------------------------------------------------------------------------------- TITLE: MICROVASCULAR SURGERY SOURCE: Dept. of Otolaryngology, UTMB, Grand Rounds DATE: April 8th, 1992 RESIDENT PHYSICIAN: LANE SMITH, M.D. FACULTY: RAYMOND WEISS, M.D. DATABASE ADMINISTRATOR: Melinda McCracken, M.S. ------------------------------------------------------------------------------- "This material was prepared by resident physicians in partial fulfillment of educational requirements established for the Postgraduate Training Program of the UTMB Department of Otolaryngology/Head and Neck Surgery and was not intended for clinical use in its present form. It was prepared for the purpose of stimulating group discussion in a conference setting. No warranties, either express or implied, are made with respect to its accuracy, completeness, or timeliness. The material does not necessarily reflect the current or past opinions of members of the UTMB faculty and should not be used for purposes of diagnosis or treatment without consulting appropriate literature sources and informed professional opinion." MICROVASCULAR SURGERY I. INTRODUCTION AND GENERAL PRINCIPLES A. Definition: an island flap with an axial vascular or neurovascular pedicle which is dissected from its normal position, moved to a distant site, then reattached using microsurgical techniques. B. Advantages of Free Flaps 1. Strong blood supply leads to improved wound healing. 2. One stage reconstruction. 3. Almost unlimited flap size and number of choices. 4. Ability to move accurately Tailor flap to defect. 5. Ability to get good match in size, color and function (when neurovascular flap used). 6. Early mobilization. 7. Improved vascularity. 8. Possibility of functional reconstruction (sensory/motor). C. Disadvantages 1. Technically quite difficult to perform. 2. Requires specialized intensive post op care by nurses and physicians. 3. Lengthy operation. 4. Risk of vascular thrombosis and flap death. 5. Donor site defects. 6. Requires special surgical instrumentation and frequent practice. D. Indications for Free Flaps - In general, the simplest procedure that will provide adequate aesthetic coverage of a defect is the best approach. As a surgeon's ability and knowledge of free-flap transfers increase usually his indications for use of free flaps increase. 1. Lack of adequate tissue surrounding damaged of surgical area for local or regional flap reconstruction (such as a previously irradiated area). 2. Replacement of composite defects (such as mandibular defects in which both bare and soft tissue are needed to repair the defect). 3. Need for good neuromuscular function. A neurovascular free flap can provide function as well as tissue coverage and bulk to defect which may not be possible with other types of local or reground flaps. (For example, pectoralis minor neurovascular flap for facial nerve and soft tissue damage to the face or radial forearm flap after neurogrossectors. 4. Need for immediate one-stage reconstruction. 5. No other available flap. 6. Total esophageal reconstruction (may be method of choice vs. gastric pull-up). E. Contraindications for Free Flaps 1. Severe cardiovascular disease. 2. Severe atherosclerosis. 3. Lack of availability of a suitable recipient vessel. 4. Extreme old age (relative contraindication). 5. Inability to tolerate long surgical procedure. 6. When better coverage, cosmesis or function can be obtained with a local or regional flap. 7. Lack of adequate nursing or physician support. II. INSTRUMENTATION A. No. 2-5 jewelers forceps. B. Castroreijo needle holders. C. Atraumatic microvascular clamps. 1. Acland single clamps, sliding framed double clamps, fixed frame double clamp. 