Hypothermia is a promising neuroprotective treatment. This study aims to explore and optimize the intervention scheme of intra-arterial hypothermia (IAH) in a middle cerebral artery occlusion and reperfusion (MCAO/R) rat model. The MCAO/R model was established with a thread that could be retracted 2 h after occlusion. Cold normal saline was injected into the internal carotid artery (ICA) through a microcatheter in different infusion conditions. Grouping followed an orthogonal design (L₉[3⁴]) based on three critical factors closely associated with IAH: perfusate temperature (4, 10, 15 °C), infusion flow rate (1/3, 1/2, 2/3 blood flow rate of ICA), and duration (10, 20, 30 min), resulting in 9 subgroups (H₁, H₂ to H₉). A myriad of indexes were monitored, such as vital signs, blood parameters, changes in local ischemic brain tissue temperature (T_b), ipsilateral jugular venous bulb temperature (T_jvb), and the core temperature of the anus (T_core). After 24 h and 72 h of cerebral ischemia, cerebral infarction volume, cerebral water content, and neurological function were assessed to explore the optimal IAH conditions. The results revealed that the three critical factors were independent predictors for cerebral infarction volume, cerebral water content, and neurological function. The optimal perfusion conditions were 4 °C, 2/3 R_ICA (0.50 ml/min) for 20 min, and there was a significant correlation between T_b and T_jvb (R = 0.994, P < 0.001). The vital signs, blood routine tests and biochemical indexes showed no significant abnormal changes. These findings revealed that IAH was safe and feasible with the optimized scheme in an MCAO/R rat model.

低温是一种有前途的神经保护治疗方法。本研究旨在探索并优化大脑中动脉闭塞再灌注（MCAO/R）大鼠模型的动脉内低温（IAH）干预方案。MCAO/R模型采用可在闭塞后2小时回缩的线建立。在不同输注条件下通过微导管将冷生理盐水注入颈内动脉（ICA）。分组采用正交设计 (L ₉ [3 ⁴ ])，基于与 IAH 密切相关的三个关键因素：灌注液温度 (4、10、15 °C)、输注流速 (1/3、1/2、2/3) ICA 的血流速率）和持续时间（10、20、30 分钟），产生 9 个亚组（H ₁、H ₂至 H ₉）。_{监测生命体征、血液参数、局部缺血脑组织温度（T b}）、同侧颈静脉球温度（T _jvb）、肛门核心温度（T _core）等多项指标。脑缺血24 h和72 h后，评估脑梗死体积、脑含水量和神经功能，探讨最佳IAH条件。结果显示，这三个关键因素是脑梗塞体积、脑含水量和神经功能的独立预测因子。最佳灌注条件为4℃、2/3 R _{ICA （0.50 ml/min）20 min，T b}与T之间存在显着相关性。_jvb（R = 0.994，P  < 0.001）。生命体征、血常规及生化指标未见明显异常变化。这些结果表明，在 MCAO/R 大鼠模型中，采用优化方案进行 IAH 是安全可行的。