Surgical Principles

Compare use of a scalpel vs. scissors

Scalpel

Best for dense tissue like skin or fascia

Minimal collateral damage

Scissors

Best for loose tissue like adventitia or fat

More crushing damage

Compare mechanism of cautery vs. electrosurgery

Cautery = Direct heat produced AT THE TIP by using low-voltage current (current does NOT pass through the patient)

Electrosurgery = Heat produced WITHIN the tissue via resistance of flow as current passes through the patient

Compare uses of cautery vs. electrosurgery

Cautery = Disbudding

Electrosurgery = Cutting OR coagulation depending on the electrical waveform selected

Compare the 2 types of electrosurgery (mechanism and advantages/disadvantages)

Monopolar Electrosurgery

Mechanism: Active electrode at surgical site and return electrode (dispersive pad) elsewhere on patient

• Current passes through patient and resistance generated produces heat

• Resistance inversely proportional to SA (resistance decreases as current spread through body)

Disadvantage: Cannot work in wet field (eg. blood) as current will disperse throughout fluid and target tissue will not heat effectively

Bipolar Electrosurgery

Mechanism: Active AND return electrode at surgical site

• Current passes through tissue grasped by forceps

Advantage: Works in ALL types of environments (eg. fluid)

Laser Surgery

• Mechanism

• 2 Uses

Mechanism: Light amplification by stimulated emission of radiation (monochromatic, highly coherent in infra-red, visible or near Uv)

Uses:

1. Tol to ablate/vapourise/weld tissue

2. Photodynamic cancer therapy = Photosensitive drug taken up by tumour and laser applied to kill tumour

Fluoroscopy (eg. C-arm)

Imaging modality to produce real-time radiographs to assist with orthopaedic repair

6 Reasons to perform surgery

1. Therapeutic

2. Diagnostic (eg. ex-lap, biopsy)

3. Increase suitability of use (eg. desexing, dehorning)

4. Palliative

5. Biomedical research

6. Cosmesis

Definitions

1. -ostomy

2. -oplasty

3. -rrhaphy

4. -pexy

5. -desis

1. -ostomy = Permanent/semi-permanent stoma (opening) eg. colostomy bag or gastrostomy tube

2. -oplasty = Reconstructive/reparative surgery to restore function or appearance eg. rhinoplasty

3. -rrhaphy = Suturing a structure to close a defect/rupture eg. herniorraphy/tenorraphy

4. -pexy = Fixation eg. gastropexy

5. -desis = Attach together eg. arthordesis

6 Advantages and 4 disadvantages of minimally invasive procedures (eg. endoscopy)

Advantages

1. Reduces duration of hospital stay (less $)

2. Faster surgery time (minimal closure)

3. Less exercise restriction (minimal closure)

4. Superior cosmesis (smaller scar)

5. Reduced pain (do not need to stretch abdominal wall with retractors)

6. Magnified field and excellent lighting

Disadvantages

1. Surgeon’s hands remove from tissue (no manipulation/palpation)

2. Haemorrhage = Visibility issues and more difficult to stop

3. Requires specialised/expensive equipment and new skill

   1. Arthroscopy impossible for canine hip

Triangulation in endoscopy

Concept required for skin incision for endoscopic techniques

• Apex = Lesion on interest

• Point in base = Scope viewing point

• Other point on base = Instrument

Separate incisions for scope and instrument

Halsted’s Principles (7/8)

1. Handle tissue gently

   • Reduce necrosis and post-op infection

   • Reduce pain and dysfunction

   • Speed up healing

2. Meticulous haemostasis

   • Better surgical field visualisation

   • Reduce haemorrhagic shock

   • Reduce post-op infection

3. Preserve blood supply

4. Strict aseptic technique

   • Reduce post-op infection

5. Avoid tension on wound edges

   • Reduce tissue strangulation (necrosis) and dehiscence

6. Eliminate dead space between tissue planes

   • Dead space accumulates blood/serum which delays healing is a growth medium for bacteria

7. Meticulous approximation of all wound layers

   • Promotes rapid healing

   • Increases wound strength

   • Reduce post-op infection

8. Minimise foreign material in wound (eg. suture material and glove powder)

5 Questions to ask when deciding to operate

1. Has a definitive diagnosis been made?

2. Is surgery the ONLY/BEST treatment? What are the alternatives? Minimally invasive techniques?

3. Logistics: When? How? Who? Where?

4. Harm to the patient during/after surgery

5. Owner considerations: Coping with aftercare, expectations, cost

Determinants of surgical risk

Table

List the 4 phases of wound healing (+ duration)

1. Acute inflammatory (lag) phase = Day 0 - 5

2. Debridement phase

3. Proliferative (repair) phase = Day 3 - 14

4. Remodelling (maturation) phase = Week 2 - year 1

Phases overlap and problems arise if one phase is absent or prolonged

Acute Inflammatory (Lag) Phase

• 3 Functions

• 6 steps (+ descriptions)

Functions:

1. Haemostasis

2. Prevent infection

3. Lay groundwork for subsequent steps of healing

6 Steps:

1. Skin retraction = Defects becomes larger due to normal skin elasticity and external tension from muscle pull

2. Haemorrhage = Haemorrhage due to injured blood vessel to clean wound surface and inoculate wound with cells for healing

