Conventional Nerve Stimulation Research Articles

Immediate analgesic effect of two modes of transcutaneous electrical nerve stimulation on patients with chronic low back pain: a randomized controlled trial.

ABSTRACTObjective To compare and assess the immediate analgesic effects of conventional and burst transcutaneous electrical nerve stimulation in patients with chronic low back pain.Methods We conducted a three-arm single-blinded randomized controlled trial. A total of 105 patients with non-specific chronic low back pain aged between 18 and 85 years were randomly assigned into the following groups: Placebo Group (sham electrical stimulation), Conventional TENS Group (continuous stimulation at 100Hz for 100µs with sensory intensity), and Burst TENS Group (stimulation at 100Hz modulated at 2Hz for 100µs with motor-level intensity). All groups received a single application of transcutaneous electrical nerve stimulation for 30 minutes. The outcomes, namely, pain intensity, quality of pain, and pressure pain threshold were measured by the visual analog scale, McGill pain questionnaire, and algometry, respectively. The patients were evaluated before and immediately after the transcutaneous electrical nerve stimulation application.Results Pain intensity (visual analog scale score) and quality of pain (McGill pain questionnaire score) significantly decreased (p<0.05) in Intervention Groups (Conventional TENS Group and Burst TENS Group). A positive effect was observed in the interventions compared to the Placebo Group in all domains of the McGill pain questionnaire (p<0.05), excepting for the pain intensity. Pressure pain threshold significantly increased (p<0.05) immediately after the transcutaneous electrical nerve stimulation application in both Intervention Groups, but not in the Placebo Group. For significant difference was found during assessment when comparing both Intervetion Group.Conclusion Both transcutaneous electrical nerve stimulation modes were effective for pain modulation. Moreover, there was an increase in the pressure pain threshold. No significant results were found to indicate the best mode for the treatment of chronic low back pain.Clinical Trial Registration: RBR-59YGRB.

Vagus nerve bundle stimulation using 1505-nm laser irradiation in an in-vivo rat model.

Laser nerve stimulation using near-infrared laser irradiation has recently been studied in the peripheral nervous system as an alternative method to conventional electrical nerve stimulation. Bringing this method to the vagus nerve model could leverage this emerging stimulation approach to be tested in broader preclinical applications. Here, we report the capability of the laser nerve stimulation method on the rat vagus nerve bundle with a 1505-nm diode laser operated in continuous-wave mode. Studies of the stimulation threshold and laser-induced acute thermal injury to the nerve bundle were also performed to determine a temperature window for safe, reliable and reproducible laser stimulation of the rat vagus nerve bundle. The results show that laser stimulation of the vagus nerve bundle provides reliable and reproducible nerve stimulation in a rat model. These results also confirm a threshold temperature of >42°C with acute nerve damage observed above 46°C. A strong correlation was obtained between the laser time required to raise the nerve temperature above the stimulation threshold and the mean arterial pressure response. Advantages of the method such as non-contact delivery of external stimulus signals at mm scaled distance in air, enhanced spatial selectivity and electrical artefact-free measurements may indicate its potential to counteract the side effects of conventional electrical vagus nerve stimulation.

Towards Safe Infrared Nerve Stimulation: A Systematic Experimental Approach.

Neural activation by infrared nerve stimulation (INS) gains growing interest as a potential alternative to conventional electric nerve stimulation, since unambiguous advantages like contact-free operation, enhanced spatial selectivity and lack of (electrical) stimulation artifacts are promising for both future electrophysiological research and clinical application. For the systematic investigation of laser nerve activation, we recently introduced a novel experimental approach. Comprising a defined focused beam profile, it enables remote controlled, contact-free pulsed laser stimulation of the rat sciatic nerve, simultaneous to high-speed temperature measurement in vivo. Up to now, successful neural activation with single laser pulses (2 - 6 mJ) was observed in all performed experiments, however, it strongly depended on the particular nerve location. Hence, we depict the investigation of spatial dependency of the nerve response and identify `regions of excitability' on the nerve surface, that are highly susceptible to INS. By means of thermal imaging, we simultaneously monitored the nerve surface temperature, where we observed progressing temperature build-up during single pulse stimulation with repetition rates above 4 Hz. In this work, we present current results of our ongoing research.

