend - combination of coagulation and cutting
- Fulguration/Spray - coagulation/charring of tissue over a wide area
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- Uses a coagulation waveform with the diathermy held slightly away from tissues
- Creates electric arc discharge through ionized air gap between electrode and tissue
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- Surgeon related
- Place in quiver when not in use
- Do not apply monopolar to end appendages
- Use short bursts in patients with pacemakers
- After alcohol cleaning, wait at least 5 minutes for drying
- Plate factors
- Place diathermy pad on hairless skin with no air gaps to prevent burns
- Prevent pooling of flammable fluids
- Position away from heart but close to operation site
- Patient related
- Remove all metal objects
- Manage pacemaker appropriately
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- Preoperative
- Have cardiac technician and cardiologist check the pacemaker and its mode
- Inform anesthesia - for surgery below umbilicus, pacemaker adjustment may not be needed
- Switch to asynchronous mode to prevent interference from monopolar diathermy
- Intraoperative
- Prefer bipolar diathermy when possible
- If using monopolar, use short bursts only
- Stop immediately if arrhythmias occur
- Keep magnets ready - they activate asynchronous mode, forcing the pacemaker to pace regardless of intrinsic rhythm
- Postoperative
- Recheck pacemaker and restore to original settings
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- In bipolar diathermy, alternating current passes between the two tips of the forceps through the intervening tissue
- Only has coagulation mode. No cutting mode
- In monopolar diathermy, the circuit completes through the patient's body
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- It is the application of thermal energy through a probe to achieve coagulation necrosis of target tissue
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- For diathermy: Use water (ball-tip configuration, rarely used) [saline prohibited due to current flow]
- For radiofrequency: Use normal saline [compatible since it only involves heating]
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- There are no absolute contraindications
- Avoid placing the grounding pad over metal implants
- Use bipolar diathermy in patients with pacemakers
OT DESIGN
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- Close to emergency department and radiology departments
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- There will be 4 zones - OCAD
- Outer zone = OT reception and rest of hospital
- Clean zone = OT reception to theatre doors
- Aseptic zone = within OT itself - further divided into
- Restricted zone (induction and scrub rooms)
- Aseptic zone (OT itself)
- Disposal zone = separated from other areas
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- Location within hospital
- Different areas in OT
- Within OT
- Lighting - 40,000 Lux
- Type of ventilation
- Filter, air quality monitoring
- Temperature 18-23 degrees
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- Lighting - 40,000 lux at operation site
- Temperature - ideal 18-23°C - compromise between patient and staff comfort
- Humidity - 30-60%
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- Plenum is air flow down a pressure gradient → subject to turbulence and eddies
- Laminar flow is air flowing in parallel layers with no cross current, eddies or disruption, NO turbulence
- For air to be laminar flow, it must be at 9mls/hour or 0.3m/s. 200-400 changes per hour!
- It can be horizontal (easier to install) or vertical
- Vertical laminar flows can cause "entrainment" whereby contamination is deflected inwards into the wound
- This led to the development of the Howorth enclosure that allows air to flow in the shape of an inverted trumpet, down and out [aka exponential flow]
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- The ideal operating theater ventilation system combines laminar flow with a Howorth enclosure, ultraclean air, and HEPA filtration.
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- The landmark 1982 Lidwell MRC Trial (multicenter study of 8,052 joint replacements) found vertical flow more effective than horizontal flow in joint replacements.
