**2.2 General conditions**

*Vascular Biology - Selection of Mechanisms and Clinical Applications*

where the primary closure of the wounds, the cure by secondary intention or the skin grafts were in the lower steps of this ladder and the flaps in the higher [4, 5]. With the improvement in optical tools, it became easier to perform the vascular

anastomoses that allowed free flap transfer and to set up skilled teams. As the tissue transfers became more dynamic and the microsurgery success rates rose, the benefits became more and more evident [5]. It was proven that the transfer of healthy tissues to the hand or head and neck allowed surgeons to achieve faster and better recoveries in areas of high functional demand, also with much more aesthetically acceptable results and lower morbidity. The same happened to breast surgery, where reconstructions with a natural shape and adequate volume could be achieved; the scars were hidden in the distance, and there was no need to use prosthesis. In lower limb osteomyelitis, free muscle flaps became the alternative to amputation. In addition, the advent of perforator flaps, mainly due to the contributions of Song and Koshima [5], thanks to whom it was not necessary to take the underlying muscle to transfer a fasciocutaneous flap, made it possible to further minimise the morbidity of these microsurgical interventions. Finally, a revision of the reconstructive ladder was proposed, the simplicity of the reconstruction would prevail, but pursuing the best aesthetic and functional results. So, a switch to a reconstructive elevator was made. In this way, microsurgical reconstructions became the first-line option for many patients and the technique was extended to a multitude of

Multiple aspects regarding the environment in the operating room and the position are particularly important in microsurgery. It is imperative to have enough field to allow an easy movement. This aspect, which is less substantial in *macro-*surgery, becomes absolutely fundamental in microsurgery. Mention it at the beginning, does

A two-team approach is usually chosen in reconstructive microsurgery, one will raise the flap and the other will set the recipient site where this is going to be transplanted [7]. Therefore, all the time spent planning disposition is properly invested. This is true both for placing the patient in the proper position, and for the surgeon to adopt a comfortable and durable posture. Since the surgery will be prolonged, we must meticulously paddle all bony prominences of the patient and the areas at risk of neurovascular compression. It must be encouraged to take all the necessary anaesthesia monitoring measures at the beginning, just to avoid emergencies or interruptions during delicate stages of surgery. It is also sensible to foresee how the

The comfort of the surgeon is a must when it comes the time to perform the microvascular anastomosis, primarily regarding the back, scapular and muscular groups. The sutures used usually size about 75–100 μm and the vessel lumen just a few millimetres; therefore, any tremor will greatly hinder the precision and success of the anastomoses. We cannot afford mistakes at any point of the microvascular anastomosis. The surgeon must be perpendicular disposition to the vessels and seated in a self-regulating chair that allows a self-sufficient height adjust. He or she should also be with the feet on a flat surface, the arms supported on a cloth and the hands on some comfortable place of the field to work only with the intrinsic

**204**

muscles of the hand [1].

centres [5, 6].

**2.1 Ergonomy**

**2. Basic principles in microsurgery**

nothing but tries to emphasise its relevance.

microscope will be arranged in the room.

After having invested enough time planning the operating room configuration, it is time to choose the vessels in the recipient area, since those of the flap are already determined and are assumed to be healthy because of their undamaged origin. It is essential to emphasise that the dissection must be very scrupulous, some groups advocate applying tension to the tissues around the vessel, without any direct pulling or forceps grasping on it, as not to generate any intimal traumas that may cause a thrombotic source [8, 9]. Any injury to the intima of the vessel, unnoticed or not, will expose the subendothelial collagen of the lumen, leading to a thrombotic focus. There are situations where it is impossible not to manipulate the vessel, as it happens in cervical dissections for oncological reasons; in these cases, a high incidence of thrombosis in the recipient vein has been demonstrated [6].

We must choose healthy vessels, without excessive fibrotic or irradiated tissue around them, this will allow us to perform a clean dissection, achieving a blood-less field. If blood accumulates in the field, we should spare no expense in abundantly rinse the area and review haemostasis. Blood has a red light refraction that deteriorates the sight with usual optical tools and releases procoagulant factors inducing vascular thrombosis [10, 11]. In limbs with previous surgeries or trauma, in case of doubt, we must carry out explorations such as angiography or Doppler, to check the availability of adequate vessels [12–15]. We should recruit as much vessel length as necessary to prevent any tension in the anastomosis, since the use of vein grafts, although may be needed, should be avoided due to its higher incidence of complications.

