|Year : 2016 | Volume
| Issue : 4 | Page : 569-575
Systemic versus perineural dexamethasone as an adjuvant to bupivacaine in combined femoral and sciatic nerve blocks in lower-limb vascular surgeries: a prospective randomized study
Hala E Abdel Naim, Khaled A Elshafaie, Sherif M Soaida, Mohammed M Abdel-Haq, Kareem M Nawar
Department of Anesthesia, ICU, and Pain Management, Faculty of Medicine, Cairo University, Cairo, Egypt
|Date of Submission||09-Dec-2015|
|Date of Acceptance||27-Mar-2016|
|Date of Web Publication||12-Jan-2017|
Sherif M Soaida
Department of Anesthesia, Kasr Al-Ainy Hospital, Cairo University, Kasr Al-Ainy Street, Cairo 11562
Source of Support: None, Conflict of Interest: None
Background and aim
Various peripheral nerve block techniques have been described to deliver anesthesia and analgesia that allow better functional recovery and shortened hospital stay following major lower-limb surgeries. We aimed to compare the possible effect of perineural dexamethasone versus systemic dexamethasone after nerve stimulator-guided combined femoral and sciatic nerve blocks in lower-limb vascular surgeries.
Patients and methods
After obtaining approval from the ethical committee of Kasr Al-Ainy University Hospital and obtaining written informed consent, 63 patients aged 18–70 years were randomly allocated into three equal groups. Group P received perineural dexamethasone plus bupivacaine 0.5%, group I received intravenous dexamethasone plus perineural bupivacaine 0.5%, and group B received perineural bupivacaine 0.5% alone. We compared the onset and duration of sensory and motor blockade, duration of analgesia, and hemodynamic changes.
Sensory and motor block onset showed nonsignificant difference between the three groups. Sensory block duration was significantly longer in group P than in groups I and B. Motor block duration was significantly prolonged in groups P and I when compared with group B. Motor block duration was longer in group P than in group I; however, the difference was statistically nonsignificant (p-value 0.34). The duration of analgesia was significantly longer in group P than in the other groups, and significantly longer in group I compared with group B.
The use of equal doses of perineural or intravenous dexamethasone as an adjuvant in single injection combined femoral and sciatic nerve blocks is associated with extended duration of sensory and motor blocks, extension of postoperative analgesia duration, and reduced postoperative analgesic requirements.
Keywords: anesthesia, dexamethasone, nerve block, perineural, regional
|How to cite this article:|
Abdel Naim HE, Elshafaie KA, Soaida SM, Abdel-Haq MM, Nawar KM. Systemic versus perineural dexamethasone as an adjuvant to bupivacaine in combined femoral and sciatic nerve blocks in lower-limb vascular surgeries: a prospective randomized study. Ain-Shams J Anaesthesiol 2016;9:569-75
|How to cite this URL:|
Abdel Naim HE, Elshafaie KA, Soaida SM, Abdel-Haq MM, Nawar KM. Systemic versus perineural dexamethasone as an adjuvant to bupivacaine in combined femoral and sciatic nerve blocks in lower-limb vascular surgeries: a prospective randomized study. Ain-Shams J Anaesthesiol [serial online] 2016 [cited 2018 Oct 24];9:569-75. Available from: http://www.asja.eg.net/text.asp?2016/9/4/569/198258
| Introduction|| |
A variety of peripheral nerve block (PNB) techniques have been described to provide anesthesia and effective analgesia with a decreased incidence of systemic drawbacks, permitting better functional recovery and shortened postoperative hospital stay following major lower-limb surgeries.
Continuous PNBs have superseded epidural blocks as the analgesic gold standard following some lower-limb surgeries such as vascular surgeries as they can cover analgesia for 48–72 h postoperatively, avoiding possible complications associated with neuroaxial blocks. Generally, proximal sciatic nerve, femoral nerve, and lumbar plexus blocks were found superior for usage in the inpatient setting . PNBs provide multiple benefits in high-risk patients in the form of cardiovascular stability and decreased opioid requirements ,.
A documented side effect of continuous nerve block is persistence of motor blockade, a drawback that might delay patient ambulation. When formulating a plan for postoperative pain control following lower-limb surgery, however, consideration must be given to the frequent side effects associated with alternative modalities of analgesia, such as systemic opioids (postoperative nausea and vomiting, sedation, pruritus, and constipation), and the observation that inadequate analgesia can lead to painful restriction of limb movement .