2. The clamps should be specifically made for microvascular surgery and not have closing pressures greater than 30 g/mm2. D. Microscope with 4-30x magnification. E. Microvascular suture 8/0 to 10/0 nylon (best) or proline suture on 75 to 100 cm needles for most head and neck procedures. (50-75 cm for smaller vessels.) F. Vessel dilators. G. Curved and straight spring-handled microscissors. III. SURGICAL TECHNIQUE A. Preparation: must spend time practicing in microsurgical laboratory. The techniques used in conventional surgery are generally not applicable to microsurgery. Practice first on rubber glove stretched over jar lid and then on rat vessels. B. General principles of microvascular surgery. 1. Each maneuver must be delicate and accurate. Avoid excessive trauma traction as it can damage the vessels intima or cause spasm and lead to thrombosis. 2. Avoid vessel dying - causes spasm. Vessels should be constantly bathed in 37 degree centigrade normal saline or Ringer's solution. 3. Avoid vessel cooling and contact with fresh blood - causes spasm. 4. Avoid excessive tension at anastomosis site. 5. Avoid laxity (due to redundancy in vessel length). This can allow kinking or twisting of vessels and lead to thrombosis. Make sure geometry of the flap is correct. 6. Loose sutures can fall into vessel lumen or cause leakage at the anastomotic site and lead to thrombosis. 7. Sutures too tight can cause strangulation and cause damage intima leading to thrombosis. 8. Accurate alignment of intima. 9. Blood vessels smaller than 2.5 mm should be anastomosed using the interrupted suture technique. 10. The vessels should be adequately mobilized with as long a pedicle as possible. The greater the mobilization, the easier the anastomosis is. (Like to have at least 2-3 cm.) Excess perivascular tissue should be trimmed under 6x to 10x magnification. 11. Team approach: often best to have one team harvest the flap and a second team prepare the recipient area. 12. Most of the operation is performed using a pencil grip to hold instruments and resting the hand (fifth digit) on the operating surface. The wrists are supported by a rolled towel. C. Suture Technique: End to End Anastomoses. 1. Simplest, most reliable, most-widely used method. 2. Strip adventitia from end of each vessel 2-3 mm (under 10x to 16x magnification) but no more than 2-3 mm. This prevents adventitia from being caught in lumen during anastomoses. Grasp with jeweler's forceps, pull over cut end of vessel and trim with curved microscissors. 3. Framed approximator clamp applied. The two ends of the vessels should be close enough so that there is little tension during the anastomosis. (Remember clamps will need to be placed so you can flip it over for the posterior anastomoses. 4. Blood in the lumen should be flushed out heparinized saline c #22 angiocath attached to tuberculin syringe. 5. Vessel spasm can be reversed with topical lidocaine and/or gentle dilation. 6. Needle grasped with two-headed technique (grasp suture with one hand 2 needle diameters away from swaged end and forceps in other hand.) 7. Needle held just beyond middle portion, 1-2 mm back from needle holder. 8. Three guide sutures placed 120 degrees apart and left long. (Triangle method) Then equal number of interrupted sutures is placed between each guide suture. Enough for anastomoses without leak. (Usually a total sutures, sutures placed in this order.) a. Two guides sutures placed 120 degrees apart. b. Two interrupted sutures in between these for anterior wall closure. c. Third guide suture placed in middle of posterior wall. (120 degrees from each guide suture.) d. Two sutures placed on side (between posterior and left guide sutures) and two placed on other side (between posterior an right guide sutures) to close posterior wall. e. When guide sutures not exactly 120 degrees apart post. wall be asymmetric resulting in twisting at anastomoses. 9. Needle entry point should be 2x the thickness of the vessel wall away the edge. 10. Equal symmetrical entry should be taken from each edge. Uneven placement leads to vessels overlapping and thrombus. 