Surgery Flashcards
Asepsis
Stages of surgical site preparation
a) Pre-operative assessment
b) Hair removal
c) Aseptic skin preparation
a)
- check condition of patient’s skin
b)
- clippers used as standard, firstly with direction of hair growth, then against hair growth
- protect open wounds, eyes, mucoud membranes
- loose hair removed
c)
- removes gross dirt and transient microbes
- reduces microbial numbers to sub-pathogenic level temporarily
- use grid method
Asepsis
Skin antiseptics
a) Ideal properties (6)
b) Properties of chlorhexidine
a)
- rapid action
- residual action
- non-irritant
- cost effective
- easy to apply
b)
- broad spectrum, but no activity against mycobacteria or bacterial spores
- rapid onset of action and excellent residual activity
- remains effective in presence of organic matter
- minimal skin irritation, no systemic toxicity
- ototoxic and toxic to cornea, conjunctiva and neural tissue
Asepsis
Skin antiseptics
a) Properties of povidone iodine
b) Properties of alcohols
c) Chloraprep features
a)
- broad spectrum, prolongued contact times required to kill bacterial spores
- slower onset of action, no residual activity
- inactivated by organic matter
- contact dermatitis in 50% dogs, iodine is absorbed so systemic toxicity possible
- safe for use on eyes, mucous membranes etc
b)
- broad spectrum, minimal effect against bacterial spores
- very rapid onset, but no residual activity
- drying action on skin, systemic toxicity possible in newborns
- cannot use on eyes, ears, mucous membranes
c)
- chlorhexidine (2%)/alcohol combination (70%)
- alcohol increases effectiveness of chlorhexidine
Asepsis
Sterilisation techniques
a) Physical methods (2)
b) Chemical methods (3)
a)
- heat
- radiation
b)
- ethylene oxide
- hydrogen peroxide gas plasma
- cold sterilisation chemicals (gluteraldehyde)
Surgical site infections
a) Define SSI
b) When does infection occur
c) Host factors that increase risk of wound infection (5)
a) Infections that occur within 30 days of surgery, or within 1 year if an implant is placed
b)
- When number of bacteria > 10^5 per gram of tissue
- Most commonly endogenous bacteria (resident flora)
- Can be exogenous bacteria
c)
- geriatric patients
- systemic illness (esp endocrinopathies)
- immunosuppressive therapy
- poor or excessive body condition
- remote infection
Surgical site infections
Anaesthesia and SSI
a) What drug is associated with SSIs
b) Duration of anaesthesia and SSI
a)
- Propofol: the lipid emulsion is capable of supporting bacterial growth
- Ensure correct storage, ensure no contamination of multiuse vials
b)
- Increased duration increases SSI risk
- Hypothermia, hypotension, reduced oxygen delivery to tissues contribute
Surgical site infections
a) When should surgical sites be clipped
b) How does rate of infection change with every 1 hour increase in surgical time and why
a) After induction of anaesthesia (3x more likely to become infected if clipping done before induction)
b)
- Doubles
- migration of bacteria onto skin surface and multiplication of bacteria remaining on surgical site
- increased tissue trauma and dessication of tissues
Surgical site infections
Type of surgery and risk of SSI
a) Clean
b) Clean-contaminated
c) Contaminated
d) Dirty
a)
- non traumatic, no break in asepsis
- no entry of alimentary, genito-urinary and respiratory tract
- infection rate 2.5-5%
b)
- minor break of asepsis
- entry of alimentary, resp tract, oropharynx or vagina, but no/minor contamination
- genito-urinary or biliary tract entered with no infection
- infection rate 2.5-9%
c)
- major break in asepsis
- gross spillage of GI tract
- entry of genitourinary or bilary tract in presence of infection
- infection rate 5-20%
d)
- acute bacterial infection
- infection rate 18-25%
Surgical haemostasis
Summary of primary haemostasis
- formation of platelet plug following exposure of collagen in vessel wall
- vessel injury results in vasoconstriction and exposure of subendothelial matrix
- platelets adhere, vWF acting as bridge
- platelets activate and release granule contents attacting more platelets
Surgical haemostasis
Summary of secondary haemostasis
- series of enzymatic reactions forming fibrin and stabilise platelet plug
- requires calcium
- intrinsic, extrinsic and final common pathways
- requires coagulation factors produced by liver and vitamin K
Surgical haemostasis
a) Control of haemostasis (3)
b) Problems with primary haemostasis (3)
a)
- anti-thrombin III
- plasminogen is broken down to plasmin
- fibrin to fibrin degradation products
b)
- thrombocytopaenia (not enough platelets)
- thrombocytopathia (platelets don’t function correctly)
- Von Willebrand’s disease
Surgical haemostasis
a) Problems with secondary haemostasis (2)
b) Problems affecting primary and secondary haemostasis (2)
c) Patients at risk (4)
a)
