This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a colleague Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (6) Citing Articles via Google Scholar Google Scholar Articles by van Geffen, G. J. Articles by Gielen, M. Search for Related Content PubMed PubMed Citation Articles by van Geffen, G. J. Articles by Gielen, M. Related Collections Pediatrics Regional Anesthesia

---

PEDIATRIC ANESTHESIA

Ultrasound-Guided Subgluteal Sciatic Nerve Blocks with Stimulating Catheters in Children: A Descriptive Study

From the Institute for Anesthesiology, Medical Centre, Radboud University, Nijmegen, the Netherlands.

Address correspondence and reprint requests to Geert Jan van Geffen, MD, Radboud University, Medical Centre, Institute for Anesthesiology, PO Box 9101, 6500 HB Nijmegen, The Netherlands. Address e-mail to G.vanGeffen{at}anes.umcn.nl.

	Abstract

Top Abstract Introduction METHODS RESULTS DISCUSSION REFERENCES

 
We describe our clinical experience of combining ultrasound guidance and nerve stimulation for the insertion of subgluteal sciatic catheters in children. Ten children scheduled for lower limb surgery with a combined general anesthetic and a subgluteal sciatic catheter placement for both operative anesthesia and postoperative pain relief were studied. Under ultrasonographic guidance the sciatic catheter was placed using an 17-gauge 50-mm Arrow® continuous peripheral nerve block needle and a 19-gauge stimulating catheter (Stimucath®). The minimal electrical current required for muscle contraction on the stimulating needle and catheter differed widely among patients. Based on the visualization of the spread of local anesthetic during injection through the catheter, a successful prediction for the sciatic block was made in all patients. All catheters were successfully placed and provided excellent postoperative pain relief without complications.

	Introduction

Top Abstract Introduction METHODS RESULTS DISCUSSION REFERENCES

 
Ultrasonographic guidance for continuous peripheral nerve blocks (CPNB) can be helpful for optimizing catheter positioning and by directly documenting the spread of local anesthetic during injection. Direct visualization of nerves and surrounding structures may improve the quality and success rate of nerve blocks and avoid complications (1).

For an effective CPNB, placement of the catheter near the target nerve is essential. Verification (or confirmation) of a correct nonstimulating catheter position can be determined by clinical effects after injection of a local anesthetic. However, since the introduction of stimulating catheters in peripheral nerve block (PNB) techniques, neurostimulation by the catheter itself can verify its position (2,3).

We report our initial experience of combining ultrasound guidance with a stimulating catheter for the placement of continuous subgluteal sciatic nerve blocks in children.

	METHODS

Top Abstract Introduction METHODS RESULTS DISCUSSION REFERENCES

 
This case series was approved by the ethics committee of Radboud University and informed consent was obtained from the parents of all children. Ten ASA physical status I-II children, aged 2 to 14 yr, undergoing lower limb surgery with a continuous subgluteal sciatic nerve block for postoperative pain relief were prospectively studied.

The children were premedicated with oral midazolam 0.4 mg/kg and rectal paracetamol 15 mg/kg 30 min before surgery. Anesthesia was induced by inhaled sevoflurane in the parents' presence. After induction of anesthesia an IV cannula was inserted and propofol 1 mg/kg and fentanyl 1 µg/kg were administered IV to facilitate endotracheal intubation. Anesthesia was then maintained with sevoflurane (end-tidal concentration 1.5%–2%) in air and oxygen.

For the subgluteal approach to the sciatic nerve (4), the children were positioned in Sims position with the operative side uppermost and the upper ankle positioned on the lower knee. After disinfection and sterile draping, sterile gel was applied to the subgluteal area. A linear 5–10 MHz ultrasound probe (Sonosite Titan, Bothell, WA) was placed transverse with the long axis of the probe lying between the greater trochanter and ischial tuberosity (Fig. 1). The sciatic nerve was viewed in cross-section and was visualized lateral to the long head of the biceps femoris muscle.

View larger version (119K): [in this window] [in a new window]   Figure 1. Patient, ultrasound probe, and needle positioning during ultrasound-guided subgluteal sciatic nerve block.

