[Thoracic Truncal Block : Trends and Future Perspectives].

With recent changes in surgical procedures and perioperative management, there has been a growing interest in peripheral nerve blocks of the trunk in patients undergoing thoracic and breast surgery. Tho- racic truncal blocks include paravertebral, pecs, intercostal, and retrolaminar blocks. Previous studies have demonstrated that paravertebral block provides similar analgesic effects and better hemodynamic stability compared with epidural analgesia. In addition, the results of several studies suggest that paravertebral block may improve long-term outcomes such as pre- vention of chronic pain and decrease in recurrence or metastasis after breast cancer surgery. Pecs blocks are novel ultrasound-guided blocks intended to provide analgesia of the anterior chest wall while avoiding seri- ous complications associated with epidural anesthesia and paravertebral block. The novel ultrasound-guided techniques for intercostal nerve blocks have also been reported. Although some case series support that these pecs and intercostal nerve blocks appear to be safe and effective, prospective randomized studies to confirm their clinical usefulness are lacking. Whether to con- duct these thoracic truncal blocks or not will become a standard clinical practice for thoracic and breast sur- gery is yet to be determined.

Synergistic effect of combining two nondestructive analytical methods for multielemental analysis.

We developed a new analytical technique that combines prompt gamma-ray analysis (PGA) and time-of-flight elemental analysis (TOF) by using an intense pulsed neutron beam at the Japan Proton Accelerator Research Complex. It allows us to obtain the results from both methods at the same time. Moreover, it can be used to quantify elemental concentrations in the sample, to which neither of these methods can be applied independently, if a new analytical spectrum (TOF-PGA) is used. To assess the effectiveness of the developed method, a mixed sample of Ag, Au, Cd, Co, and Ta, and the Gibeon meteorite were analyzed. The analytical capabilities were compared based on the gamma-ray peak selectivity and signal-to-noise ratios. TOF-PGA method showed high merits, although the capability may differ based on the target and coexisting elements.

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.

Incidence and effects of unintentional intraneural injection during ultrasound-guided subgluteal sciatic nerve block.

BACKGROUND: The present study was conducted to determine the incidence of unintentional intraneural injection during ultrasound-guided subgluteal sciatic nerve block using a low-frequency transducer. We also observed the effects of intraneural injection using ropivacaine and mepivacaine. METHODS: Enrolled in the study were 325 patients undergoing arthroscopic knee surgery, who each received a subgluteal sciatic nerve block under ultrasound guidance using 1.5% mepivacaine with 1:400,000 epinephrine or 0.5% ropivacaine. A block needle was inserted in-plane with the ultrasound transducer (5-2 MHz curved array) and advanced slowly under real-time ultrasound guidance until it was positioned immediately adjacent to the nerve. Twenty milliliters of either anesthetic was then injected to produce a circumferential spread. An ultrasound video was recorded and used to examine whether the local anesthetic was injected intraneurally. Sensory and motor blockade was evaluated for 30 mins after completion of the block. Duration of the block and any neurologic complications were also examined. RESULTS: Intraneural injection was detected in 46 patients (16.3%; 95% confidence interval, 12.3%-20.3%). Onset of sensory and motor blockade was significantly faster in patients with intraneural injection than those without either mepivacaine or ropivacaine. Duration of sensory blockade was similar between patients with and without intraneural injection. No patient developed postoperative neurologic complications. CONCLUSIONS: Unintentional intraneural injection occurred at an incidence rate of 16.3% for the ultrasound-guided subgluteal approach to the sciatic nerve. Intraneural injection of mepivacaine or ropivacaine hastened the onset of blockade but did not affect block duration, and it did not result in clinical neural injury in our small sample of patients.

[Continuous peripheral nerve block with a catheter placed under ultrasound guidance for analgesia after major orthopedic surgery].

BACKGROUND: This prospective study was conducted to investigate the effects and complications of continuous peripheral nerve blocks after major orthopedic surgery using a catheter placed under ultrasound guidance. METHODS: We studied 182 adult patients who underwent one of three types of major orthopedic surgery and received peripheral nerve blocks with one or two perineural catheters: continuous femoral nerve block after reconstruction of the anterior cruciate ligament, n=93; continuous femoral with or without sciatic nerve block after total knee arthroplasty, n=39; and continuous brachial plexus block after arthroscopic surgery of the shoulder, n=50. All the patients received additional single peripheral nerve block and/or general anesthesia for surgery. A continuous injection of 0.2-0.25% ropivacaine was started immediately after surgery at a rate of 4-6 ml x hr(-1), with a 3 ml patient-controlled bolus available every 30 min, and lasted for at least 48hr. Pain was evaluated at rest and during movement, RESULTS: Despite large inter-individual variation, continuous peripheral nerve block produced satisfactory postoperative analgesia without any apparent major complications. CONCLUSIONS: Peripheral nerve block and catheter placement under ultrasound guidance may help manage postoperative analgesia after orthopedic surgery easily, reliably and safely.

Ultrasound-guided peripheral nerve blocks for anterior cruciate ligament reconstruction: effect of obturator nerve block during and after surgery.

