Laboratory Training in Microsurgical Techniques and Microvascular Anastomosis

Yasuhiro Yonekawa, MD, Rosmarie Frick, MD,* Peter Roth, MD, Ethan Taub, MD, and Hans-Georg Imhof, MD

It should never be forgotten that there is far more to microsurgery than the mere possession of a highly perfected optical instrument. Without bipolar coagulation, specialized instruments, and, above all, knowledge and skill in atraumatic microtechniques, the microscope alone is of little value. Perfection of atraumatic microsurgical technique is best acquired by operating on small-diameter blood vessels (0.8 mm to 1.5 mm) in animals. (MG Yasargil) Copyright �9 1999 by W.B. Saunders Company

M 'icrosurgery remained a specialized technique until the .early 1970s. It has since become an indispensable compo-

nent of practice, not only in neurosurgery, but also in most other surgical disciplines, including veterinary and experimen- tal medicine. Professor M. G. Yasargil, the pioneer of microneu- rosurgery and founder of the Zurich Microsurgery Course, recommended that trainees spend at least 3 months learning microsurgical techniques in the laboratory before proceeding to practical neurosurgery. 1 Unfortunately, this recommenda- tion has mostly been ignored. In connection with the general underestimation of the need for and importance of bypass surge D , and since the 1986 report of the International Cooperative Study, which cast doubt on its effectiveness in stroke prevention, training in the technique of microvascular anastomosis has been particularly neglected.2 In this article, laboratory training as it is provided in Zurich, will be presented as an illustration of systematic basic training in cIinical microsurgery, focusing on microvascular anastomoses for bypass surgery.

General Remarks

Microsurgery is not just surgery under the operating micro- scope. 29 To perform microsurgery correctly, exact knowledge of the operating microscope, microinstruments, suture materials, bipolar coagulator, armrest, and the operating table and stool is needed. They must be handled smoothly and effectively to take advantage of the magnification and good illumination, which in turn enable good discrimination. This knowledge, the basic experience needed in using these tools, and the associated new mode of hand-eye-brain coordination can be systematically acquired only in the laboratory (pioneered by Donaghy in 1958) 3 through practice of tissue and organ dissection. This

From the Department of Neurosurgery, University Hospital Zurich, Zurich, Switzerland.

*Instructor, Zurich Microsurgical Course. Address reprint requests to Prof. Y. Yonekawa, Department of Neurosur-

gery, University Hospital ZUrich, Frauenklinikstrasse 10, CH-8091 Zurich, Switzerland.

Copyright �9 1999 by W.B. Saunders Company 1092-440X/99/0203-0006510.00/0

training culminates in the performance of microvascular anas- tomosis on a vessel approximately 1 mm in diameter, which constitutes the main objective of laboratory training.

Attention must be given to posture, the optimal height of the operating table and stool, and the placement of the operating microscope; the locations of microinstruments, foot pedals for focusing, and the bipolar coagulator. Trainees must become accustomed to arranging all of these correctly.

Microsurgery should be performed in the upright position with both elbows held at right angles. A comfortable posture should be maintained so that long operations will be possible. Ideally, both the elbows and the wrists (at least) should be supported. For this purpose, the use of the armrest is most suitable.4, 5 As Dr. Acland said, "Without the arm rest, microsur- gery cannot be performed optimally." If no armrest is available, the elbows may be supported by holding their medial aspect close to the trunk. The "touching your hands technique ''6 recommended by Acland, in which unused fingers of both hands are touching while microsurgical maneuvers are per- formed, is an excellent technique for practice in the laboratory but is not always possible in the operating room.

The basic prerequisite for microsurgery is a restful and quiet atmosphere, both internally and externally. ~,7,8

Operating Microscope

Knowledge of the structure of the operating microscope is a prerequisite (Fig 1). The surgeon must know how to focus at optimal magnification manually or with pedals or mouthpiece. The standard combination of a 12.5X eyepiece and a 200-mm objective enables a range of magnifications from 4• to 25• selectable by turning the magnification knob (Table 1).

Binocular stereoscopic vision is crucial; the appropriate binocular distance and the appropriate positions of the 2 ocular lenses must be determined at the very beginning of training.

Grasping the microinstruments and bringing them into the operative field without deviating one's eyes from the micro- scope prevents waste of operative time as well as eye fatigue.

