Different analgesic effects of adenosine between postoperative and neuropathic pain

Background

Adenosine is an endogenous neuromodulator in both the peripheral and central nervous systems. Adenosine inhibits pain signals by hyperpolarizing neuronal membrane.

Methods

To clarify the effects of adenosine on pain signals, we tested intrathecal adenosine injection in two neuropathic pains (spinal cord compression and chronic constriction of sciatic nerve) and postoperative pain (plantar incision).

Results

In all three kinds of pain models, significant shortening of withdrawal latencies to thermal stimulation were detected from 24 h to 1 week after the surgery. Significant improvements of pain sensation were observed in all three models after intrathecal injection of Cl-adenosine 24 h after surgery. At 72 h after surgery, intrathecal Cl-adenosine injection inhibited hyperalgesia in the two neuropathic pain models but not in the postoperative pain model. Adenosine A1R messenger RNA (mRNA) expression significantly decreased in the plantar incision model. Adenosine A1R protein levels also decreased compared with the other two models and normal control.

Conclusions

These results suggest that adenosine effectively inhibits pain signals in neuropathic pain but is less effective in postoperative pain because of the decrease in adenosine A1 receptors.     

Long current impulses may be required for nerve stimulation in patients with ischemic pain

Purpose

To report on the efficacy of peripheral plexus catheters in the treatment of ischemic pain in spite of nerve stimulation with long current impulses.

Clinical features

Tw o patients with severe neuropathic ischemic foot pain are described. A 56-yr-old man with diabetes, renal failure, and autonomic neuropathy presented with severe ischemic foot pain. Opioids produced excess sedation and hypotension. A 62-yr-old woman was admitted after femoralpopliteal bypass and developed a reperfusion pain syndrome not relieved with opioids, gabapentin, amitryptiline, and clonidine. In both patients, a sciatic plexus catheter was placed with resolution of pain. Conventional nerve stimulation, which uses a pulse duration of 0.1 msec, did not result in muscle contraction. However, by using a nerve stimulator capable of delivering a 1.0 msec impulse duration, a muscle twitch or paresthesia endpoint ensued allowing for successful catheter placement.

Conclusion

Peripheral plexus catheters provide a safe alternative to systemic analgesics for pain relief in patients with ischemic foot pain. However, conventional nerve stimulation techniques may not elicit a motor response in patients with underlying neuropathy, and the use of nerve stimulators capable of delivering long current impulses is recommended.     

A simple and successful sonographic technique to identify the sciatic nerve in the parasacral area

Background

The purpose of this study was to describe detailed sonographic anatomy of the parasacral area for rapid and successful identification of the sciatic nerve.

Methods

Fifty patients scheduled for knee surgery were included in this observational study. An ultrasound-guided parasacral sciatic nerve block was performed in all patients. The ultrasound probe was placed on an axial plane 8 cm lateral to the uppermost point of the gluteal cleft. Usually, at this level the posterior border of the ischium (PBI), a characteristically curved hyperechoic line, could be identified. The sciatic nerve appeared as a hyperechoic structure just medial to the PBI. The nerve lies deep to the piriformis muscle lateral to the inferior gluteal vessels, and if followed caudally, it rests directly on the back of the ischium. After confirmation with electrical stimulation, a 20-mL mixture of 1% ropivacaine and 1% lidocaine with epinephrine was injected.

Results

The sciatic nerve was identified successfully in 48 patients (96%). In those patients, the median time required for its ultrasonographic identification was ten seconds [interquartile range, 8-13.7 sec], and the block success rate was 100%.

Conclusion

The described sonographic details of the parasacral area allowed for rapid and successful identification of the sciatic nerve.     

Neuromuscular choristoma of the sciatic nerve and lumbosacral plexus: an association with nerve-territory undergrowth in the pelvis affecting soft tissue and bone

Background

Neuromuscular choristomas (NMC) are rare congenital lesions with differentiated muscle found within peripheral nerves. Patients often present with progressive neuropathy, undergrowth of the affected limb, and limb length discrepancy. In the sciatic nerve (the most common location of NMC), this may lead to specific manifestations in the distal limb, including progressive neuropathy, a shortened atrophic limb and a cavus foot. We hypothesized that the presence of NMC of the sciatic nerve (proximal to the sciatic notch) extending to the lumbosacral plexus could lead to abnormalities in proximal nerve territories (i.e., nerve, muscle and bone) within the hemipelvis.

