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Flashcards in Microsurgery Deck (22):
1

A 45-year-old woman undergoes reconstruction of the right breast with a deep inferior epigastric artery perforator flap. Postoperatively, the flap shows signs of ischemia and is reexplored. During flap salvage, which of the following agents should be administered to inactivate thromboxane?

A) Aspirin
B) Dextran
C) Heparin
D) Hirudin
E) Streptokinase

The correct response is Option A.

Aspirin, or acetylsalicylic acid, inhibits the enzyme cyclooxygenase. Cyclooxygenase ordinarily functions to form multiple compounds from arachidonic acid, including thromboxane and prostacyclin. Thromboxane is a platelet aggregator and vasoconstrictor. Prostacyclin is also a platelet aggregator. By decreasing formation of these compounds, aspirin acts as an anticoagulant.

Dextran is a polysaccharide whose mechanism of action is thought to involve decreasing platelet aggregation by altering the electric charge of platelets, as well as by decreasing blood viscosity. Dextran also acts as a volume expander.

Heparin is a glycosaminoglycan that binds to antithrombin III and enhances its ability to inactivate thrombin (which ordinarily converts fibrinogen to fibrin), as well as clotting factors IX, X, XI, and XII. Heparin may also additionally decrease thrombosis by causing nitric oxide-mediated vasodilation.

Hirudin is derived from the medicinal leech Hirudo medicinalis and functions by directly inhibiting thrombin, in contrast to heparin, which requires the antithrombin III cofactor.

Streptokinase is a thrombolytic agent that functions by activating plasminogen and its conversion to plasmin. In turn, plasmin breaks down fibrin into fibrin degradation products.

 

2

A 38-year-old woman undergoes bilateral breast reconstruction using microvascular free tissue transfer from the abdomen. The patient is evaluated 8 hours later because the right breast flap appears mottled and engorged. Administration of which of the following is CONTRAINDICATED in this patient?

A) Heparin irrigation to the flap vessels
B) Papaverine to the flap vessels
C) Systemic heparin
D) Systemic thrombolytics
E) Thrombolytics to the flap vessels

The correct response is Option D.

Heparin may be used locally or systemically during flap salvage attempts in an effort to encourage further propagation of clot and irrigate existing thrombus. Papaverine and thrombolytic agents are used locally on or within the flap vessels, but not systemically due to concern for systemic complications.

 

3

A 28-year-old woman with a traumatic lower extremity wound undergoes free tissue transfer reconstruction. Venous anastomosis is completed with a 3-mm coupler device. Which of the following is the proven benefit of using a coupler device?

A) Decreased anastomosis time
B) Decreased thrombosis
C) Decreased twisting of vessels
D) Ease of use
E) Improved kinking

The correct response is Option A.

The only reliable information gleaned from available data is that the use of a coupler for venous anastomoses does decrease the operative time in performing the vascular technique. Most studies point to an improved patency rate in venous anastomoses as well, but this remains open to interpretation.

All the available published data point to one factor with the greatest influence on patency rates: adherence to sound and well-established microvascular technique principles. There is no proof that end-to end, end-to-side, running or interrupted, eversion or mattress, etc., has any superiority over other techniques in patency rates.

At the present time there are no adequate reliable data regarding use of sutureless techniques and their long-term outcomes in a clinical setting.

Other options have not been proven as benefits of a coupler device over other techniques.

 

4

A 39-year-old woman successfully undergoes immediate bilateral breast reconstruction with coverage with free deep inferior epigastric artery perforator free flaps. Postoperative flap monitoring is planned. Vascular compromise is most likely to occur during which of the following time periods postoperatively?

A) 0–1 days
B) 2–3 days
C) 4–5 days
D) 6–7 days
E) 8–9 days

The correct response is Option A.

Free flaps can be monitored by several different modalities in the postoperative period. The main reason for monitoring free flaps postoperatively is to detect vascular complications in a timely fashion, before permanent injury to the flap occurs, and to maximize the possibility of flap salvage. Reviews of large consecutive series of free flaps indicate that the most likely time period for a vascular compromise is early on, usually within the first 24 hours after successful transfer from the operating room. Therefore, postoperative monitoring protocols should be designed to closely follow flap perfusion during this period of time. Vascular events leading to issues with flap perfusion do occur at later times, but such events are generally infrequent and more difficult to salvage.

