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Microvascular Free Flaps

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Microvascular Free Flaps

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    1. Microvascular Free Flaps Emma McNeill Specialist Registrar in ENT Freeman Hospital

    2. Contents Principles Physiology Pre-operative preparation Anaesthetic considerations Equipment Techniques Flap monitoring

    3. Reconstructive ladder

    4. Free tissue transfer Seidenberg 1959 Reconstruction of cervical oesophagus with jejunum 1973 – Microvascular anastomosis 1980s –Further free flaps described Principle Transplant of skin, fascia, muscle, tendon, nerve, bone Reanastomosis of donor artery and vein to recipient site Viable tissue with risk of ischaemia

    5. Zones of perfusion Zone I Macrocirculatory circulation Zone II Capillary circulation Zone III Interstitial space Zone IV Cell and cell membrane Zones of perfusion and flap survival – 1 essential for flap survival – flap failure can occur at each level Zone 2 – no-reflow phenomenon – adequate vascular supply loss of nutritive blood flow 3 includes capillary wall – intersitial space inc oedema starlings law, capillary permeability failure of metabolites to enter Ultimate detemination of flap survival - cellsZones of perfusion and flap survival – 1 essential for flap survival – flap failure can occur at each level Zone 2 – no-reflow phenomenon – adequate vascular supply loss of nutritive blood flow 3 includes capillary wall – intersitial space inc oedema starlings law, capillary permeability failure of metabolites to enter Ultimate detemination of flap survival - cells

    6. Physiology of flap survival Ischaemia Separation from macrocirculation Thrombus formation at anastomosis Impaired venous outflow Impaired lymphatic drainage Microcirculatory changes Hyperadrenergic state Flap survival Fibrin layer Neovascularization Angiogenic growth factors Basement membrane dissolves Migration of endothelial cells Capillary loops 13 hours Platelt adherence exposure to intima Lymphatic failure inc osmotic pressure in interstitl space starlings law failure to pass into cell Microcirculatory changes erythrocyte sludging in capillary lumen leucocyte adherence to cell wall Capillary loops become patent or direct growth into flap join preexisting vessels13 hours Platelt adherence exposure to intima Lymphatic failure inc osmotic pressure in interstitl space starlings law failure to pass into cell Microcirculatory changes erythrocyte sludging in capillary lumen leucocyte adherence to cell wall Capillary loops become patent or direct growth into flap join preexisting vessels

    7. Improving flap viability Hyperbaric oxygen Free radical scavenging Vasodilators Neovascularisation Reducing plasma viscosity (Delay phenomenon) Hyperbaric oxygen – increases oxygen carrying capacity, reduces leucocyte adherence SOD Alpha blockers decrease sympathetic release, vasoactive anaesthetics – isoflourane nitrous oxide, topical nitroglycerine Neovascularisation – vascular endothelial growth factor Pedicled flap, raising in stages before transferring, ischaemia improves survival Plasma viscosity - haematocrit SOD Hyperbaric oxygen – increases oxygen carrying capacity, reduces leucocyte adherence SOD Alpha blockers decrease sympathetic release, vasoactive anaesthetics – isoflourane nitrous oxide, topical nitroglycerine Neovascularisation – vascular endothelial growth factor Pedicled flap, raising in stages before transferring, ischaemia improves survival Plasma viscosity - haematocrit SOD

    8. Procedure Removal of cancer Dissection of flap from surrounding tissue Identification of vascular pedicle Identification of vessels in defect Division of vascular pedicle Anastomosis of vessels Closure of defect Closure of donor site

    9. Free tissue transfer Advantages Tissue versatility Tissue orientation Restore shape, function and sensation Tolerant of radiotherapy Improved cosmesis High success rates Disadvantages Training 2 operative teams Longer operative times Intensive post-op management Donor site morbidity

    10. Gillie’s Ten Commandments Thou shalt make a plan Thou shalt have a style Honour that which is normal and return it to its normal place Thou shalt not throw away a living thing Thou shalt not bear false witness against thy defect Thou shalt treat the primary defect before worrying about the second Thou shalt provide yourself with a lifeboat Thou shalt not have a routine Thou shalt not covet your colleagues forehead flap Thou shalt not do today what can be put off until tomorrow When in doubt, don’t! Replace in kindReplace in kind

    11. Choice of flap Size of defect Tissues required Skin Fascia Muscle Bone Jejunum Sensate flap Blood supply of flap/ donor site Surgical skill Extent and location of tumourExtent and location of tumour