- inherited deficiences (eg haemophilia A, factor XII)
- acquired factor deficiencies (eg liver disease, rodenticide poisoning)
b)
- disseminated intravascular cagulopathy (DIC)
- angiostrongylus vasorum infection (lungworm)
c)
- those with inherited disease: vWD (especially dobermans), factor XII, haemophilia A
- young dogs eating slugs/snails/grass, with inadequate worming
- polytrauma
- diseases predisposing DIC (eg haemangiosarcoma)
Surgical haemostasis
Initial tests for clotting disorders
a) Platelet count techniques (3)
b) Important things to note in platelet counts
c) Bucosal bleeding time technique
d) When is bucosal bleeding time prolongued
a)
- Blood film
- Manual count with haemocytoeter
- Machine count
b)
- Feline platelets are relatively large and prone to clumping
- Cavalier king charles spaniels have giant platelets with low counts
- should be no major bleeding unless count is below 55,000 cells/μl
c)
- crude test of primary haemostasis: primary cut in mucosa
d)
- only if there are severe defects
- Thrombocytopaenia, thrombocytopathia, vWD
Surgical haemostasis
Tests for secondary haemostasis
a) OSPT
b) APTT
a)
- evaluates extrinsic and common pathways
b)
- evaluates intrinsic and common pathways
Surgical haemostasis
a) Normal circulating blood volume in dogs
b) Normal circulating blood volume in cats
c) Causes for surgical blood loss (4)
a) 80-90ml/kg
b) 60-70ml/kg
c)
- pre-existing haemorrhage (internal/external)
- surgical haemorrhage
- incomplete haemostasis
- removal of blood-filled masses/organs
Surgical haemostasis
Methods of haemostasis in case of haemorrhage (10)
- Pressure haemostasis – digital or packing cavity with swabs.
- Ice cool saline
- Surgical forceps
- Ligation
- Diathermy
- Vascular clips
- Tourniquet placement
- Vessel sealing devices
- Elevation of tissue
- Topical agents
Wound healing
What are the three phases of wound healing and what they consist of
- inflammatory phase: haemostasis → early inflammation → late inflammation
- proliferative phase: angiogenesis → fibroblast migration → collagen synthesis → wound contraction → epithelialisation
- maturation phase: collagen remodelling
Wound healing
Inflammatory phase
a) Haemostasis
b) Early inflammation
c) Late inflammation
a)
- vasoconstriction
- platelet plug
- coagulation cascade
b)
- neutrophil migration to wound, phagocytosis of bacteria and necrotic material
- debridement due to enzyme release
c)
- influx of macrophages, release of cytokines (3-5 days post injury)
- excessive organic material or infection can prolongue inflammatory phase
Wound healing
Proliferative phase
a) Angiogenesis
b) Fibroblast migration
c) Collagen synthesis
d) Wound contraction
e) Epithelialisation
a)
- new blood vessel development providing nutrients and oxygen
b)
- fibroblasts differentiate from adjacent tissue mesenchymal cells and migrate into wound
- deposition of extracellular matrix
c)
- collagen production increases wound strength
- granulation tissue forms by 7 days (resistant to infection, provides epithelialisation surface)
d)
- myofibroblasts orientate along lines of tension and reduce wound surface area (less effective where skin is tight)
e)
- epithelial cells migrate from wound edges across healthy granulation tissue (must be flat surface)
- begins 4-5 days post-injury
- produces a thin, hairless scar
Wound healing
Maturation phase
- 2-4 weeks post-injury
- remodelling of collagen into basket-weave configuration, increasing wound strength (80% of original skin strength)
- continues up to 1 year
Wound healing
Causes of delayed healing
a) Inflammatory phase (5)
b) Epithelialisation (4)
a)
- infection/inflammation
- foreign material
- dessication
- necrosis of superficial tissue layers
- continuing damage
b)
- excessive moisture
- friction
- movement
- tension
Wound healing
Important aspects for optimal wound healing of GI tract (4)
- include submucosa within sutures (provides majority of tensile strength of GI tract)
- ensure sutures are a minimum of 3mm from wound edge, outside zone of inflammation, as collagenase is produced and reduces wound strength
- preserve blood supply to tissue
- avoid tension at the surgical site
Wound healing
Important aspects for optimal wound healing of
a) Fascia
b) Urinary bladder
a)
- use long-tasting sutures in continuous pattern
- ensure surures are at least 3mm from wound edge (outside zone of inflammation)
- avoid high mechanical forces in early postop
- heals slowly compared to other tissues as has limited vasculature
b)
- ability to heal very rapidly, although UTI can impact healing
- regains 80-100% strength within 21 days
Wound healing
Cat differences in cutaneous wound healing
- much slower than dogs
- production of granulation tissue can take 19 days (7.5 days in dogs)
- contraction and epithelialisation at 14 days: 44% in dogs, 13% in cats
