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ORIGINAL ARTICLE
Year : 2012  |  Volume : 6  |  Issue : 1  |  Page : 29-33  

Comparison of ultrasound-guided anterior versus transgluteal sciatic nerve blockade for knee surgery


Assistant Professor and Consultant Anesthesiologist, Department of Cardiac Science, College of Medicine, King Fahad Cardiac Center, King Saud University, Riyadh, Kingdom of Saudi Arabia

Date of Web Publication14-Nov-2012

Correspondence Address:
Raed A Alsatli
Department of Cardiac Science, P.O.Box: 7805, (Internal 92), Riyadh 11472
Kingdom of Saudi Arabia
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0259-1162.103368

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   Abstract 

Background: Ultrasound-guided sciatic nerve block, in combination with femoral nerve and lateral femoral cutaneous nerve blocks, is frequently used to induce anesthesia for lower limb surgery. The anterior approach to the sciatic nerve is performed in the supine position and repositioning of the patient between injections is avoidable. We compared the relative utility and efficiency of anterior versus transgluteal sciatic nerve blocks in conjunction with femoral nerve and lateral femoral cutaneous nerve blockade.
Materials and Methods: Twenty-four patients were enrolled in this prospective double-blind randomized study and were randomly divided into two equal groups: Anterior (Group A) and transgluteal (Group T). We evaluated the following parameters: ultrasound view quality, procedural duration, onset time to block, quality of anesthesia during surgery and postoperative analgesia, required administration of supplemental sedation or narcotics during surgery, amount of pethidine administered within 24 hours post surgery, and overall patient satisfaction.
Results: There were no significant differences between patient groups with regard to the demographic data, onset time to block, quality of ultrasound view, use of narcotics to augment the anesthesia during surgery, and patient satisfaction. Although procedural completion time for the sciatic injection alone was shorter in Group T, the total completion time of all blocks together was significantly less in Group A.
Conclusion: Ultrasound-guided anterior blockade of the sciatic nerve has advantages over the transgluteal approach - it provides efficient anesthesia and results in excellent patient satisfaction.

Keywords: Anterior, knee surgery, transgluteal, ultrasound-guided sciatic nerve block


How to cite this article:
Alsatli RA. Comparison of ultrasound-guided anterior versus transgluteal sciatic nerve blockade for knee surgery. Anesth Essays Res 2012;6:29-33

How to cite this URL:
Alsatli RA. Comparison of ultrasound-guided anterior versus transgluteal sciatic nerve blockade for knee surgery. Anesth Essays Res [serial online] 2012 [cited 2022 Aug 19];6:29-33. Available from: https://www.aeronline.org/text.asp?2012/6/1/29/103368


   Introduction Top


There is increasing interest in implementing the ultrasound to assist in peripheral nerve blocks. Sciatic nerve blockade is one of the most commonly used techniques in our practice and is associated with a high success rate when properly performed. It is particularly well-suited for surgery on the knee, calf, Achilles tendon, ankle, and foot. It provides complete anesthesia of the leg below the knee with the exception of the medial strip of skin, which is innervated by the saphenous nerve. When combined with a femoral nerve or lumbar plexus block, anesthesia of almost the entire leg is achieved.

The transgluteal approach for blocking the sciatic nerve is widely used for surgery and pain management of the lower extremities. The sciatic nerve is located deeper in the anterior approach than in the posterior approach, and the anterior access requires greater operator skill and experience. It was first described by Beck et al., [1] who used the greater trochanter as the injection landmark; after which new techniques with other landmarks are described. The anterior approach has the advantage that the sciatic nerve block can be performed without changing the patient's position when combined with femoral nerve block, or when the patient cannot be repositioned for other reasons such as trauma. [2]

In this prospective randomized double-blind study, we compared anterior versus transgluteal sciatic nerve blockade combined with femoral and lateral femoral cutaneous nerve blocks, and evaluated the quality of the ultrasound view of the sciatic nerve, onset time of block, completion time of the sciatic nerve block and of all blocks together, quality of anesthesia during surgery and postoperative analgesia, required administration of sedation or narcotics during surgery, total pethidine required within 24 hours postoperatively, and overall patient satisfaction.


   Materials and Methods Top


This study was approved by our Institutional Ethics Committee, and written informed consent was obtained from all patients. Twenty-four patients undergoing minor knee surgery were included in this study and 12 patients each were randomly assigned by computer into either the anterior group (A) or the transgluteal group (T). Inclusion criteria included the American Society of Anesthesiologists (ASA) I - II patients undergoing minor knee surgery (e.g., meniscectomy, arthroscopy, meniscal repair). Exclusion criteria included any neurological disease, known allergy to Lidocaine, Bupivacaine or pethidine, history of alcohol or drug abuse, any psychiatric disorder, diabetic neuropathy, and obese patients (body mass index: BMI>45).

All patients followed a strict preoperative fasting rule. In the Operating Room, the patients were connected to routine noninvasive monitors such as electrocardiography (ECG), non-invasive blood pressure (NIBP) monitoring, and peripheral oxygen saturation (Spo 2 ). A peripheral intravenous cannula was inserted and Lactated Ringer's solution 2 ml/kg/hour was started.

