A new technique for ilio‐inguinal and iliohypogastric nerve block

Abstract

We would like to describe a potential pitfall which may be encountered when performing ilio-inguinal and iliohypogastric nerve blocks and a technique for overcoming the problem. The iliohypogastric nerve lies deep to the external oblique aponeurosis and the ilio-inguinal nerve lies between the internal oblique and transversus abdominus muscle (Fig. 3). The fascia click technique to block these nerves is dependent upon eliciting two distinct ‘pops’ or ‘clicks’ as the needle is advanced through the external oblique aponeurosis and subsequently the internal oblique muscle. This is facilitated by the use of a short bevelled needle. However, some force may be required to penetrate the skin with such a needle. This can obliterate the cushion of subcutaneous fat between the skin and the external oblique aponeurosis (Fig. 4) and a lack of awareness of this cushion effect may result in the initial puncture penetrating both the skin and external oblique aponeurosis simultaneously. If the needle is then advanced to elicit two ‘clicks’ or ‘pops’ the needle tip will be deep to the transvs. abdominus muscle and local anaesthetic deposited in this space is likely to block the femoral nerve [4]. The initial puncture with a short bevelled needle penetrates both the skin and external oblique aponeurosis. The sharp introducer needle penetrates the skin and maintains the cushion of subcutaneous tissue. This pitfall may be avoided by using a sharp introducer needle to puncture the skin. We recommend using a 22G pencil-point spinal needle (Whitacre) and its introducer to perform this block. The introducer needle is sharp and one can be certain of puncturing only the skin. The spinal needle is then inserted through the introducer into the subcutaneous tissue (Fig. 4). The 22G spinal needle provides good feedback in terms of a distinct ‘pop’ as the external oblique aponeurosis and the internal oblique muscles are penetrated. In our experience this approach results in improved success of the block and reduced complication rates. In particular, transient femoral nerve palsy is less likely. The principle described is applicable to any block where loss of resistance or ‘pops’ need to be felt with a blunt needle as it penetrates fascial layers such as the iliacus compartment block and the rectus sheath block.