A 5-cm, 17-gauge insulated CPNB needle (Arrow International, Reading, PA) and a stimulating catheter (Stimucath, Arrow International) were used. Under ultrasound guidance the sciatic nerve was approached. The needle was introduced at a 45 degree angle to the skin and perpendicular to the probe. The neurostimulator was clipped to the proximal end of the needle and was set to deliver a stimulating current of 0.5 mA with a pulse duration of 0.1 ms. When the needle was judged to be lying adjacent to the nerve based on ultrasonographic evidence, the current was gradually increased until a motor response, either plantar or dorsiflexion in the foot, was observed. The minimum stimulating current was noted and then the ultrasound probe was put aside.

The nerve stimulator clip was removed from the needle and attached to the proximal end of the stimulating catheter and the neurostimulator was set to 1.5 mA in order to obtain muscle contraction while advancing the catheter. The stimulating catheter was gradually advanced beyond the tip of the needle for a maximum distance of 3 cm. If muscle twitching disappeared while advancing the catheter, the catheter was withdrawn and the needle rotated 90 degrees before repeating the catheter advancement. After removing the needle and internal stylet, the catheter was tunneled subcutaneously for approximately 3 cm and secured by a snap-lock device and a transparent dressing. The threshold stimulating current through the catheter was noted.

With the catheter in position, ultrasound imaging of the sciatic nerve in the subgluteal region was repeated at the time of ropivacaine 0.75% (0.4 mL/kg) injection. Prediction of block success was made based on the ultrasound observation of local anesthetic spread pattern.

At end of surgery, all children also received a single-shot ultrasound-guided fascia iliaca compartment block as described by Dalens et al. (5) using a 40 mm Stimuplex® D needle with 30° bevel. (B. Braun, Melsungen, Germany). The spread of 0.5 mL/kg ropivacaine 0.2% was followed by ultrasound and again a prediction of a successful block was made.

In the postanesthesia care unit, all children received rectal paracetamol 15 mg/kg and diclofenac 1 mg/kg. Bupivacaine 0.25% was infused at a rate of 0.1 mL · kg^–1 · h^–1 through the stimulating catheter. Additional IV morphine 0.05 mg/kg was administered as a bolus if pain relief was judged insufficient. This postoperative pain treatment was prescribed according to our hospital's postoperative pain protocol.

When possible, sensory block in the distribution of the sciatic and femoral nerve was tested by applying frozen ampules of saline to the blocked extremity. Motor block was not tested because of the dressing and immobilization of the legs.

The severity of postoperative pain was evaluated using Children's and Infant's postoperative Pain Scale in children up to 4-yr-old and the McGrath faces scale in schoolchildren from 4- to 8-yr-old. These scales were modified to visual analog pain scales (range, 1–10) as used in older children to compare the results.

Depending on the type of surgery, catheters were left in situ for 2 to 5 postoperative days.

Once daily all children were visited by our acute pain service to record pain scores, parent satisfaction scores, and any complications. If pain scores exceeded 4, a continuous IV infusion of morphine 0.01 mg · kg^–1 · h^–1 was started and the dose gradually diminished until pain scores decreased below 4. Parents were asked to score on a 10-point scale to indicate whether they were satisfied with the postoperative pain relief (0 = very unsatisfied, 10 absolutely satisfied).

	RESULTS

Top Abstract Introduction METHODS RESULTS DISCUSSION REFERENCES

 
Patient demographics, surgical procedure, and electrical threshold for needle and catheter data are summarized in Table 1. The mean procedure time took 9 ± 2 min. Based on the spread of local anesthetic during injection through the catheter, a successful block was predicted in all children. In all patients, a sensory block was demonstrated in the sciatic and saphenous nerve distribution.

In two children the postoperative pain score was 4 immediately after surgery but additional pain treatment was declined. In all remaining children, pain relief was excellent (i.e., visual analog scale score <4) and no additional morphine was needed during the postoperative course. In 2 patients who had undergone a lower limb amputation, multimodal pain therapy (including IV morphine 0.01 mg · kg^–1 · h^–1) was prescribed to prevent the development of phantom pain even when the pain score was <4

All parents were satisfied or very satisfied with postoperative pain relief (median satisfaction score of 8; range, 8–10). Nausea, vomiting, or disturbed sleep was not reported. Oral diet resumed the day after surgery. An accidental electrical power disconnection was noted in the infusion pump for patient 10. A rescue bolus of 0.2 mL/kg ropivacaine 0.75% was required to relieve severe pain in this patient 24 h after the initial ropivacaine bolus. The pain score decreased to 3 within 1 h. No other complications were noted.

