Effects of epidural anesthesia on the cardiovascular response to a rapid increase in isoflurane concentration.
OBJECTIVE
To 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.


METHODS
Prospective study.


METHODS
Operating room at a university hospital.


METHODS
45 ASA physical status I female patients scheduled for elective surgeries with general anesthesia.


METHODS
Patients 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.


RESULTS
Heart 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).


CONCLUSIONS
Epidural anesthesia can blunt circulatory responses to a sudden increase in isoflurane concentration.
Nakayama
M
M
Department of Anesthesiology, Sapporo Medical University School of Medicine, Japan. miyabi@zc4.so-net.ne.jp
Tsuchida
H
H
Kanaya
N
N
Namiki
A
A
D000328:Adult; D000704:Analysis of Variance; D000767:Anesthesia, Epidural / Q000145:classification* / Q000379:methods; D000771:Anesthesia, Intravenous; D018685:Anesthetics, Inhalation / Q000008:administration & dosage*; D018686:Anesthetics, Intravenous / Q000008:administration & dosage; D000779:Anesthetics, Local / Q000008:administration & dosage; D001794:Blood Pressure / Q000187:drug effects*; D017558:Elective Surgical Procedures; D004562:Electrocardiography / Q000187:drug effects; D005260:Female; D006321:Heart / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D007530:Isoflurane / Q000008:administration & dosage*; D008012:Lidocaine / Q000008:administration & dosage; D008159:Lumbar Vertebrae; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D011446:Prospective Studies; D013840:Thiamylal / Q000008:administration & dosage; D013904:Thoracic Vertebrae
D018685:Anesthetics, Inhalation; D018686:Anesthetics, Intravenous; D000779:Anesthetics, Local; D013840:Thiamylal; D008012:Lidocaine; D007530:Isoflurane; D010100:Oxygen