Neostigmine‐induced weakness: what are the facts?

Neostigmine‐induced weakness: what are the facts?

Feasibility and safety of nerve stimulator attachment to energy-based devices: A porcine model study

BackgroundRecently, several energy-based devices (EBDs) have been developed and applied in the context of thyroid surgery. EBDs can reduce operation time, blood loss, and postoperative pain. Compared to conventional electrocautery, EBDs operate at a relatively lower temperature and produce minimal lateral tissue damage. Yet, during device operation, the tip of the EBD is hot enough to cause thermal nerve damage, increasing the need for surgeons to be cautious about EBD application. To increase the safety of EBDs, we attached nerve stimulators to the tips of two EBDs and compared them to conventional monopolar nerve stimulation using a porcine model. MethodsThree piglets (30–40 kg) underwent total thyroidectomy after orotracheal intubation with a nerve integrity monitor (NIM) electromyography (EMG) endotracheal tube. Nerve stimulators were attached to two EBDs (Harmonic Focus®+ and LigaSure™). After dissection and identification of six recurrent laryngeal nerves in the three piglets, both of the EBDs with attached nerve stimulators and a conventional monopolar nerve stimulator were applied near the nerve and EMG parameters were recorded using the NIM 3.0 system. The stimulus intensity was varied from 5 mA to 1 mA and the maximum distance and amplitude at which nerve detection was achieved were measured. ResultsThere were no statistically significant differences between the maximum distance or mean amplitude obtained from nerve stimulators attached to EBDs and those obtained from the conventional nerve stimulator. Additionally, there were no adverse EMG events related to the use of nerve stimulators attached to EBDs. ConclusionsAttachment of a nerve stimulator to an EBD for nerve detection during thyroidectomy was as safe and effective as attachment of a conventional nerve stimulator. Use of a nerve stimulator attachment may reduce the likelihood of EBD-associated nerve damage during thyroid surgery.

P 124 Auricular vagus nerve stimulation in subjects with major depression – Pulsatile vs. continuous stimulation

Conventional vagus nerve stimulation (cVNS) is approved to treat major depression. Within this context, auricular VNS (aVNS) is of increasing interest due to its non-invasiveness. Still, the question of optimum stimulation parameters has to be solved. 50 subjects with major depressive disorder were stimulated over 20 min. in the area of the auricular branch of the vagus nerve. Control stimulation (CS) was done at the ear lobe. Before and after each stimulation the participants were asked to rate their actual affective state. 30 participants were stimulated continuously, while in 20 subjects, stimulation was interrupted every 5 min. for 30 s. (pulsatile stimulation). Only using pulsatile stimulation, participants significantly more often rated to feel better (F1,18=12.35; p = 0.002) and to be more optimistic (F1,18=12.24; p = 0.003) after aVNS than after CS. Using pulsatile as well as using continuous stimulation, subjects indicated to be more happy (F1,18=24.61; p < 0.001 and F1,28=8.03; p = 0.008, resp.). Rating of pictures of the Internatonal Affective Picture System (IAPS) showed no statistical significant difference between the stimulation methods. Stimulating in a pulsatile way showed more difference between aVNS and CS than stimulating in a continuous way. Self rating of the emotional state by means of a visual analogue scale seems to be a reliable tool for the examination of non-invasive stimulation techniques.

