Microsurgery Flashcards
A 54-year-old woman undergoes breast reconstruction using a deep inferior epigastric artery perforator (DIEP) flap. Arterial thrombosis is noted after performing the microanastomosis. Which of the following is more likely to occur with local administration of tissue plasminogen activator (tPA) as an adjunct to revision microanastomosis as compared with revision microanastomosis alone (without tPA)?
A) Decreased flap salvage rate
B) Decreased incidence of fat necrosis
C) Increased flap salvage rate
D) Increased incidence of fat necrosis
E) Increased incidence of operative hematoma
The correct response is Option B.
Administration of tissue plasminogen activator (tPA) during revision of a microanastomosis has a decreased rate of subsequent fat necrosis. The suspected mechanism of action is thrombolysis of distant “shower” emboli in the microvasculature.
The administration of tPA as an adjunct to microanastomotic revision has no effect on flap salvage rates. In addition, there is no change in hematoma risk since the dose is low (2 mg) and is usually injected directly into the flap artery, which is maintained locally in the flap. Only if larger doses of tPA were given systemically would there be a risk of operative hematoma.
2018
An 18-year-old man is brought to the emergency department for thumb replantation. After an uneventful microsurgical anastomosis of the digital arteries and veins, papaverine is applied to the vessels. This medication works as a vasodilator through which of the following mechanisms?
A) Blocking calcium channels
B) Decreasing platelet aggregation
C) Inactivating thrombin and factor Xa
D) Inhibiting glycoprotein IIb/IIIa
E) Inhibiting phosphodiesterase
The correct response is Option E.
Papaverine is a phosphodiesterase inhibitor and is a commonly used vasodilating agent in microsurgery. It is administered as a liquid, directly to the adventitia of blood arteries, leading to vasodilation. The proposed mechanism of action of papaverine is by induced increase in cyclic adenosine monophosphate (AMP) levels, causing smooth muscle relaxation in the vessels. It is this mechanism of papaverine that has also led to its use for treatment of cardiac and neurovascular vasospasm.
Nifedipine is another common topical vasodilator, which is a calcium channel blocker. The remaining choices are all used to prevent clotting. Glycoprotein IIb/IIIa inhibitors are antiplatelet agents along with aspirin. Heparin inactivates thrombin and factor Xa through an antithrombin dependent mechanism.
2018
A 42-year-old woman presents with a Gustilo Type IIIB open tibial fracture with a large area of soft-tissue loss. Rectus abdominis free flap reconstruction is planned. CT angiography shows a patent posterior tibial artery; however, the peroneal and anterior tibial vessels are not suitable for use because they do not traverse past the level of the fracture. Compared with end-to-end anastomosis, which of the following is the main advantage to using end-to-side arterial anastomosis in this scenario?
A) Allows anastomosis in zone of injury
B) Decreases ischemia time
C) Facilitates visualization
D) Minimizes kinking of vessels
E) Preserves distal blood supply
The correct response is Option E.
In this clinical scenario, the patient has a one-vessel runoff in the lower extremity. Preservation of the distal blood supply is critical and that is the main advantage of an end-to-side anastomosis.
In general, an end-to-side anastomosis is more technically difficult with longer ischemia time. Kinking of the vessels is still possible with end-to-side anastomosis and therefore is not a major advantage to this technique. There is no added benefit in visualizing the vessel and it is generally more difficult to see the entire vessel compared to an end-to-end anastomosis. This technique does not preferentially allow for an anastomosis in the zone of injury.
Finally, it is controversial whether or not the flap survival rate is different between end-to-side and end-to-end anastomosis. An early paper by Godina shows an advantage for end-to-side; however, many subsequent papers have contradicted these results.
2018
A 50-year-old woman undergoes reconstruction of a postburn neck contracture with a free anterolateral thigh flap. On postoperative day 2, the flap is explored for vascular compromise and is successfully salvaged. On postoperative day 3, the flap suffers vascular compromise and is explored again. During the operation, the anastomoses are revised using vein grafts. Which of the following factors is most strongly associated with unsuccessful flap salvage in this patient?
