Kim Y J, McFarlane C, Warner D S, Baker M T, Choi W W, Dexter F
Department of Anesthesiology, Yonsei University, Seoul, Korea.
Anesth Analg. 1996 Dec;83(6):1223-8. doi: 10.1097/00000539-199612000-00016.
Lidocaine and MgSO4 are often coadministered to patients with pregnancy-induced hypertension. This study examined whether MgSO4 alters the lidocaine-seizure threshold in the rat and, if so, whether systemic MgSO4 administration is as effective as intracerebroventricular MgSO4 infusion. In Experiment 1, rats were administered 50% MgSO4 or 0.9% NaCl intravenously (IV) (20 microL/h) for 5 days. In Experiment 2, rats were administered 0.9% NaCl, 0.8% MgSO4, or 2.0% MgSO4 (10 microL/h) via intracerebroventricular infusion for 24 h. All rats then underwent continuous IV lidocaine infusion until onset of electroencephalographic seizures. In Experiment 1, plasma [Mg2+] was greater in the MgSO4 group (5.1 +/- 1.5 mg/dL vs 1.8 +/- 0.3 mg/dL) but neither the dose of lidocaine required to induce seizures (MgSO4 = 19 +/- 2 mg/kg; saline = 23 +/- 5 mg/kg) nor brain [Mg2+] (MgSO4 = 794 +/- 17 micrograms/g; saline = 788 +/- 33 micrograms/g) were changed. In Experiment 2, intracerebroventricular MgSO4 increased both brain [Mg2+] (2% MgSO4 = 923 +/- 79 micrograms/g; saline = 788 +/- 35 micrograms/g) and the lidocaine seizure dose (2% MgSO4 = 39 +/- 7 mg/kg; saline = 26 +/- 3 mg/kg). Although intracerebroventricular administration of MgSO4 produces an anticonvulsant effect, chronic hypermagnesemia does not alter whole brain [Mg2+] and therefore offers no protection from lidocaine-induced seizures in this model.
利多卡因和硫酸镁常联合用于妊娠高血压患者。本研究检测了硫酸镁是否会改变大鼠的利多卡因惊厥阈值，若有改变，全身给予硫酸镁是否与脑室内注入硫酸镁一样有效。在实验1中，大鼠静脉注射（IV）50%硫酸镁或0.9%氯化钠（20微升/小时），持续5天。在实验2中，大鼠通过脑室内注入0.9%氯化钠、0.8%硫酸镁或2.0%硫酸镁（10微升/小时），持续24小时。然后所有大鼠接受持续静脉注射利多卡因，直至脑电图出现惊厥。在实验1中，硫酸镁组的血浆[Mg2+]更高（5.1±1.5毫克/分升 vs 1.8±0.3毫克/分升），但诱发惊厥所需的利多卡因剂量（硫酸镁=19±2毫克/千克；生理盐水=23±5毫克/千克）和脑内[Mg2+]（硫酸镁=794±17微克/克；生理盐水=788±33微克/克）均未改变。在实验2中，脑室内注入硫酸镁增加了脑内[Mg2+]（2%硫酸镁=923±79微克/克；生理盐水=788±35微克/克）和利多卡因惊厥剂量（2%硫酸镁=39±7毫克/千克；生理盐水=26±3毫克/千克）。虽然脑室内注入硫酸镁产生了抗惊厥作用，但慢性高镁血症并未改变全脑[Mg2+]，因此在该模型中不能预防利多卡因诱发的惊厥。