Methods

A retrospective review of all cases of sciatic nerve NMCs diagnosed at the Mayo Clinic was performed.

Results

Seven patients were identified with sciatic nerve NMCs extending proximal and distal to the sciatic notch. Four patients with NMCs had denervation of muscles within the pelvis and ipsilateral undergrowth of bone which resulted in three cases of hip dysplasia. To our knowledge, the finding of proximal nerve-territory soft tissue and bony undergrowth (including hip dysplasia) in patients with NMCs involving the sciatic nerve and lumbosacral plexus has not previously been recognized.

Conclusion

This finding will aid in both the diagnosis of the disease and an understanding of associated conditions.     

Antinociceptive effect of intrathecal administration of taurine in rat models of neuropathic pain

Purpose

Taurine is the most abundant amino acid in many tissues. Although taurine has been shown to be antinociceptive, in this report, our focus is to elucidate the mechanism and action site on neuropathic pain. This study used behavioural assessments to determine whether taurine attenuates neuropathic pain in the spinal cord.

Methods

Chronic constriction injury (CCI) to the sciatic nerve and streptozotocin-induced diabetic neuropathy were introduced to male Sprague-Dawley rats. We then assessed the antinociceptive effect of spinal injections of taurine (100, 200, 400, or 800 μg) using electronic von Frey, paw pressure, and plantar tests. To explore the effect of taurine on motor function, a rotarod test was performed, and in order to determine which neurotransmitter pathway is involved in taurine’s action, we examined how several antagonists of spinal pain processing receptors altered the effect of taurine 400 μg in a paw pressure test.

Results

Taurine alleviated mechanical allodynia, mechanical hyperalgesia, and thermal hyperalgesia in CCI rats and suppressed mechanical allodynia and hyperalgesia in diabetic rats. Significant effects were observed at 200 μg in both models. On the other hand, taurine dose-dependently affected motor performance, and a significant effect was seen at 400 μg. The antinociceptive effects were reversed completely by pretreatment with an intrathecal injection of strychnine, a glycine receptor antagonist.

Conclusion

The present study demonstrated that intrathecal administration of taurine attenuates different models of neuropathic pain, and these effects seem to be mediated by the activation of glycinergic neurotransmission. These findings suggest that taurine may be a candidate remedy for neuropathic pain.     

Ultrasound-guided ilioinguinal/iliohypogastric nerve blocks for chronic pain after inguinal hernia repair

Purpose

The aim of this study was to evaluate the outcome of ilioinguinal and iliohypogastric nerve blocks in patients with chronic pain after herniorrhaphy, by comparing nerve stimulator and ultrasound guidance to administer the block.

Methods

A total of 43 patients who received nerve blocks for chronic inguinal post-herniorrhaphy pain received standardized questionnaires. Nerve stimulator–guided blocks were performed prior to January 2009, and thereafter, ultrasound-guided blocks were performed using a local anaesthetic solution and a corticosteroid.

Results

The questionnaire was completed by 38 patients (88 %). The inguinal hernia repair was performed for a median 16 months (range 3–219) ahead of the nerve blocks. A median of 2 pain treatments (range 1–7) was calculated. Median follow-up was 21 months (range 3–68). According to the DN4, 21 patients (55.3 %) no longer reported neuropathic pain. Subjectively, 32 % no longer reported moderate-to-severe pain. After ultrasound-guided blocks, a higher VAS score (at rest and during activities), a higher proportion of daily pain and more anxiety and depression are reported compared to blocks performed after nerve stimulator guidance.

Conclusions

Ilioinguinal/iliohypogastric nerve blocks can be effective to treat chronic inguinal pain following surgery of the groin. The use of ultrasound was not superior to nerve stimulator–guided blocks. These blocks could be considered prior to more invasive procedures such as neurectomy.     

