Continuous Lumbar Plexus Blocks

Maria Matuszczak

Didier Sciard

A. Psoas Compartment Approach

Patient Position: Lateral, with the side to be blocked upright.

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

Needle Size and Catheter: 18-gauge, 38-, 50-, or 100-mm insulated introducer needle, and a 20- or 21-gauge catheter.

Skin–Nerve Distance: 2.5 cm at one year, increasing to 8.0 cm in adolescents. Distance from skin to lumbar plexus depends also on the weight (Fig. 59-1).

Volume and Infusion Rate: (Table 59-1); maximum initial bolus volume of ropivacaine 0.2%. Dosage of ropivacaine 0.2% for continuous infusion: 0.4 to 0.5 mg/kg/h.

Anatomic Landmarks: The highest point on the iliac crest is identified. A line is drawn from this point to the spine processes (SP). The posterior superior iliac spine (PSIS) is identified. A parasagital line to the vertebral spine is drawn passing through the posterior superior iliac spine. The intersection of these two lines is the point of insertion of the introducer needle (Figs. 59-2, 59-3).

Approach and Technique: The needle is introduced perpendicular to the skin or lightly directed posteriorly in an appropriately anesthetized/sedated child. After bone contact with the transverse process of L4 or L5, the needle is redirected to the cranial or caudal direction (angle between 30 and 45 degrees) and 1 cm deeper until a contraction of the quadriceps (femoral n.) is elicited. With an appropriate muscle response still present at a current of 0.5 mA and after negative aspiration for blood the appropriate amount of local anesthetic solution is slowly injected. Maintaining the introducer needle in the same
position, the catheter is threaded 2 cm beyond the needle tip. The introducer needle is removed and the catheter is secured in place with benzoin and a transparent adhesive dressing. Blood pressure has to be monitored because of a possible epidural or subarachnoid injection. The absence of epidural spread is assessed by the presence of an adequate reaction to pinprick of the opposite leg after emergence.

Figure 59-1. Distance skin to lumbar plexus.

Tips

This block should only be performed by an anesthesiologist trained in pediatric regional techniques.
The technique described above is Winnie’s approach; we do not use Chayen’s approach because of a higher incidence of epidural spread reported in the literature.
The shortest needle that can easily reach the plexus has to be used because of the potential risk of visceral organ (kidney) puncture.
Ultrasound guidance can help to determine the depth of the lumbar plexus.
Peritoneal or visceral infection, trauma to the lumbar spine, lumbar vertebral deformities, and coagulopathy are contraindications for this block.
A slow injection (1 mL/10 seconds) of the local anesthetic is advised.
The absence of epidural spread is assessed by the presence of an adequate reaction to a pinprick of the opposite leg after emergence from anesthesia.
A stimulating catheter can be used in older children.