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Transcript of Microsurgery
Presented by:Hassan AlNaeem Principles of microsurgery and free tissue transfer Indications For Microsurgical Reconstruction: Arterial wall Histology: 1.Tunica intima: 2.Tunica media: 3.Tunica adventitia: Veins wall have the same three layers: Thinner wall and larger diameter than corresponding arteries.
The internal elastic lamina is absent and there is much less muscle in the media.
Many veins have valves with two cusps formed by infolding of the tunica intima. Highest level on reconstructive ladder.
Hand and Digit replantation or reconstruction.
Functional Muscle Transfer.
Vascularized bone and nerve graft. Vessel Healing Process: Platelets adhere to and cover the vessel ends, suture holes, and areas of denuded endothelium.
Fibrin wont form unless the collagen is exposed, large denuded areas or external constriction from outside. Vessel Healing Process: Over the next 24-72 Hrs: platelets gradually disappear
Formation of pseudointima within the first 5 days.
Critical period of thrombus formation is within the first 3-5d. Vessel Healing Process: Between 1-2 weeks: Endothelial regeneration: If only the endothelial layer is damaged: Causes of endothelial damage: New endothelium covers the anastomotic site.
The elastic and muscular layers rarely return to their pre-injury state.
Deeper layers heal by migration and proliferation of fibroblasts, Reconstituted from surrounding cells and regeneration is completed in 7-10 days. Damage involves the underlying subendothelial structures: Regeneration is by migration and differentiation of myoendothelial cells from the cut vessel ends.
Proliferation of fibroblasts with collagen deposition and myointimal thickening at the anastomotic site. Simple dissection and exposure of the vessels from their beds.
Injury due to using microvascular clips.
Needle and suture penetration and technique of placement (large needle, obliquely placed, repeated puncture, unequal placement distances, loosely tied or too many suture). Prevention of endothelial injury: Gentle dissection.
Careful controlled placement of sutures.
Side branches tied or coagulated away from the main vessel.
Keep the exposed vessel moist.
Prevent vasospasm (xylocaine).
Avoid damage caused by clips (closing pressure <30 g/mm2). Tissue response to ischemia: For successful free transfer.
The flap tissue must be able to tolerate a period of ischemia and the anastomosed vessels must remain patent and allow sufficient flow to meet its metabolic requirements. Ischemic tolerance Sequence of ischemia time Interruption of blood flow due to flap elevation (primary ischemic insult) causes a shift to anaerobic metabolism with production of lactic and carbonic acid leading to localized acidosis. Sequence of ischemia time Depletion of cellular ATP causes Na+/K+ pump failure with loss of functional membrane integrity:
Cells swell due to Na+ influx.
Ca2+ influx causes organelle damage, release of lysosomal proteolytic enzymes and oxygen derived free radicals (02, H202, 0H-). Acid and cellular toxins cannot be cleared since circulation is interrupted.
Endothelial swelling leads to obstruction of capillary lumen and increased permeability.
Acidosis & protein breakdown products cause platelet & RBC aggregation with blood viscosity and formation of microthrombi.
Cell death. Sequence of ischemia time No reflow phenomenon Ischemic tolerance of tissue is exceeded.
Cellular and vascular damage becomes irreversible.
Reestablishing of arterial blood supply does not perfuse the tissue. No reflow phenomenon Endothelial cell swelling and increased capillary permeability:
i.increased viscosity and microthrombi formation in the ischemic phase.
ii.micro vessel obstruction.
Denervation (sympathectomy) causes transient release of catecholamines from sympathetic nerve terminals with subsequent vasoconstriction.
reperfusion injury. When flow is re established, increased microcirculatory resistance leads to sluggish flow and rapid thrombosis
Pulsatile flow may still be observed in the pedicle if sufficient AV shunts exist within the flap
Thrombolytic therapy may be of benefit in re establishing flow. No reflow phenomenon Ischemia induced reperfusion injury Restoration of blood flow in an ischemic injured tissue leads to an inflammatory response:
Neutrophils become sequestered and activated.
Release O2 free radicals, leukotrienes, thromboxanes.
Further increase in endothelial damage, capillary permeability, platelet aggregation.
Thrombosis (secondary ischemic insult). Clinical course: initially well perfused flap which begins to fail a few hours post-operatively.
Anti inflammatories:prostaglandin inhibitors and free radical scavengers may be of benefit.
Ischemic preconditioning. Ischemia induced reperfusion injury coagulation & thrombosis Begins immediately at site of vessel injury with exposure of subendothelial lipoproteins and collagen.
consists of platelet plug formation (white clot) and the coagulation cascade which leads to a fibrin clot (red clot). Coagulation may follow two paths:
1.intrinsic: all factors are required.
