• M Nakayama, H Tsuchida, N Kanaya, and A Namiki.
• Department of Anesthesiology, Sapporo Medical University School of Medicine, Japan. miyabi@zc4.so-net.ne.jp
• J Clin Anesth. 2000 Feb 1;12(1):14-8.

Study ObjectiveTo compare circulatory variables to an abrupt increase in isoflurance concentration via mask in patients who received either upper thoracic or lumbar epidural anesthesia, or neither.DesignProspective study.SettingOperating room at a university hospital.Patients45 ASA physical status I female patients scheduled for elective surgeries with general anesthesia.InterventionsPatients received thoracic (TEA group) or lumbar (LEA group) epidural anesthesia, or neither (control group) (n = 15 per group). An epidural catheter was inserted through the T1-T2 intervertebral space in the TEA group or L2-L3 in the LEA group, and 10 mL of 2% lidocaine without epinephrine was injected. Two minutes after induction of anesthesia with thiamylal, the inspired isoflurane concentration was rapidly increased from 0.5% to 5% and maintained for 5 minutes.Measurements And Main ResultsHeart rate and mean arterial pressure (MAP) were measured every minute. Mean analgesic levels obtained by epidural block were C4-T6 and T10-S1 in the TEA and LEA groups, respectively. Heart rate increased after the increase in isoflurane concentration in all groups, but increased significantly less in the TEA group than in the control or LEA groups (p < 0.05). Isoflurane also increased MAP in the control group throughout the 5-minute period, but only at the first minute of inhalation in the TEA and LEA groups. The increases in MAP in the TEA and LEA groups were significantly less than that in the control group (p < 0.05).ConclusionEpidural anesthesia can blunt circulatory responses to a sudden increase in isoflurane concentration.

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