A) Anatomic site
B) Multiple reexplorations
C) No use of anticoagulants
D) No use of thrombolytic agents
E) Postoperative day of initial reexploration
The correct response is Option B.
The need for multiple reexplorations has been found to be a predictor for unsuccessful free flap salvage.
Free flap reconstruction of the breast has been associated with higher flap survival rates than other anatomic areas, such as the head and neck and extremities.
Higher free flap survival rates have been observed when vascular compromise occurs earlier in the postoperative period (postoperative days 0 to 2) compared with later.
Anticoagulants, such as heparin, are sometimes used during free flap salvage attempts. However, their use has not been found to impact flap survivability. The same has been found with regard to thrombolytic agents, such as tissue plasminogen activator.
2018
A 48-year-old woman undergoes delayed reconstruction of the right breast with a deep inferior epigastric artery perforator (DIEP) flap. Medical history includes failed tissue expander–based right breast reconstruction because of infection 5 months ago. On postoperative day 5, the patient comes to the emergency department with a swollen, purple flap, which she noticed after showering. The venous anastomosis is revised and flap thrombolysis is performed with tissue plasminogen activator, successfully restoring flap perfusion. Which of the following clinical factors is LEAST likely to increase this patient’s risk of thrombotic flap complications?
A) Antiphospholipid syndrome
B) Antithrombin deficiency
C) BRCA1 or BRCA2 genetic mutation
D) Factor V Leiden mutation
E) Perioperative tamoxifen therapy
The correct response is Option C.
This patient has developed a late venous thrombosis and may be predisposed to a hypercoagulable state. The BRCA1 and BRCA2 genes are tumor suppressor genes involved in DNA repair. Mutations in these genes dramatically increase a woman’s risk of developing breast and ovarian cancer over her lifetime, and are the most common cause of hereditary forms of breast and ovarian cancer. But BRCA genetic mutations do not appear to increase the risk of blood clots over baseline and would be unlikely to contribute to this patient’s condition.
The other options are incorrect because each carries higher than average risk of blood clots. Perioperative tamoxifen therapy increases the risk of thromboembolic events in general and for flap complications and flap loss during microvascular breast reconstruction in particular. Tamoxifen is an estrogen receptor antagonist and is used both to treat and prevent breast cancer. Some authors recommend cessation of tamoxifen at least 14 days prior to microvascular breast reconstruction to minimize thrombosis risk.
Factor V is a protein involved in the coagulation cascade. Factor V Leiden mutation is an inherited condition that confers a hypercoagulable state, increasing the risk of thrombotic complications.
Antithrombin III is a protein similarly involved in anticoagulation. Deficiency may be either inherited or acquired, and it confers an increased risk of venous thrombotic events.
Antiphospholipid syndrome is an acquired autoimmune disorder which also confers a hypercoagulable state. Venous or arterial thrombosis, as well as fetal loss, are characteristic of this disorder. Some patients will have an associated autoimmune disease, such as systemic lupus erythematosus.
2018
A 55-year-old man with a history of squamous cell carcinoma undergoes glossectomy and reconstruction with a free radial forearm flap. Intraoperatively, the patient experiences hypotension, and norepinephrine is administered. Which of the following is the most likely effect of this treatment on the outcome of the free flap?
A) Delayed wound healing
B) Microvascular thrombosis
C) Partial flap loss
D) Total flap loss
E) No effect
The correct response is Option E.
In patients undergoing free flap reconstruction, the use of vasopressors is typically avoided when possible because of concerns that vasoconstriction of the anastomoses will result in microvascular thrombosis. When feasible, intravenous fluid administration should be attempted first to address hypotension. However, numerous studies have examined the effect of intraoperative vasopressors on free flap reconstructions and have generally not found an increased risk of postoperative complications.
