A LAPAROSCOPIC MODEL OF MAJOR ARTERY INJURY FOR COMPARATIVE EVALUATION OF EFFECTIVENESS OF THE OPEN AND ENDOVASCULAR OPERATIONS FOR VASCULAR TRAUMA

A LAPAROSCOPIC MODEL OF MAJOR ARTERY INJURY FOR COMPARATIVE EVALUATION OF EFFECTIVENESS OF THE OPEN AND ENDOVASCULAR OPERATIONS FOR VASCULAR TRAUMA

Reva V.A., Samokhvalov I.M., Sokhranov M.V., Telitskiy S.Yu., Yudin A.B., Seleznev A.B., Denisov A.V., Adamenko V.N., Yablokov I.P.

Kirov Military Medical Academy,
State Scientific Research Testing Institute of Military Medicine,
Saint-Petersburg, Russia

Vascular trauma is one of the most challenging topics in the modern trauma surgery. The standard approach to treatment of arterial trauma is open surgery, but endovascular treatment is used more often in trauma, although the models for investigating such injuries are poorly described in the literature.
Objective – to develop an adequate experimental model of severe closed injury to the magistral artery presented as occlusive thrombosis of vascular lumen, with ability for evaluating effectiveness of open and endovascular procedures in acute phase of vascular trauma.
Materials and methods. Seven sheep weighting from 25 to 35 kg underwent acute experiments including multiple repeated clamping of the left external iliac artery (EIA) with a blunt injury to the EIA and achievement of the intraluminal thrombus formation. Thrombus achievement was controlled by means of angiography using a catheter placed through the animal’s carotid artery. Blood flow velocity parameters – peak systolic blood flow and pulsatility index – were measured with an ultrasound device.
Results. Six out of seven animals underwent successful operation with full traumatic occlusion of the EIA. One animal had its artery perforated during the repeated clamping process. The average time for making thrombosis was 55 (40–70) minutes. Formation of thrombosis was associated with significant reduction of both the measured parameters in the animals’ left posterior limbs compared to the right (uninjured) limbs.
Conclusion. The developed experimental model allows performing comparative studies of effectiveness of open and endovascular procedures in closed magistral arterial injures with a high level of reproducibility.

Key words: arterial trauma; trauma surgery; endovascular surgery; thrombosis; laparoscopy

Wounds and damages of the magistralveins of the extremities present one of the most complex problems in the modern trauma surgery, since they are accompanied by high risk of limb amputation and death. The standard technique for treating the damages of the magistral arteries is opened surgical intervention, but it requires extensive vascular approaches for proximal and distal control of bleeding with subsequent trauma and blood loss [1]. From other side, low invasive endovascular techniques have been becoming popular. They allow arresting the bleeding and/or restoring the blood flow in the extremity through the puncture in the femoral artery or the humeral/radial arteries [2, 3]. Despite of all advantages of the techniques of stenting and endoprosthetics (implantation of the stent-graft) for arteries, their use is still rare, particularly, because of some contraindications [3, 4].
One of the significant limitations of the magistral arteries stenting is a “fresh” thrombotic occlusion, which often results in a vascular damage [3]. Theoretically, the attempt for recanalization and placement of the stent with delivery system through the fresh occlusion can cause the distal bed embolization with small clots with undesired consequences in view of progressing ischemia. But the experimental and clinical studies are limited with single observations [5, 6].
The objective of the study – to develop an adequate experimental model of severe closed injury to the magistral artery presented as occlusive thrombosis of vascular lumen, with ability for evaluating effectiveness of open and endovascular procedures in acute phase of vascular trauma.

