The effect of intraoperative infiltration of the operation site with bupivacain on the development of chronic pain is the object of our trial. We hypothesize that the occurrence of chronic pain in the goup of patients receiving the infiltration will be 50% less than in the placebo group receiving normal saline. The study is a randomized controlled triple blinded trial with a sequential study design.

264 patients scheduled for an inguinal hernia repair using one of three procedures (Lichtenstein, Barwell and TEP = total extraperitoneal hernioplasty) are being randomly allocated intra-operatively into two groups. Group I patients receive a local injection of 20ml Carbostesin® 0.25% at the end of the operation according to a standardised procedure. Group II patients get a 20 ml placebo (0.9% Saline) injection. We use pre-filled identically looking syringes for blinded injection, i.e. the patient, the surgeon and the examinator who performs the postoperative clinical follow-ups remain unaware of group allocation. The primary outcome of the study is the occurrence of developing chronic pain (defined as persistent pain at 3 months FU) measured by VAS and Pain Matcher® device (Cefar Medical AB, Lund, Sweden).

In addition to a sample size re-evaluation three interim analyses are planned after 120, 180 and 240 patients had finished their 3-months follow-up to allow for early study termination.

Inclusion Criteria:

• Adult patients (≥ 18 years) with primary or recurrent single or double sided symptomatic but not incarcerated inguinal hernias with an elective hernia repair are included.
• No other interventions (i.e. umbilical hernia) are allowed.
• Written informed consent needs to be obtained.

Exclusion Criteria:

• Patients with legal incompetence,
• Pregnant and nursing women,
• Patients with presence or history of active malignancy or systemic diseases,
• Under immunosuppressive treatment,
• With systemic or severe local inflammation or infection,
• With wound healing disorders and with physical or mental incapacity, which makes it impossible to obtain informed consent are excluded.
• As pacemakers interfere with the electrical stimulation of the Pain Matcher® and vice versa patients with pacemakers or other implanted electrical devices were also excluded.