 

5

A 43-year-old woman is evaluated 6 hours after undergoing delayed breast reconstruction with deep inferior epigastric artery perforator flaps. On Doppler examination, arterial signals are present. Capillary refill time is 3 seconds on the right and 1 second on the left. A photograph is shown. Which of the following is the most appropriate management of the left breast?

A) Administration of systemic heparin
B) Administration of systemic tissue plasminogen activator
C) Application of leeches
D) Return to the operating room
E) Observation

Q image thumb

The correct response is Option D.

The most appropriate management is exploration of the left flap to assess anastomotic patency and pedicle orientation. This flap is hyperemic with brisk capillary refill and present arterial signals. These are all signs of venous insufficiency, and emergent exploration is indicated to assess the vascular pedicle for kinking or thrombosis. Application of leeches will drain excess blood from the flap but will not address the underlying problem. Observation is unacceptable because there are signs of venous insufficiency, and this requires urgent intervention. Systemic heparin will prevent further clot formation but will not dissolve an acute clot or resolve pedicle kinking. Systemic tissue plasminogen activator would greatly increase this patient’s risk of bleeding. This agent should only be used within a flap.

 

6

A 48-year-old woman is evaluated for immediate bilateral breast reconstruction using coverage with deep inferior epigastric artery perforator free flaps. Which of the following conditions is most likely to be associated with hypercoagulable state?

A) Celiac disease
B) Graves disease
C) Rheumatoid arthritis
D) Systemic lupus erythematosus
E) Type 1 diabetes mellitus

The correct response is Option D.

In some cases, patients with systemic lupus erythematosus (SLE) can develop antibodies against platelet membrane phospholipids, increasing adhesion and aggregation of platelets, and producing a state of hypercoagulability. Although not all patients with SLE will develop these antibodies, a history of SLE should raise concern when evaluating a patient for a free flap reconstruction.

All of the other options are autoimmune diseases, but none are typically associated with coagulopathies.

7

A 48-year-old woman had delayed microsurgical breast reconstruction. Two hours after surgery, the patient has swelling of the breast and increased drain output. On examination at the bedside, the flap appears purple with capillary refill time of 1 second. Heart rate is 70 bpm, blood pressure is 110/60 mmHg, and most recent hematocrit is 28%. An arterial signal is identified in the skin paddle with a handheld Doppler. Which of the following is the most appropriate next step in management?

A) Application of nitroglycerin paste
B) Operative reexploration
C) Pinprick of the flap
D) Placement of leeches
E) Streptokinase therapy

The correct response is Option B.

The patient described has venous insufficiency after microsurgery and the next step in management is emergent reexploration in the operating room.

Multiple studies confirm that earlier reexploration improves flap salvage rates. The rate of reexploration ranges from 6 to 14%; in these cases, the flap salvage rate ranges from 36 to 94%. Time of return to the operating room is associated with flap salvage. The majority of microvascular complications occur in the first 48 hours, and the majority of these complications are due to venous thrombosis. Common presenting signs include a purple or blue skin discoloration, brisk capillary refill, edema, oozing, or hematoma.

Release of sutures and pinprick of a flap and application of nitroglycerin paste can improve venous congestion in pedicled flaps, but do not obviate the need for reexploration in a microsurgical flap. Placement of leeches is a salvage option and often used when intraoperative maneuvers are unsuccessful. Streptokinase has been described for use in cases where a clot is found within the vascular system, but this should be reserved for use during reexploration, not before.

8

A 64-year-old man is evaluated 2 days after undergoing soft-tissue coverage of an open distal tibia fracture with a free rectus abdominis flap. On examination, the flap appears dark and swollen. Doppler signals are not present. The patient is brought to the operating room for reexploration, and thrombus is noted within the artery and vein. In addition to thrombectomy, which of the following is the most appropriate treatment to salvage this flap?