11. Needle placement a two-handed action under 20x to 30x magnification. The needle lumen is cannulated with microforceps (in larger vessels the adventitia is grasped) to provide counter pressure as the needle is placed between them. 12. Therefore after needle penetrates wall, pull needle through along arch of needle. 13. Two pass technique usually used. (Definitely for guide suture placement as these must be very accurate.) For similar size vessels each suture should approximate same relative point along opposite vessel edge. One pass technique can be used after guide suture placement. 14. Knots tied under 16x mag. Need to tie knots flat, accurately (not too much or too little tension). Double logs (surgeons knot) used for first throw on guide sutures, simple square knot used for other sutures. 15. After anterior wall suture clamp is flapped over and posterior wall sutured. D. Venous Anastomosis 1. Use same technique as for arterial anastomoses. 2. Usually more difficult than arterial anastomoses as veins walls are thinner and veins are more collapsible. 3. Usually require fewer sutures the arterial anastomoses. E. Releasing Clamps 1. Both anastomoses (venous and arterial)should be complete prior to clamp release. 2. First irrigate anastomoses with 1% lidocaine. 3. Release venous clamp first, then arterial. 4. Some leakage will occur and usually stops with pressure. Brisk bleeding will require additional sutures. F. Vessel Mismatch 1. Careful placement of sutures for mismatches of up to 2:1 lumen diameter. (Interrupted suture farther apart on larger diameter vessel.) 2. When difference between 2:1 to 3:1 in lumen diameter beveling or spatulation needed. a. Beveling: the oblique cut should not be more than 30 degrees. b. Spatulation: a longitudinal incision made in cut end of smaller vessel for distance. c. If discrepancy exceeds 3:1, end to side anastomoses used. G. End to Side Anastomoses 1. Angle of union between donor and recipient should be as small as possible. Angles less than 60 degrees minimize turbulent flow. 2. Often donor vessels can be spatulated or beveled to decrease angle of anastomoses. 3. An elliptical excision of the recipient vessel wall is made. 4. The initial guide sutures should be placed 180 degrees apart (only two used). These two ends will also be the most likely site of anastomoses leakage. H. Continuous Suture Technique 1. Advantage: much quicker and less anastomotic leakage (50% faster). 2. Disadvantage: narrows the vessel lumen. 3. The technique should only be done on larger vessels (vessels > 2.5 mm diameter) and on end to side anastomoses. 4. Works best on end to side anastomoses for large veins. I. Interpositional Vein Grafts 1. Can be used when vascular pedicles won't reach. 2. Good choices are sapheuous veins in legs. 3. For the arterial anastomoses the veins must be "reversed" so that valves do not obstruct low. Doesn't matter in the venous system. 4. Free suture placed through distal end serves to orient vessels. IV. MECHANICAL AIDS A. Many different techniques exist for making the anastomoses simpler or quicker; but none have definitely been proven to be better or safer. B. Lasers: Have been used to weld vessels but still require placement of guide sutures. Supposedly they are faster and cause less foreign body reaction. C. Stapling devices: require a lot familiarity with the mechanical devices. Inflexibility with regard to tailoring the anastomoses when there are discrepancies in vessel size. Patency rates appear lower than with suture techniques and they're not applicable to vessels smaller than 1.5 mm. V. PATENCY AND PREVENTING THROMBOSIS A. Patency tests: 1. Venous patency easily seen as vessels translucent. 2. Direct observation of exspansile pulsation indicates patency. 3. Longitudinal pulsation indicates partial or complete obstruction. 4. Flicker test and strip tests indicate patency but one reserved for laboratory use only as they cause trauma to vessels. 