	DISCUSSION

Top Abstract Introduction METHODS RESULTS DISCUSSION REFERENCES

 
This is the first report describing the use of ultrasound and stimulating catheters for the placement of CPNB in children. All regional anesthetic blocks can be performed in pediatric patients, although the anatomical landmarks and structures vary with age and constitution. Infants and children have larger total body water content than adults, which gives their tissue a unique ultrasonographic characteristic. Moreover, because of the superficial location of most nerves in children, the nerves to be targeted are readily visualized and excellent ultrasound images can be obtained (6).

The risk of developing complications as a result of placing PNBs in asleep pediatric patients is low (7). The use of ultrasound can minimize the risks even further. Intravascular injection can be detected by the absence of tissue expansion on injection. Moreover, it is suggested that a distinction between extraneural from intraneural injection can be made on the basis of the ultrasonographic appearance of tissue expansion versus increased nerve diameter, although this needs further research (8).

Only a few reports on the application of ultrasound-guided PNB in children have been published (9,10). It was shown that the amount of local anesthetic could be reduced while at the same time the speed of onset and duration and quality of the block improved. The ultrasonographic appearance of the sciatic nerve and its division in the popliteal fossa in children has been described (11). Gray et al. (12) performed an ultrasound-guided sciatic nerve block in a 7-year-old child.

In our patients, we chose the subgluteal approach for the placement of the sciatic nerve blocks so that we would not disturb the operating field and because of the ability to easily fixate the catheter in this region. In all children we could clearly identify the sciatic nerve. It appeared as an oval shaped hypo-echoic "honeycomb" pattern of the sciatic nerve fascicles surrounded by the hyper-echoic pattern neurolemma (Fig. 2). Under "real-time" short axis ultrasonographic guidance, the needle tip was brought adjacent to the sciatic nerve (Fig. 3). Although this approach avoids a long painful trajectory through the muscle, the needle cannot be visualized over its complete path. Although in two cases we could see the target nerve being pushed away by the needle, we did not get a motor response (Fig. 4). This observation is in accordance with Urmey and Stanton (13), who showed that a sensory response (paresthesia) resulting from nerve contact was not associated with the ability to elicit a motor response in 70% of patients. Anatomic heterogeneity within peripheral nerves, with sensory and motor fibers mixed together, may account for this observation. It is possible for a needle to enter a nerve without contacting any motor neuronal tissue.

View larger version (86K): [in this window] [in a new window]   Figure 2. The ultrasonographic image of the sciatic nerve is shown in short axis (transverse view) in the subgluteal region (arrow). The nerve is situated 2.5 cm below the skin.

View larger version (85K): [in this window] [in a new window]   Figure 3. The ultrasonographic image (short-axis view) of the needle tip (indicated by arrow), which lies in close proximity to the sciatic nerve. Small arrows point to shadowing of the needle.

View larger version (84K): [in this window] [in a new window]   Figure 4. Ultrasonographic image (short-axis view) of bulging of the sciatic nerve (arrow) by needle contact (without muscle contraction), before injection of local anesthetic.

The Arrow® stimulating needle and catheter with its 5-mm bare tip behave like noninsulated needles. Thus they require more current to stimulate the nerves (14). Pham Dang et al. (2) also observed high values of stimulation current through the catheter. The manufacturer of the needle recommends 1 mA as an acceptable minimal current, but there are no studies demonstrating the final stimulus current intensity for noninsulated needles that ensure a high success rate. However, with the application of ultrasound in the practice of PNB, electrical nerve stimulation may no longer be needed. The needle is now visualized in relationship to the nerve and the only predictor for a successful block is the circumferential spread of local anesthetic around the nerve.

Continuous catheter techniques are becoming popular for children and are already applied in the ambulatory setting (15). CPNB allows complete pain relief, early mobilization, and rapid return home, which is a psychological advantage for children and parents. Disposable infusion devices can be used as an alternative to standard infusion equipment (16).

