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Microvascular Surgery General Considerations

last modified on: Tue, 03/20/2018 - 13:27

Microvascular Surgery General Considerations

Return to: Microvascular Surgery Protocols 

 

  1. GENERAL CONSIDERATIONS
    1. Indications
      1. As the ease of performance of microsurgery has increased over the past 10 years, the number of clinical situations suitable for these procedures has increased as well. The large number of donor sites currently available allows selection of flaps with a vast array of reconstructive potentials including bone flaps, cutaneous flaps, innervated muscle flaps, sensate flaps, fascial flaps, and composite flaps composed of several tissue types. These donor sites also allows flap selection based on desired tissue volume and consistency. Free tissue transfer is now safely done on patients at the extremes of age as the overall duration of operative procedures have been shortened. In general, the indications for microsurgical reconstruction fall into several main areas.
        1. Reconstruction of surgical defects following oncologic ablative surgery
        2. Reconstruction of traumatic defects (including replantation)
        3. Reconstruction and rehabilitation of congenital defects
        4. Reconstruction with vascularized tissue to facilitate rehabilitation of a compromised wound
    2. Contraindications
      1. For flap specific contraindications (see individual protocols)
      2. Medical status that precludes an extended operative procedure: This contraindication is relevant to performance of any major head and neck procedure.
      3. History of coagulopathy resulting in a hypercoagulable state, such as polycythemia.
      4. Relative contraindications include connective tissue disorders, vasculitis, peripheral vascular disease, severe obesity, venous insufficiency, and any other disorder that may impact the coagulation and healing status of the patient.
      5. The patient's physiologic status is much more important than chronologic age in determining the appropriateness of a free tissue transfer procedure.
    3. Pertinent Anatomy
      1. See Individual flap protocols
  2. PREOPERATIVE PREPARATION
    1. Evaluation
      1. General medical evaluation including medical clearance for a prolonged procedure: This evaluation is particularly important in head and neck cancer patients who frequently manifest a variety of comorbid illnesses.
      2. Oto-dental prosthetic consultation: The dental prosthetic or facial prosthetic rehabilitation should be planned prior to surgery. The surgical plan should incorporate the needs of the prosthetic rehabilitation.
      3. Donor site: Careful evaluation of the intended donor site through history and physical examination is needed to exclude the possibility of prior trauma to the intended flap tissues or vascular pedicle.
      4. Recipient site: The availability of recipient vessels should be determined through history, chart review of previous neck procedures, and physical examination.
      5. Flap selection: The defect reconstructive requirements and goals should be reviewed to determine the most appropriate flap type selected.
        1. Bone requirements, potential need for osseointegrated implants
        2. Surface area coverage requirements
        3. Long-term volume requirements including need for permanent volume, need for thin soft tissue coverage, and color match needs
        4. Potential utility of a sensate flap or motor innervation of a muscular flap
      6. It is prudent to always have an alternative reconstructive procedure in mind if the first choice becomes untenable.
    2. Potential Complications
      1. See Individual flap protocols
      2. All patients should be aware of the potential problem of vascular flap failure and the possibility of returning to the operating room for flap salvage attempt or revision with an alternative flap.
      3. Variable results with either sensory or motor innervation of the flap should be discussed.
      4. Although not actually a complication, all patients should be aware of the potential need for flap debulking and revision in the final rehabilitation process.
  3. NURSING CONSIDERATIONS
    1. Room Setup
      1. See Free Flap Room Setup
    2. Instrumentation and Equipment
      1. Special Instrumentation
        1. Two-headed microscope with variable focal length (if unavailable, then use 250 mm lens)
        2. Microvascular instruments
        3. Microvascular clamps
        4. Loupes may be used as an alternative to performance of the microvascular anastomosis with a microscope. The microscope should be available if the vessels encountered are unusually small.
        5. 8-0 and 9-0 nylon sutures
        6. Synovis (R) microvascular anastomotic device --see instrument trays:
          1. Synovis Clip Applier Tray, Long
          2. Synovis Clip Applier Tray, Short  
          3. Microvascular Anastomotic Techniques
    3. Preoperative Medications
      1. Perioperative antibiotics administered as indicated for the ablative procedure (see Perioperative Antibiotic protocol).
      2. Unless contraindicated, all patients receive a preoperative dose of IV Decadron (8 to 10 mg) and two postoperative doses at 8-hour intervals.
    4. Intraoperative Medications
      1. Continue perioperative antibiotics and Decadron for procedures lasting longer than 8 hours.
      2. Warmed PhysioSol solution is used to keep the flap and vessels moist throughout the case.
      3. Do not use epinephrine-containing injection solution at the recipient or donor sites.
      4. Heparin solution 10,000 units/liter is used to irrigate the vessels.
      5. Papaverine solution 60 mg per 500 ml for irrigation is used to break vascular spasm.
      6. Dextran 1 (a short chain Dextran, MW = 1,000 Daltons, serves as a test dose prior to beginning Dextran 40. Dextran 1 acts to bind antibodies to Dextran if they are present with a resultant anaphylactoid response. This does not, however, result in precipitation of antigen-antibody complexes as would occur if Dextran 40 were administered.)
      7. If no response occurs following the administration of 20 ml of Dextran 1, Dextran 40 at 25 ml per hour may be started prior to the anastomosis. Dextran 40 is continued for five days.
    5. Prep and Drape
      1. See Individual flap protocols