PURPOSE: Three studies were conducted to determine whether and how the obturator nerve bears relevance to intra- and postoperative pain in patients undergoing anterior cruciate ligament (ACL) reconstruction using a hamstring autograft. METHODS: Patients undergoing arthroscopic ACL reconstruction using a hamstring autograft were enrolled in three studies. In the first study, we studied the analgesic effect of combined posterior lumbar plexus (PLP) and sciatic nerve blocks as well as combined femoral, lateral femoral cutaneous, and sciatic nerve blocks during and for 24 h after surgery. The second study was conducted to compare the analgesic effect of the combination of femoral, lateral femoral cutaneous, and sciatic nerve blocks with and without an obturator nerve block. Finally, we compared a postoperative continuous femoral nerve block and PLP block both during and for 48 h after surgery. RESULTS: In the first study, patients receiving the PLP block required significantly less fentanyl intraoperatively than those given the femoral nerve block. In the second, significantly less fentanyl was required during surgery for patients with the obturator nerve block than for those without. Finally, the continuous postoperative PLP block showed higher visual analog pain scores than those with the continuous femoral nerve block during movement at 48 h. CONCLUSION: The present results suggest the involvement of the obturator nerve in ACL reconstruction using a hamstring autograft. However, although obturator nerve blockade is crucial for intraoperative analgesia, a continuous obturator nerve block is not necessary beyond 24 h postoperatively.

Ultrasound-guided anterior approach to sciatic nerve block: a comparison with the posterior approach.

BACKGROUND: Although the anterior approach to the sciatic nerve block has rarely been performed due to lack of reliable surface anatomical landmarks and technical difficulty, ultrasound guidance may make performance of this approach easier. In this study, we evaluated the clinical use of the ultrasound-guided anterior approach to sciatic nerve block and compared this approach with the posterior approach in adults. METHODS: One hundred patients undergoing minor knee surgery were randomly divided into two groups to receive anterior and posterior (subgluteal) approaches to sciatic nerve block, using 1.5% mepivacaine 20 mL with epinephrine combined with femoral and lateral femoral cutaneous nerve blocks. Both approaches to sciatic nerve block were performed using a low-frequency, 5 to 2 MHz, curved array transducer. Measurements included block execution time, depth and size of the nerve, needle depth, onset time of sensory and motor blockade, and duration of the block. RESULTS: The sciatic nerve was located significantly deeper and the needle depth was significantly greater in patients undergoing the anterior approach compared with the subgluteal approach. Both approaches were similar for execution time of sciatic nerve block, but the former took less time than the latter to perform all combinations of blocks. Although sensory block in the posterior femoral cutaneous nerve was achieved less often with the anterior approach compared with subgluteal approach (14.9% and 68.1%, respectively; P < 0.001), there were no differences in success rate, onset time or duration of blockade of the peroneal and tibial nerves between the two groups. CONCLUSION: The anterior approach to sciatic nerve block is performed as easily and successfully as the posterior approach using ultrasound guidance.

[Ultrasound-guided sciatic nerve block].

Theoretically, sciatic nerve block can be used alone or in combination with lumbar plexus block or femoral nerve block for anesthesia and/or analgesia of lower limb surgery. However, clinical use of sciatic nerve block was limited by technical difficulties in performing the block since techniques used relies only on surface anatomical landmarks. Recent advances in ultrasound technology allow direct visualization of nerves and other surrounding structures and have increased the interest in performing many kinds of peripheral nerve blocks including sciatic nerve block. Preliminary data suggest that ultrasound-guided technique can help perform the sciatic nerve block more reliably and safely. In this article we describe the anatomy of the sciatic nerve, sonographic features, and technique of three major approaches including subgluteal, anterior, and popliteal approaches. The use of this technique for postoperative analgesia is also discussed.

[Use of ultrasound for thoracic paravertebral block].

Thoracic paravertebral block is the technique of injecting local anesthetic adjacent to the intervertebral foramina, resulting in unilateral somatic and sympathetic nerve blockade. Previous studies have reported its effectiveness for thoracic surgery including breast surgery and relief of postoperative and chronic pain of unilateral origin from the chest and abdomen. The technique is relatively easy to learn and safer than thoracic epidural. Its clinical advantages include the inhibition of stress and pressor responses to surgical stimuli, maintenance of hemodynamic stability, low incidence of complication, long duration of analgesia, and few contraindications. Recent advances in ultrasound technology can further increase the effectiveness and the safety of thoracic paravertebral block, although identification of the nerve and needle is not still possible.

The interaction between gamma-aminobutyric acid agonists and diltiazem in visceral antinociception in rats.

UNLABELLED: To examine whether the gamma-aminobutyric acid (GABA) receptor agonists and L-type voltage-dependent calcium channel blockers potentiate each other on the visceral antinociceptive effects at the spinal cord, we assessed visceral nociception with colorectal distension (CD) test in rats with an intrathecal catheter. The measurements were performed after intrathecal administration of a GABA agonist (muscimol or baclofen), a calcium channel blocker (diltiazem), or the combination of the two. CD threshold did not change after muscimol 0.1 microg, baclofen 0.01 microg, or diltiazem 100 microg, but increased slightly after muscimol 1 microg and baclofen 0.1 microg. When muscimol 0.1 microg or 1 microg was administered with diltiazem, the increase in CD threshold was significantly larger than muscimol alone (at 5 min, 26.2% versus 0.6% MPE (maximum possible effect) or 84.5% versus 19.5%MPE, respectively; P < 0.01). The CD threshold after the combination of baclofen 0.1 microg and diltiazem also showed a significantly larger increase than that seen after baclofen alone (at 5 min, 48.0% versus 14.3% MPE; P < 0.01). Motor paralysis observed with muscimol 1 microg did not increase when muscimol was coadministered with diltiazem. In conclusion, intrathecal diltiazem in combination with a GABA agonist, muscimol or baclofen, potentiated the GABA agonists-induced visceral antinociception without increasing motor paralysis. IMPLICATIONS: Intrathecal administration of diltiazem in combination with a gamma-aminobutyric acid (GABA) agonist, muscimol or baclofen, potentiated the GABA agonists-induced visceral antinociception but did not affect motor paralysis. The present results indicate that the coadministration of the two types of drugs may be clinically useful.