Getting accustomed to working in the center of the field of the operating microscope will bring many advantages, both for the trainee and for other members of the operative team, who will be able to follow the procedure on the video monitor.

Suturing Practice With Plastic Tubes

The instrument tray used for laboratory training of microsurgi- cal technique is shown in Fig 2.

In this segment of microsurgical training, trainees learn to handle the forceps, needleholders, and scissors. Trainees su-

Operative Techniques in Neurosurgery, Vol 2, No 3 (September), 1999: pp 149-158 1 4 9

Fig 1. Setting of the microsurgical laboratory training course using operating the Zeiss OPMi-1 microscope.

ture materials of braided 6-0 and monofilament 10-0 nylon, as well as plastic tubes used as simulated blood vessels.

The instruments should always be held in the same position as a pen or chopsticks. This position, with the wrists and the elbows supported, enables a steady, expedient movement of the instrument tip.

Trainees should be accustomed to loading up the needle with the needleholder two-thirds of the distance from the tip of the needle. The needle or suture should not be held too strongly, This will damage it. The same holds true for suturing with jeweler's forceps, it will damage or cut the suture. The vessel wall should not be held with the tips of the forceps. Before piercing the wall with the needle, both ends of the forceps should be inserted into the lumen to provide opposing pressure to the needle tip (Fig 3).

The bite of tissue from the edge of the anastomosis should measure about 3 times the width of the needle. This size of bite will not result in tears in the vessel wall or narrowing of the anastomosis.

Knots should be tied with 2 forceps or 1 forceps in the left hand and a needleholder in the right hand. Knots are tied by first making a loop with an end of suture, and then pulling the other end through the loop with the other forceps, as shown in Fig 4. Although doubling the single loop tie is standard, the double loop tie method ("surgical knot") is helpful to approxi- mate the separated ends of the vessels to be anastomosed. The sutures have to be tied in a direction perpendicular to the

TABLE 1. Magnification With the OPMi-1 Operation Microscope (Valid for Long Tubes, f = 160 mm)

Control Knob Setting Objective Lens (mm) 6 10 16 25 40 Eyepiece

200 3 5 8 13 20 300 2 3 5 8 13 10 • 400 1.5 2,5 4 6 10 200 4 6 10 16 25 300 2.5 4 6 10 16 12.5 x 400 2 3 5 8 13 200 5 8 13 20 32 300 3 5 8 13 20 16 • 400 2.5 4 6 10 16 200 6 10 16 25 40 300 4 6 10 16 25 20 x 400 3 5 8 13 2O

NOTE. Magnification obtained by combination of the eye piece and the objective piece.

suture line so that their tails cannot come into the lumen of the vessel and so they do not cross over each other. Tails of sutures should be cut optimally to 4 to 5 times the width of the needle or suture to keep the suture tails from crossing each other or entering the vessel lumen. The sutures should be evenly spaced.

The following procedures are to be performed on the plastic tubes: closure of longitudinal incision (arteriotomy), end-to- end anastomosis, and end-to-side anastomosis. Anastomoses are practiced with 6-0 sutures, and later with 10-0 sutures, on plastic tubes 3 mm and 1 mm in diameter, respectively.

Practice of Dissection in Live Animals

Microsurgical dissection can be practiced optimally only in live animals, both because injured vessels bleed only in vivo, and because only live tissues can be discriminated by their color and consistency in the normal way under magnification and good illumination.

The rat is anesthetized by the intraperitoneal injection of Hypnorm (Janssen Pharmaceutica, Beerse, Belgium) (fluani- sone and fentanyl) 1.0 mL&g followed by the additional intramuscular injection of small doses of Nembutal (Abbott Laboratories, North Chicago, IL) (pentobarbital) 50 mg/mL) 0.07 mL/100 g, if necessary.

Sharp dissection with scalpel and scissors is preferable to blunt dissection because it results in less traction, and, hence, less injury, to the neighboring tissues. Whatever damage oc- curs can be more easily repaired.

In a rat, the following dissections can be performed: (1) tracheal dissection followed by tracheotomy and intubadon with a plastic tube; (2) dissection of the carotid arteries and jugular veins after incising the skin and reflecting it as a flap; (3) dissection of the femoral arteries and veins after a skin incision in the inguinal region; and (4) dissection of the vena cava and aorta after midline laparotomy (Fig 4A).

At the completion of the exercise, the skin flap and incision are closed neatly with sutures. The animal is then killed with a lethal overdose of the anesthetic agent.

