Effect of Previous Irradiation on Vascular Thrombosis of Microsurgical Anastomosis: A Preclinical Study in Rats

Abstract

Background: The objective of the present investigation was to compare the effect of neoadjuvant irradiation on the microvascular anastomosis in cervical bundle using an experimental model in rats.

Methods: One hundred forty male Sprague-Dawley rats were allocated into 4 groups: group I, control, arterial microanastomosis; group II, control, venous microanastomosis; group III, arterial microanastomosis with previous irradiation (20 Gy); and group IV, venous microanastomosis with previous irradiation (20 Gy). Clinical parameters, technical values of anastomosis, patency, and histopathological parameters were evaluated.

Results: Irradiated groups (III and IV) and vein anastomosis groups (II and IV) showed significantly increased technical difficulties. Group IV showed significantly reduced patency rates (7/35) when compared with the control group (0/35). Radiotherapy significantly decreased the patency rates of the vein (7/35) when compared with the artery (1/35). Groups III and IV showed significantly reduced number of endothelial cells and also showed the presence of intimal thickening and adventitial fibrosis as compared with the control group.

Conclusion: Neoadjuvant radiotherapy reduces the viability of the venous anastomosis in a preclinical rat model with a significant increase in the incidence of vein thrombosis.

Fig. 1.

Flowchart of the experimental study. Time lapse between the radiotherapy (RT) and the day of the surgery and time tracking are detailed. FU, follow-up.

Fig. 2.

Tests carried out for planning the radiation field. A, Cervical topographical study by computed tomography (CT). B, C, CT images obtained showing depth, characteristics, and localization of the cervical neurovascular bundle; coronal (B) and sagittal (C) sections. D, Tridimensional reconstruction.

Fig. 3.

Infrastructure of the radiotherapy unit. A, Cobalt-60 treatment unit Theraton used in the experimental study; it magnifies the cross-shaped Cerrobend plate placed in the middle of the radiation beam. B, Four simultaneous 2 × 2 cm field irradiations, which allow us 4 rats at the same time. C, 4-cm² frontal field over the left hemicervical region. D, Irradiation of 4 rats simultaneously.

Fig. 4.

Data represent mean values of body weight on the day of the surgery and at 2, 4, and 6 weeks postoperative. Numbers represent P values of the significant differences observed between groups.

Fig. 5.

Vascular patency vs thrombosis. Data represent the percentage of thrombosis rates in the 4 groups. Numbers represent P values of the significant differences observed between groups.

Fig. 6.

Anastomosis technical evaluation. Data represent the mean result of the different parameters evaluated in the 4 groups. Numbers represent P values of the significant differences observed between groups.

Fig. 7.

Histological evaluation. Data represent the mean result of the different parameters evaluated in the 4 groups. Numbers represent P values of the significant differences observed between groups.

Fig. 8.

Arterial histological section. H&E staining. A, Longitudinal section, ×10; group I: any histological alterations in the vascular structure are observed. B, Longitudinal section, ×10; group III: tunica intima hyperplasia. C, Coronal section, ×10; group III: organized thromboembolism on the anastomosis site.

Fig. 9.

Venous histological section. A, H&E staining; longitudinal section, ×10; group II: any histological alterations in the vascular structure are observed. B, Masson’s trichrome staining; longitudinal section, ×10; group IV: endothelial discontinuity, muscular layer disorganization, and adventitial fibrosis. C, Coronal section, ×10; group IV: organized thrombus on the anastomosis site.