The MEC90 of Epidural Ropivacaine Blunting Hemodynamic Changes to Pneumoperitoneum

The MEC90 of Epidural Ropivacaine Blunting Hemodynamic Changes to Pneumoperitoneum in the Patients Undergoing Laparoscopic Gastrectomy

Investigators want to find the concentration of epidural ropivacaine, which can block hemodynamic changes in the onset of pneumoperitoneum in the laparoscopic gastrectomy.

According to previous patient's response, the investigators will allocate the concentration of ropivacaine of next patient during Co2 insufflation. And, for this allocation of concentration of ropivacaine, the investigators use biased coin design up-and-down method.

Based on the practices, the starting concentration is 0.375 %, and the step size of concentration is 0.125%.

Inclusion Criteria:

• patients undergoing laparoscopic gastrectomy that require pneumoperitoneum
• patients who has epidural catheter to manage postoperative pain control
• patients who agree to our study

Exclusion Criteria:

• patients who don't agree to our study
• BMI<16.0 or BMI>35
• cardiovascular disease, pulmonary disease, renal disease
• alcoholic abuser or drug abuser
• any use of local anesthetics or drugs which have an influence on cardiovascular system from beginning of induction