Cubitus valgus and tardy ulnar nerve palsy due to an intracapsular ulnar nerve

Background

We describe a patient with tardy ulnar neuropathy and cubitus valgus deformity found to have an intracapsular ulnar nerve.

Methods

An 89-year-old woman presented with severe neuropathic pain in the ulnar digits of the hand, advanced degenerative arthritis of the elbow, and tardy ulnar nerve palsy. Her pain was exacerbated with elbow movement, particularly flexion. She had paralysis of ulnar nerve innervated muscles, hypersensitivity with absence of two-point discrimination in her ulnar 1–1/2 digits, and a fixed ulnar claw deformity. She also had a grossly unstable elbow.

Results

Plain films revealed a cubitus valgus deformity (38°), an absent radial head, a dislocated proximal radioulnar joint and advanced arthritic changes. Ultrasonography revealed an indistinct ulnar nerve within the cubital tunnel which penetrated the joint. Electrophysiological studies revealed evidence of a severe ulnar neuropathy at the level of the elbow. Intraoperatively, an attenuated 2 cm length of the retrocondylar ulnar nerve was observed to be incorporated into the joint capsule tethered by a fibrous/synovial band which was released. A large effusion was drained. The ulnar nerve was transposed subcutaneously. The capsular rent was repaired in layers. She noted immediate and sustained (2 year follow-up) pain relief and regained moderate function in her interossei.

Conclusions

We believe that the chronic cubitus valgus deformity and secondary degenerative elbow joint changes led to an altered course of the nerve and attenuation of the medial joint capsule such that the ulnar nerve spontaneously buttonholed itself intra-articularly.     

Efficacy of an ultrasound-guided subsartorial approach to saphenous nerve block: a case series

Purpose

The saphenous nerve, a branch of the femoral nerve, is a pure sensory nerve that supplies the anteromedial aspect of the lower leg from the knee to the foot. There is limited evidence of the effectiveness of ultrasound-guided techniques to block the saphenous nerve. We therefore undertook a retrospective case series to investigate the efficacy of an ultrasound-guided subsartorial approach to saphenous nerve block.

Methods

During a four-month period, all patients receiving a subsartorial saphenous nerve block for lower extremity surgery at our institution had their medical records reviewed. Patient demographics and data were recorded, including block characteristics, intraoperative anesthetic management, pre-block, post-block, and postoperative pain scores, as well as postoperative analgesic dosing. Preoperative block success was defined by minimal intraoperative analgesic administration and a pain score of 0 in the postanesthesia care unit not requiring analgesic supplementation. Postoperative block success was defined by reduction of pain score to 0 without need for additional analgesic dosing.

Results

Thirty-nine consecutive patients were identified as receiving an ultrasound-guided subsartorial saphenous nerve block. Overall, this ultrasound-guided technique was found to have a 77% success rate.

Conclusion

This case series shows that an ultrasound-guided subsartorial approach to saphenous nerve blockade is a moderately effective means to anesthetize the anteromedial lower extremity. The success rate is based on stringent criteria with an endpoint of postoperative analgesia. A randomized prospective study would provide a more definitive answer regarding the efficacy of this technique for surgical anesthesia.     

Ultrasound-Guided Methylene Blue Dye Injection for Parathyroid Localization in the Reoperative Neck

Background

The goal of this study was to review a single institution’s experience using intraoperative ultrasound-guided (ioUSG) methylene blue dye injection for the localization and removal of enlarged parathyroid glands in patients with primary hyperparathyroidism and a history of previous neck surgery.

Methods

We performed a retrospective review of nine consecutive patients who underwent reoperative parathyroidectomy using ioUSG methylene blue dye injection.

Results

All patients had successful resolution of their hyperparathyroidism, with at least a 50 % decrease in intraoperative parathyroid hormone level after resection. One patient had transient recurrent laryngeal nerve paresis. There were no permanent recurrent laryngeal nerve injuries or cases of permanent hypoparathyroidism.

Conclusions

Blue dye injection is a safe and effective method of localizing diseased parathyroid glands in the reoperative neck.     

