Continuous Sciatic Nerve Blocks

Maria Matuszczak

Didier Sciard

A. Parasacral Approach

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

Indications: Anesthesia and postoperative analgesia for surgery below the knee; postoperative physiotherapy and complex regional pain syndrome.

Needle Size and Catheter: 18-gauge, 25-, 38-, or 50-mm insulated introducer needle, and a 20- or 21-gauge catheter.

Skin–Nerve Distance: The depth of the sacral plexus at this level has not yet been investigated in children. The plexus can be found at 15- to 50-mm depth.

Volume and Infusion Rate: (Table 60-1); 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 posterior superior iliac spine, and the ischial tuberosity.

Approach and Technique: A line is drawn between the posterior superior iliac spine and the ischial tuberosity; this line is divided in three. In an appropriately anesthetized/sedated child, the needle is introduced perpendicular to the skin, at the junction of the cranial third and the caudal two-thirds of that line. A sciatic nerve stimulation 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 (Fig. 60-1).

Table 60-1. Maximum Initial Bolus Volume of Ropivacaine 0.2%—Parasacral Approach

kg	2–10 kg	15 kg	20 kg	25 kg	30 kg	40 kg	50 kg	60 kg	70 kg
mL	1 mL/kg	15 mL	17.5 mL	20 mL	22.5 mL	25 mL	25 mL	30 mL	30 mL

Figure 60-1. Parasacral catheter placement.

Tips

The needle is introduced perpendicular to the skin or 30° in the cranial direction.
At this level the sciatic nerve is close to the internal iliac vessels (sciatic vascular trunk).
If there is bone contact, the needle needs to be inserted more caudally on the line between the posterior superior iliac spine and the ischial tuberosity.
A stimulating catheter can be used in older children.

Suggested Readings

Dadure C, Capdevila X. Continuous peripheral nerve blocks in children. Best Pract Res Clin Anaesthesiol 2005;19(2):309–321.

Dadure C, Pirat Ph, Raux O, et al. Perioperative continuous peripheral nerve blocks with disposable infusion pumps in children: a prospective descriptive study. Anesth Analg 2003;97:687–690.

Dalens B. Regional anesthesia in infants, children, and adolescents. Baltimore: Williams & Wilkins, 1995.

Ivani G, Mossetti V. Continuous peripheral nerve blocks. Paediatr Anaesth 2005;15:87–90.

B. Anterior Approach

Patient Position: Supine, with the leg in a neutral position.

Indications: Anesthesia and postoperative analgesia for surgery below the knee; postoperative physiotherapy and complex regional pain syndrome.

Needle Size and Catheter: 18-gauge, 50- to 150-mm insulated introducer needle, a 20- or 21-gauge catheter.

Skin–Nerve Distance: 3 cm at one year, increasing to 11 cm in adolescents (Fig. 60-2)

Volume and Infusion Rate: (Table 60-2); 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: Anterior superior iliac spine, the pubic tubercle (inguinal ligament), and the greater trochanter of the femur.

Approach and Technique: A line is drawn between the anterior superior iliac spine and the pubic tubercle (inguinal ligament line). Next, a parallel line is drawn passing
through the greater trochanter. A perpendicular line is drawn at the junction of the medial third and the lateral two-thirds of these lines. The intersection of the perpendicular line and the line passing through the greater trochanter presents the site of needle insertion. In an appropriately anesthetized/sedated child, the insulated needle, connected to a nerve stimulator (1.5 mA, 2 Hz, 0.1 ms) is introduced perpendicular to the skin. Within 3 to 11 cm, a sciatic nerve stimulation 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.

Figure 60-2. Distance skin to sciatic nerve, anterior approach distance.

Table 60-2. Maximum Initial Bolus Volume of Ropivacaine 0.2%—Anterior Approach

kg	2–10 kg	15 kg	20 kg	25 kg	30 kg	40 kg	50 kg	60 kg	70 kg
mL	1 mL/kg	15 mL	17.5 mL	20 mL	22.5 mL	25 mL	25 mL	30 mL	30 mL

Tips

A femoral nerve stimulation may be elicited within a depth of 1 to 4 cm.
The needle has to be withdrawn very carefully in order not to displace the catheter.
If the femur is contacted the needle has to be introduced more medially.
To the authors’ knowledge this approach was not yet used for continuous infusion in smaller children. The youngest patient with continuous infusion was 15 years old (43 kg).
A stimulating catheter can be used in older children.

Suggested Readings

Beck GP. Anterior approach to sciatic nerve block. Anesthesiology 1963;24:222–224.

Chelly JE, Greger J, Howard G. Simple interior approach for sciatic blockade. Reg Anesth 1997;22:114.

Dadure C, Capdevila X. Continuous peripheral nerve blocks in children. Best Pract Res Clin Anaesthesiol 2005;19(2):309–321.

Dadure C, Pirat Ph, Raux O, et al. Perioperative continuous peripheral nerve blocks with disposable infusion pumps in children: a prospective descriptive study. Anesth Analg 2003;97:687–690.

Dalens B. Regional anesthesia in infants, children, and adolescents. Baltimore: Williams & Wilkins, 1995.

Ivani G, Mossetti V. Continuous peripheral nerve blocks. Paediatr Anaesth 2005;15:87–90.

Raj PP, Parks RI, Watson TD, et al. A new single-position supine approach to sciatic-femoral nerve block. Anesth Analg 1975; 54:489–493.

C. Subgluteal Approach

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

Indications: Anesthesia and postoperative analgesia for surgery below the knee; postoperative physiotherapy and complex regional pain syndrome.

Needle Size and Catheter: 18-gauge, 25- to 100-mm insulated introducer needle, a 20- or 21-gauge catheter.

Skin–Nerve Distance: 2 cm at one year, increasing up to 6 cm in adolescents (Fig. 60-3).

Volume and Infusion Rate: (Table 60-3); maximum initial bolus volume of ropivacaine 0.2%. Dosage of ropivacaine 0.2% for continuous infusion: 0.4 to 0.5 mg/kg/h.

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