Surgery of the lumbar spine is characterized by diffuse and severe postoperative pain. In recent years, some case reports indicate that the thoracolumbar interfascial plane block (TLIPB) can reduce postoperative pain after spinal surgery, which targets the dorsal roots of the thoracolumbar nerves by depositing local anesthetic at the level of third lumbar vertebra between the multifidus and longissimus muscles. However, a new approach of the TLIPB technique by injecting local anesthetic between the longissimus and iliocostalis muscles, that is the Lateral TLIPB. According some relevant literature reports show that this technique simpler to perform and reduces the risk of neuraxial puncture. So, the purpose of this study is to investigate the efficacy and safety of the Lateral TLIPB combined with patient controlled intravenous analgesia (PCIA) is superior to PCIA in reducing postoperative pain in patients undergoing spinal surgery.

Although the number of spinal surgeries has been increasing for many years, the methods for perioperative pain relief have remained limited. According to some report show that surgery of the lumbar spine is characterized by diffuse and severe postoperative pain. Pre/postoperative oral opioids, gabapentinoids, nonsteroidal antiinflammatory drugs are frequently included in multimodal analgesia for spinal surgery, but the effect was not satisfactory. The ultrasound-guided thoracolumbar interfascial plane block (TLIPB) is a peripheral nerve block, which injecting local anesthetic between the muitifidus and longissimus muscles at the level of 3rd lumbar vertebra and can block the dorsal rami of thoracolumbar nerves. TLIPB have the potential to provide long-lasting postoperative analgesia and reduce opioid consumption while minimizing the motor block associated with neuraxial and plexus blocks. However, a new approach of the TLIPB technique by injecting local anesthetic between the longissimus and iliocostalis muscles, that is the Lateral TLIPB. Comparing with the TLIPB, Lateral TLIPB have some advantages, first; ultrasonographic identification of the multifidus and longissimus muscles may be difficult, and it is easier to find the plane between the longissimus and iliocostal muscles, so, the success rate of puncture is higher; secondly; lateral to medial needle advancement can cause inadvertent neuroaxial puncture. A medial to lateral approach may be safer to perform to avoid dural puncture. So, the purpose of this study is to investigate the efficacy and safety of the Lateral TLIPB combined with patient controlled intravenous analgesia (PCIA) is superior to PCIA in reducing postoperative pain in patients undergoing spinal surgery.

This study was approved by the institutional review board of the First Affiliated Hospital of Chongqing Medical University. The protocol design is in accordance with Consolidated Standards of Reporting Trials (CONSORT) statement. All potentially eligible participants will be asked to give written informed consent before they are enrolled in this study. This study is a prospective, randomized, double-blind, controlled clinical trial guided by the standard of good clinical practice (GCP), and eligible participants are divided into two groups: group Lateral TLIPB and group PCIA, and primary assess the outcomes of the intensity of acute pain after Lumbar disc surgery.

Participants in group Lateral TLIPB will receive a single injection local anesthetic at the level of third lumbar vertebra between the longissimus and iliocostalis muscles on either side of the spine, and combined with PCIA post-operatively.

Participants in group PCIA will receive the equal volume of 0.9% normal saline between the longissimus and iliocostalis muscles on either side of the spine and PCIA post-operatively.

The primary outcome of this study is the intensity of acute pain after Lumbar disc surgery.The secondary outcomes of this study rescue medication and adverse events associated with the post-operative analgesia.

This study will be conducted under the supervision of an independent auditor. Every week, the auditor checked the data of the participants the day after the surgery was conducted. Assessment of pain intensity and prognostic outcomes must be confirmed by the auditor in sample population. When there is disagreement between surgeon and anesthesiologists in evaluating the prognosis of patients, the auditor must solve this disagreement by discussion with evaluators. Data will be double-entered by two statisticians with limitation of access and locked during statistical analysis.

Inclusion Criteria:

1. men or woman and 18～65 years old
2. clinical diagnosis of umbar disc herniation and will receive selective Lumbar disc surgery

Exclusion Criteria:

1. age below 18 years or over 65 years;
2. American Society of Anesthesiologists grade III or greater;
3. Diabetes;
4. allergic to local anesthetics;
5. cognitive impairment or communication problems;
6. received opioids、NSAID or tranquilizers (treatment for over 1 wk before the surgery);
7. history of alcohol or drug abuse;
8. severe hepatic or renal impairment ;
9. post-operative severe complications(e.g. pyogenic infection)