Surgery

• Asepsis is The exclusion of all pathogenic microorganisms before they can enter an open surgical wound or contaminate a sterile field
• sterilisation is The destruction of ALL microorganisms (bacteria, viruses, spores) on an inanimate object (e.g. operating rooms, instruments)
• disinfection is The destruction of pathogenic organisms on inanimate objects
• asepsis is The destruction or inhibition of growth of most pathogenic microorganisms on animate organisms
• sources of contamination that threaten the surgical field:

  Human sources – airborne, droplet and contact

  Contaminated instruments and the environment

  Animal sources – skin, hair, naso-pharynx, faeces

  Inanimate sources – fomites and air
• Aseptic techniques are CLEAN techniques

  Sterile techniques work within a sterile field i.e. absent of microorganisms
• general principles of sterile technique:

  -          Scrub to remove dirt, oil, bacteria.

  -          Once gowned and gloved always face the sterile field – Front of gown is considered sterile from the chest level to the sterile field

  -          Do not lean over or touch a non-sterile area

  -          Arms and hands should be above waist level

  -          Hands clasped in front of body

  -          Scrubbed personnel should avoid changing position

  -          Sterile items and persons only to be used in sterile field

  -          All items opened onto sterile field should not breach sterility
• Hospital methods to reduce pathogens:

  • Regular hand washing – all staff/visitors

  • Gloves if handling likely sources of pathogens e.g. wounds, high risk patients, equipment

  • Clean or dispose of equipment between patients

  • Proper equipment storage

  • Regular equipment cleaning

  • Dirty laundry – wash at 60°C or above

  • Scheduled/regular cleaning of surfaces

  • Proper maintenance – hospital: heating ventilation, air conditioning

  • Minimise unnecessary traffic/personnel

  • Isolation of patients with known pathogenic microorganisms
• Levels of sterility:

  • Critical

  – equipment or implants entering the body below the skin or mucous membranes

  – require sterilisation and sterile technique e.g. implants

  • Semi-critical

  – equipment that contacts the skin or mucous membranes only for surgical purposes without penetration of the body

  – require cleaning and disinfection e.g. vaginoscopes

  • Non-critical

  – equipment that contacts mucous membranes or intact skin not directly associated with surgery

   – require cleaning and disinfection e.g. laryngoscope, dental
• surgical pack prep:

  1.      Cleaning of instruments – Removes gross contamination, organic material and inorganic salts

  2.      Sterilisation

  – High temperature – steam autoclave, dry heat

  – Low temperature (Chemical) – Ethylene oxide, gas plasma

  – Ionising radiation

  – Liquid emersion – Glutaraldehyde, Peracetic

  3.      Packaging –

  -          Sterilisation wraps

  -          Container systems

  -          Steri reel or sterilising pouches

  4.      Allow packs to dry and cool before removal from autoclave

  5.      DATE and place in storage.
• Sterile surgical packs:

  • Placing packs on top of each other during cooling may promote condensation of moisture

  • Strike-through contamination – moisture carries bacteria from a non-sterile surface to sterile surface

  • When packs are dry - store wrapped packs in cabinets to avoid dust-borne bacteria

  • Stored away from ventilation ducts, sprinklers

  • Low humidity, low air turbulence constant-controllable room temperature

  • Handle gently, avoid bending, compression

  • pack remains sterile unless it is – Opened, Gets wet, Torn, Seal breaks, Damaged
• Sterilisation methods

  • High temperature – steam autoclave, dry heat

  • Low temperature (Chemical) – Ethylene oxide, gas plasma

  • Ionising radiation

  • Liquid emersion – Glutaraldehyde, Peracetic acid
• Regardless of sterilisation technique – instrument and linens must be first cleaned of gross contamination

  Reliability/method depends on:

  o Number, type and inherent resistance of micro-organisms present

  o If other materials are present that could shield or inactivate the sterilising agent e.g. organic matter

  o Equipment type to be sterilised – lumens, heat-sensitive, moisture-sensitive devices
• Steam sterilisation aka autoclave:

  Steam sterilisation is practical and reliable (at least for sterilising heat tolerant medical supplies). Materials are saturated with steam under pressure, rapidly destroying microorganisms by coagulating and denaturing proteins.

  Minimum time and temperature important (3-4 minutes at 132-135c for 3-4 minutes minimum)
• Ethylene oxide is ssed for items that don’t withstand heat (low temperature sterilisation)

  Alkylates proteins, DNA and RNA.