Steuerung der axillären Multiinjektionstechnik zur Plexusanästhesie

Background

Ultrasound guidance is still a young method in regional anesthesia when compared to nerve stimulation and only a few studies exist comparing these two techniques in an axillary multiple injection approach.

Aim

This prospective, randomized, observer-blinded study compared an ultrasound-guided (SONO) quadruple injection axillary block (out of plane, perineural) with a nerve stimulation-guided (STIM) triple injection axillary block for upper limb surgery.

Material and methods

A total of 60 patients were randomized to either the SONO (n?=?30) or STIM (n?=?30) group. For the block 40–50 ml mepivacaine 1.5?% (plexus) and 5–10 ml mepivacaine 0.5?% (subcutaneous in the medial skin of the arm) was used. Anesthesia time was recorded as the primary end point. After evaluation of block-related pain using a visual analog scale (VAS) a blinded observer tested sensory and motor function of the median nerve (MED), ulnar nerve (ULN), radial nerve (RAD), musculocutaneous nerve of the upper limb (MUC) and medial cutaneous nerve of the forearm (CAM) at defined times. The main outcome variable was onset time (defined loss of sensory/motor function).

Results

No differences were observed between the groups in terms of onset time (single nerves 10–20 min, plexus 20–25 min) and success rate (SONO 90?%, STIM 89?%). Patient satisfaction as measured by block-related pain score (VAS 2 cm), complications (vascular puncture SONO 7?%, STIM 11?%; paresthesia SONO 21?%, STIM 22?%) and patient acceptance (SONO 92?%, STIM 91?%) showed no differences. Performance time was shorter in the SONO group (6.68?±?1.72 min vs. 8.05?±?2.58, p?=?0.02).

Conclusion

Nerve stimulation-guided axillary plexus blocks performed by trained anesthesiologists may result in similar onset times and success rates compared to ultrasound-guided blocks.     

Brief review: Piriformis syndrome: etiology, diagnosis, and management

Purpose

In this narrative review, we aim to provide the pathophysiology and diagnostic criteria of the piriformis syndrome (PS), an underdiagnosed cause of buttock and leg pain that can be difficult to treat. Based on existing evidence, frequencies of clinical features are estimated in patients reported to have PS. In view of the increasing popularity of ultrasound for intervention, the ultrasound-guided technique in the treatment of PS is described in detail.

Source

A literature search of the MEDLINE^® database was performed from January 1980 to December 2012 using the search terms e.g., “ piriformis injection”, “ ultrasound guided piriformis injection”, “ botulinum toxin”, “pain management”, and different structures relevant in this review. There was no restriction on language.

Principal findings

A review of the medical literature pertaining to PS revealed that the existence of this entity remains controversial. There is no definitive proof of its existence despite reported series with large numbers of patients.

Conclusion

Piriformis syndrome continues to be a controversial diagnosis for sciatic pain. Electrophysiological testing and nerve blocks play important roles when the diagnosis is uncertain. Injection of local anesthetics, steroids, and botulinum toxin into the piriformis muscle can serve both diagnostic and therapeutic purposes. An ultrasound-guided injection technique offers improved accuracy in locating the piriformis muscle. Optimizing the therapeutic approach requires an interdisciplinary evaluation of treatment.     

Distale Blockaden des N. ischiadicus

Background and objectives

The design of this study is related to an important current issue: should local anesthetics be intentionally injected into peripheral nerves? Answering this question is not possible without better knowledge regarding classical methods of nerve localization (e.g. cause of paresthesias and nerve stimulation technique). Have intraneural injections ever been avoided? This prospective, randomized comparison of distal sciatic nerve block with ultrasound guidance tested the hypothesis that intraneural injection of local anesthetics using the nerve stimulation technique is common and associated with a higher success rate.

