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Preventing Sheep Carotid Artery Spasm for Vascular Graft Surgery and Computed Tomography Angiography
Ziyu Wang1,2, Hugh Paterson3, Lisa Partel4
1School of Life and Environmental Sciences, Faculty of Science, the University of Sydney, Sydney, Australia.
Abstract:
The development of small-diameter vascular grafts requires testing in large animal models before advancing to clinical trials. Vascular graft interposition implantation in sheep carotid arteries (CAs) is the most widely used model, but ovine CAs are prone to severe spasm following surgical manipulation, potentially impairing graft performance assessment. There is paucity in the literature on reducing sheep CA spasm using effective vasodilator therapeutic protocols. In this study, four healthy Merino cross White Suffolk wethers (1-2 years, 52.1 ± 0.8 kg) underwent CT angiography and CA graft surgery. CT angiography using iodinated contrast agent was performed with innominate artery access through the CA or ascending aortic arch access through the femoral artery. Sheep then underwent right CA sham surgery or left CA vascular graft implantation. A variety of vasodilators, including papaverine, sodium nitroprusside, verapamil, and their combination, were tested for preventing or treating CA spasms intraoperatively. Blood flow was reassessed immediately after CA surgery using CT angiography. The results showed that innominate artery access through the CA for CT angiography in sheep induced presurgical CA spasm with reduced arterial flow. Conversely, ascending aortic arch access through the femoral artery for CT angiography did not cause CA spasm and maintained arterial flow. During CA graft surgery, surgical trauma induced CA spasm, which was prevented by localized intra-arterial administration of vasodilators papaverine hydrochloride and verapamil before significant surgical manipulation.
Insights
Sheep carotid artery (CA) spasm during vascular graft surgery can be reduced. Localized vasodilators, papaverine hydrochloride and verapamil, effectively prevented spasm, improving graft assessment in this animal model.
Area of Science:
- Biomedical Engineering
- Surgical Research
- Vascular Surgery
Background:
- Small-diameter vascular grafts require large animal models for pre-clinical testing.
- Sheep carotid arteries (CAs) are a common model, but prone to spasm, complicating graft assessment.
- Effective vasodilator protocols to mitigate sheep CA spasm are lacking.
Purpose of the Study:
- To evaluate methods for reducing sheep carotid artery (CA) spasm during vascular graft surgery.
- To compare CT angiography access routes for their impact on CA spasm.
- To assess the efficacy of specific vasodilators in preventing intraoperative CA spasm.
Main Methods:
- Four sheep underwent CT angiography and carotid artery (CA) graft surgery.
- CT angiography was performed via innominate artery (CA access) or ascending aorta (femoral artery access).
- Vasodilators (papaverine, sodium nitroprusside, verapamil) were tested intraoperatively; papaverine and verapamil were administered locally before manipulation.
Main Results:
- Innominate artery access for CT angiography induced presurgical CA spasm and reduced flow.
- Ascending aortic arch access via femoral artery did not induce spasm and maintained arterial flow.
- Localized intra-arterial papaverine hydrochloride and verapamil prevented surgical trauma-induced CA spasm.
Conclusions:
- Ascending aortic arch access is preferable for CT angiography in sheep to avoid presurgical CA spasm.
- Localized administration of papaverine hydrochloride and verapamil effectively prevents intraoperative sheep CA spasm.
- This optimized protocol can improve the reliability of vascular graft performance assessment in sheep models.
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