MATERIALS AND METHODS

The experimental studies included seven Edilbay sheep (female) with the body weight of 25-35 kg. The studies were conducted on the basis of State Scientific Research Testing Institute of Military Medicine (Saint-Petersburg) and complied with the requirements of the European Convention for the protection of vertebrate animals used for experimental and other scientific purposes (Stasbourg, 1986) and the Rules for Research with Use of Experimental Animals (the application for the Order of Health Ministry of USSR, August 12, 1977, No.755). The study protocol was approved by the ethical committee of Kirov Military Medical Academy, Saint Petersburg (No.163, June 30, 2015). The animals were not fed 24 hours before surgery, but they could drink water. Premedication included the intravascular introduction of Zoletil 100 (Virbac, France) with the dosage calculated according to the body mass, and subsequent tracheal intubation in the surgery room. Anesthesia was supported with shift to breathing with gas mixture with 2-4 % isoflurane. After supine positioning, the wool in the region of the neck and the abdomen was removed, and the surgical field was prepared.
The left carotid artery (CA) was exposed by means of the incision in the plane of the vascular bundle of the neck. The 6 Fr introducer was placed in the retrograde manner for arterial pressure monitoring and angiography. This introducer was also placed into the left jugular vein for supporting infusion therapy (Ringer solution or Sterofundin (B. Braun. Germany)) with drop infusion rate of 20 ml/h.
Thrombosis was modelled with use of laparoscopy and mobile endosurgical complex KST-EKh (EFA Medica, Saint Petersburg) with the basic set of the endosurgical tools. 10 mm port was introduced under the xyphoid process in the abdominal cavity (Hassen technique), and the carbon dioxide was pumped, with abdominal pressure maintenance at the level of 15 mm Hg. The second 10 mm port was introduced along the median line (more caudal direction) in the point of transection with the conventional line connecting the superior iliac spines. Two 5 mm ports for the manipulators were introduced inward from iliac spines on both sides (Fig. 1). The abdominal peritoneum was dissected in the region to the left from the urine bladder in Trandelenburg position on the right lateral position (Fig. 2a). The left superficial iliac artery was separated along the distance of 5-6 cm, with lateral deflection of the iliac femoral lymphatic node (Fig. 2b). For thrombosis modelling in the middle part of the artery (3 cm), we used the multiple application and removal of the laparoscopic dissector and/or cannula holder (Fig. 2c). The length of the 3 cm region was estimated according to angiography data with X-ray contrast line VascuTape® (LeMaitre Vascular Inc., USA). 30 minutes later, the clamps were removed from the injured part of the artery with use of the laparoscopic tools (Fig. 2d). In case of preserved pulsation in the external iliac artery (EIA) and its patency confirmed by angiography (Fig. 3a), the procedure was prolonged for 15 minutes and more – for achieving thrombosis. After termination of pulsation, the diagnostic angiography was conducted that confirmed the occlusive pattern of thrombosis (Fig. 3b).

Figure 1. General appearance of surgery with laparoscopic modelling of closed occlusive traumatic thrombosis in the left external iliac artery

Figure 2. The stages of laparoscopic surgery for modelling arterial thrombosis: a) separation of a region of the left external iliac artery (EIA) over the length of 5-6 cm; b) application of traumatic clamps to the targeted segment of EIA over the length of 3 cm

   

Figure 3. The angiographic picture of pelvic arteries of a sheep during surgery with modelling occlusive thrombosis: a) angiography during placing the clamp onto the left EIA; b) “stop-contrast” at the level of the clamp placement shows the successful achievement of thrombosis

   

The combination of 5 Fr catheter Simmons Sidewinder, the multi-targeted catheter brought through the introducer into CA, and 260 cm guide Emerald (all tools by Cordis Endovascular, USA) was used for trespassing the acute angle in the region where the brachiocephalic trunk deviates from the artery and for catheterization of the terminal part of the aorta. With their use, the multi-targeted diagnostic catheter 5 Fr was placed into the entrance of the left EIA with use of S-arch (SM-20HF, Listem Corporation, Southern Korea), and the set of images with the contrast media Scanluxe-300 (Sanchemia Pharmazeutika AG, Austria) was made. After acquisition of the picture of “stop-contrast’, we recorded the achievement of thrombosis, the laparoscopic tools were removed and abdominal desufflation was carried out. The animals were drawn from the experiment after termination of surgery by means of intrasurgical injection of concentrated potassium chloride.
The study protocol was conducted for each experiment, with recording the following data: morphometric findings, general information on surgery, time for achieving arterial thrombosis and amount of introduced drugs.
This study was conducted with the financial support from the Russian Scientific Fund as a part of the scientific project No.17-73-20318.