3. Vessel reaction/vasoconstriction = Traumatised epithelium → Phospholipid membrane injury and arachidonic acid release

   • Arachidonic acid cascade induces peripheral vasoconstriction (5 - 10 minutes post-injury)

   • → Hypoxia and decreased pH within wound and tissue

4. Vasodilation and increased permeability of venules

   • In response to cytokines (eg. histamine, serotonin, bradykinin, prostaglandins, leukotrienes) secreted from mast cells in damaged tissue

5. Cellular response (<30 minutes) = Recruitment and activation of platelets from peripheral bloodstream → Degranulation results in mitogen and chemoattractant release (important for directing and initiating wound healing)

6. Clot formation = Plasma proteins (eg. fibrin and clotting factors) to form haemostatic plug, reduce dead space and form framework for repair

2 Functions of a scab

Scab = Clot exposed to air causing the surface to dry and contract

Function:

1. Protect wound from external contamination

2. Maintain internal homeostasis to allow epithelial cells to migrate beneath the scab

Debridement Phase (Inflammatory)

• Timing

• 5 Steps

Timing: ~6hr after injury

Steps:

1. Fibrin released (by activation of intrinsic and extrinsic haemostasis mechanisms) to stabilise provisional wound matrix (clot)

   • “Provisional” = Lag

2. Neutrophil recruitment (peaks at day 2) stimulated by exposed collagen → Phagocytosis of debris and bacteria AND release of chemoattractants to augment inflammatory response

3. Neutrophils die or become phagocytosed

4. Monocyte migration = Phagocytosis, Ag presenting cells and release of growth factors which induces the proliferative phase

5. Lymphocytes

Proliferative (Repair) Phase

• 4 features (+ descriptions)

1. Fibroplasia = Migration of fibroblasts for collagen synthesis and granulation tissue formation

   • Fibroblasts predominate the wound bed by day 4 (arrive from day 2) → Necessary for ECM and type I collagen synthesis

     • Peak at day 7 - 8 after injury → Release collagen and

   • ECM rich in fibronectin, hyaluronan and proteoglycan (provide a scaffold for cell migration and tissue remodelling)

   • Type III collagen deposited → Maturation to type I collagen (increase tensile strength)

     • High vascularity and beginning of granulation tissue

   • Fibroblasts → Myofibroblasts which contribute to wound contraction

2. Epithelialisation = Epithelial cells proliferate and migrate from wound edges via contact-guidance and -inhibition

   • Contact guidance = Migrating epidermal cells roll/slide over each other across the basal lamina or along fibrin deposits

   • Relies on keratinocyte stem cells from adjacent tissue (basement membrane, hair follicles, sweat and sebaceous glands) → Recruitment and proliferation

     • Hence, deep wounds with complete disruption of the basement membrane are slower to heal (lack of keratinocyte stem cells for epithelialisation)

   • Requires healthy granulation tissue

   • Migrate from residual epithelium (periphery)

   • New epidermis at wound margins by day 4 - 5

     • Rapid re-epithelialisation when partial thickness abrasions (basal membrane and keratinocyte population still present)

3. Angiogenesis = New blood vessel formation

   • Occurs with decreased O2 tension, high lactate and low pH within wound

   • Initiated by vasculogenesis (NEW blood vessel formation) → Dense capillary network

     • Initiated from bone marrow progenitor cells

   • Driven by angiogenic growth factors:

     • VEGF (Vascular Endothelial Growth Factor)

     • FGF-2 (Fibroblast Growth Factor-2)

     • PDGF (Platelet-Derived Growth Factor)

   • Endothelial cell migration = Involves migration and proliferation to create new capillary structures

   • Reversal of hypoxia → Increased blood flow and reversal of hypoxia

4. Wound contraction = Wound borders are drawn together to reduce SA for epithelialisation

   • Occurs when fibroblasts predominate

   • Reduces wound surface area by 40 - 80% depending on location of wound

   • Dependent on differentiation of fibroblasts → Myofibroblasts

   • Collagen reinforces contracted wound

6 Disadvantages of wound contraction/2nd intention as a method of healing

Increases skin tightness and reduces function

1. Limited movement when formed over flexor surfaces

2. Stenosis of body opening (eg. anus)

3. Insufficient contraction = Large areas of thin epithelium which can abrade and split open

4. Cosmesis

5. Expensive bandage changes and hospital visits

6. Prolonged healing

5 Functions of granulation tissue

1. Provide surface area for epithelial cell migration

2. Provide fibroblasts for collagen formation

3. Assists in wound contraction

4. Provides blood supply

5. Barrier against systemic infection and local infection

4 Features of maturation (remodelling) phase

1. Continued epithelialisation and wound contraction

2. Hyaluronan from provision wound matrix replaced with proteoglycans within ECM

   • Angiogenesis and wound metabolic activity decreases

   • Cytokines and growth factors stimulate decline

3. Collagen content increases with organisation/alignment of collagen into bundles and collagen cross-linking

4. Remodelling via proteinases

Scar tissue strength over time

Weaker than original tissue with gradual gain over time (never as strong as original tissue)

