Mangla et al. BMC Res Notes (2015) 8:808 DOI 10.1186/s13104-015-1714-7 BMC Research Notes TECHNICAL NOTE Open Access Endovascular external carotid artery occlusion for brain selective targeting: a cerebrovascular swine model Sundeep Mangla1*† , Jae H. Choi2,3†, Frank C. Barone2, Carol Novotney4, Jenny Libien5, Erwin Lin6 and John Pile‑Spellman3,7 Abstract Background: The choice of an animal model for cerebrovascular research is often determined by the disease sub‑ type to be studied (e.g. ischemic stroke, hemorrhage, trauma), as well as the nature of the intervention to be tested (i.e. medical device or pharmaceutical). Many initial studies are performed in smaller animals, as they are cost-effective and their encephalic vasculature closely models that of humans. Non-human primates are also utilized when confir‑ mation or validation is required on higher levels and to test larger devices. However, working with primates is com‑ plex and expensive. Intermediate sized animal models, such as swine and sheep, may represent a valuable compro‑ mise. Their cerebrovascular anatomy, however, comes with challenges because of the natural higher external carotid artery perfusion and the existence of a rete mirabile. We describe a modification to the traditional swine cerebrovas‑ cular model that significantly enhances selective brain hemispheric perfusion, limiting external carotid perfusion and dilution. Results: We investigated whether unilateral endovascular coil-embolization of external carotid artery branches in swine would lead to increased brain perfusion, altering cerebral circulation so that it more closely models human cer‑ ebral circulation. Equal amounts of approximately 4 °C cold saline were injected in 6 Yorkshire pigs into the ipsilateral common carotid artery before and after embolization. Hemispheric temperature changes from pre- and post-embo‑ lization were obtained as a measure of brain perfusion and averaged and compared using non-parametric statistical tests (Wilcoxon signed rank test, Mann–Whitney U Test). Graphs were plotted with absolute changes in hemispheric temperature over time to determine peak temperature drop (PTD) and corresponding time to peak (TTP) following the cold bolus injection. There was a 288 90 % increase in ipsilateral brain cooling after embolization indicating improved selective blood flow to the brain± due to this vascular modification. Conclusion: We have developed an effective, selective vascular brain model in swine that may be useful as a practi‑ cal and cost-reducing intermediate step for evaluating target dose–responses for central nervous system drugs and brain selective interventions, such as local hypothermia. Keywords: Animal research, Cerebrovascular, Endovascular intervention, Selective cooling, Swine model Background models to test novel devices and therapeutic strategies. Research involving the cerebrovascular system has con- The choice of an animal model is determined by a vari- tinued to accelerate, as has the need for innovative animal ety of factors, including the disease subtype to be stud- ied (e.g. ischemic stroke, hemorrhage, trauma), as well as the nature of the intervention (i.e. medical device or *Correspondence: [email protected] †Sundeep Mangla and Jae H. Choi contributed equally to this work pharmaceutical) to be tested [1]. Many initial studies are 1 Division of Interventional Neuroradiology, SUNY Downstate Medical performed in smaller animals (mice, rats, rabbits), as they Center, 470 Clarkson Ave, B7525, Brooklyn, NY 11203, USA are cost-effective and their encephalic vasculature closely Full list of author information is available at the end of the article © 2015 Mangla et al. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/ publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Mangla et al. BMC Res Notes (2015) 8:808 Page 2 of 6 models that of humans. Non-human primates (e.g. 15–20 cmH2O, end-tidal CO2 35–45 mmHg, positive end Baboons, Macaques) are also utilized when confirma- expiratory pressure 3–5 cmH2O, and sigh every 15 min to tion is required (i.e. to test larger devices or to improve 25–30 cmH2O. Two intravenous lines were placed within human validation). The increased complexity and bilateral ear veins for IV access (replacement fluid Nor- expense of working with primates, however, limits the mosol-R 5–10 ml/kg/hr). An arterial line was placed in capacity of many research teams to execute these higher either the contralateral hind or fore limb to obtain con- level validations. Intermediate sized animal