This article will briefly review the rationale for DHCA in the setting of cerebral aneurysm treatment. We will then use the main aspects of the protocol practiced by the senior author (WLY), as a point of departure to review the issues regarding anesthetic and perioperative management. Rationale The ability to temporarily eliminate or reduce blood flow into an aneurysm gives the surgeon an important advantage—without flow, an aneurysm is converted from a hard, pulsating mass into a soft, collapsed sac, allowing more aggressive manipulation of the aneurysm to complete its dissection. With most aneurysms, temporary occlusion of the proximal parent artery or arteries will effectively control blood flow into the lesion. With large or complex aneurysms, the aneurysm mass may prevent optimal visualization and clip application to the neck. Collapse of the aneurysm mass creates more working space for dissection and precise clip application. Deep hypothermic circulatory arrest is used for aneurysms that cannot be adequately controlled by conventional surgical or endovascular techniques. Aneurysms in the anterior circulation are, in general, accessible enough to be managed with temporary clipping. Aneurysms that defy conventional treatment are typically in the posterior circulation and large (10 –25 mm in diameter) or giant (25 mm in diameter) in size. 11 Often these aneurysms cannot be collapsed easily because of the breadth of the neck, the complexity of the arterial branches at the base, the presence of thrombus or endovascular coils in the lumen, artheroma or calcium in the walls, and fusiform configuration. These anatomic features make direct clipping more difficult and lower the efficacy of conventional techniques. The surgeon’s ability to manage these anatomic factors is directly related to operative exposure. When proximal and distal arteries are inaccessible with these complex aneurysms, DHCA may provide the only safe and effective means of vascular control. Deep hypothermic circulatory arrest should be considered an option of last resort for these unusual aneurysms, when all conventional techniques have failed or have been carefully considered. Rarely, DHCA has also been proposed or described for other central nervous system lesions, such as tumors 8 or arteriovenous malformations, 12 but this discussion is not