    12. Microvascular flaps and vascular supply

    13. Radial forearm flap Tissue Skin, fascia (tendon, bone) Arterial supply Radial artery Venous drainage Venae comitantes Cephalic vein Sensation No Length Start of brachial artery to antecubital fossa

    14. DCIA flap Tissue Bone, periosteum, iliacus +/- skin paddle Arterial supply DCIA from external iliac Venous supply Large calibre venae Sensation No Length of flap pedicle 4-7 cm DCIA – large calibre vessel 1.5 -4mm, size depends on bone required, OMFS mandibular reconstruction – up to 15cm of cancellous boneDCIA – large calibre vessel 1.5 -4mm, size depends on bone required, OMFS mandibular reconstruction – up to 15cm of cancellous bone

    15. Fibula flap Tissue Bone, periosteum, soft tissue +/-skin paddle Arterial supply Peroneal artery Venous drainage Large calibre venae Sensation No Flap length Relative to length of bone 25cm of cancellous bone25cm of cancellous bone

    16. ALT flap Tissue Skin, fascia and soft tissue Arterial supply Lateral femoral circumflex artery Venous drainage Large venae comitans Sensation Lat femoral cutaneous n. Flap size 8x25 cm

    17. Pre-operative preparation Patient factors Age Nutritional status Tobacco Vascular disease Diabetes mellitus Ability to tolerate long anaesthetic Extent of disease Previous reconstruction Handedness Haematological conditions Donor/ recipient sites Vascular sufficiency Doppler Allen’s Test Angiography Length and width of flap Tissue requirements Morbidity at donor site Previous radiotherapy

    18. Anaesthetic considerations Patient fitness Temperature Theatre Infused fluids Non-operated body Pain control Adrenaline release Blood pressure Hypotensive Flap perfusion Blood volume

    19. Surgical equipment Jewellers forceps, vessel dilating forceps, microvascular clamps, needle holders, microscissors 8 9 or 10 ehtilon or nylon Operating microscope or loupes 2.2 to 4.5 magnification Jewellers forceps, vessel dilating forceps, microvascular clamps, needle holders, microscissors 8 9 or 10 ehtilon or nylon Operating microscope or loupes 2.2 to 4.5 magnification

    20. End-to-end anastomosis Most straight forward Vessels prepared, stripped of soft tissue and adventitia trimmed. Held in microclamps Ethilon perpendicular ,minimal trauma flushed with heparinized ringers lactate. 3 stay sutures 120 apart, suture between, rotat – e suture between 9 evenly spaced sutures Test for patency – flicker test, strip test – grab distal to anastomis , empty of blood, 2nd clip refillsMost straight forward Vessels prepared, stripped of soft tissue and adventitia trimmed. Held in microclamps Ethilon perpendicular ,minimal trauma flushed with heparinized ringers lactate. 3 stay sutures 120 apart, suture between, rotat – e suture between 9 evenly spaced sutures Test for patency – flicker test, strip test – grab distal to anastomis , empty of blood, 2nd clip refills

    21. End-to-side anastomosis Discrepancy between size of vessels Technically more difficult Suture back wall firstDiscrepancy between size of vessels Technically more difficult Suture back wall first

    22. Post-op monitoring

    23. Post op monitoring Lactacte levels Doppler Nasendoscopy Window Antibiotics Haematocrit Drainage Pulse, BP, Urine output Donor site Microdialysis catheter fed into flap – lactate and glucose levels criteria for ischaemiaMicrodialysis catheter fed into flap – lactate and glucose levels criteria for ischaemia

    24. Graft failure Most likely in first 48 hours Exploration Inspect vascular pedicle for compression and patency Thrombus – separation of vessels, embolectomy Removal of flap if unable to restore circulation No-reflow phenomenon Reperfusion injury No reflow – arterial and venous drainage established failure of circulation at capillary and interstitial level Reperfusion injury – build up of free radicals at cellular and interstital layer – restoration of supply washout of free radicals No reflow – arterial and venous drainage established failure of circulation at capillary and interstitial level Reperfusion injury – build up of free radicals at cellular and interstital layer – restoration of supply washout of free radicals

    25. Leeches Hirudo medicinalis Venous insufficiency Hirudin – selective thrombin inhibitor Local anaesthetic Ingest 20ml of blood Dressing to prevent migration Prophylactic antibiotics

    26. New developments Arista haemostatic powder Laser assisted microvascular anastomosis Samonte and Fried Vascular closure staple clips Thermal fusionThermal fusion

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