A) Aspirin
B) Intra-flap heparin
C) Intra-flap tissue plasminogen activator
D) Systemic dextran
E) Systemic urokinase

The correct response is Option C.

The most appropriate treatment in this patient is thrombectomy to restore flow within the artery and vein and administration of intra-flap tissue plasminogen activator (tPA) to dissolve clot formed within the flap.

Systemic urokinase will carry a high risk of bleeding from all surgical sites and is unlikely to dissolve clot in both the arterial and venous systems of the flap. Administration of intra-flap heparin will prevent further clot formation but will not dissolve the clot in the flap pedicle. Systemic dextran following thrombectomy might prevent clot formation and has mild thrombolytic properties, but it is not nearly as effective as tPA in lysing clot within the flap. Aspirin will potentially prevent further clot formation but has no thrombolytic properties and a slow onset of action.

 

9

A 154-lb (70-kg), 54-year-old man is evaluated because of oliguria and malaise 2 days after he underwent subtotal glossectomy with reconstruction with a free radial forearm flap. History includes chronic renal insufficiency (baseline creatinine concentration was 1.8 mg/dL and is now 3.3 mg/dL). After the procedure, administration of aspirin 81 mg by mouth daily and dextran 40 at 20 mL/hr was initiated. Temperature is 99.9°F (37.7°C), heart rate is 88 bpm, respiratory rate is 20/min, and blood pressure is 110/60 mmHg. On examination, the flap is pink and soft. Urine output is 15 mL/hr. Which of the following is the most appropriate management?

A) Administer a 500-mL bolus of Ringer's lactate
B) Administer a diuretic
C) Administer dopamine
D) Discontinue dextran
E) Return to the operating room for neck exploration

The correct response is Option D.

This patient is presenting with an uncommon but major complication of dextran administration, specifically acute renal failure, thought to be caused by either direct toxic effect on the tubules and glomeruli or intraluminal hyperviscosity. Surgeons who employ its use must be aware of this potential side effect as well as other serious side effects such as anaphylaxis, volume overload, pulmonary edema, cerebral edema, and platelet dysfunction. At-risk patients include those with a history of diabetes, renal insufficiency, or vascular disorders. It is recommended to avoid dextran in patients with chronic renal insufficiency for this reason.

This head and neck cancer patient also was on aspirin for anticoagulation. It should be noted that a prospective randomized study of dextran- and aspirin-related complications in 100 patients undergoing microsurgical flap reconstruction for head and neck malignancy demonstrated that aspirin and dextran were actually equally efficacious in preventing flap failure. However, despite this, it was demonstrated that patients on dextran had a 3.9- to 7.2-fold increased relative risk of systemic complications after 48 and 120 hours of dextran infusion, respectively. Given this, aspirin should be used over dextran if anticoagulation is desired.

A 500-mL bolus of Ringer’s lactate would not be warranted because it contains potassium, which would already be elevated in acute-on-chronic renal failure and would exacerbate the hyperkalemia.

Administration of a diuretic would not be warranted in this case because there is no evidence of fluid retention.

Low-dose dopamine is commonly administered to critically ill patients in the belief that it reduces risk of renal failure by increasing renal blood flow. This has never been definitely proven, however, in multiple trials. This patient has chronic renal insufficiency exacerbated by dextran administration. Low-dose dopamine has not been demonstrated to confer any benefit in this clinical scenario.

If a hematoma, arterial insufficiency, or venous congestion were suspected, returning to the operating room would be the next most appropriate step. As this is not the working diagnosis, this would be inappropriate.

 

10

A 53-year-old woman is evaluated in the recovery room during the first hour after microsurgical breast reconstruction with a free flap. On examination, the skin paddle appears bluish with a rapid capillary refill. There is a strong cutaneous arterial Doppler signal. Which of the following actions is most appropriate to increase the likelihood of flap salvage in this patient?

A ) Administration of systemic heparin
B ) Administration of systemic tissue plasminogen activator
C ) Application of a body warmer
D ) Application of leeches
E ) Emergent exploration

The correct response is Option E.