Carotid Artery Dissection

The carotid artery of the rat is approximately 1 m m in diameter, a suitable size for practice of microsurgical anastomo- sis (Fig 4). The flow in the vessel enables detection of leaks from the suture line and judgment of the patency of an anastomosis.

The carotid artery should be dissected over about I cm of its length without using the bipolar coagulator. A single coagula- tion of the feeding vessel of the sternocleidomastoid muscle may be necessary. The dissected muscle is pulled caudolater- ally with a sling of 3-0 silk suture or with a hook fashioned from a paper clip, as shown (Fig 4C). The omohyoid muscle is likewise pulled craniolaterally. During the dissection, and whenever the carotid artery is handled, it should not be held by its wall. Pinch only the adventitia or periadventitia, if neces- sary, Mild or minimal manipulation of vessels prevents mechani- cal spasm (which is observed more frequently at the time of dissection of the femoral artery) and wall injury. The vagus nerve should also be handled cautiously to prevent its reflex. Saline, warmed if possible, should be put on the operative field frequently to avoid desiccation. This will also alleviate vaso- spasm and keep the microcirculation in good condition.

1 5 0 YONEKAWA ET AL

Fig 2. Instrument tray for basic laboratory training: (1) 6-0 braided suture, (2) 10-0 monofi lament su- ture. (3) Disposable plas- tic syringe with a blunt needle mounted with a beveled end silastic tube. (4) Hemoclips. (5) Needle for skin suture, (6) Clip connector. (7) Coagulator forceps. (8) Jeweler's for- ceps No. 4. (9) Jeweler's forceps No. 0. (10) Micro- scissors, (11) Clip applica- tor. (12) Surgical forceps. (13) Needle holder for macrosurgery. (14) Re- tractors made of rubber bands and paper clips. (15) Scissors for macro- surgery. The micro-needle holder, razor blade, and ra- zor blade holder can be added to these.

End-to-End Anastomosis (Fig 3)

A rubber dam is inserted under the dissected carotid artery. This serves to isolate the artery from the neighboring tissue and prevent unintentional suturing or injury. The rubber dam is also used to obtain hemostasis at the suture line when it is rolled up and wrapped around the completed anastomosis. The rubber dam may be triangular in shape to facilitate insertion under the carotid artery.

The carotid artery is clipped with 2 hemostatic clips and divided midway between them. It is important to know that the vessel becomes shorter by approximately one-third after it is cut.

A silastic tube, with a beveled tip at one end and connected to a syringe at the other end, is inserted into each free lumen. The lumens are rinsed with saline to remove remaining blood. This could be more easily and effectively achieved with a fine, blunt needle, but the use of silastic tubing provides good training in the handling of delicate vascular walls.

As for the suturing technique pioneered by Jassinowsky, the golden rule in microvascular anastomosis is that sutures must pass through all the layers of the vessel wall, as originally stated by Carrel and later reiterated byJacobson. 9,1~

First, 2 interrupted sutures are placed on diagonally oppo- site sides of the anastomotic plane. One tail of each suture is cut long, so that they can function as stay or holding sutures. The double loop tie method may help approximate shrunken vessel ends.

To complete the anastomosis of a vessel 1 m m in diameter, 8 interrupted sutures around the anastomotic plane are both necessary and sufficient; 6 further sutures are required. The endothelial-intimal layers of both ends of the artery should be neatly approximated. The exposure of collagenous tissue to the lumen resulting from injury to the endothelial-intimal wall or other reasons will lead to thrombocyte aggregation and clot formation and, hence, to occlusion of the anastomosis. Strip- ping the adventitia or periadventitia at the end of the vessel to

be anastomosed may keep collagenous tissue out of the lumen and is therefore a useful, though not essential, maneuverJ 2

The next step is to insert a silastic tube about 5-ram long with a beveled tip into the vessels between the diagonal sutures. This tube serves as a stent to prevent inadvertent injury to the intima of the still-to-be-sutured opposite wall and to provide an overview of the suture line to allow the optimal placement of sutures at equal distance. The beveled tip enables easy insertion and removal from the lumen. This tubing tech- nique 13,14 may be omitted in suturing practice, but, in fact, we prefer to do it not only for practice, but also during clinical anastomosis. Incidentally, no significant endothelial injury resulting from the use of stents for anastomosis has ever been documented by electron microscopy.15

Three additional sutures are placed between the diagonal sutures on each side; first the front, and then the back. The middle suture of these 3 can be placed first and then 2 sutures on either side of it, between it and the diagonal sutures; or sutures can first be placed next to each diagonal suture and the middle suture placed last. The latter method has turned out to be especially useful and suitable for clinical end-to-side anasto- moses (Fig 5).

