Continuous parasacral sciatic nerve block: Two case reports

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Regional Anesthesia 22(5):469-472, 1997

C o n t i n u o u s Parasacral Sciatic N e r v e Block: T w o Case R e p o r t s Gary F. Morris, FRCPC and Scott A. Lang, FRCPC

Objective. This study investigated the use of a continuous parasacral sciatic nerve block for anesthesia and postoperative analgesia for lower extremity surgery. Methods. A continuous parasacral sciatic nerve block was performed in two patients (triple ankle arthrodesis and below-knee amputation). The sacral plexus was identified using an insulated Tuohy needle and a nerve stimulator. A catheter was placed near the elements of the sacral plexus via the "I'dohy needle. Results. In both patients, surgical anesthesia was successfully established through the parasacral catheter with lidocaine 1% (I/200,000 epinephrine), and postoperative analgesia was successfully established with a bolus of bupivacaine 0.375% (11200,000 epinephrine) and maintained with a continuous infusion of bupivacaine 0.1% (8 mL/h) for 48 hours. Conclusion. We conclude that continuous parasacral sciatic nerve block can provide anesthesia and long-term analgesia for operative procedures of the foot and leg. Reg Anesth 1997: 22: 469--472. K e y words: regional anesthesia, local anesthesia, sciatic nerve, obturator nerve, saphenous nerve, sacral plexus.

Case Reports

Sciatic n e r v e blocks can provide anesthesia and analgesia for surgical p r o c e d u r e s of the l o w e r extremity, particularly_ f o r those b e l o w the k n e e (1). A l t h o u g h c o n t i n u o u s sciatic n e r v e blocks h a v e b e e n described (2,3), a c o n t i n u o u s parasacral (4) a p p r o a c h - - w h i c h is u n i q u e l y different f r o m "peripheral" sciatic n e r v e blocks as it blocks the e l e m e n t s of the sacral plexus r a t h e r t h a n the sciatic n e r v e - - h a s not b e e n characterized. After receiving a p p r o v a l f r o m o u r Institutional R e v i e w Board, w e enrolled t w o patients in an observational pilot study of a n e w m e t h o d for p l a c e m e n t of an indwelling c a t h e t e r to provide anesthesia a n d p o s t o p e r a t i v e analgesia in the distribution of the sciatic nerve. We report the results of this pilot investigation as t w o case reports.

Case I

A 62-year-old, 43-kg Caucasian w o m a n w i t h severe r h e u m a t o i d arthritis was scheduled for a left triple ankle arthrodesis. She requested a regional anesthetic. After obtaining informed consent, we p e r f o r m e d a c o m b i n a t i o n of femoral and parasacral sciatic n e r v e blocks. A left femoral n e r v e block was p e r f o r m e d utilizing a n e r v e stimulator (Digistim II, Neurotechnology, Houston, TX) with a pulse width of 200 ~ts and a stimulating frequency of 1 Hz. The n e r v e stimulator was attached to a 22-gauge Teflon insulated needle (Bekton Dickinson, M o u n t a i n View, CA). After a brisk m o t o r response was elicited in the quadriceps muscle at 0.2 mA, 10 m L of 1.5% lidocaine with 1/200,000 epinephrine was injected. Following the femoral n e r v e block, the patient was m o v e d to the right lateral decubitus position for p e r f o r m a n c e of a left continuous parasacral sciatic n e r v e block. The parasacral sciatic n e r v e block was p e r f o r m e d using landmarks described b y M a n s o u r

From the Department of Anesthesia, Royal University Hospital, University of Saskatchewan, Saskatchewan, Canada. Accepted for publication February 17, 1996. Reprint requests: Dr. S.A. Lang, Department of Anesthesia, Royal University Hospital, 103 Hospital Drive, Saskatoon, Saskatchewan, Canada, S7N OW8.

