Ultrasound Guided Erector Spinae Plane Block in Patients Undergoing Video-assisted Thoracoscopic Surgery (VATS) Lobectomy or Wedge Resections - a Pilot Randomized Control Trial

Video assisted thoracoscopic surgery (VATS) has become an increasingly popular technique in thoracic surgery with improvement in technology. It provides significant advantages over open thoracotomy procedures including reduced acute pain, reduced mortality, improved post-operative pulmonary function, and shorter hospitalization stays. Nevertheless, there is still considerable amount of post-operative acute pain with VATS lobectomies. Controlling post-operative pain is crucial because increased acute pain has been associated with the development of chronic pain.

Many patients receive either thoracic epidural (TEA) or paravertebral blocks (PVB) to treat post-operative pain in thoracotomy procedures as these techniques remain the gold standard. In contrast to thoracotomy procedures, it is unclear which is the best approach to analgesia is in VATS. A few studies have found no benefit in pain scores, patient satisfaction, pulmonary function, and incidence of side effects when comparing TEA with opioid patient controlled analgesia in VATS. Other studies have found minimal benefit in pain scores with TEA. The PVB has been used as alternative to TEA. One prospective observational study using PVB and continuous intercostal catheter demonstrated lower pain scores in VATS lobectomy. A randomized control trial (RCT) comparing PVB with wound infiltration in VATS lobectomy showed lower pain scores, lower morphine consumption, and higher patient satisfaction. However, both TEA and PVB have potential serious side-effects and complications. Complications of TEA include severe hypotension, epidural abscess, epidural hematomas and spinal cord injury. PVB have less incidence of hypotension but may involve risks like pneumothorax, pleural and vascular puncture, and higher systemic absorption of local anesthetics. PVB is also technically challenging and its spread is not reliable likely due to the presence of the endothoracic fasica. In addition, placement of both TEA and PVB require appropriate discontinuation of anticoagulants. Intercostal nerve blocks have been used as an analgesic alternative to TEA and PVB. One RCT found patients who had received intercostal blocks undergoing bilateral VATS for hyperhidrosis had lower pain scores in the post-anesthesia recovery unit (PACU). A combined retrospective and prospective study examined the analgesic effect and duration of intercostal blocks in patients undergoing VATS. The authors found that intercostal blocks decreased morphine consumption in the first 24 hours and the analgesic effect of the block lasted approximately 16 hours. Intercostal blocks appear to have some analgesic effect in the immediate post-operative period but are short-lived unless a catheter is placed. The standard practice for post-operative pain management for VATS lobectomy at St. Joseph's hospital consists of intercostal blocks performed by the thoracic surgeons at the end of surgery in combination with patient-controlled analgesia (PCA).

A novel regional technique called the Erector Spinae Plane (ESP) block has been recently described. This interfascial block involves ultrasound guided injection of local anesthetics posterior to the erector spinae muscle and superficial to transverse process of thoracic vertebrae at appropriate level. The ESP block appears to target the dorsal and ventral rami of the spinal nerves as they leave the intervertebral foramen. Cadaveric examination of ESP block showed extensive cranial-caudal spread of the block, approximately four dermatomes above and below the site of injection. The ESP block has been successfully applied in multiple clinical settings. For example, several patients suffering from chronic thoracic neuropathic pain achieved significant analgesia after receiving ESP blocks. ESP blocks have also been used as a rescue analgesia for a patient who failed a TEA after thoracotomy. Other applications include ventral hernia repair in abdominal surgery. The simplicity and safety of the ESP block has been proposed as its main advantages. Because it is a superficial interfascial plane block, it is distant from both the spinal cord and pleura. The ESP block is technically an easy to perform under ultrasound guidance due to its superficial location. There is also theoretically less possibility of needle related complications as the transverse process acts as a backstop for needle advancement. A catheter can be placed easily during the ESP block allowing continuous infusion and prolonged analgesia.

Given the importance of providing adequate analgesia in VATS lobectomy and wedge resections and lack of consensus amongst surgeons and anesthesiologists for the optimal analgesic technique, the investigators are proposing a prospective observational study to examine the analgesic efficacy of the ESP block in VATS lobectomy or wedge resections as a potential alternative to TEA, PVB and intercostal blocks. The investigators are hoping the results of this study will provide framework for future larger comparative studies.