A Novel Minimally Occlusive Microvascular.33

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  SPECIAL TECHNIQUE APPLICATION A N OVEL  M INIMALLY  O CCLUSIVE  M ICROVASCULAR A NASTOMOSIS  T ECHNIQUE  U SING A  T EMPORARY I NTRALUMINAL  S HUNT : A P ROSPECTIVE  T ECHNIQUE TO M INIMIZE  B RAIN  I SCHEMIA  T IME DURING  S UPERFICIAL T EMPORAL  A RTERY - TO -M IDDLE  C EREBRAL  A RTERY  B YPASS Kartik G. Krishnan, M.D. Department of NeurologicalSurgery, Carl Gustav CarusUniversity Hospital,Dresden, Germany Papuna Tsirekidze, Cand.med. Department of NeurologicalSurgery, Carl Gustav CarusUniversity Hospital,Dresden, Germany Thomas Pinzer, M.D. Department of NeurologicalSurgery, Carl Gustav CarusUniversity Hospital,Dresden, Germany Gabriele Schackert, M.D.,Ph.D. Department of NeurologicalSurgery, Carl Gustav CarusUniversity Hospital,Dresden, Germany Reprint requests: Kartik G. Krishnan, M.D.,Department of NeurologicalSurgery, Carl Gustav CarusUniversity Hospital,Fetscherstraße 74,D-01307 Dresden, Germany.Email:Kartik.Krishnan@uniklinikum-dresden.de Received,  June 21, 2004. Accepted,  January 13, 2005. OBJECTIVE:  To describe a new technique of suturing microvessels with persistentperfusion via a temporary intraluminal microshunt. METHODS:  Experiments were conducted in Wistar rats. Abdominal aorta grafts wereexplanted from donor rats. A soft silicon microcatheter was introduced into the lumen of this graft. The abdominal aorta of a recipient rat was prepared for end-to-side microvas-cular anastomosis. Acland clamps (S&T AG, Neuhausen, Switzerland) were applied, anda linear arteriotomy was made. One end of the graft-clad microcatheter was introducedinto the lumen and occluded with a fenestrated Acland clamp. At a more distal part, asimilararteriotomywasperformed,andtheotherendofthemicrocatheterwasintroducedintothelumenandclampedwithafenestratedAclandclip.Thiscreatedatemporaryshuntthrough the graft-clad microcatheter. Then, the graft wasanastomosed to the arteriotomiesat both ends, over the microcatheter, in an end-to-side manner. The microcatheter wasexplantedfromthevessellumenthroughanarteriotomyinthemiddleofthegraft.Thegraftwasclippedshorttoclosethisarteriotomy.Themeantotalocclusiontimebeforeperfusionwas reestablished amounted to 3.7 minutes. This experiment was repeated in 12 animals(6withand6withoutheparin)withouttechnicalcomplications.Ascontrols,conventionalanastomoses were made in 2 animals. RESULTS:  Suturing microvessels mandates their occlusion during the period of anastomo-sis. Although ischemia is well tolerated by other tissue types, the brain is quite sensitive toeven short windows of ischemia. Nonocclusive anastomotic techniques have been devel-oped recently. These are confined to vessels with luminal diameters greater than 3 mm.We have evolved a novel technique that can be used with microvessels, as pertinent tosuperficial temporal artery-to-middle cerebral artery bypass. CONCLUSION:  We have described a new technique for performing microvascularanastomoses over a temporary intraluminal microcatheter shunt. KEY WORDS:  Intraluminal microvascular bypass, Microanastomosis, Temporary shunt Neurosurgery 57[ONS Suppl 1]:ONS-191–ONS-198, 2005   DOI: 10.1227/01.NEU.0000163605.15414.55 T he anastomosis of microvessels was firstdescribed by Harry Buncke in 1957 (9, 10,13). Its development was closely associ-ated with the advent of surgical optical magni-fication and the microminiature suture material(9, 11, 12). These were milestones in the devel-opment of replantation and transplantation sur-gery. Neurosurgical practice saw such a revolu-tion when Yas¸argil and Yonekawa (52) firstdescribedtheextracranial-intracranialmicrovas-cular anastomosis for treating ischemic strokesin 1967. For a variety of indications, the pre-ferred donor artery is the superficial temporalartery (STA), and the most frequently revascu-larized recipient vessel is the M3 segment of themiddle cerebral artery (MCA) (18, 20, 35, 38, 41,43, 52). Since its first description, this type of surgeryhasseenwaxingandwaningpopularity N EUROSURGERY   VOLUME 57 | OPERATIVE NEUROSURGERY 1 | JULY 2005 | ONS-191  and application (16, 24, 25, 30, 33, 38, 51, 53). Contemporarystandards encourage the surgeon to be highly selective in settingthe indication for an extracranial-to-intracranial (EC–IC) bypass,especiallyowingtothedangerofirreversiblecomplicationsfromoccluding the recipient brain artery during the time of anasto-mosis, among other pathophysiological reasons.Because the microvascular anastomotic technique was used pri-marily in replanting fingers and transplanting microvascular softtissue flaps that tolerate ischemia very well for hours (12, 14), therewere no concerns with regard to the occlusion of the microvesselsduring the