Noninvasive vagus nerve stimulation: A novel promising modulator for cardiac autonomic nerve system dysfunction

Despite modern strategies, patients with cardiac diseases are still at high mortality rate due to neurohormonal activation and autonomic imbalance with increase in sympathetic activity and withdrawal of vagal activity. It is well known that conventional vagus nerve stimulation (VNS) could suppress the sympathetic tone and enhance the vagal tone, and prevent and reverse cardiac remodeling to break the vicious cycle between autonomic imbalance and cardiac remodeling [ [1] Hamann J.J. Ruble S.B. Stolen C. Wang M. Gupta R.C. Rastogi S. et al. Vagus nerve stimulation improves left ventricular function in a canine model of chronic heart failure. Eur. J. Heart Fail. 2013; 15: 1319-1326 Crossref PubMed Scopus (80) Google Scholar ]. However, traditional VNS has to implant a bipolar electrode around the cervical vagus nerve and a generator subcutaneously in the chest wall. This may cause complication or side effects including wound infection, electrode malfunction, coughing, swallowing difficulty and dysphagia [ 2 Spuck S. Tronnier V. Orosz I. Schönweiler R. Sepehrnia A. Nowak G. Sperner J. Operative and technical complications of vagus nerve stimulator implantation. Neurosurgery. 2010; 67: 489-494 PubMed Google Scholar , 3 Elliott R.E. Morsi A. Kalhorn S.P. Marcus J. Sellin J. Kang M. et al. Vagus nerve stimulation in 436 consecutive patients with treatment-resistant epilepsy: long-term outcomes and predictors of response. Epilepsy Behav. 2011; 20: 57-63 Abstract Full Text Full Text PDF PubMed Scopus (225) Google Scholar ]. The potential noninvasive approach for VNS, a transcutaneous electrical stimulation of the auricular branch of the vagus nerve (ABVN), has been proven to be effective on cardiac protection against cardiac diseases induced by disordered autonomic tone [ [4] Yu L. Scherlag B.J. Li S. Fan Y. Dyer J. Male S. et al. Low-level transcutaneous electrical stimulation of the auricular branch of the vagus nerve: a noninvasive approach to treat the initial phase of atrial fibrillation. Heart Rhythm. 2013; 10: 428-435 Abstract Full Text Full Text PDF PubMed Scopus (114) Google Scholar ].

Effect of burst TENS and conventional TENS combined with cryotherapy on pressure pain threshold: randomised, controlled, clinical trial

ObjectiveTo assess the immediate effect of conventional and burst transcutaneous electrical nerve stimulation (TENS) in combination with cryotherapy on pain threshold and tolerance in healthy individuals. DesignRandomised, controlled trial. SettingUniversity laboratory. ParticipantsOne hundred and twelve healthy women. InterventionsVolunteers were allocated at random to seven groups (n=16): (1) control, (2) placebo TENS, (3) conventional TENS, (4) burst TENS, (5) cryotherapy, (6) cryotherapy in combination with burst TENS, and (7) cryotherapy in combination with conventional TENS. Pain threshold and tolerance were measured by applying a pressure algometer at the lateral epicondyle of the humerus, before and after each intervention. Main outcome measuresThe primary outcome measure was pressure pain threshold. ResultsA significant increase in pain threshold and tolerance at the 5% level of significance was recorded as follows: burst TENS {pain threshold: mean difference 1.3 [95% confidence interval (CI) 1.4 to 1.2]; pain tolerance: mean difference 3.8 (95% CI 3.9 to 3.7)}, cryotherapy [pain threshold: mean difference 1.3 (95% CI 1.4 to 1.2); pain tolerance: mean difference 1.9 (95% CI 1.8 to 2.0)] and cryotherapy in combination with burst TENS [pain threshold: mean difference 2.6 (95% CI 2.4 to 2.8); pain tolerance: mean difference 4.9 (95% CI 5.0 to 4.8)]. Cryotherapy in combination with burst TENS provided greater analgesia compared with the other groups (P<0.001). ConclusionThese results support the use of cryotherapy in combination with burst TENS to reduce induced pain, and suggest a potentiating effect when these techniques are combined. No such association was found between cryotherapy and conventional TENS.

