Applied Basic Sciences
Chapter 29 Clinical environment
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Structured oral examination question 1#
source p. 1652
Sterilization
EXAMINER
What is the difference between sterilization and disinfection?
What is the difference between sterilization and disinfection?
CANDIDATE
Sterilization is the process that destroys all forms of microbial life and is carried out in healthcare facilities by either chemical or physical methods. Disinfection however, is a process that eliminates all pathogenic microorganisms, except bacterial spores or viruses.
Sterilization is the process that destroys all forms of microbial life and is carried out in healthcare facilities by either chemical or physical methods. Disinfection however, is a process that eliminates all pathogenic microorganisms, except bacterial spores or viruses.
EXAMINER
What about cleaning?
What about cleaning?
CANDIDATE
Cleaning is a physical process that removes contamination but does not necessarily destroy microorganisms.
Cleaning is a physical process that removes contamination but does not necessarily destroy microorganisms.
EXAMINER
What forms of sterilization are you familiar with in the orthopaedic setup?
What forms of sterilization are you familiar with in the orthopaedic setup?
CANDIDATE
High-temperature sterilization of which pre vacuum type is most commonly used for sterilization of instruments and linen. Low-temperature sterilization, of which ethylene oxide and hydrogen peroxide gas plasma sterilization are more commonly used for temperature-sensitiv e instruments such as arthroscopes and drill and saw systems.
High-temperature sterilization of which pre vacuum type is most commonly used for sterilization of instruments and linen. Low-temperature sterilization, of which ethylene oxide and hydrogen peroxide gas plasma sterilization are more commonly used for temperature-sensitiv e instruments such as arthroscopes and drill and saw systems.
EXAMINER
How are instruments or linen sterilized?
How are instruments or linen sterilized?
CANDIDATE
Instruments and linen are sterilized in a controlled environment called the central sterile supply department (CSSD) that is divided into areas where the following is carried out: I. Decontamination: manual or mechanical in water with detergents or enzymatic cleaners. Mechanical cleaners include ultrasonic washers. II. Packaging: following a visual inspection instruments are wrapped in a sterilization wrap or kept in rigid containers or instrument trays. III. Sterilization, either high- orlo w-temperature depending on the instrument or item. IV. Instruments or linen are then stored inseparate sterile storage rooms.
Instruments and linen are sterilized in a controlled environment called the central sterile supply department (CSSD) that is divided into areas where the following is carried out: I. Decontamination: manual or mechanical in water with detergents or enzymatic cleaners. Mechanical cleaners include ultrasonic washers. II. Packaging: following a visual inspection instruments are wrapped in a sterilization wrap or kept in rigid containers or instrument trays. III. Sterilization, either high- orlo w-temperature depending on the instrument or item. IV. Instruments or linen are then stored inseparate sterile storage rooms.
EXAMINER
Can you think of any factors that can affect the efficacy of the sterilization process?
Can you think of any factors that can affect the efficacy of the sterilization process?
CANDIDATE
Factors that affect the process are inadequate cleaning beforehand, high residual protein or salt before sterilization, biofilm accumulation instrument design (e.g. reduced lumen diameter or increased length of arthroscope, sharp bends, screws, hinges).
Factors that affect the process are inadequate cleaning beforehand, high residual protein or salt before sterilization, biofilm accumulation instrument design (e.g. reduced lumen diameter or increased length of arthroscope, sharp bends, screws, hinges).
EXAMINER
How are sterilization processes monitored?
How are sterilization processes monitored?
CANDIDATE
Sterilization procedures should be routinely monitored by: I. Mechanical indicators that record time pressure and temperature. II. Chemical indicators that are usually heat- or chemical-sensitiv e inks that change colour when one or more sterilization parameters are present.
Sterilization procedures should be routinely monitored by: I. Mechanical indicators that record time pressure and temperature. II. Chemical indicators that are usually heat- or chemical-sensitiv e inks that change colour when one or more sterilization parameters are present.
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III. Biological indicators are the only process that directly monitors the lethality of a given sterilization process by using commercial preparation of spores. The presence of biological indicators following a sterilization process indicates the inadequacy to kill the microbial contaminates. This is a relatively inexpensive mode of monitoring.
EXAMINER
How are sterile instruments transported from CSSD to theatres?
How are sterile instruments transported from CSSD to theatres?
CANDIDATE
Sterile instruments should be transported in covered or enclosed trolleys with solid-boft om shelves that are cleaned and disinfected after each use.
Sterile instruments should be transported in covered or enclosed trolleys with solid-boft om shelves that are cleaned and disinfected after each use.
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Structured oral examination question 2#
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Tourniquet use
EXAMINER
What is Figure 29.1 demonstrating?
What is Figure 29.1 demonstrating?
Figure 29.1 Tourniquet.
CANDIDATE
This picture shows a pneumatic tourniquet with an airline to connect to a pneumatic device. Tourniquets are a useful adjunct in maintaining a relatively bloodless operative field.