period when the suturing was performed. However, brain tissue is known to be quite sensitive to the occlusion of mi-crovessels and resulting ischemia (24, 26, 27, 30). This is one of thereasons that the STA–MCA bypass technique still remains the do-main of few neurological surgeons trained in anastomosing mi-crovessels in a time-conserving and rapid manner.To avoid or prevent temporary cerebral artery occlusion foranastomosis, Tulleken et al. developed a novel technique of excimer laser-assisted nonocclusive anastomosis (8, 26, 27,45–47, 49). However, the excimer laser-assisted nonocclusiveanastomosis is suitable for arteries of a large caliber, such asthe intracranial internal carotid artery or the intracranial ca-rotid bifurcation, and seldom the M1 segment of the MCA.The literature resources available to us do not describe amicrovascular anastomosis of vessels less than 3 mm in diam-eter without occluding the vessels involved.We have evolved a new “minimally occlusive” microvascularanastomosis technique in the rat aorta model. This technique FIGURE 1.  The steps of minimally occlusive microvascular anastomosisin the rat aorta model.  Center , schematic representation of the abdominalaorta of the rat with the graft-clad microcatheter functioning as a tempo-rary intraluminal shunt in situ.  A , a soft silicon microcatheter is intro-duced into the graft;  B , a longitudinal arteriotomy is performed in the rataorta;  C , the microcatheter is introduced into the lumen of the aorta andthe occlusive clamp is replaced with a fenestrated Acland clamp, renderingthe temporary shunt functional;  D , the stay sutures are placed, and the graft is rotated 180 degrees to suture the back wall of the anastomosis first;  E , now the graft is rotated back to suture the front wall;  F , afterthe anastomosis is completed at the distal site, the catheter is withdrawnthrough an arteriotomy in the middle of the graft. *, notice the tip of themicrocatheter seen through the translucent wall of the graft as it isbeing withdrawn. K RISHNAN ET AL . ONS-192 | VOLUME 57 | OPERATIVE NEUROSURGERY 1 | JULY 2005 www.neurosurgery-online.com  seems to be simple and easily repeatable and may possibly findits application in STA–MCA bypass in the future. MATERIALS AND METHODS Animal Model Fourteen Wistar rats weighing 300 to 350 g were used forthe acute experimentation. Anesthesia was administered byencasing the animals in an NO-CO 2  gas mixture for 30 secondsand then intraperitoneal injection of a mixture of ketamine 10mg/ml plus xylazine 20 mg/ml (100:3; 10  g/g body weight).This provided anesthesia for the whole period of surgery, stillnot affecting the cardiac output or blood pressure. The abdom-inal aorta (measuring approximately 1.5–2 mm in diameter,roughly the same diameter as the M3 segment of the MCA)was used. After completion of the microvascular anastomoses,the animals were kept under anesthesia for 2 hours to checkpatency and notice any early thrombotic reactions. Thereafter,the animals were killed via exsanguination. Experimental Model and Technique The portion of the abdominal aorta spanning between themesenteric vessels and its bifurcation into the common iliacarteries was explanted from the donor rats. This was approxi-mately 3 cm in length. A soft and flexible silicon microcatheter(Elite/Boston Scientific, Natick, MA) was introduced into thelumen so that it appeared to be clad with the graft ( Fig. 1A ). Thiswas preserved in heparinized (six animals) or nonheparinized(six animals) Ringer solution until transplantation.In the recipient animal, the abdominal aorta was exposedand carefully dissected from the point of its mesenteric branches up to its bifurcation. The connective tissue layer andadventitia were cleared from the sites of the planned microa-nastomoses. Conventional Acland clamps (S&T AG, Neu- TABLE 1. Time required for performing the minimally occlusive microvascular anastomoses (interrupted microsuture technique)according to the described model a  Experimentno.Occlusion time (s)Total occlusion time (s)(without perfusion)Time required (min:s)ProximalarteriotomyDistalarteriotomyFor MOVAmicroanastomosisFor conventionalmicroanastomosis 1 124 120 260 26:18; 24:20 —2 100 100 228 20:15; 23:22 —3 100 80 200 22:24; 24:30 —4 110 90 220 24:05; 23:42 —5 100 100 220 22:40; 22:38 —6 104 96 218 24:30; 26:48 —7 95 95 202 23:15 a ; 20:30 b  —8 92 98 212 22:4 a ; 24:04 b  —9 100 98 218 20:18 a ; 21:14 b  —10 98 110 220 21:28 a ; 24:12 b  —11 108 100 215 20:24 a ; 22:20 b  —12 97 112 225 22:30 a ; 23:10 b  —13 c  — — — — 19:42 b, d  ; 21:55 b, d  14 c  — — — — 18:25 b, d  ; 19:48 b, d  Mean 103 s (1.7 min) 100 s (1.7 min) 220 s (3.7 min) 23:00 (min:s) 19:58 b, d  (min:s) a MOVA, minimally occlusive microvascular