models, such tinuous pressure recordings and intermittent blood sam- as swine and sheep, may represent a valuable compro- pling. Systemic temperature probe was placed within the mise for cerebrovascular research [2–5]. However, their esophagus or rectum to monitor body core temperature pre-encephalic vasculature has been considered prob- and to prevent body cooling using a circulating warming lematic because of their pre-cerebral rete that is bilater- blanket. A urinary catheter was placed to monitor out- ally connected to the common carotid artery (CCA) by put. After stable surgical anesthesia was achieved Vecu- the ascending pharyngeal artery (AsPharA) [6, 7]. This ronium (Norcuron) was administered with a loading dose rete supplies their Circle of Willis (CoW) through two of 0.05–0.1 mg/kg and maintained at 0.8–1.2 mcg/kg/ small internal carotid arteries (ICA) that branch off of the min. After the experiments the animals were euthanized rete. Furthermore, in animals the carotid system contrib- with an intravenous injection of 160 mg/kg of Fatal Plus utes proportionally more blood to the external carotid (Pentobarbital). Finally, the brain was extracted, fixed in arteries (compared to humans) to supply their snout and formalin, and evaluated for ischemic damage by gross relatively massive facial and masticatory muscles [8]. and histopathologic (H&E stain) examination. Here, we describe a modification to the traditional swine cerebrovascular model that significantly enhances selec- Intracranial probe placement tive brain hemispheric perfusion while limiting exter- The animals were placed prone, and surgical dissection nal carotid perfusion and dilution. We believe that this of the cranium was performed from immediately ante- modification will enhance our ability to evaluate brain- rior to the ears to approximately 7–10 cm anterior to the selective therapeutics and diagnostics, and target dose- orbits. The bregma was located and burr holes were cre- responses in this larger non-primate model, a model ated 2 cm cephalad and 1.5–2.0 cm lateral to the sagittal particularly well-suited for investigating larger endovas- suture bilaterally with the Raumedic (Helmbrechts, Ger- cular devices and central nervous system drugs. many) manual drill system. The dura was pierced bilat- erally and the intracranial probes for temperature and Methodology intracranial pressure (ICP) (Neurovent, Raumedic) were Animal care advanced approximately 3.5–4.5 cm into the cranial vault Procedures were conducted in accordance with all Fed- and frontal lobes from the osseous surface and secured. eral and State animal welfare laws, regulations, poli- Probe positioning was confirmed with appropriate physi- cies and guideline, in compliance with the ARRIVE ologic measurements for expected ICP and temperature guidelines, and with approval by the SUNY Downstate on the Raumedic monitors. Medical Center Institutional Animal Care and Use Com- mittee. Six female white Yorkshire swine (35–55 kg, ages Endovascular vessel modification and vessel blood flow 18–36 weeks), were used in this study. Free access to food measurements and water was given until the night before the proce- Each animal underwent surgical dissection of superficial dure, at which time only water was allowed. Sedation was fascial and muscular planes for an ultrasound-guided induced by atropine 0.04 mg/kg IM and Telazol 2–5 mg/ groin approach of the common femoral artery. Access kg IM. General anesthesia was induced with inhalant iso- was established using a micropuncture needle and wire, flurane (3–5 %) by mask with 100 % oxygen at 3–5 L/min with serial dilatation and placement of a 7-French 15 cm and maintained by 1–3 % isoflurane inhalant. To provide sheath (Pinnacle, Terumo, NJ) that was applied to a con- balanced anesthesia/analgesia isoflurane was combined tinuous heparinized flush solution. After vascular access with Fentanyl at 50 µg/kg initial bolus followed by contin- and intracranial probe placement 4000 IU Heparin was uous administration at 30–100 µg/kg IV. Hemodynamic administered IV as a bolus with additional 2000 IU/h for monitoring (heart rate, systolic and diastolic blood pres- the duration of the study procedure. Ultrasound studies sure) and expired air CO2 monitoring were performed of bilateral CCAs were performed to assess maximum continuously. Endotracheal intubation was performed diameter (Dmax, intima to intima) and peak systolic via tracheotomy. Animals were ventilated at respira- velocity (psFV at 60° angle with cursor parallel