  Downsides: flammable, explosive and a lengthy cycle time (12-24 hours plus 2 hours purge time)

  Can be hazardous to patients and staff and requires aeration following sterilisation.
• Gas plasma sterilises through combined use of hydrogen peroxide gas and the generation of UV photons and free radicals during the plasma phase

  Low-temperature sterilisation

  • Good for heat-sensitive instruments (similar to EtO)

  • Safe – no operator or patient risks

  • Vapour phase – fast processing

  • 38 minutes at 50°C, immediate use

  • Disadvantage – dependance on actual thickness of microorganisms to be inactivated – photons need to reach the DNA
• Chemical (cold) sterilisation:

  Glutaraldehyde 2%–

  Used for non-corrosive to metals, rubber and plastics– Delicate lensed instrument sterilisation (scopes)

  – Alkylating agent – alters RNA, DNA, proteins

  – Organic matter may prevent penetration so items must be clean and dry before sterilisation

  – Respiratory and dermal irritant and sensitiser– items must be rinsed in sterile water and dried with a sterile towel

  • Sterilisation takes 10 h at 20-25oC

  • Disinfection – 10 min at 20-25oC
• indicators of sterilisation available:

  -          Chemical indicators

  Used in steam, gas and plasma st. Paper strips or tape changes colour when temperature is achieved e.g. bowie dick tape. HOWEVER does not indicate time. TST (time, steam, temp) strips change when all 3 achieved.

  -          Biological indicators

  Highly resistant, non-pathogenic spore forming bacteria – contained in a vial or paper strip – placed in the steriliser with the items

  • After the cycle has finished the vial is cultured

  • Perform this check weekly
• factors causing failure of sterilisation:

  – Inadequate cleaning of the instrument or object to be sterilised

  – Instruments left closed

  – Packs wrapped too tightly

  – Improper loading in autoclave or chamber

  • Air space needed between packs to allow flow of steam

  – Mechanical failure of sterilisation
• preparation of patients for surgery:

  • Dietary restriction, Excretions

  • Treatment of hair – no. 40 blade. Ideally outside surgery suite

  • Scrub patient (wearing disposable gloves), using swabs and antiseptic solution, until clean, using a grid pattern

  • Final prep in theatre - using a grid pattern

  • Skin antiseptics – Alcohols have the most rapid kill rates (approximately 98-99% kill rate within 30-60 seconds of application) – Chlorhexidine has a 96% kill rate a 30 seconds, 98% at 3 minutes – Povidone-iodine has a 77% kill rate within 3 minutes
• Ideal properties of suture material: One single ideal material does not exist.

  • Strengths, sizes, permanent or absorbable are all considered when choosing a material.

  Ideally suture material should have good handling characteristics so it’s easy to work with, have low tissue reactivity and be non-capillary so it doesn’t draw fluid and bacteria into the suture. It should not support bacterial growth, should knot securely, absorb predictably, be affordable, non-carcinogenic and non-allergenic. It should also be easy to sterilise without degrading.
• All sutures gradually lose tensile strength, but the rate depends on the material and the environment they’re in (Infection / inflammation)

  The rate of strength loss should be proportional to the rate of strength gain in the wound ( Depends on tissue. Muscle, fat, skin – few days. Fascia – weeks. Tendons – months). Absorbable sutures are removed by hydrolysis or phagocytosis.
• There is a common misconception that any buried suture must be absorbable. This is not the case but permanent materials may turn wound contamination into infection or may act as a focus of infection. If planning on leaving a permanent material in the body then must be careful to minimise the risk of infection
• • Monofilament - single strand

  ➢ little drag

  ➢ high memory - remove from pack and it try's to maintain it shape – impacts knot security

  ➢ Non-capillary

  ➢ Careful with needle holders as can damage the suture and weaken it

  • Multifilament – several braided strands

  ➢ rough, increased drag (which also increases inflammation)

  ➢ Capillarity - spaces in suture that can harbour bacteria

  ➢ softer, easier to handle

  ➢ more friction, more contact – better knot security

  • ‘pseudomonofilaments’

  ➢ ensheathed multifilament materials

  ➢ Supramid (multifilament, coated, non-absorbable polyamide)
• • Natural sutures

  ➢ found in nature e.g. silk, catgut

  ➢ enzymatic degradation and phagocytosis - immune response and tissue reaction

  ➢ unpredictable absorption

  • Synthetic sutures

  ➢ man-made e.g. PDSII, Vicryl, Monocryl etc

  ➢ dissolved by hydrolysis

  ➢ very predictable absorption
• Suture coatings modify the surface characteristics of a suture material.