Before sectioning the donor artery to which we are going to transfer our flap, we must ensure that it has a good flow, we should ideally evince pulse [8]. Once sectioned, it will only be valid if we observe the exit of an abundant spurt of pulsatile blood. On the other hand, the vein that receives the blood from the flap in the recipient area must have at least the diameter that the vein of the flap has; otherwise, a bottleneck will form and prevent a good return and a venous congestion may develop in the flap.

Once the vessels in the receiving area are all set, we proceed to review the haemostasis and the perfusion of our previously dissected flap, then we release and transfer it [8, 10]. We should section the artery first and then the vein, as to avoid any congestion. Then we have to adapt the flap in the recipient area, since after anastomosis the flap will become edematised and its fixation in some deep spaces will be complex. This fixation is a mandatory prior step in all free flaps but in those in which the anastomosis lies in a deeper plane. In the head and neck reconstruction, small and intricate spaces make it advisable to do the fixation at first; but in breast reconstruction, we can only secure it with a gauze before microvascular anastomosis [6].

When performing the anastomosis, we prefer to adjust each vessel end in a simple microvascular clamp, tension-less approximate both ends and perform the microvascular anastomosis sparing as much proximal dissection as possible between the vessels of the flap pedicle and between the ones of the recipient area. On the other hand, we can place the anastomosis vessels end in a double microvascular clamp and approximate them [16]. The anastomosis should be placed on a rubber contrast and this over a wet gauze to avoid pooling and elevate the anastomosis from the surrounding field, full of thrombogenic debris [10] (**Figures 1** and **2**).

It is characteristic of the lumen of vessels to show a diameter smaller than that seen before severing them. This phenomenon is known as vasospasm. To mitigate it, we must perform a mechanical dilatation of the vessel lumen with specific dilator forceps and with agents such as lidocaine 1–2% or papaverine 3%, the latter being our preference [8–11]. Another dilatation technique is to abundantly rinse lumen with heparinised serum (200–300 IU/ml) [11–17]. It is key to remove the adventitia next to the anastomosis; we usually remove 2–3 mm with cutting technique, by pulling the adventitia over the lumen of the vessel and making a section parallel to the light. Aggressive adventitectomies leave the proximity of the anastamosis lacking *vasa vasorum*; this can cause ischemia in the vessel wall and, secondary to this, a failure or a pseudoaneurysm. On the other hand, the adventitia is highly thrombogenic, its entry with a knot into the lumen can be disastrous [18]. No technique completely removes the adventitia, but the sharp dissection seems more respectful with the intima [19]. Before carrying out the anastomosis, we must ensure that there are no intimal lesions in the lumen of the vessel, venous valves or branches, that may cause turbulence or resistance to flow in the vicinity of anastomosis [8].

There is debate about which anastomoses to perform first, whether arterial or venous. If there is no limitation for the position of a vessel deeper than another, as happens in breast reconstruction where the internal mammary vein usually has a more medial position, we can choose any one of them [6, 8]. Many groups choose to start with the arterial anastomosis to minimise isquemia time, taking into account that they do not usually experience added venous congestion. We usually start with the venous anastomosis to avoid any congestion within the flap that can cause a thrombus in its internal circuit. At the time of removing the clamps, once the anastomosis is completed, it is clearly preferable to remove the venous one first.