5. Best test is probably intraoperative Doppler Ultrasound Flowmeter. B. The chance of thromboses is greatest at the site of anastomoses 15 to 20 minutes following the anastomoses. 1. The anastomose should be observed during this period of time. 2. If partial obstruction occurs gentle squeezing with forceps or massaging vessel may break up the thrombus. 3. If complete thromboses occurs or when in doubt resect damaged area and repeat anastomoses. C. Vascular Thrombosis 1. Most commonly due to technical error in suture placement or use of a damaged vessel. 2. After the first 20 minutes critical period is first 3 to 5 days. Usually if flap goes 5 days it will not thrombose. The vascular pedicle cannot be safely divided for at least 8 days. 3. Venous thrombosis most common cause if flap failure. a. This is because venous anastomosis more tenuous than arterial and more difficult to preform. b. Veins more easily compressed, damaged or twisted. D. Healing 1. Pseudointima 5 days. 2. Intima healed complete by 2 weeks. 3. Completely flat and smooth at 8 weeks. E. Gentle technique: As discussed earlier avoid trauma, twisting, kinking (good geometry of flap), cooling, drying of vessels or clamp pressures above 30 g/mm2. Make sure intima of each vessel closely approximated with accurate suture placement. F. Pharmacologic Agents. 1. There is debate as to their proven usefulness in vessels larger than 1.5 mm (although most clinicians use some anticoagulant). 2. Baker give 5-10 grain ASA 9 day and persantine 25 mg TID. They also use LMN dextran (Dextran 40 10% solution), 50 cc intraop, and 25 cc/hr postop x 3-5 days. 3. Some use just heparin 5000 U/sq BID or low-dose drip. 4. TPA, stertor streptokinase, and urokinase have been used to lyse clots these vessels with success. VI. PREOPERATIVE WORK-UP A. Determine need for size, function of flap and availability of appropriate recipient vessels. Your recipient vessels to be reachable and about the same size as donor vessels. B. Check for any vascular diseases or systemic diseases (such as diabetes) which affect vascularity or clotting problems (hyper or hypocoagulation). C. The donor site should not have been irradiated or have had other surgeries nearby which affect it. D. Check circulation of donor site with doppler or arteriogram and be sure there is adequate collateral circulation to the donor site. VII. SPECIFIC FLAPS A. Recipient vessels: In head and reconstruction the best recipient vessels are probably the transverse cervical artery and the external jugular vein. Other good choices include the superior thyroid artery and facial arteries, any of the branches of the external carotid arteries and sometimes the external carotid itself (a less optimal choice). An end to side anastomosis to the internal jugular vein or transverse cervical veins are also very good for venous drainage. The common or internal carotid arteries probably should not be used. B. Flap geometry: Some experienced surgeons have noted problems with flap circulation have been more commonly secondary to poor choice of flap geometry than to anastomotic problems. In the head and neck the side to side motion in the head and neck will result in vessel kinking and thrombosis. The most favorable geometry allows for the vessels to lie longitudinally in the neck. C. Pectoralis Minor 1. Blood supply: Pectoral Branch of Thoracoacromial artery. 2. Nerve: medial pectoral nerve. 3. Anatomy: a flat triangular muscle lying just under pec major. Attaches to ribs 2-5 and coracoid process. 4. Surgical approach: pec major elevated medially to expose pec minor. 5. Advantages: a. Minimal to no post-operative disability. b. Size, shape, lack of bulk good for facial soft-tissue and reanimation procedures. c. Good reinnervation potential. d. Can be used as a composite graft when includes underlying rib. 6. Disadvantages: a. Short vascular pedicle (usually < 3 cm). b. Sometimes not enough bulk. D. Scapular Flap 1. Blood supply: Subscapular and its branch circumflex scapular artery. Venous drainage is vena comitantes. 