- However, more recent studies have questioned its effectiveness:
- Hooper et al. (NZ NJR JBJS 2011) found no significant difference in infection rates between laminar flow and space suits
- Bischoff et al. (Lancet 2017) meta-analysis showed no evidence that laminar air flow reduces SSI risk in replacement and abdominal surgery, recommending against installation
- Gastmeier et al. (Journal of Hospital Infection 2012) systematic review found no difference in infection rates with or without laminar flow
- Pinder et al. found no difference in infection rates between plenum and laminar flow in NHS hospitalshttps://online.boneandjoint.org.uk/doi/full/10.1302/0301-620X.98B9.37184
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- HEPA stands for High Efficiency Particulate Air filter
- It removes at least 99.97% of dust, pollen, mold, bacteria, and airborne particles sized 0.3 microns
- Modern HEPA filters incorporate UV light to increase efficiency
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- For laminar system:
- Air containing less than 10 CFU/m3 (colony forming units) around the theater table
- Up to 20 CFU/m3 permitted in the periphery
- For plenum system - < 35CFU/m3 is considered efficient
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- Passive or Active monitoring is performed every 3 months:
- Passive monitoring (cheaper) uses settle plates - standard petri dishes with culture media exposed to air to collect bacteria
- 13 plates positioned: 4 corners, 4 lengths, 4 mid-diagonal, 1 center
- Active monitoring uses a Casella Slit Sampler that draws a measured volume of air through a particle collection device (liquid or solid culture medium) - measured as CFU/m3
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- It is a positive pressure ventilation system
- Provides 15-25 air changes per hour
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- Airborne - accounts for 95%
- Internal - from the patient themselves
- Equipment:
- Clothing - bacterial strike-through occurs when bacteria migrate through clothing
SCRUBBING AND CLEANSING
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- I usually use chlorhexidine scrub because:
- 1. Chlorhexidine decreases bacteria count by 99%, iodine by 97%.
- 2. Chlorhexidine lasts longer than iodine
- 3. Chlorhexidine has bactericidal and bacteriostatic effects
- Cochrane review 2015 Tanner et al. found alcohol rubs to be at least as effective as aqueous scrub.
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- Iodine - bactericidal, active against fungi and viruses
- Chlorhexidine - disrupts cell membrane; bactericidal and bacteriostatic
- Alcohols - bactericidal, inactive against fungi, spores
- Hexodane = chlorhexidine + alcohol
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- I usually use disposable, hydrophobic, and non-woven polyester clothing with a mesh size less than 80 microns to prevent strike through (unlike standard cotton, which is prone to it)
- I am aware of woven, reusable materials like Gore-Tex, which has a pore size of < 0.2 microns, but it is expensive.
- Woven vs. non-woven/Gore-Tex/disposable
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- Woven vs. Non-woven
- Woven
- Standard cotton - open weave with large pore size of 80 microns, inefficient at preventing bacterial migration; prone to strike through
- Ventile - Cotton product with closed weaving and much smaller pore size of 20 microns, better at preventing bacterial dispersion
- Gore-Tex - woven polyester laminated to a film of polytetrafluoroethylene with pore size of 0.2 microns. Very effective barrier but maintains open structure to allow air exchange
- Non-woven
- Disposable type - Appears as a random mat
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- Body exhaust suits are older technology using tubes, while space suits are newer systems using positive air pressure
- Hooper et al. JBJS 2011 NZ NJR - showed no difference in infection rates with space suits
- hooper2010.pdf
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- It is the direct migration of bacteria through clothing, especially when the fabric becomes wet
Surgical Site Infection (consolidation)
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- Pre Op
- Pre-operative screening for MRSA with possible decolonization using body wash and repeat nose swabs
- Ensure no active infection
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- OT design and sterility
- Proper aseptic zones
- Ventilation type
- Lidwell study shows 2x reduction but remains controversial
- Air quality maintenance - regular assessment by active or passive technique (<10 CFU)
- Pre-operative systemic antibiotics (4x reduction)
- Antibiotic-loaded cement (2x reduction)
- Attire - body suits (2x reduction but controversial); if not using body suits, use waterproof, non-woven material to prevent strike through
- NICE intraop guidelines
- Use iodine-impregnated drapes (Ioban) if no allergy
- Double-glove technique
- Use hexodane (first choice) if skin is not next to mucous membrane; second choice is povidone-iodine with alcohol
- Minimize OR traffic - ensure proper door closure and control human traffic
- Equipment - ensure sterility through autoclave maintenance and Bowie-Dick tape checks
- Minimize blood transfusion need through meticulous hemostasis
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- Maintain good wound care and follow-up
- Proper patient cohorting with isolation of MRSA patients in wards
- Avoid unnecessary wound dressing changes
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- Yes
- TKR/THR
- Spine surgery -
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Go to the ant, O sluggard; consider her ways, and be wise. Proverbs 6:6