      2. If simultaneous recipient site surgery and flap harvest are to be performed, two nursing teams are required.
  4. ANESTHESIA CONSIDERATIONS
    1. General
      1. Table to be turned 180°
      2. Discuss availability of extremities for lines and monitoring with the anesthesia team the day prior to surgery
      3. Patient temperature maintained above 37.5°C
    2. Specific
      1. It is ideal for the systolic blood pressure to be maintained above 100 mm Hg during and following the anastomosis. This practice should be accomplished without the use of pressors. The need to avoid the use of pressors throughout the case should be discussed with the anesthesia team prior to beginning the case.
      2. Efforts at intravascular volume expansion with colloid or large volumes of crystalloid solutions are unnecessary and associated with perioperative complications.
  5. OPERATIVE PROCEDURE
    1. See Individual Flap Protocols (see: Microvascular Surgery Protocols)
    2. Dissection of the Flap and Vascular Pedicle
      1. The flap and vascular pedicle should be kept moist and warm throughout the harvest.
      2. Branches of the vascular pedicle should be ligated or clipped. Only very small branches should be bipolar cauterized.
      3. Dissection of the vascular pedicle is generally taken to the parent vessel. In some flaps, this allows harvest of a single vein rather than two venae comitantes.
      4. The vascular pedicle is not divided until the recipient vessels have been prepared.
    3. Preparation of the Recipient Vessels
      1. The external jugular vein is the most frequently used recipient vein. This vessel should be carefully protected during the extirpative procedure.
      2. The most frequently used recipient arteries are the facial artery, transverse cervical artery, and superior thyroid artery.
      3. Following completion of the extirpative procedure, usually during the evaluation of the frozen section margins, the recipient vessels are prepared. A single vascular clamp is placed, and the distal lumen is irrigated with Heparin solution. After preparation, these vessels should be kept warm and moist at all times.
    4. Contouring the Bone for Osseous Flaps
      1. If possible, some of this work can be done prior to removing the flap from the donor site. Usually, the majority of this is done after harvest on a back table.
    5. Insetting the Flap
      1. Unless the ischemia time has been inordinately long, insetting of the flap should take place prior to the microvascular anastomosis.
      2. The approximate position of the flap and geometry of the vascular pedicle are determined. Vascular pedicle length suitability and geometry should be determined before the flap is sutured in place.
      3. In composite flaps, it is occasionally easier to suture in the more posterior soft tissues prior to plating the bone into position.
    6. Microvascular Anastomosis
      1. The field should be kept moist with warm PhysioSol.
      2. The vessels should be trimmed and positioned as needed to eliminate kinking. The approximate position of the pedicle should be determined prior to starting the anastomosis.
      3. Following the anastomosis, the clamps are taken off of the veins and then the arteries.
      4. If there is an anticipated need for vein grafts, they should be harvested as soon as possible and an A-V loop done on the back table.
    7. Closure
      1. Drains should not be placed immediately adjacent to the pedicle.
      2. The position of the vascular pedicle should be noted prior to closure and the absence of any kinks in the pedicle should be determined.
      3. If there is a "best position" for the head, this should be noted.
      4. Be sure that the vascular clamp count is correct.
      5. The best position for Doppler evaluation of the flap is determined and marked. Ideally, this is the most distal point possible and not in the neck. Frequently, intraoral flaps may be evaluated with the Doppler intraorally.
  6. POSTOPERATIVE CARE
    1. An "anastomosogram" should be drawn in the chart indicating the position of all the vessels and which vessels were used. This is useful information if the patient needs to be returned to the operating room for any reason.
    2. The on-call resident is called to meet the patient and surgery team in the SNICU after they leave the OR to familiarize themselves with the flap appearance. The on call resident will do flap checks overnight every 3 hours, which will be continued by the day team for a total of 24 hours post-operatively.
    3. The flap is evaluated by the nursing staff every hour for the first 48 hours using an assessment of the Doppler signal and color. Afteward, the flap is evaluated by the nursing staff every four hours for five days.
    4. The patient's best head position should be indicated in an order written in the chart - in general, head should be midline with no pillows underneath.
    5. No circumferential ties or dressings around the neck.
    6. The most reliable method of evaluating the flap in experienced hands is pin-prick with evidence of bright red blood. Other indicators are color, feel, and Doppler.
    7. Various postoperative anticoagulation regimens may be used - all attendings (Bayon, Chang, Pagedar, Sperry) use Lovenox 40 qd (may need to decrease to 30 qd for renal impairment); additionally, Dr. Bayon uses Toradol for 5 days post-op.
    8. In general, patients are kept NPO and on strict bedrest overnight on the first night, and then activity is advanced (depending on type of flap, i.e. fibula), and tube feeds are started on POD 1. If patients are not requiring pressors or ventilation, they typically should transfer out of the ICU on POD 1.
  7. SUGGESTED READING
    1. Furnas DW, Turpin IM, Bernstein JM. Free flaps in young and old patients. Clin Plast Surg. 1983;10:149-154.
    2. Schusterman MA, Miller MJ, Reece GP, et al. A single center's experience with 308 free flaps for repair of head and neck cancer defects. Plast Reconst Surg. 1994;93:472-478.
    3. Urken ML, Vickery C, Weinberg H, Buchbinder D, Biller HF. Geometry of the vascular pedicle in free tissue transfers to the head and neck. Arch Otolaryngol Head Neck Surg. 1989;115:954-960.
    4. Urken ML, Weinberg H, Buchbinder D, et al. Microvascular free flaps in head and neck reconstruction: report of 200 cases and review of complications. Arch Otolaryngol Head Neck Surg. 1994;120:633-640.