2017
A 72-year-old man undergoes composite mandibular resection followed by fibula osteocutaneous free flap reconstruction. Patient history includes squamous cell carcinoma of the oropharynx. The morning after surgery, ischemic compromise of the flap is noted. Urgent exploration of the microvascular anastomosis is performed. Which of the following causes of flap compromise is most likely to result in failure of salvage attempts?
A) Arterial thrombosis
B) Hematoma
C) Pedicle kinking
D) Venous thrombosis
The correct response is Option A.
Arterial thrombosis is associated with lower flap salvage rates than venous thrombosis or mechanical causes. Bui et al. demonstrated salvage rates of 40%, 71%, and 90% for arterial thrombosis, venous thrombosis, or hematoma, respectively. Selber et al. demonstrated a similar tendency toward flap failure after arterial thrombosis. They also documented a 92% flap salvage rate for mechanical causes of ischemia, compared with 64.9% for vessel thrombosis. Mechanical or extrinsic causes of flap ischemia are generally easy to correct and are less likely to be associated with vessel injury. It is postulated that arterial thrombosis is more likely to be associated with endothelial injury than venous thrombosis.
2017
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.
2016
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.
2016
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.
2015
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.
2015
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
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.
2015
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.
2015
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.
2014
A 69-year-old woman with breast cancer undergoes bilateral breast reconstruction using free deep inferior epigastric perforator (DIEP) flaps. During surgery, she has onset of hypotension that is unresponsive to standard crystalloid and colloid solutions. The anesthesia team elects to administer norepinephrine to correct her blood pressure. Which of the following flap-related outcomes is most likely?
A) Flap loss
B) Hematoma
C) Reoperation
D) Wound dehiscence
E) No effect
The correct response is Option E.
There are no known increased flap complications with use of vasopressive medications. In fact, one study has shown decreased intraoperative flap complications compared with controls with the use of ephedrine. Traditional dogma is that vasopressors should be avoided during free tissue transfer due to concern that vasoconstriction or thrombosis could occur, resulting in compromised flap perfusion and subsequent flap loss. Most authors argue for standard intravenous fluid replacement or adjustment of anesthetic medications when feasible to first address the hypotension. However, numerous articles have suggested the safety of vasopressive medications in the setting of free tissue transfer. In fact, there are studies correlating excess intravenous fluid administration with increasing complication rates in free transverse rectus abdominis musculocutaneous (TRAM) flaps. As such, vasopressive medications should be considered when standard anti-hypotensive remedies have failed.
The original concern about vasoconstriction of the flap vessels with systemic vasopressor administration and resultant decreased perfusion or thrombosis has largely been disproven. This occurs likely because of sympathetic denervation due to flap transfer, sympathectomy with adventitial removal, and topical use of vasodilators, such as papaverine or nicardipine. Additionally, any vasoconstrictive effect on the flap vessels is more than overcome by increased flap perfusion caused by an elevated blood pressure.
2019
A 16-year-old boy develops a severe left first web space contracture 8 months after undergoing skin grafting for a soft-tissue avulsion injury. At the time of contracture release, a pedicled fasciocutaneous flap is planned for coverage of the soft-tissue defect. On the basis of the preoperative markings for the flap in the photographs shown, the flap pedicle is located between which of the following muscles?
A) Brachioradialis and extensor carpi radialis longus
B) Brachioradialis and flexor carpi radialis
C) Extensor digiti minimi and extensor carpi ulnaris
D) Extensor digiti minimi and the extensor digitorum communis
E) Extensor digitorum communis and extensor carpi radialis brevis
The correct response is Option C.
The photograph illustrates the markings for a reverse posterior interosseous artery (PIA) flap. The reverse PIA flap is a thin, pliable fasciocutaneous flap that can provide reliable coverage of soft-tissue defects involving the dorsal hand, metacarpophalangeal joints, and first web space. Some surgeons report success using this flap for coverage of palmar wounds and soft-tissue injuries of the thumb as well.
