The purpose of this study is to evaluate the change of the hemodynamic profiles on bio reactance technique during TURP in elderly patients.

Inclusion Criteria:

1) Twenty (ASA status I ~ III) patients, ages 65 to 80 yr old, who were scheduled for transurethral resection of the prostate under spinal anesthesia

Exclusion Criteria:

1. if there were contraindications for spinal anesthesia including hypersensitivity to any local anaesthetics, bleeding diathesis, infections at the puncture sites, or pre-existing neurological disease.
2. history of coronary artery bypass surgery
3. history of dementia
4. have a difficulty in understanding informed consent or refuse to sign the informed consent
5. patients height under 150 cm

elderly patients undergoing transurethral resection of the prostate under spinal anesthesia