2. Nerve: none 3. Anatomy: Thin pliable flap mostly skin and subcutaneous tissue (with bone if desired) 6 x 8 cm width by 10 to 18 cm length. 4. Surgical approach: Best performed in prone or lat. decubitus position with arm abducted. Raised from medial to lateral. Vessels bound in triangular space over ties minor and major. 5. Advantages: a. Long vascular pedicle 6-8 cm. b. Can be used as composite flap by including lateral edge of scapular bone. c. Can include lat. dorsi muscle in flap as thoracodorsal artery is a branch of subscapular artery. d. Very reliable. e. Donor site closes primarily. f. The shoulder must be immobilized for 4-5 days after surgery. 6. Disadvantages: a. Positioning of patient. b. Some post-op shoulder dysfunction (mild). E. Jejunum 1. 1. Blood supply: From vascular arcade based superior mesenteric artery and vein. 2. Nerve: None. 3. Anatomy: Second loop of jejunum most reliable. (1.5 to 2 feet beyond ligament of Treitz.) 4. Surgical approach: The mesentery is divided in a V-shape along the second jejunal artery and vein. Donor site closed EWD to END with a stapling device. 5. Advantages: a. Minimal donor defect (often none noticeable). b. Good for pharyngoesophageal reconstruction. 6. Disadvantages: a. Bowel or pharynx fistulas. b. Need for abdominal procedure and abdominal preparation. c. Difficult to harvest in very obese people. F. Radial Forearm Flap 1. Blood supply: Radial artery. Venous drainage through deep veins following the artery and superficial plexus. 2. Nerve: Medial and lateral cutaneous sensory nerves. 3. Anatomy: Fairly thin flap along anterior forearm, can include bone. 4. Advantages: a. Ease of pre-operative evaluation. b. Easy to elevate. c. Strong blood supply. d. Good source for mandible when bone is taken, part of radius and intraoral reconstruction. e. Can be expanded to get larger area of coverage. 5. Disadvantages: a. Possible loss of hand, must be sure ulnar system is patent. b. Must make sure fascia is left covering tendons or skin graft will stick to tendons and cause loss of function. c. Usually requires skin graft for closure. (Cannot close primarily.) d. When bone is taken pathologic, fractures may occur. G. Latissimus Dorsi 1. Blood supply: Thoracodorsal artery (a continuation of the subscapular artery). Two major branches off thoracodorsal the interior longitudinal and posterior transverse branch. The posterior transverse branch is vital to flap survival. 2. Nerve: Thoracodorsal nerve (runs in neurovascular bundle. 3. Anatomy/approach: Very large triangular muscle. Incision is made over anterior border of lat. dorsi and continued up axillae. The vessels are identified in a retrograde fashion. This flap can be included with a scapular flap. 4. Advantages: a. Large amount of tissue (25 x 35 cm) available. b. Easily closed donor defect with minimal mobility. c. Long vascular pedicle possible. d. Very reliable flap. 5. Disadvantages: a. Requires patient in lateral decubitus position. b. Sometimes flap too bulky. H. Inferior Rectus Abdominis 1. Blood supply: Inferior epigastric artery. 2. Nerve: 3. Anatomy/approach: Large flap possible. Must find IE artery arising from external iliac near the inguinal ligament. Anterior sheath of contralateral rectus can be used to help close defect. Skin can be closed primarily. 4. Advantages: a. Large flaps. b. Long vascular pedicle. c. Reliable flap. d. Can be closed primarily with minimal donor defect. 5. Disadvantages: a. Often bulky. b. Beware of hernia formation and possible poor wound healing. I. Serratus 1. Blood supply: Thoracodorsal artery. 2. Nerve: Long thoracic nerve. 3. Anatomy/approach: Long flat muscle under latissimus. Originates from first 8 ribs. Approach similar to lat. dorsi flap. 4. Advantages: a. Good donor for composite graft (vascularized rib). b. Strong blood supply, easy to raise. c. Good for facial reanimation and/or mandible defects. d. Very long vascular pedicle. e. Easily closed primarily. 