• 20% at 3 weeks

• 50% by 3 months

• 70 - 80% at end of maturation

Tissue appearance at each stage of wound healing (8)

1. Swelling (inflammatory phase)

2. Receding wound edges

3. Exudative (vasodilation in inflammatory phase bringing in fluid for wound clotting and phagocytosis)

4. Decreased tissue strength

5. Pink, cobblestone appearance (granulation)

6. Thin, whitish edges (epithelialisation)

7. Puckered appearance around edges

8. Restored tissue strength

Compare surgical vs. open wound healing

1. Blood clot

2. Inflammatory phase

3. Debridement

4. Epithelialisation

5. Fibrin

6. Granulation tissue/collagen

Surgical Wound

1. Blood clot forms in incision

2. Brief inflammatory phase

3. Minimal debridement

4. Epithelial cover by 48hr

5. Vertically oriented fibrin by day 3 - 4

6. Collagen formed by day 5 and parallel collagen and capillary orientation by day 6

Open Wound

1. Blood clot fills wound bed

2. Inflammatory response depends on damage

3. Prolonged debridement phase due to presence of devitalised tissue, infection and foreign material

4. Epithelialisation requires granulation bed and may be delayed ≥7 days

5. Fibrin clot covers wound and granulation tissue forms by day 4 - 5

3 Potential complications of surgical wound closure

1. Sutures too tight = Skin necrosis, suture abscess and delayed healing, removed prematurely by patient as uncomfortable

2. Sutures too loose = Gaping wound and open wound healing with scar tissue

3. Migrating epithelial cells down suture tracts may become keratinised and form suture abscess

4 Potential complications of open wound healing

1. Excessive granulation tissue (proud flesh) inhibits wound contraction and epithelialisation

2. Inhibited function associated with wound contraction

3. Slow epithelialisation and scar tissue formation when contraction stops before wound closure

4. Large areas of scar tissue are easily abraded by external trauma (eg. licking)

What day is wound strength the lowest? Why?

Day 5 = Old collagen broken down by neutrophils BUT delay of laying down new collagen

7 Most common causes of delayed wound healing

1. Infection

2. Excess motion (horses)

3. Self-mutilation

4. Excess tension

5. Debilitated patient: Systemic disease

6. Recumbency

7. Poor vascularity

7 Factors affecting wound infection

1. Degree of bacterial contamination (>10^5 bacteria/g tissue or mL of fluid required for infection)

2. Virulence of organism (eg. Klebsiella, Pseudomonas, E. coli vs. commensals)

3. Type of injury

   • Crushing = Severe devitalisation and vascular injury

   • Sharp laceration = Little necrotic tissue

4. Vascular insufficiency/ischaemia (eg. dehydration, shock, tissue tension, vascular injury, excessive electrocautery)

5. Foreign material

   • Harbours bacteria which the inflammatory reaction cannot reach

   • Creates chronic infection/sinus formation as macrophages cannot remove foreign material

6. Free fluid accumulation (eg. seroma)

   1. Due to improper closure which creates dead space

   2. Creates pressure that interferes with blood supply to adjacent tissue

   3. Good bacterial growth medium

7. Immunological incompetence (eg. immunocompromised, secondary to drugs, malnutrition, irradiation)

3 Causes of seroma formation after wound closure

1. Tissue rich in lymphatic vessels is transected

2. Excessive movement in wound

3. Tissue response to suture material

List 7 principles of wound management

1. History

   • Important to know timeline of injury as suturing sooner carried better prognosis

   • Cause of injury: Sharp laceration vs. HBC

   • Previous wound treatment (eg. blue spray) = Suturing NOT appropriate

2. FULL physical examination (avoid missing crucial problems)

3. Prevent further contamination

4. Lavage

5. Wound exploration

6. Debride

7. Wound therapy = Drain, closure and bandaging

6 Steps of wound management to prevent further contamination

1. Ensure owner covers wound with sterile dressing

   • Saline-soaked gauze ideal to prevent desiccation and further contamination

2. Remove bandage on admission and cover wound with sterile gauze impregnated with K-Y jelly

   • Prevents further contaminants (eg. hair and dirt) falling into the wound

3. Clip surrounding hair and use vacuum cleaner to remove

4. Trim hair at wound edges with scissors dipped in mineral oil (hair sticks to blade and not wound)

5. Scrub skin with betadine to prepare for aseptic surgery

6. Drape-off surgical site and remove wound cover

Main indication for systemic broad-spectrum antibiotics for wound management

ONLY indicated with bacterial culture and sensitivity of sterile swab from deep in the wound

• Culture AFTER flushing and consider waiting as bugs present on admission are NOT causative agents of infection later

• Do NOT use antiseptics, ointments, powders as this leads to further contamination and chemical injury to tissue

Ideal pressure for wound lavage

8 psi (high pressure may open fascial planes leading to further damage and contamination)

5 Ideal solutions for wound lavage

1. Tap water = Gross contamination before more careful lavage

2. 0.9% NaCl = Any wound to cleanse wound in conjunction with debridement and dilute bacterial load