To expose the back side of the anastomotic line, the hemo- clips are turned over. If this maneuver is not enough, the rubber dam under the carotid artery may be manipulated to make the back side easier to expose.

Three sutures are placed on the back side in the same manner as on the front side. The silastic tube is removed before the last 1 or 2 sutures are tied.

The clips are now transiently opened to detect leakage from the suture line. The distal clip is opened first, in accordance with the rule that the vessel with the lower blood pressure is always unclipped first transiently. After waiting approximately 1 to 2 minutes for platelet aggregation and sealing of the suture line, the adequacy of the suturing may be judged. The distal clip is opened again. If bleeding is still evident, the distal clip

LABORATORY TRAINING IN MICROSURGICAL TECHNIQUE 151

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Fig 3. End-to-end anastomosis. (A) The first stitch and the method of tying it. Observe that the tips of the forceps within the vessel lumen provide counter- pressures while a bite is taken with the needle (cont'd).

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should be closed again and a suture placed at the bleeding site. Small amounts of bleeding after releasing both clips can be managed by wrapping the rubber dam around the anastomosis and gently compressing the suture line without occluding the vascular lumen. Wrapping prevents removal of sealing clot from the suture line and, hence, rebleeding.

We tend to recommend additional stitches if an obvious leak is observed from the suture line, although putting in too many stitches also results in occlusion of the anastomosis. The additional stitch prevents rebleeding or pseudoaneurysm forma- tion. In the clinical situation, these complications can be calamitous. We do not recommend the use of fibrin glue 16,17 for this purpose, either in the laboratory or in the operating room.

End-to-Side Anastomosis

End-to-side anastomosis has greater use than the end-to- end anastomosis, and mastery of this technique is, therefore, essential.

Jugular Vein Dissection

To practice end-to-side anastomosis, the jugular vein should be dissected next to the carotid artery. The vein is located subcutaneously, lateral to the sternocleidomastoid muscle. It is approximately 1 mm in diameter and should be dissected as far distally as possible so that about 1 cm of its length can be obtained. The distal end is ligated with 6-0 suture and cut. The cut end is brought to the carotid artery, already dissected as described earlier, with a rubber dam underneath. The sterno-

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cleidomastoid may have to be cut to prevent strangulation of the vein, which should be passed under it. The distal end of the jugular vein is clipped and rinsed with saline through a silastic tube, as described earlier.

An elliptical hole is made in the wall of the carotid artery to receive the anastomosis. This can be done by cutting the wall longitudinally with a razor blade and tailoring the cut with scissors or by pinching the wall and cutting out an elliptical piece, leaving a hole corresponding to the opening of the venous end.

A longitudinal incision is adequate for clinical use. The long diameter of the elliptical hole or the length of the arteriotomy should be between 1 and 1.5 mm. The lumen is rinsed, as mentioned earlier, to remove the remaining blood and clot. A silastic tube is inserted as a stent. A T-tube can be used if available.

First, diagonal sutures are placed at the distal and proximal ends; next, 3 to 4 interrupted sutures are placed on each side of the suture line (Fig 5), beginning with the front side. The stent is useful when making the bite to get the intima of the artery or vein.

The sutures are placed in the order shown in Fig 5 (i.e., from each diagonal end in alternation). When the front side is finished, the same procedure is carried out on the back side. As in the technique of end-to-end anastomosis, the back side is brought into view by turning the clips and manipulating the underlying rubber dam if necessary. The silastic tube should be removed before the last i or 2 sutures are tied.

The 3 clips are opened after the completion of the anastomo-

LABORATORY TRAINING IN MICROSURGICAL TECHNIQUE 153

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-ig 4. (A) Preparation of a rat on the operating table. The skin s shaved according to the site of operation: neck (the d o t t e d f ine indicates the appropriate skin incision), abdomen (the aorta and the vena cava are shown), and the inguinal region (the Femoral artery and its branch and the inferior epigastric artery ~re shown with their accompanying veins). (B) Anatomy of the rat in the region of the carotid artery and the jugular vein. 31 3uperficial muscles are removed to show the carotid artery Nith the vagus nerve, the jugular veins, and the trachea on the �9 ight side. (C) Dissection of the carotid artery ~), by retraction ~f the sternomastoid | inferolaterally, and the omohyoid �9 superolaterally. The jugular vein @ is located at the lateral margin of the sternomastoid muscle.