Material and methods

In this study 250 adult patients were randomly allocated either to the nerve stimulation group (group NS, n?=?125) or to the ultrasound guidance group (group US, n?=?125). The sciatic nerve was anesthetized with 20 ml prilocaine 1% and 10 ml ropivacaine 0.75%. In the US group the goal was an intraepineural needle position. In the NS group progress of the block was observed by a second physician using ultrasound imaging but blinded for the investigator performing the nerve stimulation. The main outcome variables were time until readiness for surgery (performance time and onset time), success rate and frequency of paresthesias. In the NS group needle positions and corresponding stimulation thresholds were recorded.

Results

In both groups seven patients were excluded from further analysis because of protocol violation. In the NS group (n?=?118) the following needle positions were estimated: intraepineural (NS 1, n?=?51), extraparaneural (NS 2, n?=?33), needle tip dislocation from intraepineural to extraparaneural while injecting local anesthetic (NS 3, n?=?19) and other or not determined needle positions (n?=?15). Paresthesias indicated an intraneural needle position with an odds ratio of 27.4 (specificity 98.8%, sensitivity 45.9%). The success rate without supplementation was significantly higher in the US group (94.9% vs. 61.9%, p?<?0.001) and the time until readiness for surgery was significantly (p?<?0.001) shorter for successful blocks: 15.1 min (95% confidence interval CI 13.6–16.5 min) vs. 28 min (95% CI 24.9–31.1 min). In the NS subgroups the results were as follows (95% CI in brackets): NS1 88.2% and 22.7 min (19.5–25.9 min), NS2 24.2% and 43.3 min (35.5–51.1 min) and NS3 36.8% and 35.3 min (22.1–48.4 min).

Conclusions

For distal sciatic nerve blocks using the nerve stimulation technique, intraepineural injection of local anesthetics is common and associated with significant and clinically important higher success rates as well as shorter times until readiness for surgery. In both groups no block-related nerve damage was observed. The results indicate that for some blocks (e.g. sciatic, supraclavicular) perforation of the outer layers of connective tissue was always an important prerequisite for success using classical methods of nerve localization (cause of paresthesias and nerve stimulation technique). Additional nerve stimulation with an ultrasound-guided distal sciatic nerve block cannot make any additional contribution to the safety or success of the block. New insights concerning the architecture of the sciatic nerve are discussed and associated implications for the performance of distal ultrasound-guided sciatic nerve block are addressed.     

Ultrasound-guided regional anesthesia for upper limb surgery

Purpose

The purpose of this module is to review the main ultrasound-guided approaches used for regional anesthesia of the upper limb.

Principal findings

The anatomical configuration of the upper limb, with nerves often bundled around an artery, makes regional anesthesia of the arm both accessible and reliable. In-depth knowledge of upper limb anatomy is required to match the blocked territory with the surgical area. The interscalene block is the approach most commonly used for shoulder surgery. Supraclavicular, infraclavicular, and axillary blocks are indicated for elbow and forearm surgery. Puncture techniques have evolved dramatically with ultrasound guidance. Instead of targeting the nerves directly, it is now recommended to look for diffusion areas. Typically, local anesthetics are deposited around vessels, often as a single injection. Phrenic nerve block can occur with the interscalene and supraclavicular approaches. Ulnar nerve blockade is almost never achieved with the interscalene approach and not always present with a supraclavicular block. If ultrasound guidance is used, the risk for pneumothorax with a supraclavicular approach is reduced significantly. Nerve damage and vascular puncture are possible with all approaches. If an axillary approach is chosen, the consequences of vascular puncture can be minimized because this site is compressible.

Conclusions

Upper limb regional anesthesia has gained in popularity because of its effectiveness and the safety profile associated with ultrasound-guided techniques.     

Clinical aspects of ballistic peripheral nerve injury: shrapnel versus gunshot

Objectives

Ballistic injuries to peripheral nerves pose special challenges in terms of indications, timing and type of surgical intervention. The aim of the present work was to analyze our experience in the surgical treatment of peripheral nerve ballistic injuries with respect to the mechanism of injury (gunshot versus shrapnel), and identify common and dissimilar prognostic factors in both types of injury.

Methods

This study was conducted on 42 patients totaling 58 nerves. Twenty-two patients (32 nerves) were injured by gunshot and 20 patients (26 nerves) by shrapnel. Median postoperative follow-up was 33 months (range 12 months to 14 years).