This picture shows a pneumatic tourniquet with an airline to connect to a pneumatic device. Tourniquets are a useful adjunct in maintaining a relatively bloodless operative field.
EXAMINER
Can you tell me how you correctly size a tourniquet and select inflation pressure?
Can you tell me how you correctly size a tourniquet and select inflation pressure?
CANDIDATE
A correctly sized tourniquet should be at least one and a halftimes the circumference of the limb or proportional to the leg or arm diameter. There are no absolute values for inflation pressure and I consider the age of the patient condition of the skin, and an y intercurrent medical conditions such as peripheral vascular disease. In the upper limb, the inflation pressure should be 50 mmHg higher than the systolic pressure while in the lower limb the pressure should be double.
A correctly sized tourniquet should be at least one and a halftimes the circumference of the limb or proportional to the leg or arm diameter. There are no absolute values for inflation pressure and I consider the age of the patient condition of the skin, and an y intercurrent medical conditions such as peripheral vascular disease. In the upper limb, the inflation pressure should be 50 mmHg higher than the systolic pressure while in the lower limb the pressure should be double.
EXAMINER
When would you not use a tourniquet?
When would you not use a tourniquet?
CANDIDATE
Inpatients with severe crush injuries, sickle cell disease, if there is a previous history of tourniquet problems or in severe peripheral vascular disease.
Inpatients with severe crush injuries, sickle cell disease, if there is a previous history of tourniquet problems or in severe peripheral vascular disease.
EXAMINER
What forms of exsanguination are there when using a tourniquet?
What forms of exsanguination are there when using a tourniquet?
CANDIDATE
There is either exsanguination by elevation or expression. Inpatients with venous thromboembolism, infection or malignancy I would avoid exsanguination by expression as this risks spread by embolism.
There is either exsanguination by elevation or expression. Inpatients with venous thromboembolism, infection or malignancy I would avoid exsanguination by expression as this risks spread by embolism.
EXAMINER
What complications can be encountered when using tourniquets?
What complications can be encountered when using tourniquets?
source p. 1656
CANDIDATE
Local complications can be pain or compression neuropraxia, skin pressure sores, postoperative swelling or compartment syndrome. Systemic complications can be cardiorespiratory decompensation, deep vein thrombosis, cerebral infarction or alterations in acid –base balance.
Local complications can be pain or compression neuropraxia, skin pressure sores, postoperative swelling or compartment syndrome. Systemic complications can be cardiorespiratory decompensation, deep vein thrombosis, cerebral infarction or alterations in acid –base balance.
EXAMINER
What is tourniquet paralysis syndrome?
What is tourniquet paralysis syndrome?
CANDIDATE
This a flaccid motor paralysis with sensory disturbance usually affecting pain sensation rather than temperature and is caused by cuff pressure and not ischaemia. Usually, colour, skin temperature and peripheral pulses are preserved. Patients with diabetic alcoholic neuropathy or rheumatoid patients have increased susceptibility .
This a flaccid motor paralysis with sensory disturbance usually affecting pain sensation rather than temperature and is caused by cuff pressure and not ischaemia. Usually, colour, skin temperature and peripheral pulses are preserved. Patients with diabetic alcoholic neuropathy or rheumatoid patients have increased susceptibility .
EXAMINER
How is this different to post-tourniquet syndrome?
How is this different to post-tourniquet syndrome?
CANDIDATE
Post-tourniquet syndrome is are perfusion injury and is due to ischaemia after release of the tourniquet usually after 2 hours of inflation. Signs include oedema stiffness, pallor , weakness and subjective numbness.
Post-tourniquet syndrome is are perfusion injury and is due to ischaemia after release of the tourniquet usually after 2 hours of inflation. Signs include oedema stiffness, pallor , weakness and subjective numbness.
EXAMINER
What should you do about the tourniquet if you are performing a long operation?
What should you do about the tourniquet if you are performing a long operation?
CANDIDATE
Release after 2 hours. The tourniquet should be deflated for at least 20 minutes before re- inflation. After that it can remain inflated for up to 60 minutes.
Release after 2 hours. The tourniquet should be deflated for at least 20 minutes before re- inflation. After that it can remain inflated for up to 60 minutes.
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Structured oral examination question 3#
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Sutures
EXAMINER
What type of sutures do you use in your practice?
What type of sutures do you use in your practice?
CANDIDATE
I use absorbable sutures like vicryl or non-absorbable such as prolene.
I use absorbable sutures like vicryl or non-absorbable such as prolene.
EXAMINER
What are the differences between vicryl and prolene?
What are the differences between vicryl and prolene?
CANDIDATE
Vicryl is a form of braided suture and is absorbable while prole neis a monofilament suture and non-absorbable.
Vicryl is a form of braided suture and is absorbable while prole neis a monofilament suture and non-absorbable.
EXAMINER
What is the effect of braiding?
What is the effect of braiding?