The patient has a venous thrombosis. The success of free tissue transfer is greater than 90% at most major microsurgical centers. Between 5 to 25% of free flaps require reexploration due to vessel compromise, as venous congestion is more common than arterial compromise. The flap salvage rate is influenced by the timing of reexploration across multiple studies. In one study, flaps that were reexplored within 5 hours had a higher flap salvage rate.

All studies point to early recognition of flap compromise as important and rapid reexploration as the most important factor to improve flap salvage. Administration of heparin, use of thrombolytics, and application of leeches will not increase the salvage rate in the scenario described. Increasing the patient’s temperature also does not improve flap salvage.

 

11

A 76-year-old man undergoes radical resection of the floor of the mouth and reconstruction with a free tissue transfer. Which of the following is an absolute contraindication for the use of the microvascular arterial anastomotic coupler?

A ) Age of the patient
B ) Atherosclerotic calcification
C ) History of radiation therapy
D ) Vessel-size mismatch

The correct response is Option B.

The mechanical device used most commonly in the clinical management of microvascular anastomoses is the coupler. It is used commonly in venous anastomoses, and some centers also use it in arterial anastomoses. The ring-pin technique involves passing each end of the vessels to be anastomosed through a ring that has matching sets of pins and holes. The vessel ends are then everted over the corresponding pins, and a device operated by a thumb nut then pushes the two rings together. Theoretically, this produces a "perfect" anastomosis, with total eversion of the edges and exact intima-to-intima contact. This instrument has been shown to provide rapid microvascular repairs in experienced hands, with published reports of 2 to 3 minutes per anastomosis.

Stiff, nonpliable vessels resulting from atherosclerotic calcification should not be anastomosed using the coupler system because the technique requires pliable vessels being draped over the pins. Stiff vessels will not allow for this, and a poor technical outcome will result.

There have been reports of successful end-to-end, as well as end-to-side, venous anastomoses performed with the coupler.

Age, by itself, has not been proven to be a contraindication to microvascular surgery and, therefore, coupler anastomoses.

History of radiation therapy is not a contraindication to microvascular surgery or to the use of the coupler system. However, the vessels should be inspected for radiation-induced fibrosis and stiffness of some vessels. If this is the case, akin to stiffness from atherosclerotic calcification, the coupler should not be used.

One of the benefits of the coupler lies in its ability to handle vessel-size mismatches, more so with venous than with arterial anastomoses.

 

12

A 64-year-old man undergoes radial forearm free muscle flap reconstruction of a hemiglossectomy defect from resection of a squamous cell carcinoma. The procedure is uneventful. During which of the following periods of time is microvascular thrombosis most likely to occur after reconstruction?

A ) Within the first day
B ) Between 1 and 2 days
C ) Between 3 and 4 days
D ) Between 5 and 7 days
E ) Between 8 and 14 days

The correct response is Option A.

The most common time for a microvascular thrombosis to occur during head and neck reconstruction is within 12 hours of completion of the anastomosis. Often, the thrombosis occurs intraoperatively or upon arrival in the postanesthesia care unit. Nearly 90% of all thromboses occur within 24 hours. Most commonly, thromboses occur as a result of technical issues. Microvascular thrombosis can occur in a delayed manner, even 7 to 14 days postoperatively. However, the rate of these events is much lower than the initial 24 hours.

13

A 34-year-old man is scheduled to undergo soft-tissue coverage with an anterolateral thigh free flap to treat a nonhealing, complex, traumatic wound involving the distal third of the left lower extremity. Which of the following is most likely to have the greatest effect on anastomotic patency? 

A ) Anastomotic type 

B ) Anticoagulation 

C ) Magnification equipment 

D ) Surgical skill 

E ) Suture technique

The correct response is Option D. 

Acland outlined five basic factors that influence anastomotic patency: (1) surgical precision, (2) size of the vessel, (3) blood flow, (4) tension, and (5) use of anticoagulation and antithrombotic medication. 

Studies have not demonstrated the efficacy of anticoagulation in improving microvascular patency rates and free flap survival. Studies evaluating types of anastomosis, including end-to-end and end-to-side, and those comparing suture techniques, including interrupted or running sutures, have also not demonstrated significant differences in patency rate. Both loupe magnification and an operating microscope can be successfully utilized in microsurgery. 