3. LRS = Any wound as for sterile saline

4. Chlorhexidine = Contaminated/infected wounds

   • Broad-spectrum 24hr activity but some Staphylococcus aureus and G- resistance

   • Toxic to fibroblasts

5. Povidone iodine = Contaminated/infected wounds

   • Broad-spectrum activity but only for 4 - 6hr

   • Inactivated by debris, pus or blood

2 Indications and caution for antiseptic solutions with wound lavage

Indications:

1. Severely infected wounds

2. Immunocompromised patients

Caution: Use at correct concentration to avoid damage to host cells (in addition to bacteria)

3 Lavage solutions to avoid

1. Hypochlorite/Dakin’s solution

2. Hydrogen peroxide

3. Savlon

Debridement

• 2 Functions

• Best method

Function:

1. Remove all debris, necrotic/devitalised tissue to prepare the wound for suturing or selective debridement

2. Explore wound to determine limits and affected anatomical structures

Method: Sharp scalpel (NOT scissors) changed and disinfected repeatedly to prevent contamination of clean areas

2 Methods of surgical debridement (+ comparison)

1. Layered debridement = Tissue cut back to clean/viable tissue

   • Conserves vital structures

   • Ideal when closure is difficult to keep as much tissue as possible

2. En bloc debridement = Complete wide excision

   • Only when non-vital tissue is involved

   • Reduce time and cost of wound management

Debridement methods for:

1. Skin

2. Fat

3. Muscle

4. Nerves

5. Joints

6. Tendons/ligaments

7. Bone

1. Skin = Trim edges and consider staged debridement (“wait and see”) as viability of tissue may be difficult to determine/misleading due to vascular spasm

2. Fat = Debride all exposed fatty tissue to a clean plane

3. Muscle = Debride muscle which is dark, friable or fails to contract

4. Nerves = Conserve and protect from other damaged tissue

5. Joints = Lavage thoroughly, repair and immobilise

6. Tendons/ligaments = Preserve as much as possible

7. Bone = In open wounds >4hr, discard small avascular fragments and carefully preserve all bone with soft tissue attachments

   • Debride to prevent overgrowth of granulation tissue from exposed bone

   • Currettage cortex until tiny bleeding vessels are seen

Types of wound drainage

1. Surgical drain

   1. Passive drain

   2. Active drain

2. Pack wound open with saline-soaked gauze

   • Saline maintains hydration, breaks down thick discharge and absorbs drainage material

Wound classification

• 2 Functions

• Ways to classify

Functions:

1. Predict likelihood of complications

2. Select appropriate management (closure type, drainage etc.)

Classification:

1. Degree of contamination

2. Duration

3. Depth

4. Location

5. Cause

List the types of wound closure

PRIMARY WOUND HEALING

1. Primary closure (1st intention)

2. Delayed primary closure

3. Secondary closure (3rd intention)

SECONDARY WOUND HEALING (2nd intention)

Primary closure (1st intention wound healing)

• Definition

• Indications

• Examples

Definition: Close wound immediately after infliction

Indications: Clean or clean-contaminated wounds

• <4 - 6hr with minimal contamination

• Sufficient skin for closure

Examples:

1. Spay wound

2. Small contaminated wound with loose skin (resect contaminated area)

Delayed primary closure

• Definition and method

• Indication

• Example

Definition: Closure of wound 3 - 5 days AFTER injury BEFORE granulation tissue has formed

• Cover un-sutured wound with sterile dressing and attempt to close in 3 - 5 days when devitalised tissue or infection is absent

Indication: Allows judgment of tissue viability when contaminated cannot be removed definitively

Example: Tail degloving with uncertainty if tissue will fall off

• Recent wounds with secondary contusion

• Recent heavily contaminated wounds

• Clean sharp wounds of several days with no devitalised or infected tissue

Secondary Closure (3rd intention wound healing)

• Definition

• Indication

• 3 Methods

Definition: Closure of wound >5 days AFTER injury when wound has formed a bed of healthy granulation tissue

Indication: Wound requires >5d to manage infection

Methods:

1. Direct appositional suturing of two granulation surfaces

2. Undermine skin to appose skin edges

3. Completely excise granulation tissue and close wound in primary fashion (will NOT relieve tension)

Secondary wound healing (2nd intention wound healing)

• Definition

• Indications

• Advantages

• Ideal locations

Definition: Wound left open to heal by granulation tissue formation, contraction and epithelialisation

Indication:

1. Dirty/infected wounds where other methods of closure cannot be used

2. Large cutaneous defects with insufficient skin

Advantage: Practical and economic IF sufficient wound care provided

• Check contraction of wound by pinching skin together

Location: Trunk and upper limbs (faster healing than distal limbs)

EXAMPLE: Dog flank laceration after running into a car door. Wound is only a couple hours old. There is no pus, but hair and dirt is present on the surface of the SC fat and muscle

1. Classify the wound

2. How do you proceed?

3. Clinical reasoning

Classification: Contaminated wound (traumatic, but <6hr and no pus)

Management: PRIMARY CLOSURE

1. Debride edges of the wound to leave healthy tissue for apposition (remove necrotic tissue)

2. Minimally debride and irrigate wound bed to remove dirt and contaminants

3. Place Penrose drain

Clinical Reasoning: Wound is large and would take a long time to heal by secondary intention, closure would be simple, a scar would be unsightly in a short coated breed

