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Technique for Microanastomosis


- See:                                                                                                      Diagrams kindly provided by
        - End to Side Technique - Large Vessel Repair                                Donald Serafin M.D.
        - End to End - Large Vessel Repair                                                 Duke University Medical Center
        - Vein Grafting

- PreOp Preparation:
    - pharmocological agents;
    - vessel dilators;
    - approximator clamps;
               - clamp contains two atraumatic clamps attached to a retangular frame;
    - monofilament nylon;
               - sizes range from 8-0 to 11-0 w/ 75 micrometer needle;
               - 10-0 suture is used for digital vessels;
    - bipolar cautery;

- Vessel Exposure & Preparation:
    - resect vascular wall until the cut ends appear normal;
         - repairing rather than resecting injured vessels to avoid using vein grafts will usually fail due to vessel thrombosis;
    - mobilize both ends of vessel to obtain adequate length for anastomosis;
           - mobilize vessel ends to allow approximation w/ minimal tension;
           - this usually requires 2 to 3 cm;
           - remove the loose conective tissue surrounding the vessel;
           - colored plastic sheet is placed beneath vessel to make it easier to see;
    - cauterize tethering side branches w/ bipolar electrocautery;
          - small branches may be electrocoagulated 2-3 mm from parent vessel;
    - irrigate operative field w/ heparinized Ringer's lactate solution;
          - blood is cleared from vessel ends by jet of saline;
          - continue to irrigate the field intermittently with heparinized Ringer's lactate;
          - use a 25 to 30 gauge blunt tipped needle;
    - vessel dilitation
          - first performed w/ pharmologic agents (1% lidocaine);
          - if this is not optimal, dilitation is performed mechanically, dilitating the ends 1.5 times normal diameter;
                - there is some evidence that this may injure the intima;
    - approximator clamps;
          - clamp contains two atraumatic clamps attached to a retangular frame;
          - vessel ends are placed within the jaws of the clamp approximator and are positioned to permit clamp to be flipped 180 deg w/o tension;
          - damaged vascular clamps which exert greater than 30 gms/ sq mm may cause endothelial damage and subsequent thrombosis;
                - vessels should be clamped w/ the minimal effective pressure;
          - initially slide the clips as far apart as possible;
          - once vessel ends have been placed in clips, use forceps to gently slide the clips together, which will approximate the vessels;
    - adventia is removed from vessel wall;
          - pull adventia down over vessel end, cut it, & let it retract;
          - adventia may also be removed by careful circumferential trimming;
          - adventia should be stripped from the vessel ends approximately 2 mm, to prevent accidental incorporation of adventia in suture;
          - remove sufficient adventia from the vessel ends to expose all layers of the vessel wall;
    - anticoagulation:
          - before the vascular anastomosis give systemic heparin;

- Suture Technique:

    - initial suture insertion: (inside to out)
          - use double armed suture to insert needle from "inside to out" on both sides of the anastomosis;
                 - this ensures that the intimal edges will be everted;
                 - use interrupted sutures to prevent vascular constriction, and place each suture thru the full thickness of the vessel wall;
          - avoid suturing both walls together;
                 - this is best managed by prevention;
                 - this complication can be difficult to identify once the sutures have been placed;
    - place first two stay sutures approximately 120 deg apart on vessels circumference;
          - leave the ends of these sutures long for use as traction sutures;
          - by placing the two stay sutures 120 deg apart, the posterior (back wall) will fall away, making it less likely to capture both walls;
    - rotate clamp approximators to expose posterior vessel wall & place
          stitch 120 deg from initial two stitches;
          - first stay suture applied with the tip of forceps in lumen to protect back wall from needle and to provide counter pressure;
          - 2nd stay suture placed at 1/3 of vessel circumference away from 1st;
                - this allows the back wall to drop away, protecting it from the needle;
          - place more stitches in remaining spaces to complete anastomosis;
          - arteries 1 mm in diameter usually require 5 to 8 stitches, and veins require 7 to 10 stitches;
          - vessels may be gently dilated by insertion of tips of jewler's forceps;
          - walls of vessels may be grasped, but avoid rough manipulation of intima;
          - to overcome vascular spasm, apply topical lidocaine or papaverine;
    - completion of anastomosis:
          - after anastomosis is complete, first remove the distal clamp;
          - look for back filling in the vessel across the suture line, a small amount of oozing is normal;
          - cut the stay sutures and remove the clamp which is upstream;
          - if excessive bleeding is present, place additional stiches in the areas of leakage, remove clamps again, and deflate the tourniquet;
          - assess the patency of anastomosis by occluding a segment of vessel distal to the anastomosis;
    - completion of anatomosis:
          - in the report by Chen, et al, the authors compared continuous vs interrupted suture technique;
                 - total thrombosis rate was 8%, but no significant patency difference was noted between the CST and the interrupted suture technique in any vessel category.
          - ref: Comparison of continuous and interrupted suture techniques in microvascular anastomosis

