Torsion is Tolerated in Arterial End to Venous Side Anastomoses in the Rat Model

Abstract

Background End-to-side (ETS) anastomoses are necessary for many procedures in microvascular surgery, such as free flap transfers. In training courses that use the rat model, the arterial end to venous side (AEVS) anastomosis is a common training exercise for ETS anastomoses. Surgeons-in-training often inadvertently twist the artery when completing the AEVS anastomosis; however, in the clinical setting, torsion is a reported risk factor for ETS anastomosis failure. The purpose of this study was to determine if torsion in an AEVS anastomosis would have a negative effect on patency in the rat model, accurately simulating the clinical scenario. Methods All AEVS anastomoses were completed in 15 Sprague–Dawley rats divided into three torsion cohorts: 0, 90, and 180 degrees. Torsion was created in the AEVS anastomosis by mismatching the first two sutures placed between the free femoral artery end and the venotomy. Patency was verified at 0, 2, and 4 hours postoperation via the oxygenated–deoxygenated test and transit-time ultrasound blood flow measurements. Results All AEVS anastomoses were patent 0, 2, and 4 hours postoperation according to both the oxygenated–deoxygenated test and transit-time ultrasound blood flow measurements. For the average blood flow measurements at 4 hours postoperation, the proximal measurements for 0, 90, and 180 degrees were −34.3, −18.7, and −13.8 mL/min respectively, and the distal measurements were 4.48, 3.46, and 2.90 mL/min, respectively. Conclusion Torsion of 180 degrees does not affect early AEVS anastomosis patency in the rat model. This contrasts with the clinical setting, where torsion is reported to cause ETS anastomosis failure. Since AEVS anastomosis torsion is often difficult to appreciate visually, we suggested that microvascular surgery training instructors include a method to both detect and prevent AEVS anastomosis torsion, such as by marking the free femoral artery end with a marking pen or suture before beginning the anastomosis.

Three types of end-to-side microvascular anastomosis training models using rat common iliac arteries

“…In this article, three types of end-to-side microvascular anastomosis using the rat common iliac artery were presented to simulate three different anastomotic situations. There are many types of end-to-side microvascular anastomosis training models, such as those that are ipsilateral to contralateral common carotid arteries (9,10), common carotid artery to external jugular vein (11, 12), ipsilateral to contralateral common iliac arteries (7,9), and femoral artery to vein (13)(14)(15). Previously, Tayebi Meybodi et al (9), Hall (20), and we (7) have Schematic illustration shows the measurements in end-to-side anastomosis using rat common iliac arteries.…”

“…Therefore, instead of only practicing these perfectly matched end-to-side anastomoses in microsurgical laboratories, we must learn how to perform these so-called "imperfect" end-to-side anastomoses in the laboratory. Previously, many types of end-to-side microvascular anastomosis training models have been described, such as those that are ipsilateral to contralateral common carotid arteries (9,10), common carotid artery to external jugular vein (11,12), ipsilateral to contralateral common iliac arteries (7,9), and femoral artery to vein (13)(14)(15). In this article, three types of end-to-side microvascular anastomotic configurations using the rat common iliac artery (CIA), one with the proximal end of the CIA to the contralateral side of the CIA (Prox.…”

Rat Microvascular Model is Tolerant to Technical Errors

“…Past literature often reported a high patency rate of up to 100% upon applying various technical errors, given the seeming discrepancy between experimental models and clinical practice. [3][4][5][6][7][8][9][10][11] In a microsurgery training setting, suture anastomosis is often the domain with the steepest learning curve, leading to patency failure ultimately when first beginning the training. A competent proficiency to reach anastomosis patency may take over 10 times of attempts and practice.…”

“…1,2 In-depth analyses of technical error types, including vessel torsion, large or uneven bites, back wall sutures, and others, have been shown to have varying differential effects on vessel patency in a rat model. [3][4][5][6][7][8][9][10][11] Such clinical errors are considered unacceptable in the clinical world due to the increased risk of vessel thrombosis. [12][13][14][15][16][17] However, the rat model exhibits a high tolerance to select technical errors.…”

The Benefits of Expert Instruction in Microsurgery Courses

“…In depth analyses of several error types, including vessel torsion and large or uneven bites has found that vessels may tolerate these imperfections along the suture line. [8][9][10] Nevertheless, while rat femoral vessel anastomoses may survive imprecise suturing technique, human anastomoses may not be as tolerant of technical errors. Additionally, these mistakes were evaluated on rat femoral arteries and veins, which while similar to human vessels, have not been fully evaluated.…”