Nerve localization in the lower limb is performed using either ultrasonography or peripheral nerve stimulation (PNS). Ultrasonographic nerve localization provides numerous possible advantages when performing femoral, popliteal, and distal sciatic nerve blocks; however, neurostimulation remains a useful and frequently used aid to lower-limb regional anesthesia ,.
Many studies have been carried out to investigate the effect of different local anesthetic (LA) adjuvants and their effects on the quality of nerve blockade and duration of analgesia ,.
Corticosteroids have been successfully used to prolong the duration of LA action after peripheral nerve and epidural blockade. Considering systemic mechanisms of action, along with theoretical safety concerns about perineural dexamethasone, the investigation of parenteral dexamethasone as an alternate to the perineural route has been prompted.
| Aim of the work|| |
This study was designed to explore and compare the possible effect of perineural versus systemic dexamethasone on the duration of sensory and motor block after nerve stimulator-guided combined femoral and sciatic nerve blocks in patients undergoing lower-limb vascular surgeries.
| Patients and methods|| |
This double-blinded randomized controlled study is a single-institutional clinical trial that was conducted in Kasr Al-Ainy Hospital, Faculty of Medicine, Cairo University, between June 2013 and January 2015. After reading the Helsinki Declaration and following its guidelines in this investigation and after obtaining the approval of the ethical committee in Kasr Al-Ainy University Hospital and registering at http://www.clinicaltrials.gov (NCT02576782) 63 patients of both sexes, of ASA physical status I, II, and III, 18–70 years old, undergoing lower-limb vascular surgery were included in the study. Patients were excluded if they had bleeding disorders, neurological deficits involving lumbar or sacral plexuses, if they were allergic to LA, had an infection at the injection site, were on sedative or antipsychotic drugs, and/or had a BMI above 35.
Patients were randomly allocated to one of three equal study groups using Excel 2010 (Microsoft Corp., Redmond, Washington, USA). The randomization sequence was concealed in opaque sealed envelopes that were kept by the senior anesthesia staff. The envelope was opened at the beginning of the operation before block initiation. All groups received 22 ml for each of femoral and sciatic nerve blocks plus 4 ml intravenously.
- Group P: 21 patients received 20 ml bupivacaine 0.5% and 2 ml (8 mg) dexamethasone in each block, plus 4 ml normal saline (NS) intravenously.
- Group I: 21 patients received 20 ml bupivacaine 0.5% and 2 ml NS in each block, plus 4 ml (8 mg) dexamethasone intravenously.
- Group B: 21 patients received 20 ml bupivacaine 0.5% and 2 ml NS in each block, plus 4 ml NS intravenously.
The primary outcome of this study was to detect the difference between the three groups regarding the duration of sensory blockade (measured from the time of sensory loss until the time of its regain). Secondary outcomes included the duration of motor blockade (measured from the time of motor loss until the time of its regain), duration of analgesia (measured from the time of sensory loss until the time of demand for the first dose of rescue analgesia), onset of sensory and motor blockade [where the onset of sensory block was measured from the time of each block completion until the time of sensory loss in the dermatomal distribution of the blocked nerve (tested by pin prick) and onset of motor blockade was measured from the time of each block completion until attaining a motor block equal to 2 or 3 on the modified Bromage scale  in femoral and sciatic nerve blocks, respectively]. Changes in heart rate (HR), arterial blood pressure (ABP), respiratory rate, and oxygen saturation (SpO2) were also considered as secondary outcomes.
Patients were subjected to systematic preoperative assessment including history taking, physical examination, and review of routine investigations. The visual analogue pain score (VAS) was explained to all candidates (0=no pain and 10=worst intolerable pain).
On arrival at the preparation room a peripheral intravenous cannula (18 G) was inserted under LA (1 ml lidocaine 2% using a 27-G needle), and the patients were premedicated using 1–2 mg midazolam intravenously. The patients were then transferred to the operating room where basic monitoring (ECG, noninvasive blood pressure, and pulse oximetry) was initiated. Baseline HR, ABP, SpO2, and respiratory rate were recorded as preblock values.
Femoral nerve block was performed using PNS (Model ES400; Life-Tech, Stafford, Texas, USA). The patient was placed in the supine position with both legs extended and the thigh slightly abducted and externally rotated, permitting femoral artery palpation. The anterior superior iliac spine and pubic tubercle were identified and marked. Then a line was drawn between them, representing the inguinal ligament.