5. Disadvantages: a. Pt. must be lateral decubitus position. b. Loss of serratus lamper arm movement. J. Iliac Crest 1. Blood supply: Deep circumflex iliac artery. (DCIA) 2. Nerve: None. 3. Anatomy/Surgical Approach: DCIA originates from external iliac artery 1 cm from inguinal ligament. A linear incision parallel to iliac crest is made. External and internal oblique muscles are incised >= 3 cm above iliac crest to space musculocutaneous branches. 4. Advantages: a. Reliable flap. b. Good for large bony defects such as a hemi mandible. c. Minimal donor deformities. d. Defect closed primarily. 5. Disadvantages: a. Risk of damage to femoral nerve, iliac vessels, peritoneum and bowel. b. Fairly difficult to elevate and find vessels. c. Painful site of healing and long scar. K. Posterior Auricular Free Flap 1. Blood supply: Posterior auricular artery and vein. 2. Anatomy/Surgical Approach: Retroauricular tissues elevated to include posterior auricular artery which is a branch of the external carotid and originates near the mastoid tip. 3. Advantages: a. Good color match for facial defects. b. Has been used for nasal reconstruction. c. Can include auricular cartilage with this graft. d. Relatively hairless. 4. Disadvantages: a. Vascular pedicle is very short necessitating vein grafts. b. Relatively little bulk. c. Risk of facial nerve damage when working near mastoid tip. L. Other Flaps 1. Gracilis 2. Dorsalis Pedis 3. Tensor Fascia Lata 4. Omentum 5. Revascularized Rib 6. Lateral Cutaneous Thigh 7. Lateral Arm Flap 8. Fibula Flap VIII. SPECIFIC USES OF FREE-FLAPS IN RECONSTRUCTION A. Intraoral Reconstruction: Pedicle flaps sometimes too bulky and have trouble reaching posterosuperior oronasopharynx. 1. Most useful in difficult areas such as tonsillar pillars, palate posterior pharyngeal wall. 2. Good choices: Dorsalis pedis, radial forearm, tensor fascia latae. B. Mandibular Reconstruction 1. Allows for one-stage reconstruction. This is probably the best use for free flaps in the head and neck. 2. Goal is to restore competent oral sphincter and allow chewing and swallowing with good cosmesis. 3. Good choices: Iliac crest flap (often need accompanying skin graft), dorsalis pedis with second metatarsal bone, scapular flap, radial forearm, revascularized rib. C. Pharyngoesophageal Reconstruction 1. Goal is to re-establish an epithelial-lined conduit connecting oral cavity with GI tract. 2. Great deal of debate whether gastric pull-up or free flap (jejunum) is better. Often options include tubed myocutaneous flap (pec. major latissimus dorsi, trapezius, or delto pectoral flap). 3. Good choices: a. Jejunum: probably considered best choice of free flaps but has a fairly high complication rate of 15-20%. b. Radial forearm. c. Rectus abdominis. d. Scapular or latissimus dorsi. D. Facial Paralysis 1. Free flaps can provide bulk and voluntary movement in long-standing facial paralysis. They can also be used as an adjunct to other move forms of rehabilitation. 2. Free flaps definitely a second choice after primary grafting or nerve repair and 12 to 7 anastomosis. Free flaps work best after long-standing facial paralysis (.18 months) when reinnervation will no longer work. 3. Choices: a. Pectoralis Minor - probably best choice for bulk and function. b. Gracilis. c. Segmental Gracilis. d. Latissimus dorsi. E. Reconstruction After Skull Base Surgery 1. Regional and local flaps often have difficulty reaching this area and frequently do not provide enough bulk. 2. Free-flap is an excellent option with the major limiting factor being recipient vessels. Branches of the external carotid artery, occipital or superficial temporal artery can be used. 3. Good choices: Rectus abdominis flap, latissimus dorsi, lateral thigh, radial forearm, and tensor fascia latae. The rectus abdominis and tensor fascia latae flaps are particularly good