One of the main problems posed by the catheter technique is placement of the catheter sufficiently close to the target nerve to ensure effective analgesia. Block failure in nonstimulating catheters has been demonstrated in approximately 10% of cases (17). However, the ability to electrostimulate nerves using a catheter implies that the catheter is adjacent to the nerve. The manufacturer constructed the noninsulated tip of the needle and the bare tip of the stimulating catheter in the same way to ensure that the muscle twitches will be similar for the needle and the catheter if these two are at equal distances to the nerve. The electrical threshold for needle and catheter stimulation was different and very variable. Different contacts and distances between nerve, needle, and catheter might explain this finding. While advancing the stimulating catheter along the sciatic nerve in the subgluteal region, one can see not only the intensity of motor responses changing but also the characteristics, e.g., from plantar flexion to eversion of the foot. The catheter position can be regarded as optimal as long as muscle contractions can be seen while advancing the catheter. Without ultrasound guidance, we introduced the catheters as described by the manufacturer 3 cm along the nerve because it is technically impossible to hold the ultrasound probe with one hand while introducing a catheter with the other. Both the injection and spread of local anesthetic around the nerve were monitored under direct ultrasonographic visualization. The catheter itself is very difficult to visualize because its position is unpredictable along the nerve (18). The catheter can be visualized in transverse view as a hyper-echoic dot, but following it along its course is practically impossible. In longitudinal view the catheter can also be visualized, but it is technically very difficult because the transducer has a lateral resolution of 0.32 mm. The 19-gauge catheter has a transverse diameter of 0.91 mm; so only a slight movement of the transducer will make the view of the catheter disappear. An indirect means of detecting the tip of the catheter can be obtained by looking for tissue movement during introduction of the catheter or by looking for spread of 3 mL 5% dextrose solution with the ultrasound probe. Injection of dextrose 5% has the advantage that electrical stimulation through the catheter remains possible (19). If the typical "donut sign" appears, a prediction for successful block can be made. If there is inappropriate spreading of the dextrose solution, the catheter can be repositioned. In our patients, we did not plan to redirect our catheters if the pattern of spread of local anesthetic was not circumferential around the nerve because motor response on stimulation of the catheter tip suggested that the catheter was in close proximity to the nerve. After injection of local anesthetic all nerves were engulfed (Fig. 5). This implies that, regardless of the stimulation current, as long as motor responses can be seen during advancement of the catheter, the catheter tip is close enough to the nerve to provide a successful block after injection. We sometimes observed that after injection of 25% of the total amount of local anesthetic solution the nerve was already surrounded by local anesthetic.

View larger version (87K): [in this window] [in a new window]   Figure 5. Ultrasonographic image (short-axis view) of spread of local anesthetic (small arrows) around the sciatic nerve (big arrow) in the subgluteal region after injection through the catheter. More local anesthetic is spread above than beneath the nerve.

The maximum dose of local anesthetics is still not well defined for the different peripheral nerve blocks in children (20). In this study we used a bolus dose of 3 mg/kg ropivacaine to provide surgical anesthesia in the sciatic nerve distribution. At the end of the surgical procedure this block was supplemented by a single-injection fascia iliaca compartment block to provide long-lasting postoperative analgesia in the entire lower leg. For postoperative pain relief, smaller concentrations of ropivacaine may be used (21). In accordance with the postoperative acute pain protocol in our hospital, a perineural infusion of bupivacaine 0.25 mg · kg^–1 · h^–1 was started on the sciatic nerve block catheter. In the literature the local anesthetic dose for CPNB via a catheter has ranged from 0.2 to 0.4 mg · kg^–1 · h^–1 bupivacaine (22).

No differences were demonstrated in success rate between stimulating and nonstimulating catheters for femoral nerve blocks (23,24). One can speculate regarding whether a difference between these catheters can be demonstrated if smaller amounts of local anesthetic are used for "soaking" the target nerve. Theoretically, the catheter tip of stimulating catheters will be closer to the nerve if a good motor response is obtained during advancement. The combination of neurostimulation for guidance of the catheter and the direct visualization of spread of local anesthetic can probably predict a successful block with a smaller amount of local anesthetic. More studies need to be done to further elucidate the relationship between nerve stimulation currents, spread of local anesthetic, and effectiveness of the nerve block.

