Lumbar Plexus Blocks

Giorgio Ivani

Valeria Mossetti

A. Posterior Approach

Patient Position: The patient is in the lateral decubitus position, the side to be blocked lying uppermost.

Indications: Anesthesia and postoperative analgesia for hip, femur, or knee surgery.

Needle Size: A 22-gauge, 50-mm, insulated beveled needle; for older children 100 mm.

Volume: Ropivacaine 0.2% for children up to 7 years, levobupivacaine 0.5% for older children, 0.5 mL/kg.

Anatomic Landmarks: The posterior superior iliac spine, the iliac crest, and the spinous process of L4.

Approach and Technique: The site of needle insertion is the intersection between the vertical line drawn from the highest point of the iliac crest and the line drawn from the posterior superior iliac spine parallel to midline along the spinous processes of L4 and L5. The needle connected to the nerve stimulator set at 1.5 mA and 2 Hz is introduced perpendicular to the skin in search of the transverse process of L4. Then redirect the needle cranial or caudal and 1 cm deeper until stimulation of the femoral nerve is elicited (contraction of the quadriceps muscle, usually the vastus lateralis muscle). Adjust the position of the needle to maintain the appropriate muscle response with a current of 0.4 to 0.5 mA. Then, after negative aspiration, slowly inject the local anesthetic solution.

Tips

This block is more difficult and not free of complications in a pediatric patient, therefore should only be performed by anesthesiologists trained in pediatric regional anesthesia.
It is important to remember the distance between skin and nerve vary according to the age: 2.5 cm at 1 year increasing to 8 cm in adolescents.
There are some contraindications for this block: coagulation disorders, trauma of the lumbar spine, lumbar vertebral deformities, peritoneal or visceral infections.
Complications include:

Visceral organ puncture, especially of the kidney. Use the shortest needle that can reach the plexus.
Subarachnoid (high or total spinal anesthesia) or epidural (contralateral anesthesia) spread. Avoid a medial puncture direction, perform a test dose, inject slowly and while injecting watch closely blood pressure and heart rate.
Vessel puncture (paravertebral veins).

Suggested Readings

Chayen D, Nathan H, Chayen M. The psoas compartment block. Anaesthesiology 1976;45:95.

Dalens B, Tanguy A, Vanneuville G. Lumbar plexus block in children. Comparison of two procedures in 50 patients. Anaesth Analg 1988;67:750.

Johr M. The right thing in the right place: lumbar plexus block in children. Anesthesiology 2005; 102(4):865; author reply 865–866.

Sciard D, Matuszczak M, Gebhard R. Continuous posterior lumbar plexus block for acute postoperative pain control in young children. Anesthesiology 2001;95(6):1521–1523.

B. Femoral Block