because they can be used a jarrus flaps and cover or reconstruct dura and outside skin. 4. Definition of a jarrus flap: named after the Roman cow depicting their God Jarrus on both side, a jarrus flap is one which has the ability to have a double surface (fascia or skin on both sides). IX. POSTOPERATIVE CARE A. ICU nursing care for 24 to 48 hours. B. Careful Monitoring of Vascular Viability 1. Flap should be monitored hourly for color, warmth and capillary return for 24 hours post-op after which 2-4 hours observation for the next two to four days. 2. Anticoagulation a. In general this is controversial when vessels are larger than 1.5 mm (if smaller definitely anticoagulate). b. Baker use 5-10 grams of ASA q day for 3 weeks along with persantine 25 mg TID. They also use 50 cc of 10% LMW Dextran intraoperatively and 25 cc/hour for first 3 to 5 days. c. Others use heparin either 5000 units sq BID or low level perfusion at 200-250 units per hour. C. Techniques for Post-operative Monitoring of Vascular Viability of the Flap 1. Direct observation and pin-prick test. a. Probably the best method and demands least amount of equipment. b. For buried flaps attempt to provide a "window" for monitoring. c. Prick flap with 25 gauge needle. (1) White flap, cold to touch, no bleeding with pin-prick means arterial thrombosis. (2) Bluish flap, swollen, bleeds and does not stop after pin-prick means venous obstruction. (3) Slightly bluish or pink flap with one to three drops of blood after pin-prick and good capillary refill means both venous and arterial supply patent. 2. Temperature a. Possibly best method of monitors digital replantation. b. A temperature differential of 2.5 degrees C or fall below 30 degrees C means arterial or venous thrombosis. c. Arterial thrombosis causes rapid fall in temp (3 degrees C) venous causes slower fall i temp (1-2 degrees C). d. Limited applicability in head and neck because intraoral reconstructions do not lose heat. 3. Transcutaneous Oxygen a. Uses a tissue PO2 electrode. b. PO2 valves greater than 20 to 25 mm Hg mean satisfactory perfusion. c. Sudden falls in PO2 or PO2 which does not increase on administration of 100% O2 means vascular compromise. 4. Intravenous Fluorescein a. Administer 10-15 mg/kg fluorescein and measure with a fiberoptic dermoflorometer. Low dose fluorescein can be used (1.5 mg/kg) and measured with a fluorescein. b. Limited usefulness because it takes a long time for fluorescein to clear from skin (several hours) and does not provide for continuous monitoring. 5. Laser Doppler Flowmeter a. Laser light (Helium-neon laser) measures flow in capillaries. b. Continuous monitoring of relative flow is possible. c. However difficult to monitor buried flap. 6. Other new experimental techniques. a. Continuous wave ultrasound doppler. b. High frequency pulsed ultrasonic doppler velocimeter. c. Muscle contractility. D. Elevate patients head 30-35 degrees to reduce edema and improve venous return. Initially immediately after anastomosis the flap is pink colored. After 24 days the flap usually turn slightly bluish and becomes edematous. (Expect some edema.) E. Most give blood spectrum antibiotics when working in head and neck. F. If vascular occlusion occurs: 1. Most commonly occurs in the first 24 days. The vast majority within 20-30 minutes of anastomosis, although arterial thrombosis has occurred as late as 10 days post-op. 2. Most often due to problems in the recipient vessels (according to Hidalgo). Others say at the anastomotic site. 3. Venous obstruction is the most common cause. 4. Partial occlusions have been successfully treated with streptokinase, urokinase or TPA. Some people have even suggested this for total occlusion. However most advocate emergent re-exploration. G. Emergent Exploration and Reanastomosis 1. Most advocate emergent re-exploration within one to two hours at the first signs of vascular insufficiency. 