CANDIDATE
The effect of braiding is to increase the friction coefficient and hence the ability to fix knots is improved when compared to monofilament sutures.
The effect of braiding is to increase the friction coefficient and hence the ability to fix knots is improved when compared to monofilament sutures.
EXAMINER
Are there any disadvantages of using braided sutures?
Are there any disadvantages of using braided sutures?
CANDIDATE
Braided sutures have an increased risk of promoting infection duet o capillarity, as the interstices between fibres can facilitate the spread of pathogens along the fibre and thus to the placement site. In addition, braided sutures have a relatively rough surface which can cause a ‘saw effect’ when the thread passes through the tissues.
Braided sutures have an increased risk of promoting infection duet o capillarity, as the interstices between fibres can facilitate the spread of pathogens along the fibre and thus to the placement site. In addition, braided sutures have a relatively rough surface which can cause a ‘saw effect’ when the thread passes through the tissues.
EXAMINER
Can you give me examples of approximate resorption and wound support times for common sutures you use?
Can you give me examples of approximate resorption and wound support times for common sutures you use?
CANDIDATE
Monocryl: wound support 20 days Resorption 90 –120 days VICRYL : wound support 30 days Resorption 50 –70 days PDS : wound support 60 days Resorption 6 –8 months
Monocryl: wound support 20 days Resorption 90 –120 days VICRYL : wound support 30 days Resorption 50 –70 days PDS : wound support 60 days Resorption 6 –8 months
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Structured oral examination question 4#
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Electrosurgery
EXAMINER
What does Figure 29.2 demonstrate?
What does Figure 29.2 demonstrate?
Figure 29.2 Monopolar diathermy.
CANDIDATE
This shows monopolar diathermy and a return electrode.
This shows monopolar diathermy and a return electrode.
EXAMINER
How does monopolar diathermy work?
How does monopolar diathermy work?
CANDIDATE
High-frequency (400 kHz–10 MHz) AC current passes between an active electrode and an indifferent electrode or plate. As the active electrode or instrument has a much smaller surface area than the plate it has a higher current density and creates high temperatures here rather than at the plate. As a result, it avoids damage through passage of current through surrounding tissue.
High-frequency (400 kHz–10 MHz) AC current passes between an active electrode and an indifferent electrode or plate. As the active electrode or instrument has a much smaller surface area than the plate it has a higher current density and creates high temperatures here rather than at the plate. As a result, it avoids damage through passage of current through surrounding tissue.
EXAMINER
How is this different to bipolar diathermy?
How is this different to bipolar diathermy?
CANDIDATE
In bipolar diathermy the passage of high-frequency AC current is passed from the diathermy machine and then through the patient tissue that is grasped between a pair of bipolar forceps.
In bipolar diathermy the passage of high-frequency AC current is passed from the diathermy machine and then through the patient tissue that is grasped between a pair of bipolar forceps.
EXAMINER
Are there any contraindications tousing diathermy?
Are there any contraindications tousing diathermy?
CANDIDATE
Although there are no absolute contraindications tousing diathermy, care should be exercised when using diathermy inpatients with pacemakers (use bipolar diathermy only) and avoidance of application of return electrode plate over internal metal implants such as joint replacements as well as avoiding contact to external metal objects to avoid unintended leakage of current to earth and burns.
Although there are no absolute contraindications tousing diathermy, care should be exercised when using diathermy inpatients with pacemakers (use bipolar diathermy only) and avoidance of application of return electrode plate over internal metal implants such as joint replacements as well as avoiding contact to external metal objects to avoid unintended leakage of current to earth and burns.
EXAMINER
How does diathermy differ to radiofrequency ablation?
How does diathermy differ to radiofrequency ablation?
CANDIDATE
Radiofrequency ablation is a procedure in which the electrical conduction system of the heart, tumour, or other dysfunctional tissue is ablated using the heat generated from medium frequency alternating current (350–500 kHz). As this does not directly stimulate nerves or heart muscles, it can often be used without the need of general anaesthetic and in the outpatient seting with conscious sedation.
Radiofrequency ablation is a procedure in which the electrical conduction system of the heart, tumour, or other dysfunctional tissue is ablated using the heat generated from medium frequency alternating current (350–500 kHz). As this does not directly stimulate nerves or heart muscles, it can often be used without the need of general anaesthetic and in the outpatient seting with conscious sedation.
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Structured oral examination question 5#
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Infection control
EXAMINER
What does Figure 29.3 show?
What does Figure 29.3 show?
Figure 29.3 Gram-staining Gram-positiv e cocci.
CANDIDATE
This is a slide of Gram-positiv e cocci demonstrated on Gram staining.
This is a slide of Gram-positiv e cocci demonstrated on Gram staining.
EXAMINER
How is a Gram stain performed?
How is a Gram stain performed?
CANDIDATE
Gram staining initially involves staining with crystal violet solution, then fixing with iodine solution and then finally washing with alcohol. Gram-positiv e bacteria retain the dye. Gram-negativ e dye washes out so is restained with safranin-O solution.