Results

Overall postoperative outcome appears to be more favorable for gunshot-wound (GSW) patients than shrapnel-injured patients, especially in terms of neuropathic pain relief (75 % vs. 58 % respectively, p < 0.05). Presence of foreign particles in shrapnel injured patients has a negative impact on the surgical outcome in terms of rate of pain improvement (28 % compared to 67 % in patients with and without foreign particles, respectively). Nerve graft reconstruction, rather than neurolysis, seems to be the more beneficial treatment for shrapnel-induced neuropathic pain (100 % vs. 47 % in improvement rate, respectively). Early surgical intervention (median 2 months after injury) significantly relieved neuropathic pain in 83 % of shrapnel-injured patients compared to 58 % in patients operated later.

Conclusions

This study suggests that shrapnel injury is more destructive for nerve tissue than gunshot injury. Our impression is that early surgical intervention in shrapnel injuries and split nerve grafting (especially when small fragments are recognized in the nerve) significantly improve the patient’s functional activity and quality of life.     

Adenylate cyclase inhibition attenuates neuropathic pain but lacks pre-emptive effects in rats

Purpose

There is evidence that cyclic adenosine monophosphate (cAMP) transduction is involved in nociceptive processing. We previously showed that intrathecal injection of an adenylate cyclase inhibitor attenuated tactile allodynia caused by partial sciatic nerve ligation (PSNL) in rats. The present study investigates the pre-emptive effects of spinal cAMP transduction on nociceptive processing in a chronic neuropathic pain model.

Methods

Intrathecal catheterization and PSNL were performed in male Sprague-Dawley rats. Nociceptive responses to mechanical and thermal stimuli were evaluated at the hindpaw at 2 hr and at 3, 7, and 14 days after PSNL. The pre-emptive effects of the intrathecal adenylate cyclase inhibitor, SQ22536 (0.7 μmol · L^?1, 30 min before or after nerve ligation) were assessed. Also, the spatial and temporal expression profiles and immunoreactivity in the spinal cord of the cAMP response element binding protein (CREB) and its phosphorylated proteins (CREB-IR and p-CREB-IR) were analyzed.

Results

Compared with the rats treated with the vehicle, allodynia and hyperalgesia were significantly attenuated at 1–3 days by the intrathecal injection of SQ22536 performed either before or after ligation. The expression of CREB was significantly higher after ligation (P < 0.05), but differences were not observed between groups. Intrathecal injection of SQ22536, either before or after ligation, partially reduced p-CREB-IR protein expression in comparison with the vehicle control, especially after the first 3 days (P < 0.05).

Conclusion

Our results show a possible association between the increase in p-CREB and PSNL-induced neuropathic pain. However, a pre-emptive effect of adenylate cyclase inhibitor administered before surgery was not observed.     

Abdominal wall bulging after thoracic surgery, an underdiagnosed wound complication

Background

Complications after thoracic surgery have well been established, pain being the most prominent. Intercostal nerves are mixed type nerves combining motor and sensory functions. This notion is not consistent with the incidence of PTPS compared to the incidence of muscle paresis or paralysis. We would hypothesize that abdominal wall paresis or paralysis is underdiagnosed.

Methods

In our hospital, three patients developed abdominal wall paralysis after thoracic surgery and consequent nerve damage. Their cases are discussed, and a review of the literature was conducted concerning (intercostal) nerve damage on a cellular level, the anatomy of the intercostal nerve, prevention of intercostal nerve damage and surgical techniques.

Results

A cellular cascade known as Wallerian degeneration and regeneration determine whether a damaged nerve can function again. The recovery of the nerve is highly dependent on the correct function of activated Schwann cells and macrophages and is related to the amount of damage that has taken place. The anatomy of the intercostal nerve makes it susceptible to injury. Retractor placement during open thoracic surgery has shown to effect compression injury and induced mechanical deformation and damage. Given the known factors of pathophysiology and anatomy, a number of preventive measures have been tested to reduce intercostal nerve damage. Several techniques have been proposed, but the most used technique, the video-assisted thoracic surgery, has been the most effective in reducing nerve damage.

