The Spread of Paravertebral Injections in the Lumbar Plexus Area and Associated Risk Factors to Adjacent Organs: a CT Scan Based Report

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.