Comparing Erector Spinae Plane (ESP) and Transversus Abdominis Plane (TAP) Block in Inguinal Hernia

In the recent era of increased awareness towards the risks and complications of opioid treatment, pain management after common surgical interventions by the means of regional anesthesia is of renewed interest for both clinical and logistic reasons, as it is known that good pain management reduces complications and cost associated to surgery.

Regional and local anesthetic techniques after inguinal hernia surgery have been the topic of multiple studies, comparing various infiltrative methods, including wound infiltration, port site infiltration, iliohypogastric and ilioinguinal nerve block, paravertebral and transversus abdominis plane (TAP) block and epidural analgesia. Most methods investigate pain treatment in the setting of open surgery. The progressive evolution towards laparoscopic and robot-assisted methods changes the mechanisms of surgical pain and, with it, the rational for the choice of the analgesic technique adopted. The transversus abdominis plane (TAP) has become a widely used technique and has been demonstrated to be associated to a mild opioid sparing effect, but with inconsistent results.

The erector spinae plane block is a promising technique, recently described and used especially in thoracic surgery. Multiple case reports and studies in pediatrics report it to be a safe and effective method for abdominal surgery as well, but no prospective randomized trials were published to date in the adult population, particularly with regard to laparoscopic or robotic hernia repair. A prospective comparison between the two techniques is therefore needed in this specific context.

Hypothesis and primary objective:

The investigators hypothesize the superiority of the ESP-block to the TAP-block with respect to post-operative pain control after abdominal surgery, leading to a reduction in reserve analgesic consumption.

Our objective is to compare the clinical outcomes and safety of ESP block versus TAP block in patients undergoing robot-assisted TAPP inguinal hernia repair.

Primary and secondary endpoints:

Primary Endpoint:

• The highest VAS score reported between end of sedation and 6 hours after surgery or discharge of the patient, whichever comes first Secondary Endpoints
• Time to first rescue analgesic
• Total dose of rescue opioids (morphine equiavalents) in the first 24 hours after surgery
• Time of first walk after surgery
• Need for anti-nausea medication (dosage, doses and time points)
• Episodes of vomiting
• Episodes of urinary retention
• Patient's satisfaction (measured on the validated LPPS questionnaire for the perioperative patients' satisfaction )
• Length of hospital stay

Study design This is a single center, prospective, randomized, placebo-blinded, controlled superiority trial in 2 parallel arms comparing the efficacy and safety of the ESP Block and the TAP block on patients undergoing elective robot-assisted inguinal hernia repair.

Follow up will consist in the hospitalization period plus one telephone consultation at 24 hours after hospitalization.

Methods of minimizing bias:

Randomisation - Patients will be randomized in a 1:1 ratio by a computer generated random number sequence through the RedCap software system.

Blinding procedures

According to the randomization arm patients will receive:

• sham US-guided ESP block + US-guided TAP block before laparoscopic hernia repair
• US-guided ESP block + sham US-guided TAP block before laparoscopic hernia repair Allocation will take place immediately before the intervention by the means of access to centralized, real-time allocation through a computer program.

Personnel not directly involved with patient care will prepare a saline solution and a ropivacaine solution which will be allocated respectively to ESP or TAP block according to randomization.

This will allow blinding of patients, care providers and data collectors. Analysis will be done on allocation-concealed data, permitting blinded analysis.

Unbliding will be permitted if by doing so harm to one or more patients can be avoided or treated. After information of one of the principal investigators, specific patient allocation will be retrieved from the randomization program.

Other methods of minimising bias

Pain scores will be measured at 1, 3, 6, 12 and 24 hours after extubation and at the time of administration of reserve analgesics.

The administration of reserve analgesics will follow a standardized internal protocol.

Questionnaires validated to assess functional results after hernia surgery will be used for this study:

• pain: Visual Analogue Scale (VAS)
• surgical complications classification: Clavien Dindo's classification
• comorbidities : American Society of Anesthesiology (ASA) score
• validated LPPS questionnaire for the perioperative patients' satisfaction [21]
• EHS inguinal hernia classification