Depending on patient group assignment, individuals received either an anterior or transgluteal sciatic nerve block, plus femoral nerve and lateral femoral cutaneous nerve blocks, by the investigating Anesthetist. Clinical assessment of nerve blocks were performed by assistant not involved in this study . Before starting the nerve block, 1-2 mg of midazolam IV was given for anxiolysis.

In the anterior group, the patients were put in the supine position, the hip was abducted, externally rotated, and the knee flexed. An ultrasound system (Micro Maxx System, Sonosite; Bothell, WA) with a low-frequency (5 to 2 MHz) curved-array transducer (C60e) was used. The ultrasound transducer was positioned perpendicular to the skin, approximately 8 cm distal to the inguinal crease, using a sterile ultrasound gel and a sterile plastic transducer cover. After identifying the sciatic nerve as a hyper-echoic structure posterior and medial to the lesser trochanter [Figure 1], the overlying skin was sterilized with Povidone-Iodine solution, infiltrated with 2 ml of 1% lidocaine, and a 150-mm short bevel 21-gauge insulated nerve block needle was inserted (Stimuplex A, B. Melsungen AG, Germany). A nerve stimulator with a pulse duration of 0.1 ms and stimulating frequency of 2 Hz was then turned on, to elicit foot plantar flexion or dorsiflexion. The needle was further repositioned as needed to evoke a motor response at 0.7 mA or less. After negative aspiration in the syringe, to avoid intravascular injection, 15 ml of 0.25% Bupivacaine and 10 ml of 1% lidocaine was injected. This mixture was chosen to induce a faster onset of block (because of Lidocaine), and to prolong the duration of action (due to Bupivacaine).
Figure 1: The ultrasound image of the sciatic nerve in the anterior approach

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Femoral and lateral femoral cutaneous nerves were then located and blocked, using a high-frequency 13 to 6 MHz linear array transducer (HFL38, Sonosite, Bothell, WA), a 100-mm short-bevel insulated needle (Stimuplex A, B. Melsungen AG, Germany), and an injection of 10 ml of 0.25% bupivacaine and 10 ml of 1% lidocaine.

In the transgluteal approach, the patients were placed in a lateral position with the operated leg upward, and the hip and knee were flexed at approximately 45΀. The ultrasound transducer was positioned perpendicular to the skin on the line connecting the ischial tuberosity and the greater trochanter. After skin preparation, the curved array ultrasound probe was used to localize the sciatic nerve, which appeared as a hyper-echoic transverse structure between the ischial tuberosity and the greater trochanter. A local anesthetic was injected as in the anterior approach [Figure 2].
Figure 2: The ultrasound image of the sciatic nerve in the transgluteal approach

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To perform the femoral nerve and lateral femoral cutaneous nerve blocks, the patients were repositioned in the supine position, and blockade was carried out as described earlier. The sensory and motoric blocks were assessed before the patient underwent surgery. After finishing all the blocks, sterile covers were put on the same areas in both groups to blind observers to the block technique used. The quality of nerve visualization during both sciatic nerve approaches and femoral nerve localization was Documented by an anesthetist experienced in ultrasound guided nerve block. Measurements included: The onset time of the block, completion time of the block (time from insertion of the needle until needle withdrawal after completion of the injection), which was measured for the sciatic nerve alone in either of the approaches, as well as, the total procedure time for all blocks in a patient (from inserting the needle for the first sciatic block until needle withdrawal after the femoral blocks). Procedural times were recorded by an assistant. Another anesthetist who was blinded to the patient's group assignment continued the anesthesia care and documented the quality of anesthesia and analgesia, as also whether sedation with midazolam had been used if so, the patient was labeled (ultrasound guided sciatic nerve block + sedation: USGSNB + sedation or if rescue medication such as fentanyl 50 - 100 ΅g had been administered. If the patient had severe pain that was not relieved by fentanyl, their status was converted to general anesthesia, and it was considered failure of block.

Postoperatively, the visual analog scale (VAS) at rest and movement in the recovery room, and again at 2, 4, 8, 12, 16, 20, and 24 hours postoperatively, was registered. To treat pain, pethidine was given, the dose and time of administration were documented.

For statistical analysis we used the (SPSS Inc. version 19, Chicago, IL, USA). The Fisher's exact test was used for nominal variables, to compare the transgluteal and anterior groups. A non-parametric Mann-Whitney test was used to compare the variables. P values less than 0.05 were considered significant.


   Results Top


There were no significant differences between both groups regarding the demographic characteristics such as age, gender, height, and weight [Table 1].
Table1: Demographic data

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There was no significant difference between groups in the number of blocks done with or without sedation [Table 2]. Visualization of the femoral and sciatic nerve was good in both groups (except in one patient in each of the two groups). No difference was found between the groups in the quality of anesthesia; all patients in Group A had good anesthesia, whereas 11 of 12 patients in Group T had good anesthesia.
Table 2: Different variables in the transgluteal group (T) and anterior group (A) of the sciatic nerve block

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Although the mean onset time of the block was longer in Group T, this was not statistically significant. No statistical differences were found between the groups in the administration of rescue narcotics to treat pain during surgery. No significant difference in surgery duration was measured between the groups.