  They reduce tissue drag and fill internal space (e.g. in multifilament). They however reduce friction so their knots are considered less secure. Often antibacterial (NOT a suitable substitute for good asepsis and tissue handling)
• different suture sizings:

  Metric- the higher the number, the greater the suture diameter.

  Imperial – higher the number the smaller the suture

  Browne & Sharpe – wire gauge in mm for orthopaedic wire               
• suture material should be selected based on:

  • Strength, size, and rate of absorption to the tissue

  ➢ Some tissues need short support – skin and subcut (days)

  ➢ Some tissues need long support – fascia (weeks), tendon (months)

  • Avoid multifilament & permanent materials in contaminated/infected wounds

  • Leave the minimum amount of suture behind – minimise tissue trauma and amount of foreign material in the body

  ➢ continuous patterns

  ➢ small diameter, stronger material

  • Individual variation between patients – obesity, infection, malnutrition, neoplasia, drugs (steroids)
• • interrupted patterns require 4 throws

  • continuous patterns require:

  ➢ 5 throws to start

  ➢ 6-7 throws to end

  Don’t put additional throws on for good luck, bulkier knots are less secure
• Surgical needles available:

  Cutting: Used in difficult to penetrate tissue, e.g. skin. Apex of edges on inside curvature. Potential to ‘cut-out’ tissue

  Reverse cutting: Used in difficult to penetrate tissue. Stronger than similar sized cutting and less 'cut-out’

  Round bodied: Separates tissues. Pierces without cutting, e.g. subcut, fascia

  Tapercut: Combination of a RC and RB. Used for suturing tough fibrous tissue, e.g. tendon

  Bluntpoint: Have a rounded, blunt point that can dissect through friable tissue without cutting. Used for suturing soft, parenchymal organs, e.g. liver or kidney
• The hole created by a needle should be just large enough to allow passage of the suture material

  • Swaged needles preferred to closed eye needles

  ➢ Produce less tissue trauma (always sharp, fewer suture strands) but more expensive

  ➢ Eyed needles require threading, and pull a double strand of suture through the tissue
• Despite being a good material for tying good ligatures, catgut is absorbed by phagocytosis and enzymatic degradation, making it unpredictable. There is a significant inflammatory response around the suture material. The rate of absorption and loss of tensile strength is variable depending on site and wound conditions.
• Haemorrhage is the escape of blood from a vessel following vascular injury.

  Primary haemorrhage: happens immediately after a vessel is disrupted during surgery or trauma. May also occur in disorders of primary homeostasis. Can be avoided with good anatomical knowledge, accurate dissection and ligation of vessels.
• Delayed/ intermediate haemorrhage occurs within 24 hours: occurs in cases where a ligature has slipped (particularly on the ovarian stump), where there has been inappropriate electrocautery or electrosurgery use. May also happen when a blood clot is dislodged or as blood pressure returns to normal post-surgery. Also in disorders of secondary homeostasis.

   
• Secondary haemorrhage (rare): occurs 7-14 days post surgery where there is erosion of a blood vessel by a drain, implant etc.
• Tourniquets are a method of mechanical haemostasis used in surgery.

  Used on distal extremities. Compresses vessels temporarily, but once removed will start bleeding again. Care with length of time applied for- can cause necrosis due to ischaemia. Do not use if there is any vascular compromise.
• Digital pressure is a method of mechanical haemostasis used in surgery. Temporary, literally holding with your finger and saline soaked swabs. Dab, don’t wipe or you may cause more damage.

  Packing and dressings. Application of pressure and absorption of blood.
• Haemostatic forceps/ clamps are a method of mechanical haemostasis used during surgery. Definitive haemostasis for smaller vessels, temporary occlusion for a larger vessel until it is ligated. Ligation of vessels 1/3-2/3 the clip diameter. Useful for inaccessible sites and saves time, but is expensive as are single use.
• Bone wax Prevents bleeding from cancellous bone and can be kneaded to shape but is non-absorbable and interferes with bacterial clearance (effectively a foreign body). It is a method of mechanical haemostasis
• Ligatures provide deep pressure which cuts off bloodflow by tying off the vessel (mechanical haemostasis)