Under strict aseptic measures subcutaneous infiltration of 2–3 ml of lidocaine 2% at the needle insertion site was performed, followed by advancement of a 22-G, short-bevel, 5-cm long, insulated stimulating needle 1–2 cm immediately lateral to the pulse of the femoral artery and 1–2 cm below the inguinal ligament. The nerve stimulator was initially adjusted to deliver 1.0 mA.
When a visible or palpable twitch of the quadriceps muscle (patellar twitch) was observed, the stimulating current was gradually decreased until twitches were still seen or felt at 0.2–0.4 mA, which was the best response suggestive of a successful femoral nerve localization.
After a negative aspiration for blood, 20 ml of LA and 2 ml of NS or dexamethasone were injected slowly while applying distal pressure, allowing proximal spreading of LA in the femoral sheath.
Sciatic nerve block was performed using the same PNS, following the classic approach of Labat. The patient was placed in the lateral position, where the limb to be blocked is topmost with the foot positioned over the dependent leg, with minor flexion of the hip and knee. A line was drawn from the posterior superior iliac spine to the greater trochanter, and a second line was drawn from the greater trochanter to the sacral hiatus (Winnie’s modification). Under strict aseptic measures subcutaneous infiltration of 2–3 ml lidocaine 2% was carried out at the needle insertion site (intersection of a perpendicular line from the midpoint of the first line and the second line), followed by insertion of a 22-G, short-bevel, 10-cm long, insulated stimulating needle.
The nerve stimulator was initially set to provide 1.5 mA, to allow recognition of twitches of the gluteal muscles and stimulation of the sciatic nerve. Twitches of the gluteal muscles were detected first, indicating shallow needle position. Once the gluteal twitches disappeared, response of sciatic nerve stimulation was detected.
When contractions of the hamstrings, calf muscles, foot, or toes were observed, the stimulating current was slowly reduced until twitches were still visible or felt at 0.2–0.5 mA. This was the ideal response suggestive of successful sciatic nerve localization.
Following both nerve blocks; the onset and duration of sensory and motor blockade were recorded. Patients were closely monitored to detect possible side effects (LA toxicity, hematoma). HR, SpO2, and ABP were recorded every 5 min during the first 15 min, and then every 15 min. Sensory and motor blockade was assessed by an independent blinded anesthetist. Postoperatively, patients were transferred to the postanesthesia care unit and then to the intermediate-care unit. Patients were monitored for 24 h following the block and data recording was continued until the first dose of rescue analgesia.
In the postoperative period if the patients started to complain of pain (VAS >3), rescue analgesia was given in the form of pethidine 1 mg/kg intravenously, paracetamol (Perfalgan) 1 g intravenous drip, and/or diclofenac sodium (Voltaren) 75 mg intramuscularly until VAS was 3 or less. In case of inadequate or patchy block general anaesthesia would have been supplemented and the patient excluded from the study.
Using F-tests, analysis of variance (ANOVA): Fixed effects, omnibus, one-way analysis, and assuming that the mean duration of the sensory block of bupivacaine was 4 h, a two-tailed α-error probability of 0.05, and β-error probability of 0.2 (power of 80%), a total sample size of 63 patients, randomly allocated into three equal groups (21 patients each), was calculated as being required to detect a presumed minimum clinically significant difference of 10% in the duration of sensory block (effect size f=0.404). Statistical power calculations were performed using computer program G*Power 3 for Windows (Franz Faul, Universität Kiel, Germany).
Collected data were presented as mean±SD, numbers, and percentages as appropriate. Categorical variables were analyzed using the χ2-test. One-way ANOVA univariate two-group repeated-measures ‘mixed-design’ ANOVA with post-hoc Dunnett’s test as appropriate was performed. Statistical analysis was carried out using the computer program SPSS (Statistical Package for Social Sciences; SPSS Inc., Chicago, IL, USA), version 20, 2011. P values less than 0.05 were considered statistically significant.
| Results|| |
Sixty-three patients fulfilling the inclusion criteria were enrolled in this study. They received combined femoral and sciatic nerve blocks. Those patients were randomly allocated into three equal groups: group P received perineural dexamethasone plus bupivacaine 0.5%, group I received systemic (intravenous) dexamethasone plus perineural bupivacaine 0.5%, and group B received perineural bupivacaine 0.5% alone.
Demographic data did not show statistically significant difference between the three studied groups ([Table 1]).
