1、Spinal Cord Blood Flow Change by Intravenous MidazolamDuring Isoflurane AnesthesiaTomoki Nishiyama, MD, PhDBy CorallibraBackground Midazolam has been used for general anesthesia and sedation during local anesthesia or artificial ventilation. It has become clear that midazolam has an analgesic proper
2、ty mediated by GABA receptors in the spinal cord. Therefore, it is important to know the effects of midazolam on spinal cord blood flow.Methods32Cats (male; 2.5-3.5Kg; 12h)Isoflurane (4%) in 100% oxygenIsoflurane (1%) in 40% oxygenEnd-tidal carbon dioxide tensionBetween 30 and 40 mmHganesthesiamaint
3、ainventilationMethodsMonitor, Mesured5, 15, 30, 60, 90, 120 minmidazolam 0, 1, 2, or 4 mg/KgHeart rateArterial blood gas analysisTemperature37.0 0.5 Midline skin incision, L1-5 were removed, and the spinal cord was exposed.A platinum was inserted stereotaxically into the spinal cord to a depth of 1
4、mm at 2 mm lateral to the midline at L2.Spinal cord blood flow was measured eith the hydrogen clearance method.Statistical analysis was performed with repeated-measures analysis of varianceResults Arterial blood gas values before the study drug treatment without any difference. Arterial blood pressu
5、re decreased during the first 30 min after MID 2 and 4mg/Kg Heart rate did not change.Results Spinal cord blood flow increased significantly for 90 min after MID 1 mg/Kg and for 15 min after MID 2mg/Kg.Discussion Spinal cord blood flow was increased by the smallest dose of IV midazolam used (1 mg/kg
6、) without any changes in arterial blood pressure The largest dose (4 mg/kg) did not induce any changes in spinal cord blood flow but decreased arterial blood pressureDiscussion Spinal cord blood flow increased as ETco2 increased, but it did not change with mean arterial blood pressure between 50 and
7、 135 mmHg or with Pao2 more than 40 mmHg (arterial blood pressure was in the range of autoregulation)Discussion Spinal cord blood flow might change similarly to cerebral blood flow Bolus midazolam (0.15 mg/kg) decreased cerebral blood flow, but mean arterial blood pressure also decreasedDiscussion I
8、soflurane increased spinal cord blood flow within the arterial blood pressure range of 90130mmHg The decrease in arterial blood pressure in the midazolam 2 and 4 mg/kg groups may have decreased spinal cord blood flow during isoflurane anesthesia that masked the increase otherwise caused by midazolam