Reasoning of an Anomaly

report an unexpectedly high incidence of postoperative resid-ual weakness after using sugammadex for antagonism of rocuronium-induced block in a nonrandomized study conducted at 5 university-affiliated teaching hospitals in Japan. This report represents a “real world” scenario in which anesthesiologists used neither a quantitative train-of-four (TOF) monitor (which measures and displays the TOF ratio in real-time) nor a conventional nerve stimula-tor (which requires the clinician to evaluate the evoked response by subjective means, i.e., visually or tactilely).Kotake et al.

Feasibility on the Use of Intraoperative Vagal Nerve Stimulation in Gasless, Transaxillary Endoscopic, and Robotic-Assisted Thyroidectomy

Intraoperative nerve stimulation (IONS) could potentially reduce the incidence of recurrent laryngeal nerve (RLN) injury in thyroidectomy. The current study aimed at demonstrating the technical feasibility of using IONS in gasless, transaxillary endoscopic thyroidectomy (GTET) and robotic-assisted thyroidectomy (RAT) with conventional nerve stimulator probe and comparing the overall accuracy between two different nerve stimulation techniques, namely the direct RLN stimulation and the indirect stimulation via the vagus nerve (VN group), in predicting postoperative RLN function. From 2009 to 2010, 60 (17.1%) patients underwent endoscopic thyroidectomy using IONS. Thirty-three (55.0%) patients had direct intraoperative RLN stimulation (RLN group), whereas 27 (45.0%) patients had stimulation to the VN (VN group). Total number of nerves at risk was 76. The results of IONS were confirmed by the postoperative vocal cord movement on laryngoscopy. Patient demographics, surgical indications, resection type, size of dominant nodule, excised gland weight, and final pathology were similar between the two groups. The number of vocal cord palsies in the RLN and VN groups was 3 (7.3%) and 2 (5.7%), respectively. Compared with the VN group, the RLN group had a significantly lower percentage of true negatives (78.0% vs. 94.3%, P=.045) and higher percentage of false positives (14.6% vs. 0.0%, P=.018). Overall accuracy was higher in the VN group. The current study demonstrated the technical feasibility of using conventional open-nerve stimulator probe in both GTET and RAT. Indirect stimulation via the VN produced more reliable and accurate IONS test results than direct RLN stimulation.

Ambulatory Continuous Femoral Analgesia for Major Knee Surgery: A Randomised Study of Ultrasound-Guided Femoral Catheter Placement

Needle-nerve stimulation has a false negative motor response rate, which may increase needle passes. This prospective, randomised study tested the hypothesis that femoral nerve catheters placed with ultrasound-only guidance could provide comparable postoperative analgesia to those placed using a conventional nerve stimulation endpoint. Patients presenting for major knee surgery to the lead investigator were recruited. Needles introduced for femoral nerve catheter placement were initially guided with 'oblique' out-of-plane ultrasound imaging but were then prospectively randomised to either an ultrasound (n = 21) or nerve stimulation (n = 24) endpoint. An elastomeric infusion of ropivacaine 0.2% 2 ml/hour with as required hourly 5 ml boluses was continued for > 48 hours in hospital and/or in the home. Needle time under the skin and numerical rating pain score during insertion were recorded. Patients were questioned for worst numerical rating pain score, the need for supplementary ropivacaine boluses and tramadol on postoperative days one and two. There was no difference in the worst numerical rating pain score at rest and on movement and the requirement for supplementary ropivacaine boluses or tramadol during the first 48 postoperative hours. The median (quartiles) needle time under the skin was 58 seconds (51 to 76) in the ultrasound group and 120 seconds (95 to 178) in the nerve stimulation group (P = 0.001). The median (quartiles) insertion numerical rating pain score was 2 (0 to 2) in the ultrasound group and 4 (2 to 6) in the nerve stimulation group (P = 0.014). Femoral nerve catheters placed for major knee surgery using an ultrasound endpoint provided postoperative analgesia comparable to that obtained when using a nerve stimulation endpoint and were associated with a reduction in both needle manipulations and procedure-related pain.