#### **Figure 1.**

*General overview of a microvascular anastomosis. Artery microvascular anastomosis is performed in a blood-less field after vein anastomosis (in a second plane), in a higher position over a rubber medium contrast and wet gauzes. A protected 5F Redon is usually placed under the anastomosis. Dissection of the vessels in each side of the anastomosis is limited, only simple vascular clamps are employed; this eases the one-side-up technique (see below). In this figure, the first two stitches of the triangulation technique are depicted.*

**207**

**2.3 Team**

*anastomosis.*

**Figure 2.**

The use of microsurgical techniques is not limited to reference centres with a high availability of resources, although their routine use is almost exclusive of these. This is due to the disposability of a microsurgical team with several surgeons

*Examples of the limited pedicle dissection before anastomosis. In the upper picture, we can see a free epigastric flap for an axillary free lymph node transfer. Marked with a star, we see the donor posterior circumflex humeral artery; below it, the inferior epigastric artery of the free flap is shown with both veins at each side. In the lower picture, we see the free flap before the transfer. Marked with a thunder, we see the inferior epigastric pedicle severed before its entrance in the abdominal rectus muscle; the inferior epigastirc vein is marked with a heart, it has been cut near its mouth in the circumflex iliac vein and laid prepared for the lymphovenous* 

In this kind of surgery, each mistake has its consequences. So, if we perform these interventions with a very scarce and inexperienced team, these day-long surgeries can be translated into fatigue, nerve-wrecking and inaccuracies. This

trained in microvascular anastomosis and free flaps management.

*Basic Principles in Microvascular Anastomosis and Free Tissue Transfer*

*DOI: http://dx.doi.org/10.5772/intechopen.91917*

*Basic Principles in Microvascular Anastomosis and Free Tissue Transfer DOI: http://dx.doi.org/10.5772/intechopen.91917*

#### **Figure 2.**

*Vascular Biology - Selection of Mechanisms and Clinical Applications*

(**Figures 1** and **2**).

of anastomosis [8].

the microvascular anastomosis sparing as much proximal dissection as possible between the vessels of the flap pedicle and between the ones of the recipient area. On the other hand, we can place the anastomosis vessels end in a double microvascular clamp and approximate them [16]. The anastomosis should be placed on a rubber contrast and this over a wet gauze to avoid pooling and elevate the anastomosis from the surrounding field, full of thrombogenic debris [10]

It is characteristic of the lumen of vessels to show a diameter smaller than that seen before severing them. This phenomenon is known as vasospasm. To mitigate it, we must perform a mechanical dilatation of the vessel lumen with specific dilator forceps and with agents such as lidocaine 1–2% or papaverine 3%, the latter being our preference [8–11]. Another dilatation technique is to abundantly rinse lumen with heparinised serum (200–300 IU/ml) [11–17]. It is key to remove the adventitia next to the anastomosis; we usually remove 2–3 mm with cutting technique, by pulling the adventitia over the lumen of the vessel and making a section parallel to the light. Aggressive adventitectomies leave the proximity of the anastamosis lacking *vasa vasorum*; this can cause ischemia in the vessel wall and, secondary to this, a failure or a pseudoaneurysm. On the other hand, the adventitia is highly thrombogenic, its entry with a knot into the lumen can be disastrous [18]. No technique completely removes the adventitia, but the sharp dissection seems more respectful with the intima [19]. Before carrying out the anastomosis, we must ensure that there are no intimal lesions in the lumen of the vessel, venous valves or branches, that may cause turbulence or resistance to flow in the vicinity

There is debate about which anastomoses to perform first, whether arterial or venous. If there is no limitation for the position of a vessel deeper than another, as happens in breast reconstruction where the internal mammary vein usually has a more medial position, we can choose any one of them [6, 8]. Many groups choose to start with the arterial anastomosis to minimise isquemia time, taking into account that they do not usually experience added venous congestion. We usually start with the venous anastomosis to avoid any congestion within the flap that can cause a thrombus in its internal circuit. At the time of removing the clamps, once the anastomosis is completed, it is clearly preferable to remove the venous one first.