Gram staining initially involves staining with crystal violet solution, then fixing with iodine solution and then finally washing with alcohol. Gram-positiv e bacteria retain the dye. Gram-negativ e dye washes out so is restained with safranin-O solution.
EXAMINER
Can you give me some examples of how antibiotics work?
Can you give me some examples of how antibiotics work?
CANDIDATE
Antibiotics can either be bacteriocidal or bacteriostatic or have mixed properties Penicillins cephalosporins and glycopeptides like vancomycin or teicoplanin inhibit cell wall synthesis. Aminoglycosides like gentamycin affect protein synthesis. Macrolides like erythromycin inhibit tRNA synthesis. Quinolones like ciprofloxacin inhibit DNA gyrase. Tetracyclines are bacteriostatic.
Antibiotics can either be bacteriocidal or bacteriostatic or have mixed properties Penicillins cephalosporins and glycopeptides like vancomycin or teicoplanin inhibit cell wall synthesis. Aminoglycosides like gentamycin affect protein synthesis. Macrolides like erythromycin inhibit tRNA synthesis. Quinolones like ciprofloxacin inhibit DNA gyrase. Tetracyclines are bacteriostatic.
EXAMINER
Can you explain to me how resistance to antibiotics develops ?
Can you explain to me how resistance to antibiotics develops ?
CANDIDATE
Resistance can be intrinsic, where bacteria have the inherent ability to alter properties such as altering the target site or enzyme. Resistance can also be extrinsic or acquired via plasmids or mutations.
Resistance can be intrinsic, where bacteria have the inherent ability to alter properties such as altering the target site or enzyme. Resistance can also be extrinsic or acquired via plasmids or mutations.
EXAMINER
What is MRSA?
What is MRSA?
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CANDIDATE
It is a Gram-positiv e bacterium that acquires resistance to methicillin (older antibiotic) through a genetic mutation of the mecA gene resulting in penicillin-binding protein PBP2a.
It is a Gram-positiv e bacterium that acquires resistance to methicillin (older antibiotic) through a genetic mutation of the mecA gene resulting in penicillin-binding protein PBP2a.
EXAMINER
How do you prevent and treat MRS Ain your unit?
How do you prevent and treat MRS Ain your unit?
CANDIDATE
It is prevented in my unit through an MRSA screening protocol and treated by an MDT approach inline with an infection control team and microbiologists. If screening swabs test positive, then patients are treated with 5 days of nasal mupirocin and 4% chlorhexidine bath and then re- swabbed. Patients undergoing joint arthroplasty should have three negative swabs.
It is prevented in my unit through an MRSA screening protocol and treated by an MDT approach inline with an infection control team and microbiologists. If screening swabs test positive, then patients are treated with 5 days of nasal mupirocin and 4% chlorhexidine bath and then re- swabbed. Patients undergoing joint arthroplasty should have three negative swabs.
EXAMINER
What would you do if you had four consecutive total hip replacement patients that became acutely infected whilst still inpatients?
What would you do if you had four consecutive total hip replacement patients that became acutely infected whilst still inpatients?
CANDIDATE
This is a clinical governance emergency. I would expect a set protocolled action plan in my unit to be activated. I would inform my clinical leadin order to stop all elective operating. Then ext priority is the appropriate further care of the patients infected. This would involve a multidisciplinary team, barrier nursing and appropriate antibiotics instituted. A commift ee should be set up in order to investigate the outbreak responsible for reporting a t a national le vel. This should involve the microbiologist and infection control team. Every step of the pathway should be investigated starting from preoperative assessment. All staff should be tested as potential carriers. Theatre suite efficiency and ward cleanliness should be investigated particularly on whether or not ring-fencing protocols have been adhered to.
This is a clinical governance emergency. I would expect a set protocolled action plan in my unit to be activated. I would inform my clinical leadin order to stop all elective operating. Then ext priority is the appropriate further care of the patients infected. This would involve a multidisciplinary team, barrier nursing and appropriate antibiotics instituted. A commift ee should be set up in order to investigate the outbreak responsible for reporting a t a national le vel. This should involve the microbiologist and infection control team. Every step of the pathway should be investigated starting from preoperative assessment. All staff should be tested as potential carriers. Theatre suite efficiency and ward cleanliness should be investigated particularly on whether or not ring-fencing protocols have been adhered to.
EXAMINER
What will you do if you find out you YOURSELF as the surgeon has MRSA?
What will you do if you find out you YOURSELF as the surgeon has MRSA?
CANDIDATE
Firstly it is worth noting that it is likely that many clinicians will be carriers. I would take an immediate opinion from my infection control team in the trust in order to inform them and to take their advice. Given that my work as an Orthopaedic surgeon involves working in ‘high-risk’ clinical areas, the advice that I would expect to receive would be to contact Occupational Health immediately in order to commence eradication therapy and to ensure that this is successful by re- swabbing. I would cease all clinical activity un til this is the case. Non-clinical work may sometimes be possible, but this is normally subject to local protocol.