The end points of the study and statistical analysis methods

The primary end point was successful creation of thrombotic occlusion in the region of iatrogenic injury. Thrombosis was confirmed with combination of angiography and ultrasonic examination before beginning and in the end of the experiment. Ultrasonic examination was used for determination of the main characteristics of blood flow in the left (experimental) and right (control) superficial femoral artery (SFA) – peak systolic velocity (PSV) measured in cm/sec, and the pulsatility index (PI). These parameters were calculated automatically with the ultrasonic scanner S6 Pro (Sonoscape, China) on the basis of the received doppler spectrum (Fig. 4a, b).

Figure 4. Doppler spectrum in the left femoral artery (LFA) of the sheep during the experimental study with modelling arterial thrombosis in the left external iliac artery: a) background measurements before the intervention. A common three-phase spectrum of magistral blood flow is visible; b) the doppler curve after thrombosis modelling in the iliac artery. Reduced collateral blood flow  is  visible.

   

The secondary end points included the complications relating to laparoscopy and thrombosis modelling, development of contrast-induced nephropathy, ischemia-reperfusion syndrome. For laboratory confirmation of life-threatening complications, the venous blood was analyzed for estimation of urea, creatinine, lactate before and after the experiment. Also general blood analysis was conducted.
The findings were included into the records (the experimental protocols) and were combined in the Microsoft Excel (Microsoft, USA). The statistical analysis and graphing were performed with GraphPad Prism 6.0 (GraphPad Software Inc., USA) and IBM SPSS Statistics 21.0 (IBM, USA). The variables were tested for normalcy of distribution. If the normalcy criteria were unsatisfied, the findings were indicated as the median with pointing the interquartile range in the brackets. The intergroup ultrasonic parameters were compared with two-tailed Mann-Whitney test. During testing the statistical hypotheses, the critical level of significance (p) was 0.05.

RESULTS

Angiographic characteristics of the pelvis and the posterior extremities of the sheep

The results of native angiography allowed clarifying some general features of the pelvic arterial tree structure and the posterior (pelvic) extremities of the sheep. These features were required for vascular and endovascular operations. As a rule, there are two main types of branching in the terminal part of the abdominal aorta at the level of the lumbar vertebrae 3-4. In the first variant, the distal aorta divides into the left and right EIA. Then, as a rule, the short general internal iliac artery (the trunk) deviates from the entrance of the right EIA. It divides into the left and right internal iliac arteries (Fig. 3a, b). In the second variant, the iliac trunk deviates from the aorta between two EIA and forms the sol-called trifurcation. This trunk divides into the right and left iliac arteries feeding the small pelvis organs. In the small pelvis cavity, EIA (7-8 cm) divides into the deep femoral artery (DFA) and SFA. Their anatomy is well described in our previous study [7]. In the middle part, a single artery deviates from EIA – the deep artery rounding the iliac bone, which was clipped during laparoscopy for preventing the retrograde dilution of the clot. Having the similarity with the great cattle, the sheep have the region of deviation of this artery under the iliac-femoral lymphatic node (the middle sizes of 2×3 cm), which receives the lymph from the superficial inguinal lymphatic nodes and drains the part of lymph from iliac, sacral and rectal lymph nodes directly to cisterna chyli [8]. The iliofemoral lymph node has the important clinical significance for thrombosis modelling, since the appropriate approach to the targeted region of EIA is possible only with its dissection.

