Anesth Analg 2003;97:1300-1302
© 2003 International Anesthesia Research Society
PEDIATRIC ANESTHESIA
Sciatic Nerve Block in a Child: A Sonographic Approach
Andrew T. Gray, MD PhD,
Adam B. Collins, MD, and
Ingeborg Schafhalter-Zoppoth, MD
Department of Anesthesia and Perioperative Care, University of California, San Francisco, California
Address correspondence and reprint requests to Andrew T. Gray, MD, PhD, Department of Anesthesia and Perioperative Care, Rm. 3C-38, San Francisco General Hospital, University of California, San Francisco, CA 94110. Address e-mail to graya{at}anesthesia.ucsf.edu
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Abstract
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Ultrasound technology can facilitate peripheral nerve blocks in clinical practice. In this case report, ultrasound imaging was used to identify the sciatic nerve and guide local anesthetic injection in the subgluteal region of a child undergoing Achilles tendon lengthening. Sonographic guidance may be especially useful for peripheral nerve blocks in children because the neural imaging is often excellent and reference landmarks are variable.
IMPLICATIONS: In this case report, ultrasound was used to identify the sciatic nerve and guide local anesthetic injection in the subgluteal region of a child. Sonographic guidance may be especially useful for peripheral nerve blocks in children because the neural imaging is often excellent and reference landmarks are variable.
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Introduction
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In 1922, Labat (1) introduced sciatic nerve block in the gluteal region relying on bony landmarks. Various other approaches to sciatic nerve block/anesthesia have since been published. Favorable descriptions of sciatic nerve imaging near the angle between the lower border of the gluteus maximus and the long head of the biceps at the gluteal crease have been reported (2–5). This prompted us to apply ultrasound technology to guide sciatic nerve block in the posterior thigh.
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Case Report
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A 7-yr-old boy with prior Achilles tendon lengthening and mild spastic hemiparesis was scheduled for a Z-plasty because of a recidivating tight heel cord. After oral premedication with 10 mg of midazolam (the patient weighed 27 kg), anesthesia was induced by inhaled nitrous oxide and sevoflurane, and a laryngeal mask airway was placed. The child was then turned to the lateral decubitus position with the operative side up and the upper thigh flexed. The sciatic nerve was imaged in the posterior thigh near the gluteal crease (Fig. 1), and a Stimuplex® insulated needle (B. Braun Medical Inc., Bethlehem, PA) was inserted (Fig. 2). Nerve position was confirmed by electrolocation, with plantar flexion of the foot observed at 0.4 mA. The sciatic nerve block was performed with 15 mL of 0.375% levobupivacaine (Fig. 3). Fentanyl 20 µg IV and acetaminophen (Tylenol®) 650 mg rectally were given during surgery. General anesthesia was maintained with sevoflurane (end-tidal concentration 1.2%–1.4%). Both the surgery and postoperative course were unremarkable. Tourniquet time was 41 min. On postoperative examination, dense sensory and motor blockade were present. The child did not require medication during recovery and was discharged home with a small adult cast shoe 3 h after the block was performed.
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Figure 1. The sciatic nerve imaged in short axis (transverse) in the thigh just below the gluteal crease (left) and the corresponding labeled image (right). The nerve is seen between the biceps femoris/semitendinosus muscle complex (biceps) and the large gluteal muscle (gluteus maximus). The deep fascia (fascia lata) separates the gluteal muscle from adipose tissue. The block needle is out of the plane of imaging. Markers are spaced 10 mm apart.
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Figure 2. Schematic diagram illustrating the approximate position of the sciatic nerve (dotted line shown on the contralateral side), the ultrasound probe (gray), and the point of needle insertion (X) used in this patient.
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Figure 3. Ultrasound image obtained after injection of 15 mL of 0.375% levobupivacaine for sciatic nerve block. Local anesthetic spread (between arrowheads) was observed. The brightness and contrast of the nerve and local anesthetic spread have been adjusted for better visualization.
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Discussion
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Recent advances in ultrasound technology have enabled direct imaging of nerves. Most nerves have a "fascicular" (or "honeycomb") appearance (Fig. 1), with hypoechoic fascicles surrounded by hyperechoic connective tissue. From studies of bovine sciatic nerve, ultrasound scans can detect as much as one third the number of fascicles evident with light microscopy (6).
Several investigators have reported satisfactory imaging of the adult sciatic nerve in the thigh, where the nerve has a round or oval appearance (approximately 8 x 6 mm on transverse scan) and an internal punctate echotexture (2). In patients of advanced age, visibility may be compromised, in part, because of the high echogenicity of adjacent muscles (3,4). In contrast, excellent nerve visibility is anticipated in pediatric patients, suggesting a reliable clinical benefit to the use of ultrasound to guide sciatic nerve blockade in this population.
Because of the age of our patient, we chose to perform sciatic nerve block after the induction of general anesthesia. We used a laryngeal mask airway, making prone positioning of the patient for sciatic block impractical. Of published approaches to sciatic nerve block, our method most closely resembles the subgluteal "inline" technique of Sutherland (7) and the infragluteal/parabiceps technique of Sukhani et al. (8). Both studies simplify the sciatic nerve block technique by suggesting easier landmarks and use more distal needle insertion to reduce patient discomfort. The subgluteal approach also appears to benefit continuous sciatic nerve infusion by reducing the risk of peripheral catheter dislodgement (7). Nerve stimulation confirmed the approach to the nerve in both of these studies, whereas in our case, the nerve and spread of local anesthetic injection were also visualized (Fig. 3). Anatomic measurements in adult cadavers have found a relatively narrow distribution (range, 9.7–10.3 cm) between the intergluteal sulcus and sciatic nerve, independent of size and sex (9). However, every landmark or distance is a surrogate marker of the actual position of the nerve, and considerable deviation will occur in pediatric patients.
In summary, we believe that an ultrasound-guided technique may improve the success and safety of the sciatic and other peripheral nerve blocks in multiple ways, including decreasing the volume of tissue to be searched, assisting in avoiding vascular structures, and allowing direct observation of the spread of local anesthetic around neural targets. Besides direct sonographic visualization of the sciatic nerve, ultrasound may be useful to differentiate associated muscular and bony landmarks in the gluteal region, thereby increasing the safety of regional anesthetic performance. In pediatric patients, where anatomic distances, depths, and angles depend on the age and development of the child, ultrasound guidance is likely to prove beneficial practically and clinically, but more experience is needed with this technique.
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References
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- Labat G. Regional anesthesia: its technic and clinical application. Philadelphia: WB Saunders, 1922.
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- Sutherland ID. Continuous sciatic nerve infusion: expanded case report describing a new approach. Reg Anesth Pain Med 1998; 23: 496–501.[ISI][Medline]
- Sukhani R, Candido KD, Doty R Jr, et al. Infragluteal-parabiceps sciatic nerve block: an evaluation of a novel approach using a single-injection technique. Anesth Analg 2003; 96: 868–73.[Abstract/Free Full Text]
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Accepted for publication June 24, 2003.
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Abstract
Introduction