Perfusion of the flap is based on retrograde flow through the posterior interosseous artery, which sends septocutaneous perforators to the overlying skin. The axis of the flap can be marked corresponding to a line between the lateral epicondyle and the radial aspect of the ulnar styloid. The location of the posterior interosseous artery pedicle is between the extensor digiti minimi and the extensor carpi ulnaris. Retrograde perfusion through the flap relies on an intact communication of the PIA with the dorsal branch of the anterior interosseous artery, which is present in nearly all cases. This anastomosis is located 2 cm proximal to the radial aspect of the ulnar styloid; therefore, it corresponds to the pivot point of the flap. One of the advantages of this flap is that it does not require sacrifice of a major arterial source of blood to the hand.
The other responses do not correctly describe the location of the PIA. Of note, the interval between the brachioradialis and the flexor carpi radialis represents the location of the radial artery fasciocutaneous flap pedicle.
2021
A 20-year-old man undergoes harvest of the lower extremity free flap as shown in the photographs. A long length of bone is required for the reconstruction. With proximal dissection and osteotomy, which of the following nerves is at the highest risk for injury?
A) Common peroneal
B) Lateral femoral cutaneous
C) Saphenous
D) Sural
E) Tibial
The correct response is Option A.
The fibula is a long, thin triangular bone of the lower extremity. The fibula can be harvested as a free osseous or free osteoseptocutaneous flap with primary blood supply from the peroneal artery. Preservation of 4 to 6 cm of length proximally and 6 cm distally is important for the maintenance of stability of the knee and ankle. The peroneal nerve should be identified prior to proximal dissection as it wraps around the fibular neck. At this level, the nerve can be palpated and marked out to avoid injury during proximal dissection.
The common peroneal nerve arises from the sciatic nerve, running along the biceps femoris toward the posterior fibular head. It wraps around the proximal fibula at the neck, continuing laterally through a fibrous tunnel comprised of the aponeurosis of the peroneus longus, lateral gastrocnemius, and soleus muscles. Under the peroneus longus, the nerve branches into the superficial and deep branches; the superficial branch runs under the peroneus longus to innervate the peroneus longus and peroneus brevis, and it provides cutaneous sensation for the foot dorsum. The superficial peroneal nerve can be injured during anterior dissection for the skin paddle at the mid lower leg.
The deep peroneal nerve can be identified after deep dissection through the interosseus membrane into the anterior lower leg compartment. This nerve can be found between the extensor hallucis longus and extensor digitorum longus muscles. The deep peroneal nerve provides innervation to the muscles of the anterior compartment and sensation to the first web space.
The tibial nerve branches from the sciatic nerve, running through the popliteal fossa, sitting lateral to the neurovascular bundle, then proceeds deep to the gastrocnemius and soleus muscles. It then proceeds to run along the medial ankle posterior to the medial malleolus and provides sensory innervation to the plantar foot. Along its path, it provides innervation to the posterior compartments and intrinsic muscles.
The sural nerve is a sensory nerve, traditionally a confluence of the medial sural nerve from the tibial nerve and a lateral sural cutaneous nerve from the common peroneal nerve. The nerve is found superficial to the superficial posterior compartment in the posterior calf at the midline, lateral to the Achilles tendon; then it veers laterally in the ankle. This nerve provides sensation to the dorsolateral foot.
The saphenous nerve is the terminal sensory nerve of the femoral nerve; it perforates the femoral canal and becomes superficial and descends with the saphenous vein. It descends along the medial lower leg from the medial epicondyle region to the medial malleolus. Sensation is provided for the anteromedial lower leg. This nerve is unlikely to be injured in free fibula harvest given its medial leg location.
The lateral femoral cutaneous nerve arises from the posterior divisions of the L2 and L3 spinal nerves. The nerve usually exits from the lateral psoas muscle, heading towards the anterior superior iliac spine. It exits below the inguinal ligament and bifurcates. The sensory distribution is the skin of the anterolateral and lateral thigh. Given the proximal location, this nerve should not be in the region of dissection.
2021