The skill and experience of the surgeon in using an atraumatic technique for the dissection and anastomosis of the vessels, assuring good vessel apposition, and avoiding tension, compression, or kinks in the vascular pedicle, remain the most critical factors in microsurgery. 

 

14

A 68-year-old woman undergoes partial glossectomy, resection of the anterior floor of the mouth, and bilateral modified radical neck dissection to treat squamous cell carcinoma in the ventral tongue and anterior floor of the mouth. The resulting defect is reconstructed with a 5 × 6-cm radial forearm free flap. The free flap is anastomosed to the left facial artery and left internal jugular vein. The forearm donor site is reconstructed with a split-thickness skin graft from the thigh. In addition to Current Procedural Terminology (CPT) code 15758 (free fascial flap with microvascular anastomosis), which of the following is most appropriate?

A ) 13152: Complex repair mouth 2.6 €“7.5 cm 

B ) 15100: Split thickness skin graft, arm; less than 100 cm2 

C ) 35761: Exploration of vessels without repair 

D ) 40840: Anterior vestibuloplasty

E ) 69990: Use of operating microscope

The correct response is Option B. 

Free flap procedure codes are global and include: 

1. Elevation of the flap 

2. Isolation of donor flap vessels used for microvascular anastomosis 

3. Transfer of the flap to the recipient site 

4. Isolation of the recipient vessels used for microvascular anastomosis 

5. Microvascular anastomosis of one artery 

6. Microvascular anastomosis of one or two veins 

7. Inset of the flap in the recipient site 

8. Primary closure of the donor site 

If a free flap procedure involves more than one of the above global components, it is appropriate to report these as added elements, as they are considered over and above the usual free flap procedure. These can include: 

1. Vein grafts 

2. Neurorrhaphy 

3. Nerve grafts 

4. Skin grafts €“ donor site or recipient site 

5. Closure of the donor site that is more extensive than primary closure 
6. Wound preparation of the recipient site 

Additionally, CPT 69990, use of the operating microscope, is also included with the free flap codes. It should not be coded separately. 

 

15

A 73-year-old man undergoes mandible reconstruction for squamous cell cancer. A microvascular thrombosis is most likely to occur within what period of time after the completion of the microvascular anastomosis?

A ) 0 to 24 Hours 

B ) 25 to 36 Hours 

C ) 37 to 48 Hours 

D ) 49 to 72 Hours

E ) 73 to 96 Hours 

 

The correct response is Option A. 

During head and neck reconstruction, a microvascular thrombosis is most likely to occur within 12 hours of completion of the anastomosis. The thrombosis often occurs intraoperatively or upon arrival in the postanesthesia care unit. Nearly 90% of all thromboses occur within 24 hours. Most commonly, thromboses occur as a result of technical issues. Microvascular thrombosis can occur in a delayed manner, even 7 to 14 days postoperatively; however, the rate of these events is much lower than during the initial 24 hours. 

 

16

A 47-year-old woman comes to the office for elective thinning of a free flap to the forearm 6 months after undergoing an uncomplicated sarcoma reconstruction. During the procedure, a vascular clamp retained from the initial procedure is uncovered. The clamp did not adversely affect the patient's outcome or the need for the present operation. Which of the following is the most appropriate course of action? 

A ) Inform the patient only, as risk management notification is not required because of lack of harm

B ) No action is required because there was no injury or deviation from standards

C ) Notify the risk management department and inform the patient 

D ) Notify the risk management department only, as patient notification is not required because of lack of harm 

 

The correct response is Option C. 

The incidents of retained foreign bodies after surgery are estimated to be between 1/8000 to 1/18,000 operations for a mid- to large-sized hospital that performs 10,000 cases per year. This would amount to approximately one case per year. 

The most commonly retained foreign body is a surgical sponge or laparotomy pad. The most common risk factors examined are emergency operation, unexpected change in the operation, more than one surgical team involved, change in nursing staff during the procedure, high BMI, volume of blood loss, female gender, and surgical counts. The most significant risk factors are emergency surgery, unplanned change in operation, and increased BMI. 