*General overview of a microvascular anastomosis. Artery microvascular anastomosis is performed in a blood-less field after vein anastomosis (in a second plane), in a higher position over a rubber medium contrast and wet gauzes. A protected 5F Redon is usually placed under the anastomosis. Dissection of the vessels in each side of the anastomosis is limited, only simple vascular clamps are employed; this eases the one-side-up technique (see below). In this figure, the first two stitches of the triangulation technique are depicted.*

**206**

**Figure 1.**

*Examples of the limited pedicle dissection before anastomosis. In the upper picture, we can see a free epigastric flap for an axillary free lymph node transfer. Marked with a star, we see the donor posterior circumflex humeral artery; below it, the inferior epigastric artery of the free flap is shown with both veins at each side. In the lower picture, we see the free flap before the transfer. Marked with a thunder, we see the inferior epigastric pedicle severed before its entrance in the abdominal rectus muscle; the inferior epigastirc vein is marked with a heart, it has been cut near its mouth in the circumflex iliac vein and laid prepared for the lymphovenous anastomosis.*

#### **2.3 Team**

The use of microsurgical techniques is not limited to reference centres with a high availability of resources, although their routine use is almost exclusive of these. This is due to the disposability of a microsurgical team with several surgeons trained in microvascular anastomosis and free flaps management.

In this kind of surgery, each mistake has its consequences. So, if we perform these interventions with a very scarce and inexperienced team, these day-long surgeries can be translated into fatigue, nerve-wrecking and inaccuracies. This

ultimately will generate failures in the microvascular anastomosis and problems in the perfusion of the flap. Therefore, having a team that allows pauses and relays, without stopping the procedure, is a fundamental element. Likewise, this second fresh team will overcome emergencies (more frequent in the first 48–72 h) or can replace a tired first team. It seems sensible to have at least four microsurgeons, two assistants and two experienced scrub nurses [20].

A microsurgical team must function as a unit that critically analyses its results, seeking rates of failure lower than 5% in free flaps. Errors and the morbidity of the interventions must be analysed, minimising both. This constant improvement is hard to achieve if several microsurgeons are not available.

### **3. Microsurgical tools and instruments**

#### **3.1 Tools**

Microsurgery results from adapting the visual inaccuracy of our naked eye, to the fine movements of our hands. Here is where magnification arises. This can be done by two optical tools: the microscope and the magnifying loupe. In both, good lighting is essential [21, 22].

Surgical microscopes occupy a large space in the operating room but allow a magnification of up to 40× with greater illumination. In addition, they have pedals to control zoom and focus with the feet. Smaller magnification of 6–12× is usually used for the preparation of the vessels, and then it is increased up to 20× before the microanastomosis. In addition, the microscope gives us a wide range of field and provides the same vision to the surgeon and the assistant, enhancing the collaboration between them [21].

On the other hand, loupes are very cost-effective and easily transportable visual systems. The most common magnification employed in microsurgery is between 2.5× and 4.5×. In skilled hands, microscope has not proved to be superior *versus* loupes in achieving high success rates in free tissue transfers [23].

There are two types of magnifying loupes, on the one hand the compound or Galilean loupes and on the other hand the prismatic. The former consist of two lenses in line, and offer less weight and cost, although their magnification (2.5×) and depth of field are lower. The latter use a prism inside to reach a longer path of light through the lenses, which allows greater magnification and field depth, although they can be darker, heavier, more expensive and fragile [22].

#### **3.2 Basic microsurgery instruments kit**

The microsurgical instruments have evolved from ophthalmology or jewellery material to extremely specific and precise tools [7]. The basic kit is not made up of too much surgical material. This material should ideally be antireflective and cylindrical to allow its sliding from the index to the middle fingers and facilitate the passage of the needle through the tissues using only the intrinsic musculature. The size of the material should be about 16 cm to facilitate its support in the first hand commissure. In the case of working in very small fields, as in the case of hand surgery, smaller material, about 8 cm, with flat surface may be useful. Nowadays the self-locking material has lost interest, the mere requisite is just to offer little resistance when grasping to preclude any fatigue of the thenar eminence with prolonged use [24].

The basic kit consists of two scissors, a needle holder and a jeweller forceps. One of the scissors should be curved and round tipped, to be useful to dissect.

**209**

*Basic Principles in Microvascular Anastomosis and Free Tissue Transfer*

Other pair should be straight and pointed to perform the adventitectomy and to cut sutures. These pointed scissors should not be used for tissue dissection, because of the possible vessel trauma that they would generate. The jeweller forceps must have a precise closure, with enough contact between surfaces at the tip, just to handle

Other instruments that can also be useful are an aspiration system, an irrigation system and a bipolar forceps identical to jeweller forceps but protected. Our preference is to prepare a fixed suction system in the corner of the field, and to avoid introducing traditional aspirators directly over the vessels. Usually we fix a 5F Redon drain in a corner of the field or under the rubber contrast and we keep it connected to soft aspiration, in such way that it rests distant from the area of the anastomosis but does not allow pooling. We also avoid the contact of celluloses or cotton gauzes

directly with the lumen of the vessel due to their thrombogenic properties.