2.extrinsic: must be initiated by exposure to tissue lipoprotein. coagulation & thrombosis platelets bind to exposed lipoprotein through surface receptors + Von Willebrand factor ==>activated ==> degranulate:release vasoactive and chemotactic factors including VWF, fibrinogen, ADP, Ca2+, serotonin.
activates more platelets.
aggregated form when platelets bind to circulating fibrinogen. coagulation & thrombosis Platelet adhesion can be inhibited by local endothelium-produced:
2.tissue factor pathway inhibitor (TFPA).
3.protein C & S.
4.antithrombin III. coagulation & thrombosis Hypercoaguability states with high risk of thrombosis at anastomosis Congenital:
Protein C& S deficiency.
Factor V leiden. •
Plasminogen activator inhibitor deficiency.
Lupus anticoagulant. Equipments Optics surgical loupes:
At least X3.5 for dissection.
At least X4.0 for anastomosis of a vessels smaller than 1 mm. Optics an operating microscope:
200mm focal length with 6X to 40X for anastomosis.
Magnification improves resolution at a cost of decreased:
field of view.
depth of field: the zone within which objects remain in adequate focus shortens as magnification increases. Sutures Needles: Cutting or taper
Curvature. Diameter: 75 to 135 microns.
Chord Length: Needles: Suture material: Nonabsorbable:
polyamides (Nylon) - sizes down to 11-0.
silk - as small as 9-0.
Absorbable Choice of suture: larger needles are easier to handle easier to pass it through the tissue and maintain their sharpness longer but a 10-0 suture (25 MicM) on 100 micm needle leaves large unfilled hole in vessel wall. Instruments: Jeweler's forceps Adventitia forceps: Instruments: Vessel dilators Scissors Needle holders Vascular clamps Microvascular Technique: Discuss plan with anesthesiologist.
Feet flat on the floor.
Hip and knees at right angle.
Elbow at right angle.
Support hands and forearms with stacks of towels. Choose vessels outside zone of injury.
Keep vessel moist.
Cut back to healthy vessel if ends are traumatized.
Prepare vessels by dissecting 2-5 mm of adventitia from vessel ends. Microvascular
Technique: Suturing signs of microvascular trauma Always remember to check your inflow before performing the microvascular anastomosis (“spurt test”).
Also release the clamp to test inflow before anastomosis.
Flush artery and vein with heparinized
Start with more difficult anastomosis. Microvascular Technique Suture bites 1-2x the thickness of an arterial wall; 2-3x the thickness of a venous wall.
Insertion of needle tip 90˚ to vessel to ensure eversion otherwise inverted adventitia will cause thrombosis. Suture placement gently grasp vessel distal to anastomosis with two forceps; gently milk blood distally so vessel is collapsed between the two forceps then release proximal forceps blood should fill collapsed vessel if anastomosis is patent. End to Side: preserve distal flow in donor vessel (only option if donor vessel is sole inflow to region).easily accommodate size discrepancy. Sleeve technique: An invaginating technique with far fewer sutures than conventional end-to-end technique.
Similar patency rates to conventional end-to-end technique.
Indicated if there is a size discrepancy between donor and recipient vessels.
Advantages: fast, less vessel trauma, and less suture exposure.
Disadvantages: stenosis, thrombus and aneurysm formation. Cuffs and conduits technique Basic autogenous cuff technique consisting of six sutures.
Modification: fewer sutures, fat wrap, polythene cuffs, silicone rubber cuff, external absorbable splint, and metallic circle.
Patency rates similar to what achieved by manual suture. Mechanical couplers: Use only on VEINS Advantages
Disadvantages Stapling technique: Advantages Disadvantages Laser anastomosis: The 1.9-m diode laser Handling size discrepancy End to end anatomosis: Handling size discrepancy Telescoping Technique.
End to side anastomosis. Vascular grafts: Autologous vein: Prosthetic graft & allograft: Optimizing Patency Selecting high flow donor vessels.
Dissection and anastomosis well outside the zone of injury.
Anastomosing two veins for every artery.
Minimizing endothelial trauma.
Minimizing warm ischemic time. Patency tests Return of the color to and capillary oozing or venous bleeding.
Direct examination of the anastomosis under microscope.
The empty and refill patency test. Relieving Vasospasm Topical lidocaine•
Stripping the adventitia•
Hydrostatic dilitation with Heparinized saline.
Epidural, spinal or axillary block. Failure of free flap biphasic distribution.