Cases of retained foreign bodies after surgical procedures often enter into the legal realm. Proof of negligence is not required when a foreign body is erroneously left in a patient. The doctrine of res ipsa loquitur, or €œthe thing speaks for itself, € applies when a foreign body is encountered that is asymptomatic. The most important aspect is communication with the patient. Often, open lines of communication can prevent these incidents from becoming legal malpractice cases. It is important to have communication with the hospital risk management officials as well. 

 

17

A 48-year-old woman underwent delayed right breast reconstruction with a DIEP flap in which the internal mammary vessels were used as the recipient vessels. One day after surgery, the skin paddle of the free flap appears congested and Doppler examination of the perforator shows diminished arterial signal. Emergent operative exploration shows that the venous pedicle is thrombosed. Local infusion of which of the following agents is most effective in reestablishing circulation?

A ) Dextran

B ) Heparin

C ) Lidocaine

D ) Milrinone

E ) Tissue plasminogen activator

The correct response is Option E.

Tissue plasminogen activator (TPA) catalyzes the conversion of plasminogen to plasmin. Unlike the other previously used thrombolytic agents, urokinase and streptokinase, TPA is more specific because its efficacy is enhanced by the presence of fibrin. In theory, this results in fewer bleeding complications than the less specific thrombolytic agents, which are no longer available in many hospital pharmacies.

Most large free flap series report that venous thrombosis is more commonly encountered than arterial compromise. Free flap monitoring is the most important aspect of free flap care with a low threshold for reexploration critical to the success of free flap salvage. Once thrombosis of a vascular pedicle is observed and the anastomosis taken down, thrombectomy followed by thrombolysis can often result in flap salvage.

Intravenous dextran and heparin have been used for platelet inhibition and anticoagulation to improve free flap patency rates. Heparin irrigation locally is used to prepare vessels for anastomosis. Lidocaine and papaverine are used locally to vasodilate vessels. Milrinone is a systemic vasodilator but has not been shown to improve free flap patency.

 

18

A 25-year €‘old man has shortness of breath one day after undergoing radical resection of dermatofibrosarcoma protuberans of the scalp. Surgical margins are clear, and the 15-cm-diameter defect was covered with a free latissimus flap. Heparin 2500 U was administered immediately after completion of microvascular anastomosis. The patient has been receiving Ringer €™s lactate 70 ml/hr, low-molecular-weight dextran 20 ml/hr, and aspirin 81 mg daily since the procedure. Temperature is 38 °C (100.4 °F). Pulse rate is 105 bpm. Respirations are 28/min. Blood pressure is 105/70 mmHg. Crackles are heard on auscultation of the chest. Radiographs of the chest show bilateral diffuse infiltrates. Which of the following is the most likely cause of the respiratory distress in this patient?

(A) Atelectasis

(B) Bacterial pneumonia

(C) Drug reaction

(D) Postoperative fluid overload

(E) Pulmonary metastasis

The correct response is Option C.

Systemic use of dextran, even in a low €‘molecular-weight form, has been shown to result in complications. The most serious of these is adult respiratory distress syndrome. This has been seen even in young patients and appears to be related to dose; however, it may occur even after a test dose. The etiology of this reaction and its specific mechanism are not understood completely, although this specific complication from systemic administration has been shown multiple times in the literature.

Atelectasis, despite being prevalent in the immediate postoperative period, usually presents in a bilateral basilar fashion rather than diffusely throughout the lung fields. Bacterial pneumonia usually does not present early or with bilateral diffuse pulmonary infiltrates. Postoperative fluid overload in an otherwise healthy 25-year-old patient receiving 70 ml/hr of intravenous fluids is extremely unlikely. Sarcomas usually do not metastasize.

 

19

A 16-year-old boy has right hemifacial hypoplasia secondary to radiation therapy of an orbital sarcoma when he was an infant. Right hemifacial soft-tissue augmentation with a partially buried omental free flap is performed. Photographs are shown. Which of the following is the most sensitive method of monitoring perfusion of this flap and detecting early anastomotic thrombosis?
(A) Clinical observation of the flap
(B) Bedside duplex ultrasonography of the gastroepiploic vessels
(C) Quantitative fluorometry of the flap with Wood’s lamp
(D) External Doppler probe monitoring of the gastroepiploic vessels
(E) Implantable Doppler monitoring of the gastroepiploic vein 
 

The correct response is Option E.