1 5 4 YONEKAWA ET AL

Fig 5, End-to-side anastomosis and an example of the order of stitches,

sis in the following order: first the clip on the jugular vein, then the clip on the distal carotid artery, and, finally, the clip on the proximal carotid artery. After each clip is removed, the suture line should be carefully checked for leaks. Excessive leakage is managed with an additional suture.

Checking for Patency

We refer here only to patency of the microsurgical anastomosis in the acute stage, namely within several hours after its completion. Patency of the anastomosis indicates that the proper technique has been used and that the trainee has made appropriate progress. The suture line should be checked first. There should be no stenosis. Every part of the vessel should

pulsate outward (expansile pulsation); pulsation should not push along the axis of the vessel (longitudinal pulsation). The latter indicates high-grade stenosis or occlusion. Wriggling (the alternating change in the curvature of a curved vessel that occurs with each pulse beat) also indicates patency. 6

There are several maneuvers or signs used to indicate patency, as mentioned earlier. A simple and reliable method is the so-called milking method or radical pressure test. 6,7,15 The vessel is occluded with a forceps at a point distal to the anastomosis. The blood is then squeezed from this point distally with a second forceps, and the segment of vessel is kept between the 2 forceps free of blood. The proximal forceps are then released to let blood flow into the empty segment. If the segment does not fill with blood instantly, the anastomosis is not functioning adequately (Fig 6).

If micro-Doppler sonography is available, there is no need to manipulate the vascular wall with forceps.

If the anastomosis does not function, a segment of vessel should be removed around the anastomosis and cut longitudi- nally across the suture line, and the suture line should be inspected from the inside. Thus, it can be determined which suture or other technical imperfection was responsible for the formation of the clot that led to occlusion of the anastomosis. Neither oblique anastomosis to widen the anastomotic plane nor stripping of adventitia to prevent collagenous fibers coming into the lumen has been reported to influence patency, 12 although the effectiveness of oblique anastomosis had been reported elsewhere. 18

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Fig 6. Method of checking patency: "milking"(see text).

LABORATORY TRAINING IN MICROSURGICAL TECHNIQUE 155

To proceed to clinical bypass surgery, 100% patency in the above-mentioned end-to-end and/or end-to-side anastomosis must be consistently obtained.

Further Training

There are many further topics for training in microvascular surgery: closure of arteriotomy, patch graft, interposition graft, bridge formation, anastomosis of 2 vessels of different diam- eters, venous anastomosis, experimental kidney transplanta- tion, experimental Eck's fistula, etc . 1'6"8'14'19'20'32

Mastery of the end-to-end and end-to-side anastomoses is, however, the essential core of training, of which the further topics mentioned can be considered applications. Venous anastomosis requires fewer stitches than arterial anastomosis (about 2/3 as many) because of slow flow. However, to obtain good patency, venous anastomosis requires far more painstak- ing technique than arterial anastomosis. 18,21,22

To proceed to the microvascular anastomosis of vessels approximately 0.5 mm in diameter, which is often necessary in direct vascularization procedures in children with moyamoya disease or syndrome, trainees may benefit from using the femoral artery and then the epigastric artery as training vessels.

To handle vessels of this size, 11-0 or 12-0 suture material and jeweler's forceps of size 3 or 4 are needed. Five to 6 interrupted sutures around the anastomotic line are necessary and sufficient. Irrigation and the stent technique are hardly possible. Cobbet's "eccentric biangulation suture ''3~ is worth knowing about and trying in arteries of this size, although it was originally used in vessels of 1.3 to 1.6 m m in diameter. At the beginning of the procedure, 2 stay sutures are placed eccentrically, not diagonally. This enables appropriate suture placement without insertion of a stent (Fig 7).

To practice the technique of microvascular bypass in a deep

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Fig 8. A trestle mounted on the usual training table with a prepared rat for microsurgical training,

surgical field, such as superficial temporal artery to superior cerebellar artery (STA-SCA) bypass or occipital artery to anterior inferior cerebellar artery (OA-AICA) bypass, the following should be noted:

1. A trestle of around 15 cm in height with a hole approxi- mately 4 cm in diameter is placed over the rat (Fig 8). The distance between the carotid artery and the edge of the hole should be around 6 cm to 10 cm.