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(Fig. 1) (4). After the posterior superior iliac spine was identified, a line constructed between that point and the ischial tuberosity. Three fingerbreadths (6 cm) from the posterior superior iliac spine along this line, an insulated 17-gauge Tuohy needle (Becton Dickinson) was introduced and advanced. The needle was "walked" off the bony contour of the greater sciatic notch into the pelvis. With the aid of a Digistim II nerve stimulator, a brisk plantar motor response was elicited at 0.2 mA (pulse width 200 las; 1 Hz). An 18-gauge Portex catheter (Concord-Portex, Keene, NH) was then threaded through the Tuohy needle to a depth of 15 cm. Subsequently, 30 mL o f 1% lidocaine with 1/200,000 epinephrine was injected through the catheter. The injection was fractionated (5-mL aliquots), and the full dose given over 5 minutes to facilitate detection of an intravascular injection (the patient was monitored with ECG, pulse oximeter, and automatic blood pressure). The surgery did not need any supplementation. Following surgery, the patient received a bolus injection of 20 mL 0.375% bupivacaine with 1/200,000 epinephrine followed by a continuous infusion of bupivacaine 0.1% at 8 mL/h for 48 hours. In addition, a trans-sartorial saphenous nerve block (5) was performed (to

ensure prolonged sensory anesthesia in the distribution of the saphenous nerve that would outlast the aforementioned femoral nerve block with lidocaine), using 10 mL 0.375% bupivacaine with 11200,000 epinephrine. An intravenous patientcontrolled analgesia pump (PCA; Abbott Life Care, 4100 PCA plus infusor, Abbott Laboratories, Chicago, IL) was used for rescue analgesia. PCA parameters were: mode PCA, dose 0.6 mg morphine, lockout 6 minutes, 4-hour dose limit 20 mg. The patient accidentally delivered 0.6 mg of intravenous morphine over the 48-hour period w h e n she mistook the PCA button for the nurse call button. However, she stated emphatically that she never experienced any pain throughout the entire postoperative period. She had no nausea and did not exhibit signs or symptoms of local anesthetic toxicity. There were no neurologic complications.

Case 2 A 50-year-old, 87-kg Caucasian male was scheduled for a below-knee amputation for complications sustained in a motor vehicle accident. He requested a regional anesthetic. After obtaining informed consent, a combination of femoral and parasacral sciatic nerve blocks were performed in an identical m anner to that described for the patient in case 1. The combination of femoral and sciatic nerve blocks was used as the sole anesthetic for the operative procedure. After an initial bolus of 0.375% bupivacaine with 11200,000 epinephrine (20 mL), continuous postoperative analgesia was provided with an infusion of bupivacaine 0.1% at 8 mL/h for 48 hours. Rescue analgesia was provided with an intravenous PCA pump. The patient also received 75 mg indomethacin SR orally twice a day for 48 hours. No narcotic was required over the 48-hour observation period and the patient stated he never experienced pain at the operative site. He was discharged home with acetaminophen. There were no complications.

Discussion Fig. 1. Parasacral sciatic nerve block. Six centimeters along a line constructed between the posterior superior iliac spine (A) and the ischial tuberosity (C) a 17-gauge insulated Tuohy needle was inserted and advanced in a parasagittal plane (B). After brisk plantar flexion was elicited at 0.2 mA, an 18-gauge Portex catheter, was threaded through the Tuohy needle.

All described techniques for continuous sciatic nerve block attempt to place a catheter near the sciatic nerve after it has exited the pelvis via the greater sciatic foramen (2,3). An anatomical dissection along the course of the nerve in these areas readily reveals why it may be difficult to easily and reliably thread a catheter close to the sciatic nerve.

Sciatic Nerve Block

Dense connective tissue around the sciatic nerve and poorly defined fascial planes may make it difficult to thread a catheter and may also pose barriers to diffusion of local anesthetic. Moreover, in our experience and that of others (6), catheter migration and dislodgment with peripheral nerve catheter techniques can be problematic. Mansour (4) has described a parasacral approach to the sciatic nerve block which actua.lly places the needle tip (and hence the catheter) in the pelvis in the vicinity of the elements of the sacral plexus. We hypothesized that by using this technique catheter could be easily placed near the elements of the sacral plexus. Indeed, it was very easy to placethe catheter in both patients. There was little resistance to advancement, and both catheters remained functional for 48 hours despite ambulation (i.e., no dislodgment). This approach to continuous sciatic nerve block is easy to perform and deserves further investigation as it offers several potential advantages over other approaches and techniques. The obturator nerve and the entire sacral plexus are in close proximity with the parasacral approach (Fig. 2). A combination of a femoral 3-in-1 nerve block with a traditional sciatic nerve block may not reliably produce analgesia or anesthesia of the knee or hip because the obturator nerve may not be blocked (7-9). We have demonstrated that the parasacral sciatic nerve block successfully blocks the entire sacral