Firstly it is worth noting that it is likely that many clinicians will be carriers. I would take an immediate opinion from my infection control team in the trust in order to inform them and to take their advice. Given that my work as an Orthopaedic surgeon involves working in ‘high-risk’ clinical areas, the advice that I would expect to receive would be to contact Occupational Health immediately in order to commence eradication therapy and to ensure that this is successful by re- swabbing. I would cease all clinical activity un til this is the case. Non-clinical work may sometimes be possible, but this is normally subject to local protocol.
EXAMINER
Would you tell your patients?
Would you tell your patients?
CANDIDATE
All clinical work should be cancelled until full eradication therapy success has been confirmed. I will work with my clinical director in order to decide whether to transfer patients to other colleagues in order to balance the waiting list pressures. Patients should be informed of the reasons for their cancellations. In keeping with my duty of candour, I would perform an audit of all surgical cases performed in order to trace any potential MR SA infections contracted postoperatively. Should any cases be identified then these should be discussed as part of a multidisciplinary approach involving microbiology advice.
All clinical work should be cancelled until full eradication therapy success has been confirmed. I will work with my clinical director in order to decide whether to transfer patients to other colleagues in order to balance the waiting list pressures. Patients should be informed of the reasons for their cancellations. In keeping with my duty of candour, I would perform an audit of all surgical cases performed in order to trace any potential MR SA infections contracted postoperatively. Should any cases be identified then these should be discussed as part of a multidisciplinary approach involving microbiology advice.
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Structured oral examination question 6#
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Theatre design
EXAMINER
You are responsible for designing new orthopaedic theatres in your hospital. How would you go about doing this?
You are responsible for designing new orthopaedic theatres in your hospital. How would you go about doing this?
CANDIDATE
The theatre suite should be located close to the Emergency Department wards and the Radiology departments. It should be away from the general flow of the public. There should be separate preparation, aseptic and disposal z ones. The zones are there so that there are defined boundaries where specific activities can take place in the theatre environment. Outer Zone: Rest of the hospital to the theatre reception. Clean Zone: From theatre reception to the anaesthetic room doors. Aseptic Z one: Inside the theatre itself. Disposal Zone: Through the backdoor to the disposal area.
The theatre suite should be located close to the Emergency Department wards and the Radiology departments. It should be away from the general flow of the public. There should be separate preparation, aseptic and disposal z ones. The zones are there so that there are defined boundaries where specific activities can take place in the theatre environment. Outer Zone: Rest of the hospital to the theatre reception. Clean Zone: From theatre reception to the anaesthetic room doors. Aseptic Z one: Inside the theatre itself. Disposal Zone: Through the backdoor to the disposal area.
EXAMINER
What other structural aspects of design are important?
What other structural aspects of design are important?
CANDIDATE
Consideration should be given to the walls, floor and doors. Ideally wall and floor coating should allow for easy cleaning. The walls tend to be polyurethane-coated and the floor epoxy resin- coated. The floors are antistatic and the junction between floor and walls are curved to allow more efficient cleaning. Doors should open outwards as approximately 2 m3 of air is moved when a hinged door is opened. There is a minimal positive pressure gradient of 15 Pascal between the operating room and outside areas which aids the direction of flow of air if the doors open outwards. Sliding doors causeless disruption and turbulence than hinged doors and are preferred.
Consideration should be given to the walls, floor and doors. Ideally wall and floor coating should allow for easy cleaning. The walls tend to be polyurethane-coated and the floor epoxy resin- coated. The floors are antistatic and the junction between floor and walls are curved to allow more efficient cleaning. Doors should open outwards as approximately 2 m3 of air is moved when a hinged door is opened. There is a minimal positive pressure gradient of 15 Pascal between the operating room and outside areas which aids the direction of flow of air if the doors open outwards. Sliding doors causeless disruption and turbulence than hinged doors and are preferred.
EXAMINER
In considering the design of theatres what environmental factors are considered?
In considering the design of theatres what environmental factors are considered?
CANDIDATE
Lighting , temperature, humidity and ventilation. Lighting should c ast minimal shadow, should not generate heat and should be at least 40,000 lux. Modern-day LED lights are 120,000 lux. The temperature in theatres should be 18–23°C. This is a compromise between what the theatre staff feel comfortable in and the ideal temperature for the patient which is about 26°C. In order for the patient to achieve this temperature, warming devices are applied to the patient. There are two types: forced air warming devices and radiant warming devices. The forced air warming devices have been shown to affect the laminar airflow. Humidity should be 30–60%. Excessive humidity causes perspiration, and this will increase the shedding of bacteria. Ventilation could be through a plenum system or a laminar flow of ultraclean air.
