Lumbar paravertebral block (LPB) has been used for anesthesia in different settings such as in varicocelectomy and inguinal hernia repair in adults and pediatrics. Different studies considered LPB as an alternative to general and spinal anesthesia when contraindications exist, especially in elderly patients. However, the results obtained when using LPB are controversial in terms of number of injections performed and the success rates.

Patients scheduled for hernia repair who will agree to undergo different number of paravertebral injections in the thoraco-lumbar plexus area under CT guidance.

While the patient is in lateral decubitis position, LPB injections will be made using a 100 mm 22 G nerve stimulator needle (Stimuplex, B.Braun, Melsungen, Germany). The site of injection is determined by manual palpation. The number of injections ranges from one to five and the level of injections ranges from T11 to L3.

The needle is penetrated perpendicular to the skin using the following nerve stimulator settings: 5mA, 9V and 2Hz. The stimulating needle is gently manipulated into a position to allow an adequate muscular response with a stimulating current of 0.4-0.8 mA. At this point, 4-5 ml of the contrast (Telebrix 35, 350 mg/ml, Roissy CDG Cedex, France) is injected. The patients will receive the same amount of contrast, despite the different number of injections. The needles are kept in their position and afterwards followed by CT scan.

A radiologist who is blind to the study will interpret the radiological results and document the level at which the needle tip is found, the distance from the kidney and the spread of the injected contrast. In order to ensure patient's safety, different measures will be taken to keep the radiation as low as reasonably achievable.

Following the radiological practice, patients will be transferred to the operating room to undergo inguinal herniorrhaphy, and will not followed for the purpose of this study.

Inclusion Criteria:

• Older than 18 years
• Scheduled for hernia repair

Exclusion Criteria:

Patients

• with coagulation disorders,
• with infection at the injection site,
• with allergy to contrast
• receiving opioids