2. The exploration and anastomosis mostly occur within 8 to 12 hours (most say 8) after occlusion or the no reflow phenomenon occurs (ie. flap dies). 3. Free-flap survival can be increased by 8-10% with aggressive re-exploration and repair. General survival rates can approach 92-98%. REFERENCES 1. Morrison W.S, O'Brien M.B. Reconstructive Microsurgery. New York, Churchill Livingstone, 1987. 2. Baker S.R. Microsurgical Reconstruction of the Head and Neck. New York, Churchill Livingstone, 1989. 3. McDovough J.J., Gluckman J.C. Microvascular Reconstruction of the Pharyngoesophogus with Free Jejunal Graft. Microsurgery, 9:116-127; 1988. 4. Urken M.L. Vickery C., et al. The Internal Oblique-Ilia Crest Osseomyocutaneous Free Flap in Oromandibular Reconstruction. Arch Otolaryngol Head Neck Surg, 1989; 115:339-349. 5. Shestak K.C., Matlowe H.S. Oral Cavity Reconstruction. Cancer Bull, 1990; 42:25-29. 6. Urken M.L., Vickery C. et al. Free Flap Design in Head and Neck Reconstruction to Achieve an External Segment for Monitoring. Arch Otolaryngol Head Neck Surg, 1989; 115:1447- 1453. 7. Gilbert R.W., Ragnarsson R. et al. Microvenous Grafts to arterial Defects. Arch Otolaryngol Head Neck Surg, 1989; 115:970-976. 8. Urken M.L., Vickery C. et al. Geometry of the Vascular Pedicle in Free Tissue Transfers tot he Head and Neck. Arch Otolaryngol Head Neck Surg. 1989; 115:954-960. 9. Sullivan M.J., Carroll W.R. The Free Scapular Flap for Head and Neck Reconstruction. Am J. Otolaryngol 11:318-327, 1990. 10. Shusterman M.A. Free Tissue Rexonstruction of the Hypopharynx and Cervical Esophagus. Cancer Bull, 1990; 42:39-43. 11. Banis J.C. Thin Cutaneous Flap for Intra Oral Reconstruction: The Dorsalis Pedis Free Flap Revisted. Microsurgery, 9:132- 140; 1988. 12. Boyd J.B. Mandibular Reconstruction in the Young Adult Using Free Vascularized Iliac Crest. Microsurgery, 1988; 9:141- 149. 13. Swartx W.M. Microvascular Approaches to Nasal Reconstruction. Microsurgery, 1988; 9:150-153. 14. Arena S., Fritsch M., Hill E. Free Tissue Transfer in Head and Neck Reconstruction. Am J. Otolaryngol, 1989; 10:110- 123. 15. Hayden R.E., O'leary M.J. Soft-Tissue Reconstruction in Skull Base Surgery. Insights in Otolaryngology, Vol 6 No 9, Sept. 1991. 16. Hidalgo D.A., Jones C.S. The Role of Emergent Exploration in Free-Tissue Transfer: A Review of 150 Consecutive Cases. Plastic and Reconstructive Surgery, 1990; 86:492-498. 17. Fried M.P., Camenior D.S., Sloman-Mall E.R. The Efficacy of Absorbable Suture for Microvascular Anastomoses. Arch Otolaryngol Head Neck Surg, 1990; 116:1051-1059. 18. Masser M.R. The Pre-expanded Radial Free Flap. Plastic and Reconstructive Surgery, 1190; 86:295-301. 19. Shenag S.H. Reconstruction of Complex Cranial and Craniofacial Defects Utilizing Iliac Crest - Internal Oblique Microsurgical Free Flap. Microsurgery, 1988; 9:154-158. 20. Jones N.F. Postoperative Monitoring of Microsurgical Free tissue Transfers for Head and Neck Reconstruction. Microsurgery, 1988; 9:159-164. 21. Urken M.L. Composite Free Flaps in Oromandibular Reconstruction. Arch Otolaryngol Head Neck Surg, 1991; 117:724-732. 22. Wanig B.L., Keller A.J. Microvascular Free Flap Reconstruction for Head and Neck Defects. Arch Otolaryngol Head Neck Surg, 1989; 115:1118-1120. 23. Shestak K.C., Shusterman M.A. et al. Immediate Microvascular Reconstruction of Combined Palatal and Midfacial Defects using Soft Tissue Only. Microsurgery, 1988; 9:128-131. 24. Sullivan M.J., Carroll W.R., Baker S.R. Soft Tissue Reconstruction and Augmentation of the Face with Free Flaps. Facial Plastic Surgery, 1989; 6:279-288. 25. Park C. The Chondrocutaneous Postauricular Free Flap. Plastic and Reconstructive Surgery, 1989; 84:761-771. 26. Charles D.A., Fredrickson J.M., Bryce D.P. Microvascular Surgery. Arch Otolaryngology, 198; 106:80-82. ------------------------------------------------------------------------------ MICROVASCULAR SURGERY LANE SMITH, M.D. RAYMOND WEISS, M.D. April 8th, 1992