The introduction of stimulating catheters requires more expertise than introduction of a nonstimulating catheter. Switching the nerve stimulator connection from needle to catheter and maintaining good contractions while advancing the catheter requires extra manipulations. Also for the use of ultrasound in the practice of regional anesthesia, extra training is required. Our experience suggests that these skills can be easily learned. Chan et al. (25) proved that even with little ultrasound experience excellent results can be obtained. Inexperienced residents can quickly acquire "hit-the-target" technical skill in a simulated interventional procedure model (26). Although performing these PNBs in anesthetized children results in a small loss of operating time, our surgeons and nursing staff encouraged us to continue because of the excellent postoperative pain relief that we obtained with this combined technique.

In summary, the use of ultrasound made identification of the subgluteal sciatic nerve easy and facilitated needle and catheter placement in 10 pediatric patients aged 2 to 14 years. The ultrasonographic visualization of the spread of local anesthetic during injection verified the catheter position and predicted a successful block in every patient. Excellent postoperative pain relief and satisfaction scores were obtained in all children and there were no complications.

	ACKNOWLEDGMENT

 
The authors wish to express gratitude to Vincent Chan for his comments on the manuscript.

	Footnotes

 
Accepted for publication March 14, 2006.

	REFERENCES

Top Abstract Introduction METHODS RESULTS DISCUSSION REFERENCES

 