Regarding sensory and motor block onset, there was a nonsignificant difference between patients of all groups ([Table 2]). Groups P and I showed delayed sensory block regression, with significant differences when compared with group B (P<0.001 each). Similar results were found as regards the motor block duration, where it was significantly prolonged in groups P and I when compared with group B (P<0.001 each) ([Table 3]).
In addition, sensory block duration was significantly longer in group P when compared with group I (P=0.03). Motor block duration was longer in group P than in group I; however, the difference was statistically nonsignificant (P=0.34) ([Table 3]).
When comparing the duration of analgesia following nerve block administration, a significant difference was found between group P and each of group I (P=0.002) and group B (P<0.001). Furthermore, there was a significant difference in the duration of analgesia between group I and group B (P<0.001) ([Table 4]).
Perioperative hemodynamic profiles showed no significant difference between the three groups. Transient hypotension (a drop of the mean ABP ≥ 20% of the baseline values) occurred in three patients of group P (14.3%) and in four patients of group B (19%). In contrast, three patients of group I (14.3%) showed hypertensive episodes (a rise in mean ABP ≥ 20% of the baseline values), whereas it was noticed in only one patient of each of group P (4.8%) and group B (4.8%). Neither bradycardia, desaturation, bradypnea, nor tachypnea was recorded in any patient in any of the studied groups.
The nerve blockade administered was successful in all patients. None of the patients required rescue analgesia intraoperatively or postoperatively in the postanesthesia care unit. No block-related complications were recorded in any patient.
| Discussion|| |
In this study we compared the effect of perineural dexamethasone with bupivacaine 0.5% versus intravenous dexamethasone with perineural bupivacaine 0.5% as regards the onset and duration of motor and sensory block as well as duration of analgesia. Sensory and motor block onsets showed nonsignificant difference among the patients. Use of perineural dexamethasone significantly prolonged the duration of sensory block and the analgesia duration when compared with other groups. Motor block duration was significantly higher in the perineural group when compared with the bupivacaine group. Although it was longer than that in the intravenous group, the difference was statistically nonsignificant (P=0.34). Although systemic dexamethasone prolonged the clinical duration of bupivacaine-induced femoral and sciatic nerve blocks, perineural administration was superior in this context.
Our study outcome correlates well with that of Cummings et al. , who added dexamethasone 8 mg to bupivacaine 0.5% or ropivacaine 0.5% in 218 patients undergoing shoulder surgery with interscalene block. They found that the duration of analgesia of both ropivacaine and bupivacaine was significantly prolonged, with a stronger effect for ropivacaine. However, pain scores with movement on the first postoperative day were significantly lower in both the ropivacaine and bupivacaine plus dexamethasone groups.
Movafegh et al.  tested the effect of adding 8 mg dexamethasone on axillary brachial plexus block with lidocaine 1.5% in 60 patients scheduled for hand and forearm surgery. Although the onset times of sensory and motor block were equivalent in the two groups, the duration of sensory and motor blockade was significantly longer in the dexamethasone group.
A meta-analysis  has confirmed this impression by analyzing nine trials including 801 patients that tested the impact of dexamethasone (4–10 mg) on brachial plexus block. The authors concluded that perineural administration of dexamethasone with LA extends brachial plexus block effects (analgesic duration and motor block), with no detected adverse events. They stated that dexamethasone appeared to be the best means to prolong analgesia as an adjuvant to clonidine, epinephrine, or midazolam.
In contrast to the previous studies in which dexamethasone was added to LA, Shrestha et al.  found a statistically significant delay in the onset of action in the LA plus steroid group. This outcome was similar to that published in a recent systematic review carried out by Knezevic et al.  that included 14 studies, in which perineural dexamethasone delayed the onset of both sensory and motor block and the prolonged motor block duration. They also stated that smaller doses of dexamethasone (4–5 mg) had a similar effect to higher doses (8–10 mg).
Meanwhile, Noss et al.  conducted another systematic review including 11 clinical trials that investigated the efficacy of dexamethasone added to several LA agents in brachial plexus block. They found that the effect of dexamethasone on block onset was variable, with unclear clinical benefit.
Direct antinociceptive effects have been described following local administration of steroids. Johansson et al.  demonstrated that locally administered steroids limit the signal transmission of nociceptive C-fibers and change the membrane lipid-phase equilibrium. Remarkably, myelinated nerves were spared from such changes. The biologic half-life of dexamethasone is between 36 and 54 h, and its effects are most obvious in the first 48 h .