Dressing vs. bandage

Dressing = Layer of bandage in direct contact with wound

Bandage = Everything else

List 11 functions of bandages

1. Exert pressure to eliminate dead space

2. Pack a wound

3. Debride a wound

4. Absorb exudate/blood

5. Protect wound from environment

6. Protect environment from wound

7. Immobilise wound and support fractures

8. Provide comfort by reducing pain (eg. splint)

9. Vehicle for application of antibiotics and antiseptics

10. Indicator of wound secretions

11. Aesthetic appearance

5 Functions of the primary (contact) layer of a bandage

Most important layer in wound management

Function depends on stage of wound healing:

1. Debride necrotic tissue

2. Deliver medication (eg. analgesia)

3. Prevent infection or strike-through

4. Transmit wound exudates OR form occlusive seal over wound

5. Promote wound healing

Describe the classification of dressings (primary layer) + 2 descriptions

1. PASSIVE = Dressing does not change wound biology

   1. Adherent

   2. Non-adherent (semi-occlusive)

   3. Absorbent

   4. Vapour-permeable/barrier film

2. ACTIVE = Dressing interacts with wound biology to actively promote wound healing

Type of dressings required for 3 stages of wound healing

1. Inflammatory/debridement (dead tissue, bacteria, exudate) = Remove debris and fluid

2. Repair (granulation) = Protect and keep moist

3. Epithelialisation = Prevent trauma and drying out

Adherent dressings

• Indication

• Function

• Type of material

• 2 Examples

• Timeline of use

Indication: Inflammatory and debridement stage of wound healing

• Dirty, infected, necrotic, sloughing wounds

Function: Mechanically rip away bacteria, necrotic tissue and debris

• Exudate drawn out into moist gauze and dries → bacteria and dead tissue cannot retain water → they dry and stick → gauze pulls them away

Material: Woven gauze swabs (NOT pressed felt) to trap loose necrotic tissue and debris

Examples:

1. Wet-to-dry dressing

2. Dry-to-dry dressing

Timeline: Use for 3 - 5 days after injury ONLY (destroys granulation tissue)

Compare indications for wet-to-dry vs. dry-to-dry dressings

Wet-to-dry

• Indication: Less exudate, high viscosity (thick)

• Function: Sterile saline-soaked gauze dilutes exudate for easier absorption into secondary layer

  • Prevent wet swabs touching healthy tissue (maceration)

Dry-to-dry

• Indication: Lots of exudate, low viscosity (thin)

3 Advantages and 4 disadvantages of adherent dressings

Advantages:

1. Cheap and readily available

2. Easy to apply

3. Effective mechanical debridement

Disadvantages:

1. Pain on removal (requires sedation or GA)

2. Bacteria multiply in wet environments

3. Requires daily bandage change

4. Non-selective debridement (injury to healthy cells and granulation tissue)

What is a “tie-over bandage”?

Bandage sutured in place when wrapping around a body structure is not possible

Non-adherent (semi-occlusive) dressings

• Indication

• Type of material

• 3 Examples

Indication: Early repair stages (granulation tissue, some exudates and no epithelialisation)

• Protects fragile tissue while allowing fluid to escape

• Clean wounds with mild exudate (eg. post-op)

Material: Perforated polyurethane (polyester) = Primapore and melolin

Examples:

1. Primapore

2. Melolin

3. Paraffin gauze

4 Advantages and 1 disadvantage of non-adherent (semi-occlusive) dressings

Advantages:

1. Cheap

2. Easy to use

3. Does not interfere with healing

4. Absorbs a little exudate

Disadvantages: No moist wound environment and open wounds dry out

Compare primapore vs. melolin

BOTH have shiny and perforated polyurethane (polyester) which allows passage of blood/exudate away from the wound while remaining non-adherent

Primapore = Peripheral adhesive surrounding thin absorbent layer

Melolin = Thicker absorbent layer and no peripheral adhesive (needs bandage)

Jelonet (paraffin gauze)

• Type of material

• Indication/use

• 2 Disadvantages

Material: Cotton net impregnated with soft paraffin (petroleum)

Indication: Allows exudate to pass through to the secondary absorbent layer

• Ideal for skin grafts

Disadvantages:

1. Difficult to remove hydrophobic paraffin

2. Excessive paraffin causes wound occlusion → fluid accumulation → inhibits epithelialisation

Vapour-permeable (barrier film)

• Example

• Type of material

• Function

• Indication

Example: Opsite flexigrid and opsite spray

Material: Thin adhesive film often used to stick primapore on

Function: Semi-permeable (aids in moist wound healing BUT impermeable to contaminants and bacteria)

Indication: Protective barrier against irrigation/urine/discharge

• Clean wounds with NO exudate

Absorbent dressings

• 3 Examples

• Indication

Examples:

1. Allevyn

2. Nappies

3. Cotton wool

Indication: Highly exudative wounds which bandages cannot be changed

Allevyn (absorbent dressing)

• Type of material

• Use

• Indication

• 3 Advantages

Material: TWO non-adherent polyurethane layers between a highly absorbent hydrophilic core

Use: White side down and pink side up; does NOT require secondary layer

Indication: Clean wound with marked exudate

Advantages:

1. Highly absorbent (10x own weight)

2. Moist (not wet) wound environment to promote granulation tissue formation

3. Outer layer prevents strike through

Nappies (absorbent dressing)

• Type of material

• 2 Advantages

• 2 Disadvantages

• Indication

Material: Hydrophilic gel sandwich

Advantages:

1. Cheap

2. Extremely absorbent

Disadvantages:

1. NOT sterile

2. Gel toxic if ingested

Indication: Open peritoneal drainage

Cotton wool (absorbent dressing)

• 2 Advantages

• Disadvantage

Advantages:

1. Absorbent

2. Cheap

Disadvantage: May compact down and lose function (wound becomes WET not moist)

4 Types of active dressings

• Examples

• Structure

• Function

Active dressings are uncommon as $$$

1. HYDROCOLLOIDS

   • Examples: Granuflex, Tegasorb

   • Structure: Suspension of polymers eg. gelatin, pectin, carbomethylcellulose

   • Functions: Promotes moist wound healing and granulation tissue formation

     1. Polymers absorb water in a hydrophilic matrix

     2. 

        Release H2O2 to oxygenate the wound

     3. Dressing swells which applies pressure

   • NOT for infected wounds

2. HYDROGELS

   • Example: Intrasite

   • Structure: Inert cross-linked hydrophilic co-polymer (90 - 95% water)

   • Functions:

     1. Rehydrates tissue for moist wound healing

     2. Facilitates autolytic debridement

     3. Analgesic (in fridge)

   • For open clean or infected wounds (eg. deep puncture)

3. ALGINATES

   • Example: AlgiSite M

   • Structure: Seaweed derivative

   • Functions:

     1. Absorb exudate (moist wound healing)

     2. Release Ca2+ to promote haemostasis

4. COLLAGENS

   • Examples: Collamend, Vet biosist, lyophilised collagen sheets

   • Disadvantage: No clinical trials show efficacy and only 1 human product (so why would it work?)

   • Function: Promote granulation and epithelialisation?

3 Functions of the secondary (intermediate) layer of a bandage

Bulky layer to:

1. Absorb and store blood, serum, exudates and necrotic debris

2. Wick bacteria from wound

3. Protect and splint lesion (padding)

Care not to apply excessive pressure → Reduced absorptive capacity

List 3 examples of secondary bandaging material (+ functions)

1. Softban = Non-absorbent cast padding material

2. Gamgee = 100% cotton gauze cover sheet keeping cotton fibres out of wound site

3. Easifix gauze = Conforming bandage to fix the primary layer dressing

4 Functions of the tertiary (outer) layer of a bandage

1. Holds the other layers in place

2. Stops minor haemorrhage by providing pressure

3. Prevents tissue oedema

4. Obliterates dead space

List 2 types of tertiary bandage material

• Examples

• Function

• Indication

• Method of application

1. POROUS

   • Examples: Elastoplast (adhesive) and vetrap (self-adhesive)

   • Function: Evaporate fluid to create drier wound environment

   • Indication: Wet wounds and pressure application for minor haemorrhage, dead space obliteration and reduce passive oedema

   • Application:

     1. Change if strike through occurs

     2. Do NOT apply too tight

     3. Expose 3rd and 4th digits to monitor for circulation and sensation

2. WATERPROOF

   • Examples: Sleek tape ad durapore

   • Function: Occlusive bandage to protect wound from environment

   • Indication: Dry wounds or at the distal aspect of the bandage which contacts the ground

   • Application: Do NOT use for effusive wounds → tissue maceration and bacterial infection

List 4 GOOD topical agents (+ why)

1. Silver sulfadiazine = Antibacterial Ag

2. Aloe vera = Contains acemannan which activates macrophages and stabilises fibroblasts → More rapid granulation

3. Maggots (Lucilia sericata) = Sterile maggots consume dead tissue to act as wound debriding agent (stage I larvae ONLY)

4. Sugar/honey = Antibacterial, debridement and anti-inflammatory

List 5 BAD topical agents (+ why)

1. Antiseptics (eg. chlorhexidine, iodine, H2O2) = Toxic and slow healing

2. Antibiotics = Diluted, toxic, bacterial resistances, poor contact time and penetration (systemic superior)

3. Cleansing agents (eg. Aserbine, Dermisol) = Low pH irritant

4. Poultice (eg. animalintex = boric acid) = Causes inflammation (banned in human medicine)

5. Zinc bacitracin = No evidence of improved healing (except for Zn deficiency)

3 Advantages and 2 disadvantages of Manuka honey

Advantages:

1. Antibacterial properties

2. Draws out lymphatic fluid into wound (inoculates with WBC and nutrients for healing)

3. Manages multi-drug resistant bacteria

Disadvantages:

1. Tasty for animal to eat

2. No evidence in vet medicine for superior healing

Negative pressure wound therapy (NPWT)

• Mechanism

• 8 Functions

• 2 Advantages

• 4 Disadvantages

Mechanism: Large wounds packed with foam and a non-permeable film placed over op so vacuum can suck wound

Functions:

• Decreases wound exudate, oedema, wound volume, bacterial contamination

• Increases wound stimulation, contraction, granulation tissue formation, perfusion