- Technique of anastomosis of larger vessels
    - considerations:
          - prosthetic grafts 
          - vascular shunts
    - initial preparation:
          - prepare wide operative field & prepare opposite extremity for possible reversed saphenous be bypass graft;
          - debridement:
          - dilute heparin solution is flushed down the distal arterial bed;
          - embolectomy catheters are then used to remove thrombus;
          - intima is examined, extending arteriotomy as necessary;
          - obtain control of artery distal to presumed site of injury to minimize loss of blood by back bleeding;
          - inspect & palpate the site of injury to determine need for repair;
          - proximal and distal controls should be obtained at least 2 to 3 cm from site of injury so that intima can be examined;
                 - in both penetrating and blunt trauma, the intima may be damaged beyond the obvious site of injury;
                 - damaged intima requires resection;
    - remove proximal clot by flushing & distal clot by milking vessel, squeezing the distal limb, or passing a Fogarty balloon catheter;
    - excess advential tissue is excised from outer surface of vessel so that it will not be dragged into the anastomosis;
          - observe intimal as it is flushed with heparinized saline to see if there is evdience of an intimal flap;
    - before anastomosis, determine need for graft replacement by estimating amount of difficulty in approximating the severed ends;
          - in general, 1-2 cm of artery may be resected w/o graft replacement;
          - arterial anastomosis should not be performed under tension;
    - repair injured artery w/ interrupted or continuous fine monofilament sutures;
    - smaller arteries may be constricted using continuous suture techniques;
          - in children, interrupted suture repair is preferred to ensure circumferential growth;
    - prior to completion of repair, arteries are forebled and backbled;
    - closure consists of a interrupted suture, placed close together, run down the proximal aspect of the artery;
    - using a double armed needle, both sutures are passed inside to out inorder to ensure intimal eversion;
          - sutures pass thru all layers, particular care being taken to include intima;
          - suture bites taken 1 mm apart and 1 mm from edges, unless vessels are large, thick walled or diseased;
    - arteries need to be black bled and flushed, using heparin- dextran solution, followed by flushing with a dextran solution;
    - completion arteriogram is performed to assess quality of vascular reconstruction for intimal defects, suture line problems, and the adequacy of the distal runoff;

- Post Operative Management:
    - see pharmocological agents used in vascular surgery;
    - proper hydration of pt, warm environment, adequate analgesia, avoidance of hypotension, and a ban on smoking

References for Arterial Trauma

The effect of microvascular anastomosis configuration on initial platelet deposition.

The strength of microvascular anastomoses--an experimental evaluation in rats.

The Use of Arteriovenous Anastomosis for Replantation of the Distal Phalanx of the Fingers.

Early microsurgical reconstruction of complex trauma of the extremities.

Spatulated versus end-to-end anastomosis for small vessel injury.

Comparison of continuous and interrupted suture techniques in microvascular end-to-side anastomosis.

Evaluation of clinical microvascular anastomoses--reasons for failure.

Management of the contused arterial segment.

A comprehensive approach to extremity vascular trauma.

Optimal techniques for harvesting and preparation of reversed autogenous vein grafts for use as arterial substitutes: a review.