We thank Dr. Jöhr for his comments on our article published in the August 2004 issue of Anesthesiology.1He pointed out important anatomical features regarding lumbar plexus anatomy that might raise concerns about the indications of ultrasound-guided posterior lumbar plexus blocks in our series of pediatric patients.
The lumbar plexus is derived from the ventral rami of the roots L1–L5. The latter and its branches are arranged in a potential space within the substance of the psoas major muscle, the so-called psoas compartment. The iliohypogastric, ilioinguinal, and genitofemoral nerves are the most cranial branches and provide innervation of the inguinal region. They arise from the ventral rami of the roots T12–L1, L1, and L1–L2, respectively. Therefore, a posterior lumbar plexus block by means of an approach at the level L4–L5 would probably result in an incomplete or missing block of these nerves, as mentioned by Dr. Jöhr.
In adults, the iliohypogastric and ilioinguinal nerves approximately exit the psoas major muscle at L1–L2,2and the genitofemoral nerve usually exits at L4.2Nevertheless, the detailed topographic anatomy and arrangement of these nerves within the psoas major muscle in children is unknown.
In the current cases, the local anesthetic solution must have reached the cranial parts of the lumbar plexus because sufficient anesthesia and analgesia of the inguinal region was observed in all five patients. Recent investigations of ultrasound-guided posterior lumbar plexus block in pediatric patients revealed a greater extent of anesthesia and analgesia compared with adults.
It was not the aim of our study to investigate posterior lumbar plexus block for inguinal hernia repair in children, and we agree with Dr. Jöhr that it should not be the first choice for this surgical procedure. However, in our opinion, it might be a useful alternative and still represents a peripheral nerve block.
Dr. Jöhr also had concerns about the strategy of applying small volumes in the current setting. Nevertheless, one of the proven benefits of ultrasound-guided techniques is the decreased need of local anesthetics3compared with traditional approaches.
* Community Hospital Hall in Tyrol, Hall in Tyrol, Austria. firstname.lastname@example.org