Advantages: Only need to change bandage q3d

1. Less GA/sedation (animal can eat and recover from trauma)

2. Cheaper (no daily dressing changes)

Disadvantages:

1. NOT for infected wounds

2. Not over large exposed blood vessels

3. Risk of loss of vacuum

4. Gauze incorporated into healing wound

3 Functions of wound drainage

1. Obliterate dead space/anticipated fluid

   • → Accumulation of serum and blood → increases infection risk

   • → No skin adherence to underlying tissue (blood supply)

2. Channel harmful material away from wound/body cavity(eg. fluid in chest)

3. Flush solution/antiseptic/antibiotic through site after primary closure

→ Faster healing time

8 Indications of a drain

1. Impossible to completely debride wound as vital structures are contaminated (eg. tendons, bones)

2. Foreign material must be removed

3. Massive contaminated of wound is inevitable (eg. perianal)

4. Viability of wound is questionable (eg. bite wounds)

5. Dead space needs to be obliterated

6. Incomplete drainage (eg. abscess cavity that seals over)

7. Anticipated leakage (intestinal resection and anastomosis)

   • Monitor leaking into body cavity (eg. anticipated leakage from insecure closure of a hollow viscus eg. bladder or intestine)

8. Treatment of pneumothorax, recreate negative pressure in thoracic cavity after surgical intervention

Used for contaminated/dirty wounds (INCREASES likelihood of infection in clean or clean-contaminated surgery as it acts as a conduit for bacteria to enter)

7 Principles of drain placement

1. Place aseptically

2. Pass drain through stab wounds SEPARATE from incision line (never through incision as it can move and create more contamination)

3. Exit at most ventral/dependent site

4. ONE exit point (exit site at top will NOT drain and only act as entry point for bacteria)

5. Exit ports should be large enough for adequate drainage

6. Suture to skin and cover with sterile dressing ± E-collar

7. Record where and duration of drain placement

Indication of drain with TWO exit points

Inguinal or axillary area as single exit point acts as one-way valve and can draw in air when animal moves creating SC emphysema

• 2nd hole allows trapped air to escape

List 3 types of surgical drains

• Examples

• Advantages

• Disadvantages

• Indication

1. Unsutured skin (covered with absorbent bandage)

2. PASSIVE (open) DRAIN = Drainage depends on gravity and capillary action

   • Examples: Penrose, Yeates

   • Advantages:

     1. ALWAYS works

     2. Cheap

   • Disadvantages:

     1. ALWAYS open = Risk of ascending infection

     2. Approximate measure of fluid volume

     3. Exit must be ventral to the wound

   • Indication: Contaminated/infected wounds that cannot be sealed

3. ACTIVE (closed) DRAIN = Actively removes fluid either intermittently OR continuously via a suction apparatus applied to a rigid fenestrated tube to create a negative pressure in the wound

   • Examples: Jackson Pratt, Uno, mini-vac

   • Advantages:

     1. Exit at ANY point (can work against gravity)

     2. Closed wound → Decreased risk of ascending infection

     3. Accurate assessment of fluid produced

   • Disadvantages:

     1. $$$

     2. Failed drain due to premature loss of vacuum or obstructed tubing

   • Indication: Clean wounds which must be completely sealed

Compare the Penrose vs. Yeates passive drains

Penrose = Soft, thin and pliable latex rubber tubing

• Most drainage occurs EXTRALUMINALLY

• Efficient for draining soft tissue wounds

Yeates = Soft PCV, but more rigid than Penrose

• Drainage occurs INTRA- and EXTRALUMINALLY

• Useful for large volumes of fluid (increased SA available)

Increase flow rate by making single slit down tube (fenestration decreases SA and therefore, decreases drainage flow)

Maximum pressure of active drain

80mmHg

4 Indications of drain removal

1. Bacteria no longer present and inflammation reduced

2. Fluid level constant low level (<0.2mL fluid/kg/d)

   • Never get dry wound from drain presence (elicits an immune response)

3. 72hr for abscess cavities

4. Remove when no longer beneficial

5 Complications fo drain placement

1. Nosocomial ascending infection (AB resistant bacteria)

2. Foreign body reaction to drain reduces # of bacteria required for infection

   • Esp. with obstruction

   • Can flush, but introduces contamination (not recommended)

3. Drains made from rigid materials may encroach upon adjacent structures, resulting in adhesions, ulceration and inflammation

4. A drain may slip into the wound and become lost

5. Drains may tempt the surgeon to close a wound that is better left open

4 Functions of sutures

1. Wound closure

2. Ligation

3. Attach tubes

4. Stay sutures

List 3 ways to classify suture materials (+ types)

1. Origin (natural OR synthetic)

2. Persistence (absorbable OR non-absorbable)

3. Structure (multifilament OR monofilament)

List 11 features of the ideal suture material

1. Maintain adequate tensile strength

2. Stimulate minimal inflammation

3. Discourage bacterial growth

4. Non-capillary but absorbable

5. Non-electrolytic (stainless steel 316L staples #1 as they do not rust or cause electrolysis)

6. Non-allergenic

7. Non-carcinogenic

8. Good handling properties

9. Good knot security

10. Inexpensive and readily available

11. Easily sterilised

Compare absorbable (+ types) vs. non-absorbable suture

Absorbable = Temporary wound support <60d → Degrades predictably

• <21d = Short duration

• >21d = Long duration

Non-absorbable = Retains original strength for >60d

• Encapsulated within body by fibrous capsule

• Should NOT be used with infection (nidus for fistulation)

Compare natural vs. synthetic suture

Natural = Absorbed by phagocytosis → Granulation tissue and scarring

• Provokes inflammation ± immune response

• Variable resorption

Synthetic = Man-made polymers absorbed by hydrolysis (polymer + water → monomer)

• Minimal inflammation

• Predictable absorption

What does “PLUS” for suture material mean?

