EXAMINER: 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.

EXAMINER: What about cleaning?

CANDIDATE: 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?

CANDIDATE: High-temperature sterilization of which prevacuum 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-sensitive instruments such as arthroscopes and drill and saw systems.

EXAMINER: 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:

EXAMINER: 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).

EXAMINER: How are sterilization processes monitored?

CANDIDATE: Sterilization procedures should be routinely monitored by:

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   I.  Mechanical indicators that record time, pressure  and temperature.

   
   
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   II.  Chemical indicators that are usually heat- or  chemical-sensitive 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?

CANDIDATE: Sterile instruments should be transported in covered or enclosed trolleys with solid-bottom shelves that are cleaned and disinfected after each use.

EXAMINER: What is Figure 29.1 demonstrating?

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.

EXAMINER: 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 half times 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 any 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?

CANDIDATE: In patients 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?

CANDIDATE: There is either exsanguination by elevation or expression. In patients 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?

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.

EXAMINER: 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.

EXAMINER: How is this different to post-tourniquet syndrome?

CANDIDATE: Post-tourniquet syndrome is a reperfusion 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?

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.

EXAMINER: What type of sutures do you use in your practice?

CANDIDATE: I use absorbable sutures like vicryl or non-absorbable such as prolene.

EXAMINER: What are the differences between vicryl and prolene?

CANDIDATE: Vicryl is a form of braided suture and is absorbable while prolene is a monofilament suture and non-absorbable.

EXAMINER: 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.

EXAMINER: Are there any disadvantages of using braided sutures?

CANDIDATE: Braided sutures have an increased risk of promoting infection due to 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?

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

EXAMINER: What does Figure 29.2 demonstrate?

CANDIDATE: This shows monopolar diathermy and a return electrode.

EXAMINER: 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.

EXAMINER: How is this different to bipolar diathermy?