Lighting , temperature, humidity and ventilation. Lighting should c ast minimal shadow, should not generate heat and should be at least 40,000 lux. Modern-day LED lights are 120,000 lux. The temperature in theatres should be 18–23°C. This is a compromise between what the theatre staff feel comfortable in and the ideal temperature for the patient which is about 26°C. In order for the patient to achieve this temperature, warming devices are applied to the patient. There are two types: forced air warming devices and radiant warming devices. The forced air warming devices have been shown to affect the laminar airflow. Humidity should be 30–60%. Excessive humidity causes perspiration, and this will increase the shedding of bacteria. Ventilation could be through a plenum system or a laminar flow of ultraclean air.
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Structured oral examination question 7#
source p. 1668
Ventilation
EXAMINER
What forms of airflow in theatre are you familiar with?
What forms of airflow in theatre are you familiar with?
CANDIDATE
Plenum is airflow down a pressure gradient. This pressure gradient is highest in the preparation area and then airflows into theatres and then into the anaesthetic room and finally the disposal room. This type of airflow is subject to turbulence and eddies. In a plenum system there are 15–25 air changes per hour. Laminar flow or streamline flow occurs when airflows in parallel layers with no cross-currents, eddies or disruption. Laminar airflow is intended uniform, directional airflow at a constant velocity with no air turbulence. This airflow essentially moves particles floating in the airstream away from the sterile field into the return ducts and filtration systems where they can be disposed of. For airflow to be laminar the velocity of air must be 9 m/s. In a laminar flow system there are about 200 air changes per hour.
Plenum is airflow down a pressure gradient. This pressure gradient is highest in the preparation area and then airflows into theatres and then into the anaesthetic room and finally the disposal room. This type of airflow is subject to turbulence and eddies. In a plenum system there are 15–25 air changes per hour. Laminar flow or streamline flow occurs when airflows in parallel layers with no cross-currents, eddies or disruption. Laminar airflow is intended uniform, directional airflow at a constant velocity with no air turbulence. This airflow essentially moves particles floating in the airstream away from the sterile field into the return ducts and filtration systems where they can be disposed of. For airflow to be laminar the velocity of air must be 9 m/s. In a laminar flow system there are about 200 air changes per hour.
EXAMINER
What types of laminar airflow systems are there?
What types of laminar airflow systems are there?
CANDIDATE
Laminar airflow can be horizontal, vertical or newer systems in which the airflow takes the form of an inverted trumpet (exponential flow). Exponential flow (ex-flow) systems work on the principle of graded velocity, with the flow in the centre being vertical and, in the periphery, radially outwards. Because of efficiency of the ex-flow system they can function a t fewer air changes per hour than the traditional laminar flow systems.
Laminar airflow can be horizontal, vertical or newer systems in which the airflow takes the form of an inverted trumpet (exponential flow). Exponential flow (ex-flow) systems work on the principle of graded velocity, with the flow in the centre being vertical and, in the periphery, radially outwards. Because of efficiency of the ex-flow system they can function a t fewer air changes per hour than the traditional laminar flow systems.
EXAMINER
How is ultraclean air achieved in theatres and how is it monitored?
How is ultraclean air achieved in theatres and how is it monitored?
CANDIDATE
Ultraclean air is achieved by high efficiency particulate air (HEPA) filters mounted in the ventilation system. HEPA filters are 99.7% efficient filtering contaminants of 0.5 μm or greater in size. Modern HEPA filters also utilize ultraviolet light in order to increase their efficiency. Filtration systems are usually monitored regularly where a 1 m3 sample of air is obtained through a (Casella) slit sampler and introduced over an agar plateLess than 10 colony forming units/m3 (CFU/m3) defines ultra-clean air. In the plenum system, < 35 CFU/m3 or < 1 clostridium or staph aureus/m3 indicates an efficient system. In the laminar system around the theatre table it is < 10 CFU/m3, but in the periphery of the theatre it should be < 20 CFU/m3.
Ultraclean air is achieved by high efficiency particulate air (HEPA) filters mounted in the ventilation system. HEPA filters are 99.7% efficient filtering contaminants of 0.5 μm or greater in size. Modern HEPA filters also utilize ultraviolet light in order to increase their efficiency. Filtration systems are usually monitored regularly where a 1 m3 sample of air is obtained through a (Casella) slit sampler and introduced over an agar plateLess than 10 colony forming units/m3 (CFU/m3) defines ultra-clean air. In the plenum system, < 35 CFU/m3 or < 1 clostridium or staph aureus/m3 indicates an efficient system. In the laminar system around the theatre table it is < 10 CFU/m3, but in the periphery of the theatre it should be < 20 CFU/m3.
EXAMINER
What is the evidence for the use of laminar airflow in theatre?
What is the evidence for the use of laminar airflow in theatre?
