 The purpose of this project is to determine if there is a difference between paravertebral block performed with ultrasound assistance and paravertebral block performed with traditional technique in terms of twenty - four hour hydromorpone dilaudid consumption and visual analogue pain scores at rest or with deep breathing at twenty - four hours. This study will determine if ultrasound technique used for placement of paravertebral catheter facilitates safety of paravertebral catheterization and improves therapeutic effect of paravertebral blockade for pain control after thoracotomy. The investigators will also examine if ultrasound assisted paravertebral blockade improves pulmonary status in post-thoracotomy patient. 