anastomosis. b  No heparin was used; clipping-to-clip removal time. c  Experiment was performed without using the intraluminal microshunt. d  Time required for anastomosis is equal to nonperfusion time in the conventional anastomosis; additional sutures, when necessary, were placed over the bleedingleakage sites without reclipping. M INIMALLY  O CCLUSIVE  M ICROVASCULAR  A NASTOMOSIS N EUROSURGERY   VOLUME 57 | OPERATIVE NEUROSURGERY 1 | JULY 2005 | ONS-193  hausen, Switzerland) were applied at the site of the proximalanastomosis. A longitudinal arteriotomy measuring approxi-mately 2.5 mm was performed between the clamps andflushed with heparinized (12 sites) or nonheparinized (16sites) Ringer solution ( Fig. 1B ). Then, one end of the graft-cladmicrocatheter was introduced into the proximal lumen of thearteriotomized aorta ( Fig. 1C ). A fenestrated Acland clamp(usually used for clamping tubules or vas deferens whilesuturing) was applied snugly around the proximal aorta con-taining the microcatheter in its lumen. Then, the same proce-dure was repeated at a more distal point of the aorta, wherethe distal anastomosis was planned. Occlusion and total non-perfusion were timed with a stopwatch. The mean time takenfor establishing the temporary intraluminal microshunt wasapproximately 4 minutes ( Table 1 ).Then, the end of the graft was slid over the microcatheter tothe proximal anastomotic site. Stay sutures were placed, firstat the heel of the graft, and then at the toes. Rotating the graft180 degrees, the back wall was sutured ( Fig. 1D ). Then, thegraft was rotated back, and the front wall was sutured ( Fig.1E ). The interrupted suturing technique was applied. Thedistal anastomosis was completed in the same manner (Ethi-lon 11-0 sutures; Ethicon, Inc., Somerville, NJ). Releasing thefenestrated clamps provided information on any sites of anas-tomotic leakage that needed hermetic closure.A longitudinal arteriotomy was performed in the middleportion of the graft. The microcatheter was carefully drawnout of the lumen through this orifice ( Fig. 1F ). Then, the graftwas clipped proximal and distal to the site of arteriotomy, andthe orifice was closed with running microsutures. The totalocclusion time for these maneuvers was approximately 4 min-utes. During this time, perfusion took place via the normalroute (through the aorta between the sites of anastomosis).In two more animals, conventional anastomoses, withoutthe use of the intraluminal shunt, were performed for com-parison. No heparin was used here. All the experiments wereconducted by the first author (KGK). RESULTS The described microanastomotic technique over a tempo-rary intraluminal shunt was reliably repeated in 12 recipientrats. The mean perfusionless occlusion time amounted to 220seconds (range, 200–260 s). The temporary shunt and micro-vascular anastomoses functioned adequately in all experi-ments. There were no shunt or graft occlusions during the next2 hours after anastomosis, whereupon the animals were killed(this was also the case in the group without administration of heparin). There were no technical complications in performingthe microvascular anastomoses or on introducing or with-drawing the microcatheter. DISCUSSION The invention of microminiature suture materials and surgicaloptical magnification opened a new era in surgery, namely mi-crovascular surgery (10–13, 15). Neurological surgeons properlyadopted this new development to treat ischemic diseases of the brain(20,36,43,52,53).TheSTA–MCAbypasscameintoregularuse, and many centers found themselves involved (5, 20, 23, 36,37,42,43,52,53).Theinitialupsurgeofcerebralrevascularizationwas short-lived, however, owing to several conceptual, patho-physiological, and technical reasons (4, 16, 33, 43, 51). Thus, thetrend toward STA–MCA bypass faded from the general neuro-surgical scene (2, 32, 47, 49). There are many concerns regardingcerebrovascular bypass surgery. Some of them are clinical con- FIGURE 2.  A , different calibers of microcatheters used for the minimallyocclusive microvascular anastomosis technique (Elite). These catheters are fashioned from silicon and are extremely soft and bendable. Thus ( B  and C ), they allow a parent-to-recipient vessel angle ranging from 20 to 85degrees in an end-to-side anastomosis. However, the resting angle amountsto approximately 40 degrees. The bendable mechanical property of thesecatheters might easily allow anastomoses at the M1 level at depth, espe-cially if a length of the parent vessel is also brought into the operatingarea and aligned to attain an approximately 40-degree resting angle. K RISHNAN ET AL . ONS-194 | VOLUME 57 | OPERATIVE NEUROSURGERY 1 | JULY 2005 www.neurosurgery-online.com
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