Antibacterial triclosan coating (eg. monocryl PLUS)

Compare advantages and disadvantages of multifilament vs. monofilament suture (5)

Multifilament

1. Nidus for infection (decrease # of bacteria required for infection)

2. Capillary = Wicks fluid (avoid for skin and inner luminal surfaces of hollow organs as suture can contaminate deeper tissue)

3. Easier to handle

4. Superior knot security

5. More tissue drag

Monofilament

1. Less likely to collect bacteria when dragger across the skin

2. Non-capillary = Does NOT absorb fluid (will not spread contamination into deeper tissues)

3. Difficult to handle due to memory (maintains new shape when stressed)

4. Poorer knot security

5. Less tissue drag (coatings reduce drag BUT also reduce knot holding)

What suture material is best for a heavily contaminated and infected wound?

Monofilament, non-absorbable

Catgut suture

• Classification and absorption

• Material

• 2 Advantages

• 4 Disadvantages

• Indication

Classification: Natural, absorbable (short-duration), multifilament

• Lost 50% tensile strength @ 14d (complete absorption by 60d)

Material: Collagen fibres derived from submucosa of sheep or subserosa of a cow

• Chromic = Increased persistence and reduced tissue reactivity

Advantages:

1. Handles well compared to other multifilaments

2. Cheap

Disadvantages: Multifilament, natural

1. Unpredictable breakdown

2. NOT for infection

3. Inflammatory reaction

4. Capillary

Indication: Cheap closure of oral mucosa

Polyglecaprone

• Trade name

• Classification and absorption

• 3 Advantages

• Disadvantage

• Indications

Trade Name: Monocryl

Classification: Absorbable (short-duration), synthetic, monofilament

• Lost 80% tensile strength by 14d (complete absorption by day 100d)

Advantages:

1. Smooth and atraumatic

2. Highest initial tensile strength of all absorbable sutures

3. Easier to handle than other monofilaments

Disadvantage: Expensive

Indications:

1. Soft tissue (eg. bladder, skin)

2. Infected tissue

3. Ligatures

NOT linea alba

Polydioxanone

• Trade name

• Classification and absorption

• Advantage

• Disadvantage

• Indications

Trade Name: PDS II/PDO

Classification: Absorbable (long-duration), synthetic, monofilament

• Lost 14% tensile strength by 14d (complete absorption by 180d)

Advantage: Longest retention of tensile strength of all absorbable sutures

Disadvantage: Cost

Indications:

1. Linea alba, fascia

2. Contaminated wounds

3. Ligatures

NOT intradermals, tendons, SC, bladder

Polyglactin

• Trade name

• Classification and absorption

• Advantage

• Disadvantage

• Indications

Trade Name: Vicryl

Classification: Absorbable (medium-duration), synthetic, multifilament

• Lost 35% tensile strength at 14d (complete absorption by 60d)

Advantages: Easier handling and secure knots

Disadvantages: NOT for skin or bladder (nidus for urinary calculi)

Indications:

1. SC

2. General tissue/muscle approximation

3. Pedicle ligation

Caprolactam

• Trade name

• Classification and absorption

• 2 Advantages

• 3 Disadvantages

• Indications

Trade Name: Supramid

Classification: Non-absorbable, synthetic, multifilament

Advantages:

1. Cheap (available in reels)

2. Good knot tying

Disadvantages:

1. NEVER for internal structures as autoclaving does NOT make sterile

2. NEVER bury suture

3. Outer proteinaceous layer cracks and causes foreign body reaction

Indication: Skin closure with eyed needle

Polyamide/Nylon

• Trade name

• Classification and absorption

• 2 Advantages

• 3 Disadvantages

• Indications

Classification: Non-absorbable, synthetic, monofilament

Advantages:

1. High tensile strength

2. Cheap

Disadvantages: Memory and poor knot security

Indications:

1. Interrupted skin closure (remove after 7 - 10 days)

2. Fine suture for ophthalmology and nerve repairs

Polypropylene

• Trade name

• Classification and absorption

• 2 Advantages

• 3 Disadvantages

• Indications

Trade Name: Prolene

Classification: Non-absorbable, synthetic, monofilament

• NEVER fully absorbed by body

Advantage: Permanent

Disadvantage: Most difficult to handle

Indications:

1. Cardiac surgery

2. Vascular anastomoses

3. Tendons

Describe the 2 suture sizing systems

1. USP

   • 0 - 6 INCREASES

   • Added zeros (eg. 5/0 = 00000) DECREASES

2. Metric

   • Ascending scale in 1/10mm and linear

   • 3M = 0.3mm