The patients in Group A were more satisfied with the block and pain relief than those in Group T, but this result did not achieve statistical significance. This finding coincided with less average pethidine administered to patients in Group A versus Group T, although this difference did not reach statistical significance [Table 3].
Table 3: Pethidine consumption in both groups, Figure 4: Mean value of VAS ± SD at movement in relation to time transgluteal and anterior sciatic nerve block

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During the postoperative period, the VAS score at rest [Figure 3] and during movement [Figure 4] peaked in Group T at eight hours, whereas, it peaked in Group A after 20 hours. This means that the sciatic nerve block in Group A had a longer duration of action and analgesia than in Group T, although this difference was not statistically significant.
Figure 3: Mean value of VAS ± SD at rest in relation to time

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Figure 4: Mean value of VAS ± SD at movement in relation to time

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[Table 4] shows the procedural completion times. The time required to complete the sciatic block was significantly longer (statistically significant) in Group A versus Group T. Nonetheless, the total time needed to finish all the blocks was significantly Less (statistically significant) in Group A versus Group T patients. This could be explained by the fact that there was no time spent in repositioning the patient between the sciatic and femoral blocks when using the anterior approach . Failue of block has not been reported in any patient during the study.
Table 4: Completion time of sciatic nerve block in both groups: Transgluteal and anterior sciatic nerve block

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   Discussion Top


The anterior approach to sciatic nerve access and blockade was first described by Beck in 1963, who used the greater trochanter as a defining landmark. [1] Chelly et al. described a new anterior approach to access the sciatic nerve, drawing a line between the anterior superior iliac spine and the pubic symphysis. An 8-cm perpendicular line bisecting the first line was then drawn and the injection site was the intersection point of these two lines. Using this approach, complete sensory block was obtained within 15 minutes. [3] Barbero et al.[4] developed an equation to more precisely calculate the length of the above-mentioned perpendicular line (height in cm - 100/10) and claimed a better success rate in accurately localizing the sciatic nerve with this method.

In the current study we compared the anterior and transgluteal approaches for blocking the sciatic nerve, when combined with femoral nerve and lateral femoral cutaneous nerve blocks. Our results did not show a significant difference between the two groups with regard to the onset time, VAS score, pethidine requirement, and patient satisfaction, but there was a significant difference with regard to the procedural completion time. Although the anterior approach took longer than the transgluteal approach to access and block the sciatic nerve alone, the total completion time for all blocks together was significantly less when using the anterior approach. Failure of block has not been reported in any case during the study. This time advantage, coupled with the avoidance of discomfort and pain associated with intra-procedural repositioning of the patient, conferred an overall benefit of using the anterior approach versus the more conventional transgluteal method.

Junichi et al.[5] compared the ultrasound-guided anterior approach with the subgluteal approach for the sciatic nerve blockade. In addition to using a different posterior approach (i.e., subgluteal versus transgluteal, in the current study), these investigators also used a different local anesthetic (mepivacaine with epinephrine, to prolong its duration of action). Our study employed bupivacaine, which has a longer duration of action than other local anesthetics, even without additives. Chan et al.[6] in a volunteer study, demonstrated good ultrasound visualization and successful blockade of the sciatic nerve at three locations in its pathway: gluteal, infragluteal, and upper thigh, and claimed a 100% success rate, with the help of a nerve stimulator. In our study, we obtained excellent visualization of the sciatic nerve, and anesthesia was good in 92% of the cases, and moderate in 8% in the transgluteal group.


   Conclusion Top


Ultrasound-guided anterior access and blockade of the sciatic nerve versus the transgluteal protocol, saves time, provides effective anesthesia, and results in excellent patient satisfaction.

 
   References Top

1.Beck GP. Anterior approach to sciatic nerve block. Anesthesiology 1963;24:222-4.  Back to cited text no. 1
    
2.Gaertner E, Fouche E, Choquet O, Hadzic A, Vloka JD. Sciatic nerve block. In: Hadzic A, editor. Textbook of regional anesthesia and acute pain management. New York: McGraw-Hill companies; 2007. p. 517-32.  Back to cited text no. 2
    
3.Chelly JE, Delaunay L. A New anterior approach to the sciatic nerve block. Anesthesiology 1999;91:1655-60.  Back to cited text no. 3
[PUBMED]    
4.Barbero C, Fuzier R, Samii K. Anterior approach to the sciatic nerve block: Adaptation to the patient's height. Anesth Analg 2004;98:1785-8.  Back to cited text no. 4
[PUBMED]    
5.Ota J, Sakura S, Hara K, Saito Y. Ultrasound-guided anterior approach to sciatic nerve block: A comparison with the posterior approach. Anesth Analg 2009;108:660-5.  Back to cited text no. 5
[PUBMED]    
6.Chan V, Nova H, Abbas S, McCartney CJ, Perlas A, Xu DQ. Ultrasound examination and localization of the sciatic nerve, a volunteer study. Anesthesiology 2006;104:309-14.  Back to cited text no. 6
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]


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