Conclusion

Abdominal wall paralysis is an underdiagnosed complication after thoracic surgery. The amount of stress on the intercostal nerves could be reduced with less invasive techniques such as the VATS technique.     

Evaluation of behavior and expression of NaV1.7 in dorsal root ganglia after sciatic nerve compression and application of nucleus pulposus in rats

Purpose

The pathomechanisms of pain resulting from lumbar disc herniation have not been fully elucidated. Prostaglandins and cytokines generated at the inflammatory site produce associated pain; however, non-steroidal anti-inflammatory drugs and steroids are sometimes ineffective in patients. Tetrodotoxin-sensitive voltage-gated sodium (NaV) channels are related to sensory transmission in primary sensory nerves. The sodium channel NaV1.7 has emerged as an attractive analgesic target. The purpose of this study was to evaluate pain-related behavior and expression of NaV1.7 in dorsal root ganglia (DRG) after combined sciatic nerve compression and nucleus pulposus (NP) application in rats.

Methods

Rats were divided into three groups and underwent either sciatic nerve compression with NP for 2 s using forceps (n = 20), sham operation with neither compression nor NP (n = 20), or no operation (controls, n = 20). Mechanical hyperalgesia was measured every second day for three weeks using von Frey filaments. NaV1.7 expression in L5 DRG was examined 7 and 14 days after surgery using immunohistochemistry. The number of neurons immunoreactive for NaV1.7 was compared among the three groups.

Results

Mechanical hyperalgesia was found over the 14-day observation in the nerve compression plus NP application group, but not in the sham-operated or control groups (P < 0.05). NaV1.7 expression in L5 DRG was up-regulated in the nerve compression plus NP application group, compared with sham-operated and control rats (P < 0.01).

Conclusions

Our results indicate that nerve compression plus NP application produces pain-related behavior. We conclude that NaV1.7 expression in DRG neurons may play an important role in mediating pain from sciatic nerves after compression injury and exposure to NP.     

The role of electrical stimulation in ultrasound-guided subgluteal sciatic nerve block: a retrospective study on how response pattern and minimal evoked current affect the resultant blockade

Purpose

Nerve stimulation may be combined with ultrasound imaging for a block of deeply located nerves such as the sciatic nerve in the subgluteal region. At present, it is unknown how the use of nerve stimulation affects blockade after this nerve block. We retrospectively compared the effects of the two types of motor response and those of minimal evoked current above and below 0.5 mA on ultrasound-guided subgluteal sciatic nerve block using mepivacaine or ropivacaine, two local anesthetics with different onset time and duration.

Methods

We reviewed records and video images of patients who, from April 2008 until October 2011, received ultrasound-guided subgluteal sciatic nerve block combined with nerve stimulation using 20 ml of either 1.5 % mepivacaine with 1:400,000 epinephrine or 0.5 % ropivacaine. Sensory and motor blockade data for 30 min after the block and for the duration of the blockade were gathered. Patients for whom any data were missing, the video image was poor, and/or intraneural injection was observed during the block were excluded from the study. The same data were compared in two ways: regarding the motor response pattern between the response of the tibial nerve and the common peroneal nerve, and regarding the minimal current between low current (< 0.5 mA) and high current (≥0.5 mA). The primary endpoints were the onset and duration of blockade of the sciatic nerve block.

Results

We analyzed the data of 170 and 99 patients who received mepivacaine and ropivacaine, respectively. The progress of sensory and motor blockade as well as block duration was similar between different motor response patterns after both anesthetics. The proportion of patients who developed sensory block of the tibial nerve and motor block at 30 min was higher in the low minimal current group than in the other group receiving mepivacaine. Patients in the former group also had longer block duration. With ropivacaine, complete motor blockade was present at 30 min in a higher proportion of patients after lower minimal evoked current than after higher minimal evoked current.

