Few data about the electroencephalogram and its calculated indices, such as the bispectral index (BIS), have been reported in rabbits. We aimed to evaluate whether a clinically stable anesthesia was mirrored by consistent and stable BIS values and to investigate the effects of modified cerebral blood supply, due to bilateral carotid clamping and re-opening, on BIS values. We also investigated the effects of fentanyl, as an antinociceptive drug, on the BIS. Sixty-eight rabbits undergoing general anesthesia for surgical creation of carotid bifurcation aneurysms were enrolled. The BIS values were recorded at nine selected time points (TPs) during each procedure and before and after fentanyl administration. The BIS values over time were compared with two-way repeated-measures analysis of variance followed by Tukey test, while the Wilcoxon signed rank test was performed to compare values at clamping and re-opening of the carotids as well as before and after fentanyl administration. The BIS values were significantly lower during anesthesia than at the end of anesthesia and at tracheal extubation; no significant differences were found among other TPs. Adequate depth of anesthesia was mirrored by consistent BIS values among rabbits, and alteration of cerebral blood supply did not modify BIS values, except once. Following fentanyl, BIS values did not change in a clinically relevant way.

Background: Rabbit models involving neck arteries are of growing importance for the development of preclinical aneurysm models. An optimal understanding of the anatomy is primordial to allow the conception of models while minimizing mortality and morbidity. The aim of this study is to give reliable anatomical landmarks to allow a standardized approach to the neck vessels. Methods: We performed a necropsy on nine specimens from ongoing experimental studies. We measured the distance between the origins of the right and left common carotid artery (rCCA/lCCA) and between the rCCA and the manubrium sterni (MS). The structures at risk were described. Results: Female New Zealand White rabbits (NZWR) weighing 3.7 ± 0.3 kg and aged 25 ± 5 weeks were included. The rCCA origin was located 9.6 ± 1.2 mm laterally and 10.1 ± 3.3 mm caudally to the MS. In all specimens, the lCCA originated from the aortic arch, together with the brachiocephalic trunk (BCT), and 6.2 ± 3.1 mm proximally to the rCCA origin. The external and internal jugular veins, trachea and laryngeal nerve were the main structures at risk. Conclusions: The data help to localize both CCAs and their origin to guide surgical approaches with the manubrium sterni as a main landmark. Special attention has to be paid to the trachea, jugular veins and laryngeal nerves.

Preclinical animal models with hemodynamic, morphologic, and histologic characteristics close to human intracranial aneurysms play a key role in the understanding of the pathophysiological processes and the development and testing of new therapeutic strategies. This study aims to describe a new rabbit aneurysm model that allows the creation of two elastase-digested saccular aneurysms with different hemodynamic conditions within the same animal. Five female New Zealand white rabbits with a mean weight of 4.0 (± 0.3) kg and mean age of 25 (±5) weeks underwent microsurgical stump and bifurcation aneurysm creation. One aneurysm (stump) was created by right common carotid artery (CCA) exposure at its origin at the brachiocephalic trunk. A temporary clip was applied at the CCA origin and another, 2 cm above. This segment was treated with a local injection of 100 U of elastase for 20 min. A second aneurysm (bifurcation) was created by suturing an elastase-treated arterial pouch into the end-to-side anastomosis of the right CCA to left CCA. Patency was controlled by fluorescence angiography immediately after creation. The average duration of surgery was 221 min. The creation of two aneurysms in the same animal was successful in all rabbits without complication. All aneurysms were patent immediately after surgery except for one bifurcation aneurysm, which showed an extreme tissue reaction due to elastase incubation and an immediate intraluminal thrombosis. No mortality was observed during surgery and up to one-month follow-up. Morbidity was limited to a transient vestibular syndrome (one rabbit), which recovered spontaneously within one day. Demonstrated here for the first time is the feasibility of creating a two-aneurysm rabbit model with stump and bifurcation hemodynamic characteristics and highly degenerated wall conditions. This model allows the study of the natural course and potential treatment strategies on the basis of aneurysm biology under different flow conditions.

Background: Mixed-reality head-mounted display (MR-HMD) visualization and 3D-printed models may improve three-dimensional visualization in neurosurgical planning. Detailed, reproducible descriptions of the workflows, technical requirements, and practical limitations of these techniques in aneurysm clip ligation planning remain limited. Methods: Between February 2020 and June 2021, patient-specific MR-HMD visualizations and 3D-printed models were generated for 29 patients undergoing elective surgical clip ligation of intracranial aneurysms. CT and 3D rotational angiography were fused to create patient-specific holograms for MR-HMD visualization and 3D-printed models. All cases underwent standardized modality-specific processing. Preparation and manufacturing times as well as recorded workflow-related usability observations, technical advantages, and limitations were assessed. Results: The mean total preparation time (mean ± standard deviation, SD) was 40.6 ± 10.3 min for MR-HMD visualization and 108.8 ± 17.8 min for 3D-printed models, excluding printing, washing, and curing time. The average printing time for 3D-printed models was 894.9 ± 41.6 min. MR-HMD setup in the operating room averaged 7.0 ± 2.8 min. Identified limitations included manual hologram registration and repositioning after table or patient position changes, as well as the inability to track instruments or interact with the hologram. Conclusions: Both modalities could be integrated into a standardized patient-specific workflow and serve complementary functions. MR-HMD visualization supported flexible short-term visualization, whereas 3D-printed models provided a physical model for clip planning and patient education at the cost of longer preparation and production. These findings support a combined workflow in which modality selection is guided by clinical tasks and time constraints.