1. Marhofer P, Greher M, Kapral S. Ultrasound guidance in regional anesthesia. Br J Anaesth 2005;94:7–17.[Abstract/Free Full Text]
2. Pham-Dang C, Collet T, Gouin F, Pinaud M. Continuous peripheral nerve blocks with stimulating catheters. Reg Anesth Pain Med 2003;28:83–8.[Web of Science][Medline]
3. Salinas FV, Neal JM, Sueda LA, et al. Prospective comparison of continuous femoral nerve block with nonstimulating catheter placement versus stimulating catheter-guided perineural placement in volunteers. Reg Anesth Pain Med 2004;29:212–20.[Web of Science][Medline]
4. Di Benedetto P, Casati A, Bertini L, Fanelli G. Posterior subgluteal approach to block the sciatic nerve: description of the technique and initial clinical experiences. Eur J Anaesthesiol 2002;19:682–6.[Web of Science][Medline]
5. Dalens B, Vanneuville G, Tanguy A. Comparison of the fascia iliaca compartment block with the 3-in-1 block in children. Anesth Analg 1989;69:705–13.[Abstract/Free Full Text]
6. Rapp HJ, Grau T. Ultrasound-guided regional anesthesia in pediatric patients. Tech Reg Anesth Pain Manage 2004;8:179–98.
7. Giaufré E, Dalens B, Gombert A. Epidemiology and morbidity of regional anesthesia in children: a one-year prospective survey of the French-language society of pediatric anesthesiologists. Anesth Analg 1996;83:904–12.[Abstract]
8. Chan VW. Ultrasound evidence of intraneural injection. Anesth Analg 2005;101:610–11.[Free Full Text]
9. Marhofer P, Sitzwohl C, Greher M, Kapral S. Ultrasound guidance for infraclavicular brachial plexus anaesthesia in children. Anaesthesia 2004;59:642–6.[Web of Science][Medline]
10. Willschke H, Marhofer P, Bosenberg A, et al Ultrasonography for ilioinguinal/iliohypogastric nerve blocks in children. Br J Anaesth 2005;95:226–30.[Abstract/Free Full Text]
11. Schwemmer U, Markus CK, Greim CA, et al. Sonographic imaging of the sciatic nerve and its division in the popliteal fossa in children. Pediatric Anesthesia 2004;14:1005–8.[Medline]
12. Gray AT, Collins AB, Schafhalter-Zoppoth I. Sciatic nerve block in a child: a sonographic approach. Anesth Analg 2003;97:1300–2.[Abstract/Free Full Text]
13. Urmey WF, Stanton J. Inability to consistently elicit a motor response following sensory paresthesia during interscalene block administration. Anesthesiology 2002;96:552–4.[Web of Science][Medline]
14. Bashein G, Haschke RH, Ready LB. Electrical nerve location: numerical and electrophoretic comparison of insulated vs uninsulated needles. Anesth Analg 1984;63:919–24.[Abstract/Free Full Text]
15. Dadure C, Motais F, Ricard C, et al. Continuous peripheral nerve blocks at home for treatment of recurrent complex regional pain syndrome I in children. Anesthesiology 2005;102:387–91.[Web of Science][Medline]
16. Dadure C, Pirat P, Raux O, et al. Perioperative continuous peripheral nerve blocks with disposable infusion pump in children: a prospective descriptive study. Anesth Analg 2003;97:687–90.[Abstract/Free Full Text]
17. Grant SA, Nielsen KC, Greengrass RA, et al. Continuous peripheral nerve block for ambulatory surgery. Reg Anesth Pain Med 2001;26:209–14.[Web of Science][Medline]
18. Capdevila X, Biboulet P, Morau D, et al. Continuous three-in-one block for postoperative pain after lower limb orthopedic surgery: where do the catheters go? Anesth Analg 2002;94:1001–6.[Abstract/Free Full Text]
19. Tsui BC, Kropelin B. The electrophysiological effect of dextrose 5% in water on single-shot peripheral nerve stimulation. Anesth Analg 2005;100:1837–9.[Abstract/Free Full Text]
20. Mazoit JX, Dalens BJ. Pharmacokinetics of local anaesthetics in infants and children. Clin Pharmacokinet 2004;43:17–32.[Web of Science][Medline]
21. Ivani G. Ropivacaine: is it time for children? Paediatric Anaesthesia 2002;12:383–7.[Web of Science][Medline]
22. Dadure C, Capdevila X. Continuous peripheral nerve blocks in children. Best Pract Res Clin Anesthaesiol 2005;19:309–21.
23. Jack NT, Liem EB, Vonhögen LH. Use of a stimulating catheter for total knee replacement surgery: preliminary results. Br J Anaesth 2005;95:250–54.[Abstract/Free Full Text]
24. Morin AM, Eberhart LH, Behnke HK, et al. Does femoral nerve catheter placement with stimulating catheters improve effective placement? A randomized, controlled, and observer-blinded trial. Anesth Analg 2005;100:1503–10.[Abstract/Free Full Text]
25. Chan VW, Perlas A, Rawson R, Odukoya O. Ultrasound-guided supraclavicular brachial plexus block. Anesth Analg 2003;97:1514–17.[Abstract/Free Full Text]
26. Sites BD, Gallagher JD, Cravero J, et al. The learning curve associated with a simulated ultrasound-guided interventional task by inexperienced anesthesia residents. Reg Anesth Pain Med 2004;29:544–8.[Web of Science][Medline]

This article has been cited by other articles:

				J. Ota, S. Sakura, K. Hara, and Y. Saito Ultrasound-Guided Anterior Approach to Sciatic Nerve Block: A Comparison with the Posterior Approach Anesth. Analg., February 1, 2009; 108(2): 660 - 665. [Abstract] [Full Text] [PDF]

				S. M. Klein, M. P. Fronheiser, J. Reach, K. C. Nielsen, and S. W. Smith Piezoelectric Vibrating Needle and Catheter for Enhancing Ultrasound-Guided Peripheral Nerve Blocks Anesth. Analg., December 1, 2007; 105(6): 1858 - 1860. [Abstract] [Full Text] [PDF]

				A. Ganesh and G. Cucchiaro Multiple simultaneous perineural infusions for postoperative analgesia in adolescents in an outpatient setting Br. J. Anaesth., May 1, 2007; 98(5): 687 - 689. [Abstract] [Full Text] [PDF]

				A. Walker and S. Roberts Stimulating Catheters: A Thing of the Past? Anesth. Analg., April 1, 2007; 104(4): 1001 - 1002. [Full Text] [PDF]

This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a colleague Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (6) Citing Articles via Google Scholar Google Scholar Articles by van Geffen, G. J. Articles by Gielen, M. Search for Related Content PubMed PubMed Citation Articles by van Geffen, G. J. Articles by Gielen, M. Related Collections Pediatrics Regional Anesthesia