Buried free flaps and flaps without a cutaneous component can be difficult to monitor regarding postoperative flap perfusion. Early detection of anastomotic thrombosis is critical in successful salvage and revision of the failing free flap. Although color, temperature, and turgor can be used to monitor free flap perfusion, the omentum does not contain a skin paddle to help with clinical examination. An external handheld Doppler probe can identify arterial and venous signals, but correlation with the actual pedicle can be difficult to determine. Duplex ultrasound examination of the neck provides a great deal of information, such as direction of flow, alterations in flap resistance, and increased pedicle turbulence, but such imaging is not immediately available and requires the expertise of a vascular technologist. Injection with fluorescein and observation with a Wood=s lamp can assist with the qualitative assessment of flap perfusion if a skin paddle exists and can be monitored. Implantable venous Doppler monitoring will identify problems with both the arterial and venous pedicle.

A recent clinical report of 260 vascular microanastomoses with an implantable Doppler probe yielded six false-positive results and eight true-positive results. The overall free flap success rate was 99%; the reexploration rate was 8% and the salvage rate was 83%, partly due to the early detection of anastomotic thrombosis.

Doppler ultrasonography has been used to document changes in arterial blood flow after free tissue reconstruction in reconstruction of the head and neck. This modality can be helpful as an adjunctive tool in assessing flap perfusion but currently does not provide cost-efficient, continuous monitoring necessary to detect early anastomotic changes.

The photograph below shows the patient after successful reconstruction of hemifacial hypoplasia and after free tissue transfer of the omentum and secondary facelift and browlift, with intact facial nerve function.
 

A image thumb
20

Clinically proven effects of dextran include which of the following?

(A) Improved flap survival
(B) Increased systemic complications
(C) Ischemia reperfusion protection
(D) Leukopenia

The correct response is Option B.

Low-molecular-weight dextran is a polysaccharide produced by bacteria that is frequently used as an antithrombotic agent in microsurgical procedures. It is believed to have multiple actions, including decreasing platelet aggregation, increasing fibrin degradation, inhibiting alpha-2 plasmin, decreasing factor VII and von Willebrand factor and thereby altering platelet function, as well as acting as a volume expander. Anaphylactic reactions to this substance can occur, and many practitioners recommend administering a test dose of the hapten dextran one hour before starting infusion. However, severe reactions are uncommon and generally are noted early in its administration. Cases of pulmonary edema and acute respiratory distress syndrome have been reported. Some animal experiments and a few retrospective nonrandomized studies have shown improved patency rates of anastomoses in free flaps; however, conflicting data have resulted in a lack of consensus among microsurgeons. An overall increase in systemic complications (pulmonary, cardiac, anaphylactic) has been demonstrated with dextran compared with aspirin only. Improved flap survival, leukopenia, or ischemia reperfusion protection has not been demonstrated with dextran.
 

21

Which of the following is NOT a proposed mechanism of action of dextran used in microsurgery?

(A) Decreased factor VIII and von Willebrand factor
(B) Increased alpha-2 antiplasmin
(C) Increased electronegativity
(D) Structural modification of fibrin
(E) Volume expansion

The correct response is Option B.

Although the benefits of dextran 40 used during microsurgery are controversial, this agent is still used frequently. Dextran decreases factor VIII and von Willebrand factor, resulting in a decrease in platelet function. It is thought to increase the electronegativity of platelets in the endothelium, which prevents platelet aggregation, and is also thought to modify the structure of fibrin, increasing its susceptibility to degradation. It alters the rheologic properties of blood and acts as a volume expander.

Dextran inhibits, not increases, alpha-2 antiplasmin, leading to a subsequent activation of plasminogen.

Because dextran has the potential for antigenicity, a test dose of 20 mL of 150 mg/mL solution is typically administered one to two minutes before infusion.

 

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