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plexus (10), and frequently blocks the obturator nerve as well. Therefore, a femoral 3-in-1 nerve block and a parasacral sciatic nerve block may provide more complete anesthesia and analgesia of the knee and the hip. Finally, as previously noted, the parasacral catheter is easily placed and is resistant to dislodgment despite enforced ambulation. Continuous epidural analgesia with local anesthetics and narcotics reliably produces excellent pain relief and is suggested to prevent the development of chronic pain following below knee amputation (11). However, epidural techniques are associated with acceptable but undesirable side effects (12,13). Urinary retention, motor weakness, and hypotension may be particularly unpalatable in individuals having peripheral surgery who are expected to ambulate immediately after surgery. These side effects are not expected to be a problem with the parasacral catheter technique (10) and did not occur in our two patients. A continuous parasacral sciatic nerve block may not only provide excellent postoperative analgesia but, like an epidural anesthetic (11), could theoretically prevent the development of chronic pain following major surgery such as a below-knee amputation. Experiments in rats have demonstrated the ability of peripheral nerve blocks of an injured limb to attenuate the development of hyperalgesia in the contralateral limb (14). This observation supports our hypothesis that a continuous peripheral nerve block may attenuate the development of central nervous system changes that can occur after tissue damage (especially nerve injury) and may contribute to the development of chronic pain. More investigation needs to be done to ensure the efficacy and safety of this procedure. Despite the lack of problems with these two patients, there remain concerns of local anesthetic toxicity, vascular injury, visceral injury, urinary retention, and neural damage. In conclusion, we have demonstrated the clinical effectiveness of the continuous parasacral sciatic nerve block to provide adequate anesthesia for and analgesia following extensive surgery below the knee.

Acknowledgments Fig. 2. Pelvic view of the sacral plexus. A, sacral plexus; B, sciatic nerve; C, pudendal nerve; D, obturator nerve; E, sympathetic chain; F; internal iliac artery; G, internal iliac vein.

We would like to thank the secretarial staff of the Department of Anesthesia, Royal University Hospital, Saskatoon, Saskatchewan for their help in completing this manuscript.

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References 1. Chang PC, Lang SA, Yip RW. Reevaluation of the sciatic nerve block. Reg Anesth 1993: 18: 18-23. 2. Smith BE, Fisher HBJ, Scott PV. Continuous sciatic nerve block. Anaesthesia 1984: 39:155-157. 3. Singelyn FJ, Aye E Gouverneur JM. Continuous popliteal sciatic nerve block: An original technique of postoperative analgesia after foot surgery. Reg Anesth 1995:20 (Suppl 2): 59. 4. Mansour NY. Reevaluating the sciatic nerve block: Another landmark for consideration. Reg Anesth 1993: 18: 322-323. 5. Van der Wal M, Lang SA, Yip RW. Transsartorial approach for saphenous n e r v e block. Can J Anaesth 1993: 40: 542-546. 6. Berde C. Regional anesthesia in children: What have we learned? Anesth Analg 1996: 83: 897-900. 7. Lang SA, Yip RW, Chang PC, Gerard MA. The femoral 3-in-I block revisited. J Clin Anesth 1993: 5: 292-296. 8. Spillane WF. 3-in-1 blocks and continuous 3-in-I blocks (letter). Reg Anesth 1992: 17: 175-176.

9. Ritter JW. Femoral nerve "sheath" for inguina paravascular l u m b a r plexus block is not found in h u m a n cadavers. J Clin Anesth 1995: 7: 470--473. 10. Morris GF, Lang SA, Dust WN, Van der Wal M. The parasacral sciatic nerve block. Reg Anesth 1997: 22: 223-228. 11. Back S, Noreng ME Tj~llden NU. Phantom limb pain in amputees during the first 12 months following limb amputation, after preoperative lumbar epidural blockade. Pain 1988: 33: 297-301. 12. Chaney MA. Review article: Side effects of intrathecal and epidural opioids. Can J Anaesth 1995: 42: 891-903. 13. Scott DA, Beilby DSN, McClymont C. Postoperative analgesia using epidural infusions of fentanyl with bupivacaine: A prospective analysis of 1014 patients. Anesthesiology 1995: 83: 727-737. 14. Levine JD, Dardick SJ, Basbaum AI, Scipio E. Reflex neurogenic inflammation. I. Contribution of the peripheral nervous system to spatially remote inflammatory responses that follow injury. J Neurosci 1985: 5: 1380-1386.

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