The analgesic effect of systemically administered dexamethasone likely arises from a diversity of mechanisms, including peripheral and central anti-inflammatory effects. According to their classical concept of action, steroids bind to intracellular receptors and modulate nuclear gene transcription and protein synthesis , ultimately stopping the production of prostaglandins, leukotrienes, and proinflammatory cytokines . However, dexamethasone produces a relatively quick effect, which cannot be explained by the above mechanism . Dexamethasone is also thought to suppress the neuropeptide immune response in injured tissue, thus decreasing the degree of pain .
Indirect evidence has supported the assumption that dexamethasone acts locally ; the stronger analgesic effect obtained with the perineural route in the present study probably supports a peripheral site of action. However, recent studies have suggested that a systemic effect might be responsible for its clinical effect, and intravenous administration may give similar results ,. Irrespective of its definite mechanism, the finest evidence suggests that its action is through indirect mechanisms rather than by directly inhibiting neurotransmission .
The potentiating effect of intravenous dexamethasone on PNB was described by Desmet et al. , who studied 150 patients who presented for shoulder arthroscopy under interscalene block using ropivacaine 0.5%, and compared the effect of perineural dexamethasone with that of intravenous dexamethasone. Dexamethasone significantly prolonged the duration of analgesia and decreased analgesic consumption independent of the route of administration. They found the effect of intravenous dexamethasone to be equivalent to that of perineural dexamethasone.
This correlates with the work of Rahangdale et al. , who studied 78 patients undergoing ankle and foot surgery under ultrasound-guided sciatic nerve blocks using 0.5% bupivacaine with epinephrine 1 : 300 000, comparing the effect of perineural versus intravenous dexamethasone on block characteristics. There was no significant difference in motor block or analgesia duration between the perineural and intravenous dexamethasone groups.
Kawanishi et al.  observed the effects of intravenous and perineural dexamethasone 4 mg on the duration of interscalene brachial plexus block using ropivacaine 0.75% in 39 patients undergoing shoulder arthroscopy. Perineural dexamethasone significantly prolonged the duration of analgesia, even when compared with intravenous dexamethasone.
Future studies might involve the combined usage of perineural and intravenous dexamethasone within the safe total maximum dose, as this might improve the quality and duration of block.
| Conclusion|| |
The present study demonstrated that, compared with a single injection of combined femoral and sciatic nerve block, the adjuvant use of equal doses of perineural and intravenous dexamethasone in patients undergoing major vascular surgeries is associated with extended duration of sensory and motor blocks, extension of postoperative analgesia duration, and reduced postoperative analgesic requirements. The postoperative analgesic effects of perineural dexamethasone were found superior to those of intravenous administration.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
| References|| |
Hebl JR, Dilger JA, Byer DE, Kopp SL, Stevens SR, Pagnano MW, Hanssen AD et al.
A pre-emptive multi-modal pathway featuring peripheral nerve block improves perioperative outcomes after major orthopaedic surgery. Reg Anesth Pain Med 2008;33:510–517.
McLeod GA, Dale J, Robinson D, Checketts M, Columb MO, Luck J, Wigderowitz C et al.
Determination of the EC50 of levobupivacaine for femoral and sciatic perineural infusion after total knee arthroplasty. Br J Anaesth 2009;102:528–533.
Capdevila X, Macaire P, Dadure C, Choquet O, Biboulet P, Ryckwaert Y, D’Athis F. Continuous psoas compartment block for postoperative analgesia after total hip arthroplasty: new landmarks, technical guidelines and clinical evaluation. Anesth Analg 2002;94:1606–1613.
Perlas A, Brull R, Chan VW, McCartney CJ, Nuica A. Ultrasound guidance improves the success of sciatic nerve block at the popliteal fossa. Reg Anesth Pain Med 2008;33:259–265.
Casati A, Baciarello M, DiCianni S, Danelli G, De Marco G, Leone S, Rossi M et al.
Effects of ultrasound guidance on the minimum effective anesthetic volume required to block the femoral nerve. Br J Anaesth 2007;98:823–827.
Sandhya A, Ritu A, Praveen G. Dexmedetomidine prolongs the effect of bupivacaine in supraclavicular brachial plexus block. J Anaesthesiol Clin Pharmacol 2014;30:36–40.