For the lumen irrigation, we use a heparin solution with 200–250 IU/ml [11]. Washing the lumen of the vessel directly can hydrodissect the vessel wall, exposing the subintimal collagen. Therefore, we introduce a blunt-tipped lacrimal cannula into the lumen of the vessel before anastomosis to perform a gentle wash [17]. Likewise, we usually do an irrigation of the flap through the artery with 20 or 30 ml of heparin solution, prior to the transfer; this checks the correct flow in the vascular

This delicate material requires little but precise care. First of all, we should avoid falls during surgery or washing, as the tips of the material can be damaged. If this happens, the closure of the material would not be perfect and its functionality would be noticeably reduced. It is also necessary to avoid the tips of the material to be oriented towards the sides in the store box, since movements with the box closed

The material should preferably be washed by the scrub nurse or the surgeon himself, who is familiar with it and will be more careful with its handling. A final wash should be done with distilled water and dried with an air gun to prevent rust

During surgery, the material must always be clean and moist, so that the sutures do not adhere to its surface. Dirty material and damaged tips will cause problems

The most common sutures elected are the 9-0 on a 100-μm needle and the 10-0 on a 75-μm needle. Because of the ease of knotting and the low tissue reaction, the most used material in sutures is nylon. Some authors prefer polypropylene due to a

There is no stipulated standard on how to perform a microvascular anastomosis,

the choice of the specific technique is operator-dependent. However, there are certain issues that we must avoid: a narrowing of the vascular lumen, an irregular distribution of the diameters of the vessels that would generate folds and irregularities, an excessive suture material inside the vascular lumen, and above anything else transmural sutures that bite the posterior wall closing the vascular lumen [24].

with the suture technique at key moments of the intervention.

lower tissue reaction, but its knots may be less reliable.

**4. Microsurgery techniques**

*DOI: http://dx.doi.org/10.5772/intechopen.91917*

fine sutures of 75 or 100 μm.

circuit of the flap.

formation.

**3.4 Sutures**

**3.3 Instruments care**

could also damage the tips inadvertently.

*Basic Principles in Microvascular Anastomosis and Free Tissue Transfer DOI: http://dx.doi.org/10.5772/intechopen.91917*

Other pair should be straight and pointed to perform the adventitectomy and to cut sutures. These pointed scissors should not be used for tissue dissection, because of the possible vessel trauma that they would generate. The jeweller forceps must have a precise closure, with enough contact between surfaces at the tip, just to handle fine sutures of 75 or 100 μm.

Other instruments that can also be useful are an aspiration system, an irrigation system and a bipolar forceps identical to jeweller forceps but protected. Our preference is to prepare a fixed suction system in the corner of the field, and to avoid introducing traditional aspirators directly over the vessels. Usually we fix a 5F Redon drain in a corner of the field or under the rubber contrast and we keep it connected to soft aspiration, in such way that it rests distant from the area of the anastomosis but does not allow pooling. We also avoid the contact of celluloses or cotton gauzes directly with the lumen of the vessel due to their thrombogenic properties.

For the lumen irrigation, we use a heparin solution with 200–250 IU/ml [11]. Washing the lumen of the vessel directly can hydrodissect the vessel wall, exposing the subintimal collagen. Therefore, we introduce a blunt-tipped lacrimal cannula into the lumen of the vessel before anastomosis to perform a gentle wash [17]. Likewise, we usually do an irrigation of the flap through the artery with 20 or 30 ml of heparin solution, prior to the transfer; this checks the correct flow in the vascular circuit of the flap.

#### **3.3 Instruments care**

*Vascular Biology - Selection of Mechanisms and Clinical Applications*

assistants and two experienced scrub nurses [20].