Estimation of efficiency of the model

The study of the thrombosis model included only seven experimental animals with the mean weight of 31.6 (25.5-35.5) kg. One animal was excluded from the experiment ahead of schedule due to iatrogenic perforation of the left EIA during thrombosis modelling that required for ligation. Other six animals were observed up to the moment of finishing the experiment. The total amount of anesthesia was 160 (115-195) min. The animals demonstrated good tolerance to carbon dioxide insufflation with creation of intraabdominal pressure of 15 mm Hg. No signs of unstable hemodynamics and multiple organ insufficiency were observed.
Therefore, among the animals included into the experiment, the successful laparoscopic modelling of posttraumatic arterial thrombosis was in 6 animals that required 55 (40-70) minutes from the moment of application of the first clamp to confirmation of thrombosis with control angiography. Angiography required for 70 (30-80) ml of contrast medium Scanlux-300.

Ultrasonic and laboratory parameters of examination

The background values of PSV and PI did not differ between the left (injured) extremity and the right one. After thrombosis modelling we noted the significant decrease in PSV: 0 (0) cm/sec in the posterior left extremity in relation to 41.0 (22.0-55.0) cm/sec in the posterior right extremity (p < 0.0001). The similar changes were noted during measurement of PI: 0 (0) to the left and 2.24 (1.76-2.63) to the right (p < 0.0001) (Fig. 5). The biochemical parameters of the blood did not show any significant changes both in the background values and the levels of creatinine, urea and lactate at the moment of completion of the study.

Figure 5. The main ultrasonic values of blood flow rate (A, B – peak systolic blood flow rate; C, D – pulsatility index) in the superficial femoral arteries (SFA) of the left (the experiment) and right (control) extremities.