Laiq N, Khan MN, Arif M, Khan S. Midazolam with bupivacaine for improving analgesia quality in brachial plexus block for upper limb surgeries. J Coll Physicians Surg Pak 2008;18:674–678.
McNamee DA, Parks L, McClelland AM, Scott S, Milligan KR, Ahlen K, Gustafsson U. Intrathecal ropivacaine for total hip arthroplasty: double-blinded comparative study with isobaric 7.5 mg ml-1 and 10 mg ml-1 solutions. Br J Anaesth 2001;87:743–747.
Cummings KC3rd, Napierkowski DE, Parra-Sanchez I, Kurz A, Dalton JE, Brems JJ, Sessler DI. Effect of dexamethasone on the duration of interscalene nerve blocks with ropivacaine or bupivacaine. Br J Anaesth 2011;107:446–453.
Movafegh A, Razazian M, Fatemeh H. Dexamethasone added to lidocaine prolongs axillary brachial plexus blockade. Anesth Analg 2006;102:263–267.
Choi S, Rodseth R, McCartney CJ. Effects of dexamethasone as a local anaesthetic adjuvant for brachial plexus block: a systematic review and meta-analysis of randomized trials. Br J Anaesth 2014;112:427–439.
Shrestha BR, Maharjan SK, Tabedar S. Supraclavicular brachial plexus block with and without dexamethasone − a comparative study. KUMJ 2003;1:158–160.
Knezevic NN, Anantamongkol U, Kenneth D, Candido KD. Perineural dexamethasone added to local anesthesia for brachial plexus block improves pain but delays block onset and motor blockade recovery: a systematic review. Pain Physician 2015;18:1–14.
Noss C, MacKenzie L, Kostash M. Dexamethasone a promising adjuvant in brachial plexus anesthesia? A systematic review. J Anesth Clin Res 2014;5:421.
Johansson A, Hao J, Sjolund B. Local corticosteroid application blocks transmission in normal nociceptive C-fibers. Acta Anaesthesiol Scand 1990;34:335–338.
Copur MS, Ledakis P, Norvell M. Prevention of delayed emesis caused by chemotherapy. N Engl J Med 2000;343:888–889.
Gilron I. Corticosteroids in postoperative pain management: future research directions for a multifaceted therapy. Acta Anaesthesiol Scand 2004;48:1221–1222.
Taguchi H, Shingu K, Okuda H, Matsumoto H. Analgesia for pelvic and perineal cancer pain by intrathecal steroid injection. Acta Anaesthesiol Scand 2002;46:190–193.
Williams BA, Schott NJ, Mangione MP, Ibinson JW. Perineural dexamethasone and multimodal perineural analgesia: how much is too much? Anesth Analg 2014;118:912–914.
Thomas S, Beevi S. Epidural dexamethasone reduces postoperative pain and analgesic requirements. Can J Anaesth 2006;53:899–905.
Desmet M, Braems H, Reynvoet M, Plasschaert S, Van Cauwelaert J, Pottel H, Carlier S et al.
I.V. and perineural dexamethasone are equivalent in increasing the analgesic duration of a single-shot interscalene block with ropivacaine for shoulder surgery: a prospective, randomized, placebo-controlled study. Br J Anaesth 2013;111:445–452.
Abdallah FW, Johnson J, Chan V, Murgatroyd H, Ghafari M, Ami N, Jin R et al.
Intravenous dexamethasone and perineural dexamethasone similarly prolong the duration of analgesia after supraclavicular brachial plexus block. Reg Anesth Pain Med 2015;40:125–132.
Yilmaz-Rastoder E, Gold MS, Hough KA, Gebhart GF, Williams BA. Effect of adjuvant drugs on the action of local anesthetics in isolated rat sciatic nerves. Reg Anesth Pain Med 2012;37:403–409.
Rahangdale R, Kendall MC, McCarthy RJ, Tureanu L, Doty R Jr, Weingart A, De Oliveira GS Jr et al.
The effects of perineural versus intravenous dexamethasone on sciatic nerve blockade outcomes: a randomized, double-blind, placebo-controlled study. Anesth Analg 2014;118:1113–1119.
Kawanishi R, Yamamoto K, Tobetto Y, Nomura K, Kato M, Go R, Tsutsumi YM et al.
Perineural but not systemic low-dose dexamethasone prolongs the duration of interscalene block with ropivacaine: a prospective randomized trial. Local Reg Anesth 2014;7:5–9.
[Table 1], [Table 2], [Table 3], [Table 4]