**3. Microsurgical tools and instruments**

**3.1 Tools**

lighting is essential [21, 22].

tion between them [21].

**3.2 Basic microsurgery instruments kit**

hard to achieve if several microsurgeons are not available.

ultimately will generate failures in the microvascular anastomosis and problems in the perfusion of the flap. Therefore, having a team that allows pauses and relays, without stopping the procedure, is a fundamental element. Likewise, this second fresh team will overcome emergencies (more frequent in the first 48–72 h) or can replace a tired first team. It seems sensible to have at least four microsurgeons, two

A microsurgical team must function as a unit that critically analyses its results, seeking rates of failure lower than 5% in free flaps. Errors and the morbidity of the interventions must be analysed, minimising both. This constant improvement is

Microsurgery results from adapting the visual inaccuracy of our naked eye, to the fine movements of our hands. Here is where magnification arises. This can be done by two optical tools: the microscope and the magnifying loupe. In both, good

Surgical microscopes occupy a large space in the operating room but allow a magnification of up to 40× with greater illumination. In addition, they have pedals to control zoom and focus with the feet. Smaller magnification of 6–12× is usually used for the preparation of the vessels, and then it is increased up to 20× before the microanastomosis. In addition, the microscope gives us a wide range of field and provides the same vision to the surgeon and the assistant, enhancing the collabora-

On the other hand, loupes are very cost-effective and easily transportable visual systems. The most common magnification employed in microsurgery is between 2.5× and 4.5×. In skilled hands, microscope has not proved to be superior *versus*

There are two types of magnifying loupes, on the one hand the compound or Galilean loupes and on the other hand the prismatic. The former consist of two lenses in line, and offer less weight and cost, although their magnification (2.5×) and depth of field are lower. The latter use a prism inside to reach a longer path of light through the lenses, which allows greater magnification and field depth,

The microsurgical instruments have evolved from ophthalmology or jewellery material to extremely specific and precise tools [7]. The basic kit is not made up of too much surgical material. This material should ideally be antireflective and cylindrical to allow its sliding from the index to the middle fingers and facilitate the passage of the needle through the tissues using only the intrinsic musculature. The size of the material should be about 16 cm to facilitate its support in the first hand commissure. In the case of working in very small fields, as in the case of hand surgery, smaller material, about 8 cm, with flat surface may be useful. Nowadays the self-locking material has lost interest, the mere requisite is just to offer little resistance when grasping to preclude any fatigue of the thenar eminence with

The basic kit consists of two scissors, a needle holder and a jeweller forceps. One of the scissors should be curved and round tipped, to be useful to dissect.

loupes in achieving high success rates in free tissue transfers [23].

although they can be darker, heavier, more expensive and fragile [22].

**208**

prolonged use [24].

This delicate material requires little but precise care. First of all, we should avoid falls during surgery or washing, as the tips of the material can be damaged. If this happens, the closure of the material would not be perfect and its functionality would be noticeably reduced. It is also necessary to avoid the tips of the material to be oriented towards the sides in the store box, since movements with the box closed could also damage the tips inadvertently.

The material should preferably be washed by the scrub nurse or the surgeon himself, who is familiar with it and will be more careful with its handling. A final wash should be done with distilled water and dried with an air gun to prevent rust formation.

During surgery, the material must always be clean and moist, so that the sutures do not adhere to its surface. Dirty material and damaged tips will cause problems with the suture technique at key moments of the intervention.

#### **3.4 Sutures**

The most common sutures elected are the 9-0 on a 100-μm needle and the 10-0 on a 75-μm needle. Because of the ease of knotting and the low tissue reaction, the most used material in sutures is nylon. Some authors prefer polypropylene due to a lower tissue reaction, but its knots may be less reliable.

#### **4. Microsurgery techniques**

There is no stipulated standard on how to perform a microvascular anastomosis, the choice of the specific technique is operator-dependent. However, there are certain issues that we must avoid: a narrowing of the vascular lumen, an irregular distribution of the diameters of the vessels that would generate folds and irregularities, an excessive suture material inside the vascular lumen, and above anything else transmural sutures that bite the posterior wall closing the vascular lumen [24].