2. Special long instruments are necessary (needle holder, forceps, scissors, razor blade holder).

3. The objective lens should be set at f = 270 m m to 300 mm so that these long instruments can be used to operate on the carotid artery and so that their other ends will not collide with the objective lens.

Bone drilling, one of the most important parts of microneu- rosurgery, is rather difficult to practice in the rat. It should be practiced in larger animals and in cadaver dissection. In the rat, it can be performed on the clivus, which is exposed by retraction of the intubated trachea.

Fig7.

156

/ Cobbet's eccentric biangulation suture (see text).

Operating Microscope

There are many different types of operating microscope in clinical use. The laboratory should possess a simple, primitive operating microscope adequate for training purposes. In our laboratory, the Zeiss prototype (OPMi-1) is still in use (Fig 1). Its simple structure makes it easy to handle and easy to maintain. The short length of its optical system is advanta- geous for trainees with a short arm span. This is particularly important for microsurgery in the sitting position.

Instruments

Needleholder. Some surgeons recommend using a forceps to hold the needle instead of a needleholder, as there is then no need to switch instruments between stitching and tying. We recommend the latter, especially in clinical use, because it

YONEKAWA ET AL

holds effectively and surely A needleholder with a magnetic tip turns out to be rather impractical, as the needle sticks to the holder. A needleholder with a lock might be useful for deep anastomoses, but is otherwise unnecessary. A round holder allows rotation of the tip of the holder while stitching; this is useful for both deep and superficial anastomoses.

Forceps. Jeweler's forceps (Jules Saumon) are indispensable for use in training as well as in clinical practice. The O forceps is standard for normal use, particularly for dissection and anastomosis. It is used for holding tissues, for blunt dissection when necessary (by opening the tips), for knot-tying, and sometimes as a needleholder. Finer Forceps (3-4) are used to handle vessels of diameter smaller than 1 ram.

Scissors. Straight-bladed or curved-bladed scissors are used, usually with straight arms. Their total length should be rather short so that their tips can function precisely. In the depth, a bayonet-shaped, long-armed scissors will be necessary.

Clips. Many types of clip have been used for the temporary occlusion of vessels to be anastomosed: the Khodadad clip, the Acland clip, the Scoville clip, the Yasargil clip, etc. The closing pressure of the temporary clip should be low enough not to injure the vessel wall, especially the endothelium. A simple hemoclip is adequate for training purposes.

Scalpel. The scalpel should cut well, and, therefore, dispos- able blades are used in clinical practice. In the laboratory, a razor blade suffices, as it is cheap and easily available. A blade holder is needed.

Fluids

Standard usage of suture material is: i1-0 for vessels of diameter 0.5 mm, 10-0 for 1.0 mm, 9-0 for 2 mm, and 8-0 for 3 mm.

Sponges

In the laboratory 0.5 cm • 0.5 cm squares of paper toweling or tiny cotton balls are used to clear the operative field.

Instruments usually not used in the laboratory, but indispens- able in some situations in the laboratory and in all clinical practice, include

1. Bipolar coagulator Jeweler's forceps are mounted to the connector and cable for handling of the vessels to be anastomosed. Tiny vessels connecting to the segment being prepared for anastomosis should be coagulated and cut. For this purpose, the optimal, delicate regulation of coagulating power is needed, and there should be no scar formation or sticking of tissues to the tips of the coagulating forceps.

2. Suction tube. We use suction tubes of various sizes and diameters. 4 The suction pressure is regulated by the circulat- ing nurse, who adjusts the suction apparatus at the end of the draining tube. This system helps the operator concen- trate on making the necessary fine movements with the suction tip, rather than having to change the force of suction himself by opening or occluding holes in the tube.

Although further discussion of the arm rest, stool, self- retaining retractor, etc., is not possible here, they are all of cardinal importance in practical neurosurgery.