Conclusion

When ultrasound-guided subgluteal sciatic nerve block was conducted with nerve stimulation, the motor response pattern did not markedly affect the progress of sensory or motor blockade or block duration. Lower minimal evoked current was associated with faster onset in sensory and motor block and longer block duration after mepivacaine and faster onset in motor block after ropivacaine. The clinical significance of this, however, has yet to be determined.     

Postoperative Ulnar Neuropathy is not Necessarily Iatrogenic: a Prospective Study on Dynamic Ulnar Nerve Dislocation at the Elbow

Background

Patients who undergo surgery may develop ulnar neuropathy. Although the mechanism of ulnar neuropathy is still not clear, ulnar neuropathies are common causes of successful lawsuits against surgeons. Recently, the concept developed that endogenous patient factors can lead to postoperative peripheral neuropathies. We hypothesize that dynamic ulnar nerve dislocation at the elbow (DUNDE) may be a predisposing factor for ulnar irritation (i.e. neuropathy) in normal subjects.

Methods

In a prospective investigation, patients aged 20 years and older presenting in our emergency department were asked to participate. Three physicians examined both elbows of subjects included in our study for evidence of DUNDE (through clinical and sonographic examination) and for clinical symptoms related to ulnar neuropathy.

Results

Dynamic ulnar nerve dislocation was observed in 29.3 % of examined subjects. No significant difference in its occurrence was observed in relation to gender or dominant side. Physical examination with provocation tests demonstrated significantly more positive Tinel tests and spontaneous signs of neuropathy in patients with dynamic dislocating ulnar nerves (14.7 vs. 1.1 %).

Conclusion

Dynamic ulnar nerve dislocation may be linked to ulnar nerve irritability (i.e. ulnar neuropathy) in normal subjects without history of trauma, surgical procedure, or anesthesia. Considering the high incidence of this variant in the general population, our study supports previous investigations suggesting that many postoperative ulnar nerve deficits are traceable to chronic patient conditions. Our study suggests that dynamic ulnar nerve dislocation is a predisposing factor in the development of ulnar neuropathy in the postoperative period.

Notes

(1) neuropathy should be viewed as a broad definition as signs of nerve irritation/inflammation, and independently of the pathophysiology and etiology; (2) because no specific term exists in the international anatomic nomenclature (Nomina Anatomica) to designate this variant, several synonyms have been used in the literature, leading to confusion and misleading conclusions concerning its traumatic etiologies and their consequences: (a) recurrent or habitual ulnar nerve luxation (or subluxation) [1–3]; (b) recurrent or habitual ulnar nerve dislocation [4–7]; (c) ulnar nerve instability [8]; (d) laxity of the ulnar nerve [9]; and (e) ulnar nerve hypermobility [10].     

Ultrasound-guided block of the brachial plexus at the humeral canal

Purpose

Conduction block of the brachial plexus block at the humeral canal, as described by Dupre, has certain clinical indications. The aim of this preliminary study was to assess the feasibility of this technique under ultrasound guidance.

Methods

After ultrasound evaluation of the brachial plexus at the humeral canal in 61 adult volunteers, we performed ultrasound-guided blocks in another 20 adult patients. A linear 38 mm probe, 13–6 MHz, and a 50-mm insulated block needle were used to guide injection of lidocaine 1.5% with epinephrine.

Results

Ulnar and median nerves are superficial and located at similar depths. Ultrasound imaging showed the musculocutaneous nerve to be located dorsally. The radial nerve is dorsal to the plane of the musculocutaneous nerve. Relative to the brachial artery, the median nerve is situated between 12 and 1 o’clock in 66% of the cases. Relative to the basilic vein, the ulnar nerve is situated at 3 o’clock in 46% of the cases. The evaluated block sequence was radial, ulnar, musculocutaneous and median nerve; two points of puncture were mandatory, and 6.85 ± 0.37 min were required to perform the blocks. Sensory onset times were similar for the four nerves. Injectate volume was lower for the musculocutaneous nerve compared to other nerves (P < 0.05). All 20 patients experienced complete sensory and motor blocks.

Conclusion

We describe an approach to, and the feasibility of ultrasound-guided block of the brachial plexus at the humeral canal. Further study will be required to establish the effectiveness and the safety of this technique.