乳化七氟烷选择性麻醉新西兰大白兔脑、脊髓模型的建立

Emulsified Sevoflurane Selectively Blocking Spinal Cord and Brain in Rabbit Model

目的 建立选择性麻醉脊髓和脑的动物模型,探索七氟烷松弛骨骼肌作用的位点是否在脊髓。方法选择健康新西兰大白兔16只,通过体外循环技术,于第12胸椎（T12）~第1腰椎（L1）水平结扎主动脉,从而形成上半身及下半身两个相对独立的循环系统。通过七氟烷经肺或者氧合器给予到新西兰大白兔上半身或者下半身,实现选择性脑麻醉或者选择性脊髓麻醉（主要是腰骶段脊髓）。连续监测呼气末（代表脑组织）和氧合器出气口（代表脊髓）的七氟烷浓度。利用气相色谱仪,注射器两次平衡法来测量颈动脉（代表脑组织）和腹主动脉（代表脊髓）血液中七氟烷的质量浓度和分压。结果 经肺吸入1.5倍肺泡气最低有效浓度（MAC）七氟烷并达平衡状态时,呼气末七氟烷浓度高于氧合器出气口,颈动脉血液中七氟烷的质量浓度和分压高于腹主动脉（P〈0.05）,即脑组织中的七氟烷浓度和分压高于脊髓。经过10~20min洗脱期后,由氧合器给予新西兰大白兔下半身1.5 MAC七氟烷并达平衡状态时,上述指标的表现则完全相反（P〈0.05）,即脊髓中的七氟烷浓度和分压高于脑组织。结论 通过七氟烷的不同给予方式（经肺或者氧合器）,成功建立了七氟烷选择性麻醉新西兰大白兔脑、脊髓模型。

Objective To establish the rabbits model of selectively anesthetized brain and spinal cord and to explore the skeletal muscle relaxation sites of sevoflurane. Methods Sixteen adult male New Zealand white rabbits were randomly assigned to the experiment. The upper torso systemic circulation and the lower torso bypass circulation were independently established by the ligation of thoracic aorta at T12-L1 level. Sevoflurane was administered to the upper or lower torso through lungs or oxygenator to selectively anesthetized brain or spinal cord （mainly lumbar and sacro-coccygeal region）. Sevoflurane concentration from end-tidal （represented the brain） and oxygenator outlet （represented the spinal cord） was measured by an anesthetic gas analyzer. The concentration and partial pressure of sevoflurane in carotid artery （represented the brain） and abdominal aorta （represented the spinal cord） were determined using a gas chromatograph with the two-stage headspace equilibration method. Results When 1.5 mininum alveolar concentration （MAC） sevoflurane was administrated via lungs, the concentration and partial pressure of sevoflurane in the carotid artery were significantly higher than those in the abdominal aorta （P〈 0.05）, with the end-tidal sevoflurane concentration higher than that of oxygenator outlet （P〈 0. 05）, which indicated sevoflurane concentration and partial pressure in brain were higher than those in spinal cord. When 1.5 MAC sevoflurane was delivered via oxygenator, the indicators were conversed （P 〈 0. 05）, which indicated sevoflurane concentration and partial pressure in spinal cord were higher than those in brain. Conclusion Based on the unique blood supply to the spinal cord of New Zealand white rabbits, we successfully established selectively anesthetized brain and spinal cord rabbit models.