DISCUSSION

This study describes the new low traumatic model for research of the modern techniques for restoring the patency of injured arteries, their comparison with the existing standard technique for arterial reconstruction with autovenous plastics or synthetic prosthesis. The described model is a continuation of our study of possibilities of endovascular techniques in trauma surgery. Previously, we described the experimental model of a SFA closed injury, where the standard technique was used for separating the sheep’s femoral artery and modelled the acute posttraumatic thrombosis by means of application and removal of the standard hemostatic clamp [7]. Unfortunately, owing to small diameter of SFA (about 4 mm), this model has the low representativity for research of a vascular injury. The opened intervention for the iliac arteries (diameter of 6-7 mm) is consistently accompanied by high incidence of injuries, additional blood loss and extremely high risk of infectious complications after laparotomy that influence on results of the main studied procedure. Use of laparoscopic technique allowed developing the simple model of traumatic influence on the arterial wall of the big magistral artery with the diameter corresponding to SFA, popliteal, axillary or brachial artery of the human, and, from other side, to prevent the undesired consequences of laparotomy.
Our study showed that creation of arterial thrombosis according to the described technique was accompanied by significant decrease in blood flow velocity in an injured extremity in comparison with the intact extremity, i.e. it is the adequate criterion for estimating the quality of the developed model.
The literature describes the single attempts of development of the experimental model for estimation of efficiency and appropriateness of endovascular techniques for vascular injury. Some researchers demonstrated the high level of similarity between vascular bed and hemostasis system in sheep and the human. M. Cejna et al. used sheep for examining the biocompatibility of various stents and stent-grafts after implantation in uninjured iliac arteries [9]. Implantation was technically successful in all cases, and the patency was 100 % for 3 months. C. Teigen et al. tested a new model of the bifurcation prosthesis for big sheep. They did not identify any negative events during 6 months of observation [10]. A.L. Tang et al. offered the experimental model with resection of 2 cm part of ovine SFA, subsequent convergence of its boundaries with interrupted sutures for preventing the retraction of the arterial wall and with placement of the stent-graft. However this model was oriented to study of wounds or ruptures of arteries, but not to acute thrombotic occlusion [11]. Moreover, after two months of observation, only 5 of 8 stent-grafts were impassable, despite of administration of disaggregation drugs. The Brazilian researchers led by S. Belczak offered the experimental model with lateral injury (less than 50 % of the diameter) and full transection of the carotid artery of a pig for estimation of a possibility for recanalization of an injured segment with subsequent implantation of the stent-graft [12]. However the authors kept their mind on the arterial wounds. Moreover, they studied only the immediate outcome of stenting without estimation of long term results.
These studies demonstrate the attempts of the scientist of the whole world to perform experimental estimation of endovascular surgery, which is increasingly used for treatment of vascular injuries. So, American National Trauma Data Bank (NTDB) shows 27-fold increase in incidence of endovascular operations in 1997-2003 [3]. Despite this fact, most arterial injuries are still operated in opened manner. A prospective study of vascular injuries in peace time PROOVIT showed that traumatic arterial occlusion takes place in 17.7 % of all vascular injuries [3]. The endovascular techniques were used for only 7.4 % of cases (mostly for treating aorta and iliac arteries injuries).
The clinical studies of recanalization of thrombotic occlusions in injuries to the magistral arteries are quite rare and are presented by individual observations. The recent article by F. Rohlffs et al. demonstrated the possibility of end-to-end recanalization of the completely transected and clotted axillary artery with subsequent implantation of several stent-grafts [6]. The whole operation lasted for 45 minutes. There were not any signs of distal embolization of arterial bed, and the stented part of the artery was reconstructed during the subsequent opened operation several days later. A.J. Davidson et al. offered the original sutureless technique for introduction of the stent-graft directly to the defect of the arterial wall. They successfully used it for treating three patients [13]. Gore® company (USA) offered the original modification of the graft with its one part as a self-opening stent-graft Viabahn®, and other part as a synthetic PTFE prosthesis. Its use can be justified only in case of difficult approach to the artery because of formation of extensive hematoma. Puncture introduction of the stent-graft into the hard-to-reach part of the artery through the anterior wall allows retrograde filling the implant and to sew it into any region of the aorta or a big artery with easy access for revision. Therefore, M. Lachat et al. performed the revascularization of 82 renal arteries with 100 % efficiency and good long term outcomes [14]. Shunting of an injured part of the artery is also possible with use of this technique. It was demonstrated by L. Freire et al. in the model of the ligated infrarenal aorta in the pigs [15]. P. Zimmerman et al. described a successful case of recanalization of the region of acute posttraumatic thrombosis in the popliteal artery after leg dislocation and stent implantation [5]. The authors did not use the protection from distal embolism and achieved the good functional outcome. Angiography showed only short occlusion in the anterior tibial artery which was probably caused by distal embolization, but it did not influence on the long term outcome.
Our study certainly has some essential limitations. First of all, we could not trace the long term results of the experiment and investigate the morphology of the arterial wall in the injury region. Long term observation of the animals was not anticipated according to the plan of the experiment since it was oriented only to thrombosis modelling for subsequent surgical intervention. For this reason we could not estimate the extremity function over time after completion of the experiment and, as result, could not assess the intensity of ischemia-reperfusion syndrome. Although our previous study of SFA thrombosis did not show any changes in the extremity function, as well as the present study did not demonstrate any significant shifts in serum lactate, it can be expected that long term occlusion of a big artery is accompanied by disordered function of the extremity and development of reperfusion syndrome in case of blood flow restoration. Secondly, laparoscopy can be accompanied by development of infectious complications in the abdominal cavity which were not estimated in the experiment. Finally, the small sample of the animals and absence of an appropriate control group decreased the statistical power of the study. However the high level of reliability of the differences between the operated extremity and the healthy one demonstrate the efficiency of our laparoscopic model and allow recommending it for further use in estimation of efficiency of the opened and endovascular treatment techniques for a vascular injury.

CONCLUSION

Our experimental model of acute occlusive posttraumatic thrombosis of a big artery with laparoscopy technique is well reproducible and allows achieving arterial thrombosis if performed correctly. This model can be used for comparative estimation of efficiency and safety of opened and endovascular interventions for injured arteries.

Information about conflict of interests

The study was conducted without sponsorship. The authors declare the absence of any clear and potential conflicts of interests relating to publication of this article.

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