Comparison of 3 Intensities of Stimulation Threshold for Brachial Plexus Blocks at the Midhumeral Level

We conducted this prospective randomized study to compare the success rate and the onset time between 3 intensities of stimulation threshold (<0.5, 0.5-0.64, and 0.65-0.8 mA) when using a peripheral nerve stimulation at the midhumeral level. Sixty-nine adult patients undergoing elective hand surgery were studied. Blocks were performed using conventional nerve stimulation technique. Needle advance began at 2 mA (1 Hz, 0.1 millisecond). When motor response (MR) occurred at less than 0.5 mA, needle position was fixed for "group <0.5 mA." For "group 0.5-0.64 mA," the needle was withdrawn until MR occurred at greater than 0.5 mA and disappeared at less than 0.5 mA. For "group >0.65 mA," the needle was withdrawn until MR occurred at greater than 0.65 mA and disappeared at less than 0.65 mA. For each group, patients received 8 mL of ropivacaine 7.5 mg/mL on the 4 nerves (radial, median, ulnar, and musculocutaneous). Primary end point was the number of failed radial nerve sensory blocks at 30 mins. The time to perform the block was not different between the 3 groups (17 mins [SD, 7 mins] vs 13 mins [SD, 8 mins] and 13 mins [SD, 4 mins], respectively). The time required to obtain a complete sensory block was shorter for the 4 nerves in group <0.5 mA, with a statistical significance for radial and musculocutaneous nerves in group <0.5 mA versus group 0.5-0.64 mA and group >0.65 mA. Patients in group <0.5 mA had a greater success rate for complete sensory radial nerve compared with those of group 0.5-0.64 mA and group >0.65 mA at any interval times between 5 and 30 mins (P = 0.0001). Supplemental local anesthesia was provided for the 3 groups more frequently for the median nerve, with no difference between groups. Group >0.65 mA required 5 general anesthesias (20%) as compared with 1 (4%) in group <0.5 mA (P < 0.05). No adverse event (dysesthesia) occurred after 48 hrs and 45 days. We conclude that intensity of stimulation influenced onset time and success rate.

Is Ultrasound Guidance Superior to Conventional Nerve Stimulation for Coracoid Infraclavicular Brachial Plexus Block?

In different peripheral nerve blocks, it has been speculated that needle guidance by ultrasound improves onset time and success rate compared with the more frequently used nerve stimulation-guided technique. In the present study, we tested the hypothesis that ultrasound guidance improves onset time of coracoid infraclavicular brachial plexus block (IBPB) when compared with a nerve stimulation-guided technique. Seventy patients scheduled for hand or forearm surgery were randomly assigned to receive coracoid IBPB using either ultrasound guidance (group U, n = 35), or nerve stimulation (group S, n = 35). Patients were assessed for sensory and motor block every 5 mins after injection of local anesthetic. Onset time, the primary end point, was defined as the time required for complete sensory and motor block. Time required to perform the block, success rate, and time to resolution of motor blockade were also recorded (secondary end points). Onset of complete sensory and motor blockade was similar in the 2 groups (17 mins [8 mins] in group U and 19 mins [8 mins] in group S; P = 0.321). Time required to perform the block was shorter in group U (3 mins [1 min]) as compared with group S (6 mins [2 mins]; P < 0.0001). No differences were observed in success rate (89% in group U and 91% in group S; P = 0.881) and time to resolution of motor blockade (237 mins [45 mins] in group U and 247 mins [57 mins] in group S; P = 0.418). The present investigation demonstrates that ultrasound guidance and nerve stimulation provide similar onset time, success rate, and duration of motor blockade for coracoid IBPB; however, ultrasound guidance reduces the time required to perform the block.