CANDIDATE
Lidwell et al. (MRC trial) showed a reduction in deep sepsis by 50% with ultraclean air systems (3.4% down to 1.7%). There was a further reduction in deep infection rate by the additional use of systemic antibiotics (0.4%) and body exhaust suits (0.2%). Recently, there have been some publications which have questioned the effectiveness of laminar airflow. In 2011 the results from the New Zealand joint registry suggested no reduction of early deep infection rate inpatients undergoing both total hip and total knee arthroplasty.
Lidwell et al. (MRC trial) showed a reduction in deep sepsis by 50% with ultraclean air systems (3.4% down to 1.7%). There was a further reduction in deep infection rate by the additional use of systemic antibiotics (0.4%) and body exhaust suits (0.2%). Recently, there have been some publications which have questioned the effectiveness of laminar airflow. In 2011 the results from the New Zealand joint registry suggested no reduction of early deep infection rate inpatients undergoing both total hip and total knee arthroplasty.
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An observational study of trauma in England (Pinder et al.) looking at surgical site infection in laminar flow vs. plenum flow theatres showed no difference between the two. In fact, the infection rate was significantly higher in hip hemiarthroplasties when performed in a laminar airflow theatre.
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Structured oral examination question 8#
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Theatre etiquette
EXAMINER
Does the number of people in theatre matter?
Does the number of people in theatre matter?
CANDIDATE
95% of theatre-acquired infection comes from air-borne contamination. Most of this is from theatre personnel, from which 90% of skin squames come from below the neck. Rifter et al. showed that the bacteria count in the operating room air increases 3–4-fold in a theatre with 5 people compared to an empty room.
95% of theatre-acquired infection comes from air-borne contamination. Most of this is from theatre personnel, from which 90% of skin squames come from below the neck. Rifter et al. showed that the bacteria count in the operating room air increases 3–4-fold in a theatre with 5 people compared to an empty room.
EXAMINER
So, what is ‘entrainment’ and how can this be prevented?
So, what is ‘entrainment’ and how can this be prevented?
CANDIDATE
Entrainment refers to the situation which arises when theatre personnel or equipment disrupt the laminar airflow and the air (and particles) is diverted towards the operative field. There are two main ways of preventing this. First, the use of a physical barrier (e.g. the ‘side screens’ that are placed around the tent to a level where they prevent persons or equipment entering the laminar flow field). The second method to prevent entrainment is the use of the ex-flow system via its inverted trumpet effect.
Entrainment refers to the situation which arises when theatre personnel or equipment disrupt the laminar airflow and the air (and particles) is diverted towards the operative field. There are two main ways of preventing this. First, the use of a physical barrier (e.g. the ‘side screens’ that are placed around the tent to a level where they prevent persons or equipment entering the laminar flow field). The second method to prevent entrainment is the use of the ex-flow system via its inverted trumpet effect.
EXAMINER
What are your views on scrubbing?
What are your views on scrubbing?
CANDIDATE
Chlorhexidine decreases the bacterial count by 99% compared to povidone iodine, which is 97%. Chlorhexidine also lasts longer than povidone iodine Nicola yet al. found that: Alcohol rub after scrubbing has been shown to improve the effectiveness of the process. Brushes and sponges should not be used. Hot water should not be used as it decreases the antimicrobial powers of the antiseptics.
Chlorhexidine decreases the bacterial count by 99% compared to povidone iodine, which is 97%. Chlorhexidine also lasts longer than povidone iodine Nicola yet al. found that: Alcohol rub after scrubbing has been shown to improve the effectiveness of the process. Brushes and sponges should not be used. Hot water should not be used as it decreases the antimicrobial powers of the antiseptics.
EXAMINER
What should a surgeon wear in theatre to reduce infection?
What should a surgeon wear in theatre to reduce infection?
CANDIDATE
Ideally, protective gear in the form of a cap, mask, eyewear, double gloves, gowns, boots with impervious soles are essential for all surgeries. Coft on is woven and lets particles less than 80 μm through. Goretex prevents particles greater than 0.2 μm, but is expensive. Therefore, synthetic hydrophobic, non-woven, disposable clothing made from spun-laced polyester pulp with mesh size much less than 80 μm is effective and more comfortable and convenient to wear.
Ideally, protective gear in the form of a cap, mask, eyewear, double gloves, gowns, boots with impervious soles are essential for all surgeries. Coft on is woven and lets particles less than 80 μm through. Goretex prevents particles greater than 0.2 μm, but is expensive. Therefore, synthetic hydrophobic, non-woven, disposable clothing made from spun-laced polyester pulp with mesh size much less than 80 μm is effective and more comfortable and convenient to wear.
source p. 1672
Structured oral examination question 9#
source p. 1673
Peri operative bleeding
EXAMINER
What does Figure 29.4 show, and can you tell me how peri operative bleeding can be influenced by some common medication with reference to this pathway?
What does Figure 29.4 show, and can you tell me how peri operative bleeding can be influenced by some common medication with reference to this pathway?
Figure 29.4 Coagulation cascade.