Failure in the first 12 hours is almost exclusively due to technical difficulties at the anastomosis and usually at the venous side.
Late failures (8 - 14d) are less common and are primarily related to infection. Immediate intraoperative failure Usually technical: Delayed failure Multifactorial: Local factors 1. Infection:
Keys to increase success in irradiated beds:
Limited vessel dissection.
Limited electrocautery of side branches.
Use of small needles with larger sutures.
Perioperative use of anticoagulation. Systemic factors: 1. Age:
5.Peripheral arterial disease:
6.Peripheral venous disease
10.sickle cell anemia Adjuncts in Microvascular Surgery a. Physical i. Temperature.
iv. Elevation. b. Pharmacological: Adjuncts in Microvascular Surgery In elective microvascular transplant there are no definitive indications for anticoagulation.
Anticoagulation may increase the chance of hematoma at both the donor and recipient sites.
Postoperatively, if clotting becomes evident and require reexploration, anticoagulation is usually indicated if the flap is salvaged. Anticoagulants HEPARIN: polyglycosaminoglycan.
Prevent platelet induced (arterial) and coagulation induced (Venous) thrombi.
method of action:
Measurement of activity:
systemic heparin proven to decrease re-thrombosis when repairing a thrombosed anastomosis.•
postoperative SC BID dosing shown to decrease OR for thrombosis by 27%. LMWH: equal effect on venous thrombosis with decreased risk of bleed.
Measurement of activity:
Advantages: less risk of bleeding, predictable dose response, less frequent dosing, not requring monitoring.
Evidence: equivocal, studied in comparison to heparin with mixed results. Dextran: polysaccharide colloid:
Contraindications: COUMADIN: Topical vasodilators: Lidocaine:
smooth muscle depressant
30 mg/ml topically
MgSO4, chlorpromazine, nitroprusside, reserpine. Antiplatelet agents: Aspirin 50-100mg/day Fibrinolytic agents: indications: re exploration, adequate inflow but no outflow Systemic vasodilators : Chlorpromazine:
2. alpha receptor blocker
3.membrane stabilization and anti platelet effects
Nifedipine: for cold intolerance following digit replantation Promising investigational agent: 1. Monoclonal antibodies:
binds and inactivates thrombin catalyzed conversion of fibrinogen to fibrin.
more effective than heparin because:
i.It doesn’t require antithrombin III to inactivate thrombin.
ii.Its not bound by heparin neutralizing platelet factor 4. Recommendations: There are no definite indications for any anticoagulation therapy in routine microvascular surgery, and there are no hard statistics to support the use of one agent over any another.Postoperative thrombosis warrants urgent surgical exploration of the anastomosis with possible fibrinolytic and anticoagulation therapy as adjuncts.Anticoagulation therapy may be indicated when mechanical or metabolic factors are not favourable and cannot be improved.Good technique is more important than pharmacological manipulation. Monitoring Techniques Overall success rate of free tissue transplantation is 90%- 95%, and that of digital replantation 75-85%
To achieve these results: there is a 20% re-operation and exploration rate. safe & reliable
continuous & senitive to early perfusion changes.
distinguish arterial from venous occlusion.
work on all types of tissue, including buried flaps. Noninvasive.
easy to interpret.
Inexpensive. The ideal monitoring system would be: 1. Clinical
3. Transcutaneous and tissue pO2
4. Tissue pH
5. Pulse oximetry
6. Muscle contractility
9. Near-infrared Reflection Spectroscopy.
11. Cook catheter/probe – circumferential monitoring (Mahoney). At the time of anastomosis: Strip test End to Side: theoretical advantage is that vessel wall retraction maintains the arteriotomy wide open.
Ideal 2:1 ratio of anastomosis to vessel diameter.
Ideal angle of entry between 30 and 75 degrees. References Previous seminar by Dr Meshaal Alshammari, 2009
A laboratory Manual for Microvascular and Microtubal Surgery By Brian C. Cooly.
Green's text book of hand surgery, vol.2. 2005.
Mathes text book of plastic surgery, 2006.
Essential of plastic surgery, 2007.
Selected reading in plastic surgery, volume10, number 5, part 2, 2005.
Pharmacologic Optimization of Microsurgery in the New Millennium by Matthew H. Conrad, M.D., and William P. Adams, Jr., M.D.
Plastic surgery Secrets by Jeffrey Weinzweig MD.
Plastic and Reconstructive surgery board review by by Samuel J. Lin and John B.Hijjawi.
Outcomes after 1.9-m Diode Laser-Assisted Anastomosis in Reconstructive Microsurgery: Results in 27 Patients Thank you