Aportación de la ecografía al bloqueo axilar del plexo braquial con neuroestimulación múltiple

To evaluate whether ultrasound imaging of vascular nerve structures improves anesthetic block quality and decreases the incidence of vascular puncture in the performance of an axillary brachial plexus block with multiple nerve stimulation. Randomized trial enrolling 129 patients assigned to 2 groups. In group 1, axillary brachial plexus nerves were located by nerve stimulation with ultrasound guidance. In group 2, only conventional multiple nerve stimulation was used. We analyzed the number of nerves located, time required to perform the block, anesthetic quality, and the number of accidental vascular punctures. Four nerves were located in 43% of the patients in group 1 and 38% of those in group 2. More time was taken in performing the block in group 1 than in group 2 (mean [SD] of 350 [40] seconds vs. 291 [58] seconds, respectively; P < .05). The incidence of vascular puncture was significantly lower in group 1 (8%) than in group 2 (28%) (odds ratio, 4 [95% confidence interval, 2-13]; P < .01). Ten and 20 minutes after puncture, the quality of sensory and motor blockade was significantly better in group 1. Block success was similar in the 2 groups (98.5% and 94% respectively). Combining ultrasound guidance with nerve stimulation improves the anesthetic quality of an axillary brachial plexus block, decreases the likelihood of vascular puncture, and slightly increases the amount of time required to perform the procedure.

La monitorización del bloqueo neuromuscular en el punto de acupuntura MC 6 (Neiguan) reduce la incidencia de las náuseas y vómitos del postoperatorio

Electrical stimulation of the P6 acupuncture point reduces the incidence of postoperative nausea and vomiting (PONV). Neuromuscular blockade during general anesthesia can be monitored with electrical peripheral nerve stimulation at the wrist. The authors tested the eff ect of neuromuscular monitoring over the P6 acupuncture point on the reduction of PONV. In this prospective, double-blinded, randomized control trial, the authors investigated, with institutional review board approval and informed consent, 220 women undergoing elective laparoscopic surgery anesthetized with fentanyl, sevofl urane, and rocuronium. During anesthesia, neuromuscular blockade was monitored by a conventional nerve stimulator at a frequency of 1 Hz over the ulnar nerve (n = 110, control group) or over the median nerve (n = 110, P6 group) stimulating at the P6 acupuncture point at the same time. The authors evaluated the incidence of nausea and vomiting during the first 24 h. No differences in demographic and morphometric data were found between both groups. The 24-h incidence of PONV was 45% in the P6 acupuncture group versus 61% in the control group (P = 0.022). Nausea decreased from 56% in the control group to 40% in the P6 group (P = 0.022), but emesis decreased only from 28% to 23% (P = 0.439). Nausea decreased substantially during the first 6 h of the observation period (P = 0.009). Fewer subjects in the acupuncture group required ondansetron as rescue therapy (27% vs. 39%; P = 0.086). Intraoperative P6 acupuncture point stimulation with a conventional nerve stimulator during surgery significantly reduced the incidence of PONV over 24 h. The efficacy of P6 stimulation is similar to that of commonly used antiemetic drugs in the prevention of PONV.

The Use of Low-Pass Image Filtering to Facilitate Detection of Peripheral Nerves for Ultrasound-Guided Nerve Block Procedures

Ultrasound-guided nerve block (UGNB) allows anesthesiologists to perform regional anesthesia around peripheral nerves using ultrasound images for visual guidance. Compared to conventional peripheral nerve stimulation techniques, UGNB provides a safer and more effective method to perform regional anesthesia. However, identification of peripheral nerves with ultrasound can often be problematic, especially for inexperienced users. This paper provides an in depth analysis of the difficulties associated with targeting and locating peripheral nerves during UGNB and proposes a real-time image processing solution, in the form of a low-pass persistence filter, which should increase target saliency in ultrasound images.