Should saline be heparinized in the laboratory? The topical use of heparinized saline (1,000-2,500 IU/100 mL saline) is useful in obtaining patent anastomoses because of its anticoagulant effect and protective effect on the endothelium. 21-23 It has been reported to be particularly effective for microvenous anastomo- sis. In the laboratory, however, there is no need to rinse vascular lumens with heparinized saline, as the goal is techni- cal perfection. Magnesium sulfate (15% in saline) has been reported to be effective for the anastomosis of vessels of 0.5 mm diameter. 24 One percent procaine (lidocaine) has been used to reverse vasospasm, but the potent vasodilator papaver- ine has not been used for this purpose for fear of vascular wall injury because of its low pH. 21

Sutures

Continuous suturing can be taught to advanced trainees. It has little place in the technique of microvascular anastomosis 25 because it is technically difficult in clinical use and it restricts vascular dilatation. It may, however, be useful in the following situations: (1) closure of arteriotomy; and (2) when the vessels to be anastomosed are short and difficulty is expected with the suturing of the back side, trainees should suture the back side with a continuous suture, starting on the intimal side, and then proceed to the front side (one-way-up suturing method).6

During training, a single piece of 10-0 suture material can be used repeatedly, being cut after the placement of each suture. This procedure degrades the cutting ability of the needle, however, and the suture material will be inured by repeated pinching. Some surgeons prefer not to reuse 10-0 suture material for this reason. A straighter needle is appropriate for end-to-end anastomosis, a more curved one for end-to-side anastomosis.

Final Remarks

Approximately 4,000 physicians from various countries have completed the Zurich Microsurgery Course since its inception (3,500 up to the time of Professsor Yasargil's retirement in late 1992 and 500 since then). There has been a recent trend for surgeons from other disciplines to recognize the importance of this training, and they make up one-third of the participants. In neurosurgery itself, microvascular surgery is a prerequisite for almost all operations. Being able to repair a compromised major vessel with microvascular sutures enables the surgeon to operate more radically and with a better clinical outcome. The classic manual method of microvascular anastomosis has proved to be highly reliable and safe, although various nonsu- ture methods with the use of glue, absorbable splints, and CO2-YAG Laser have been tested and reported. 26-2s,33 Mastering the technique through laboratory training is thus not merely worthwhile, but indispensable for all neurosurgeons. Finally, it should be emphasized that such training on live small animals is both more fundamental, valuable, and more easily available than so-called hands-on microsurgical training on cadavers.

Conclusion

Laboratory training in microsurgery is a prerequisite for the performance of microsurgical operations in neurosurgery. Trainees should spend at least three months in the laboratory to become familiar with microsurgery technique before apply- ing it clinically. Some aspects of the Zurich Microsurgical Course, founded in 1967 by Professor Yasargil, have been presented here to show our approach to basic training in microsurgery and microvascular anastomosis.

LABORATORY TRAINING IN MICROSURGICAL TECHNIQUE 157

Acknowledgment Not to speak of my teacher Prof. Yasargil, I (YY) had the good fortune to see or assist the anastomosing techniques of Professors Acland, Donaghy, Reichman, and Peerless and the microsurgical technique of Professors Malis, Kurze, and Drake in the early 1970s. The techniques described here are largely owed to these pioneers.

We are indebted to Prof. Schmiedek and Dr. Spetzler for the opportunity to contribute to this issue. We are also thankful to Mrs. Schurter for secretarial assistance, Mr.Stillhard for the photography, and Dr. Adachi for his critical review.

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Stuttgart, New York, 1969 2. The EC-IC Bypass Study Group: Failure of extracranial-intracranial

arterial bypass to reduce the risk of ischemic stroke. Results of International Randomized Trial. N Eng J Med 313:1191-1200, 1985

3. Donaghy RMP: The history of microsurgery in neurosurgery. Chapter 27. Clin Neuro surg 26:619-625, 1979

4. Yasargil MG, Fox JL, Ray MW: The operative approach to aneurysms of the anterior communicating artery. Adv Tech Stand Neurosurg 2:113-170, 1975

5. Yonekawa Y, Yasargil MG: Extra-intracranial arterial anastomosis: Clinical technical aspects. Adv Tech Stand Neurosurg 3:45-78, 1976

6. Acland RD (ed): Practice Manual for Microvascular Surgery. Mosby, St. Louis, 1989

7. Buncke H J, Chater NL, Szabo Z (eds): The Manual of Microvascular Surgery. Davi es Medical Center, San Francisco, 1975

8. Mehdorn HM, ML)ller GH (eds): Mikrochirurgische Uebungen. Thieme, Stuttgart, 1987

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