Posterolateral thoracotomies are among the most painful procedures of surgery and may cause severe postoperative chest pain and impaired respiratory performance. Paravertebral block (PVB) is an established method of administering postoperative analgesia for thoracic procedures. PVB blocks the somatic and sympathetic nervous systems and is placed by injecting a local anesthetic (LA) into the paravertebral space where the nerve and its branches are located after exiting the intervertebral foramen. But previous study showed 5-10% of failure rate in PVB using ultrasound machine. Pressure measurement during needle advancement could improve reliability of correct needle placement. When the needle tip reaches paravertebral space, there is a sudden lowering of pressures due to respiratory cycle. Therefore, sensitivity and specificity could be improved and correct needle placement become objective and reproducible when PVB using ultrasound is combined with pressure measurement during needle advancement.

Inclusion Criteria:

• Scheduled for elective thoracotomy
• ASA status 1,2

Exclusion Criteria:

• Inability to provide adequate informed consent
• Any contraindication to the placement of thoracic paravertebral catheters
• Unstable vertebral and transverse process fractures
• Any chronic painful conditions or preoperative opioid use Any chronic painful conditions or preoperative opioid use
• Coagulation abnormalities or expectation to be on therapeutic anticoagulants postoperatively
• Allergy to any of the drugs/agents used in study protocol
• Altered mental status or emergency surgery
• Comorbid conditions such as sepsis, unstable angina, congestive heart failure

IPD sharing is needed to get permission from IRB.