Monitoring of Neuromuscular Blockade at the P6 Acupuncture Point Reduces the Incidence of Postoperative Nausea and Vomiting

Electrical stimulation of the P6 acupuncture point reduces the incidence of postoperative nausea and vomiting (PONV). Neuromuscular blockade during general anesthesia can be monitored with electrical peripheral nerve stimulation at the wrist. The authors tested the effect of neuromuscular monitoring over the P6 acupuncture point on the reduction of PONV. In this prospective, double-blinded, randomized control trial, the authors investigated, with institutional review board approval and informed consent, 220 women undergoing elective laparoscopic surgery anesthetized with fentanyl, sevoflurane, and rocuronium. During anesthesia, neuromuscular blockade was monitored by a conventional nerve stimulator at a frequency of 1 Hz over the ulnar nerve (n = 110, control group) or over the median nerve (n = 110, P6 group) stimulating at the P6 acupuncture point at the same time. The authors evaluated the incidence of nausea and vomiting during the first 24 h. No differences in demographic and morphometric data were found between both groups. The 24-h incidence of PONV was 45% in the P6 acupuncture group versus 61% in the control group (P = 0.022). Nausea decreased from 56% in the control group to 40% in the P6 group (P = 0.022), but emesis decreased only from 28% to 23% (P = 0.439). Nausea decreased substantially during the first 6 h of the observation period (P = 0.009). Fewer subjects in the acupuncture group required ondansetron as rescue therapy (27% vs. 39%; P = 0.086). Intraoperative P6 acupuncture point stimulation with a conventional nerve stimulator during surgery significantly reduced the incidence of PONV over 24 h. The efficacy of P6 stimulation is similar to that of commonly used antiemetic drugs in the prevention of PONV.

Identification and Imaging of the Nerves Responsible for Erectile Function in Rat Prostate,In Vivo, Using Optical Nerve Stimulation and Optical Coherence Tomography

The cavernous nerves on the prostate surface are responsible for erectile function. Optical diagnostic tools such as optical coherence tomography and laser nerve stimulation may assist in the identification, imaging, and preservation of these microscopic nerves during prostate cancer surgery, and thus, help preserve sexual function after surgery. The feasibility of noncontact laser stimulation of the cavernous nerves is demonstrated in an in vivo rat prostate model with comparison to conventional electrical nerve stimulation. High-resolution optical coherence tomographic images of the nerves are also obtained and compared with histology. These optical technologies may be suitable as surgical guidance tools during laparoscopic and robotic nerve-sparing prostate cancer surgery.

Reevaluation of indirect field stimulation technique to demonstrate oxime effectiveness in OP-poisoning in muscles in vitro

Organophosphorus (OP) pesticides or nerve agents cause severe intoxication by inhibition of acetylcholinesterase, finally resulting in death due to respiratory failure. The phrenic nerve diaphragm preparation is considered as the classic model to investigate the effect of OP intoxications and oxime treatment at the neuromuscular junction. However, this preparation is unsuitable for larger species or for muscle strips from biopsies where no nerve is available for stimulation. An alternative technique is the indirect field stimulation of muscles containing intramuscular nerve branches only. The proposed method by Wolthuis et al. [Wolthuis, O.L., Vanwersch, R.A.P., Van Der Wiel, H.J., 1981. The efficacy of some bis-pyridinium oximes as antidotes to soman in isolated muscles of several species including man. Eur. J. Pharmacol. 70, 355–369] was modified and experimentally reevaluated in isolated mouse diaphragms. To confirm that electrical field stimulation technique induced muscle contraction only via the neuromuscular endplate the nicotinic antagonists pancuronium or d-tubocurarine (1 μM) were given. In the presence of a nicotinic antagonist hardly any contraction was blocked after indirect field stimulation technique with very short pulses (5 μs, <0.6 A), in contrast to direct muscle stimulation (broader pulse width, or higher amplitude >0.6 A). During paraoxon circumfusion (20 min, 1 μmol/l) muscle force generation by indirect stimulation was almost completely blocked. Restoration of paralyzed muscle function to 80% of initial values could be achieved after paraoxon wash out (20 min) and circumfusion with obidoxime (1 μmol/l, 20 min). This data correspond quite well to data shown earlier when using conventional nerve stimulation techniques.

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

To report on the efficacy of peripheral plexus catheters in the treatment of ischemic pain in spite of nerve stimulation with long current impulses.Two 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 femoral-popliteal 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.Peripheral plexus catheters provide a safe alter-native 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.