CANDIDATE
This demonstrates the coagulation cascade. The common anticoagulants can cause bleeding in the following way: Aspirin inactivation of cyclo oxygenase (COX) enzyme. Warfarin: inhibition of hepatic enzymes for vitamin K (factors II, VII, IX, X). Heparin antithrombin III inhibitor. LMWH: indirect factor Xa inhibitor. Rivaroxaban: direct factor Xa inhibitor.
This demonstrates the coagulation cascade. The common anticoagulants can cause bleeding in the following way: Aspirin inactivation of cyclo oxygenase (COX) enzyme. Warfarin: inhibition of hepatic enzymes for vitamin K (factors II, VII, IX, X). Heparin antithrombin III inhibitor. LMWH: indirect factor Xa inhibitor. Rivaroxaban: direct factor Xa inhibitor.
EXAMINER
What is clopidogrel?
What is clopidogrel?
CANDIDATE
Clopidogrel is an irreversible platelet inhibitor with a half-life of 5–7 days. It is used in cardiac conditions ands tents. It should be stopped 10 days prior to surgery, giving enough time for healthy platelets to form.
Clopidogrel is an irreversible platelet inhibitor with a half-life of 5–7 days. It is used in cardiac conditions ands tents. It should be stopped 10 days prior to surgery, giving enough time for healthy platelets to form.
EXAMINER
How does tranexamic acid work? What is its role?
How does tranexamic acid work? What is its role?
source p. 1674
CANDIDATE
Tranexamic acid inhibits fibrinolysis by blocking plasmin effect on fibrin. It does not increase the proclivity for clot formation, but rather prevents the breakdown of a clot. Tranexamic acid lowers the rate of transfusion without increasing the rate of venous thromboembolism. Tranexamic acid can be delivered IV, topically or orally. For IV administration the patient requires normal renal clearance and no history of cardiac surgery or venous thromboembolism. There is litile difference in the effectiveness of the different modes.
Tranexamic acid inhibits fibrinolysis by blocking plasmin effect on fibrin. It does not increase the proclivity for clot formation, but rather prevents the breakdown of a clot. Tranexamic acid lowers the rate of transfusion without increasing the rate of venous thromboembolism. Tranexamic acid can be delivered IV, topically or orally. For IV administration the patient requires normal renal clearance and no history of cardiac surgery or venous thromboembolism. There is litile difference in the effectiveness of the different modes.
EXAMINER
What other strategies are available to reduce peri operative blood loss inoperations such asT KAs?
What other strategies are available to reduce peri operative blood loss inoperations such asT KAs?
CANDIDATE
Although tranexamic acid is the most important, other strategies exist: Periarticular injections of analgesia plus adrenalin. Fibrin sealants. Bipolar sealant – a disposable device that requires its own energy generator but promotes coagulation of periarticular soft tissues. Avoidance of tourniquet during the surgery – as this will result incontinuous cautery of bleeding during surgery. It is noted that the release of the tourniquet at the end of the procedure may cause a reflex hyperaemia which may increase the blood loss. The avoidance of suction drains.
Although tranexamic acid is the most important, other strategies exist: Periarticular injections of analgesia plus adrenalin. Fibrin sealants. Bipolar sealant – a disposable device that requires its own energy generator but promotes coagulation of periarticular soft tissues. Avoidance of tourniquet during the surgery – as this will result incontinuous cautery of bleeding during surgery. It is noted that the release of the tourniquet at the end of the procedure may cause a reflex hyperaemia which may increase the blood loss. The avoidance of suction drains.
source p. 1675
References
Hooper GJ, Rothwell AG, Frampton C, Wyatt MC, et al. Does the use of laminar flow and spacesuits reduce early deep infection after total hip and knee replacement? The ten-year results of the New
Zealand Joint Registry. J Bone Joint Surg (Br). 2011;93:85–90.
Lidwell OM, Elson RA, Lowbury RJ, et al. Ultraclean air and antibiotics for prevention of postoperative infection – a multic entre study of 8,052 joint replacement operations . Acta Orthop Scand. 1987;58:4–13.
McGovern PD, Albrecht M, Belani K, et al. Forced-air warming and ultra-clean ventilation do not mix – an investigation of theatre ventilation, patient warming and joint replacement infection in orthopaedics . J
Bone Joint Surg (Br). 2011;93(11):1533–1544.
Nicolay CR. Hand hygiene: an evidence-based review for surgeons. Int J Surg. 2006;4(1):53–65.
Odinsson A, Fins enV. Tourniquet use and its complications in Norway. J Bone Joint Surg (Br).
2006;88B:1090–1092.
Pinder EM, Boti leA, Aylin P, Loeffler MD, et al. Does laminar flow ventilation reduce the rate of infection?
An observational study of trauma in England. J Bone Joint Surg (Br). 2016;98:1262–1269.
Rifter MA, Eitzen H, French ML, Hart JB, et al. The operating room environment as affected by people and the surgical face mask. Clin Orthop Relat Res. 1975;111:147–150.