Erector Spinae Plane Block for Video-assisted Thoracoscopic Surgery

Video-Assisted Thoracoscopic Surgery (VATS) is a minimally invasive surgery that utilizes camera based scopes and specialized instruments through keyhole sized ports to remove lesions in the thoracic cavity. Despite reduced surgical trauma compared to the traditional thoracotomy approach, patients continued to experience moderate to severe postoperative pain. Pain medication such as opioids is commonly utilized for postoperative pain control but is associated with side effects. The use of nerve blocks, such as the recently described erector spinae plane block (ESPB) has been shown in case reports to reduce pain and thus has the potential to improve patient recovery and decrease the risk of pulmonary complication. This study aims to investigate the analgesic effect of ESPB in managing pain following VATS.

VATS is a minimally invasive surgical technique to remove intrathoracic lesions. Using a camera based scope and specifically designed instruments, the surgery can be initiated with three "key-hole" sized incisions. At the end of the surgery, an incision is enlarged to allow removal of surgical specimen. Chest tubes are inserted at the end of procedure and sutured in between the ribs.

While acute pain after VATS is less than the traditional thoracotomy, patients still experience moderate amount of pain within the first 24 hours. Source of pain may be from diaphragm irritation, surgical incisions and chest tubes. Because of its origin on the chest wall, pain from VATS worsens with breathing. When pain is poorly controlled, it will lead to a shallow breathing pattern called "splinting" and this can progress to respiratory distress or failure. Given the high incidence of smoking history in this patient population, many would have presented with poor baseline respiratory function. Therefore, it is important to provide good pain control to allow deep breathing and cough to reduce respiratory complications\[1\]\[2\].

Despite the smaller incisions, the incidence of chronic post-surgical pain (CPSP) after VATS is surprisingly similar to thoracotomy. The mechanism may be due to nerve compression by the trocar, an instrument inserted between the ribs to allow smooth manipulation of camera and surgical instruments in the thoracic cavity. Additionally, poorly controlled acute pain has also been postulated to lead to the development of CPSP, further emphasizing the importance of good analgesia\[1\].

Many regional analgesia techniques have been tried to improve postoperative analgesia. Thoracic epidural analgesia (TEA) remains the gold standard of pain control after thoracic surgery. Although it provides superior analgesia, its use is hindered by the rare but serious complication of epidural hematoma and abscess which may cause paralysis. Further, pain from VATS tends to be short-lived (less than 24 hours), making the risk to benefit ratio less ideal for TEA. An alternative to TEA is paravertebral block (PVB). Compared to TEA, it causes less hypotension and hematoma or abscess at the paravertebral space may be less consequential. Nevertheless, PVB is a deep block and is technically demanding which limits its wide adoption\[3\].

Erector spinae plane block (ESPB) is a novel nerve block that has been used for analgesia for surgeries of the chest and abdominal wall. Using a bony structure, the transverse process, as the end point, the block needle is very unlikely to cause injury to vital structures as is possible with TEA or PVB (for examples, the spinal cord, lungs and blood vessels). It is also technically easy to perform. ESPB has only been reported in case series but so far, no adverse events such as hypotension, hematoma or infection has been reported. ESPB has also showed promise in managing CPSP after thoracic surgery in a small case series\[4\].

Given its safety, ease of performance and efficacy, the study aims to study the analgesic efficacy of ESPB in addition to systemic analgesia compared to systemic analgesia alone in patients undergoing VATS. The hypothesis is that ESPB and systemic analgesia will provide better analgesia when compared to systemic analgesia alone.

Eligibility Criteria:
Inclusion Criteria:

1. Adult patients
2. Scheduled for an elective VATS
3. American Society of Anesthesiologists (ASA) physical status I to III

Exclusion Criteria:

1. Age \< 18
2. BMI \> 40
3. Patient refusal or inability to provide consent
4. Chronic pain conditions
5. Daily opioid use \> 60 mg of oral morphine equivalents
6. Cognitive or psychiatric condition that makes it challenge to assess pain
7. Conversion to open thoracotomy
8. Allergy to any of the drugs used in this study
9. Contraindication to nerve blocks such as infection, severe coagulopathy or pre-existing neuropathy
10. Significant systemic cardiac, respiratory, hepatic or renal diseases
11. Postoperative admission to intensive care unit