An objective assessment of nerve stimulators used for peripheral nerve blockade*

Enhancing diagnosis and treatment of superior cluneal nerve entrapment: cadaveric, clinical, and ultrasonographic insights

OBJECTIVES

Low back pain is a prevalent public health issue caused by superior cluneal nerve (SCN) entrapment. This study aimed to explore the course of SCN branches, cross-sectional area (CSA) of the nerves, and effects of ultrasound-guided SCN hydrodissection.

METHODS

SCN distance relative to the posterior superior iliac spines was measured and compared with ultrasound findings in asymptomatic volunteers. The CSA of the SCN, pressure-pain threshold, and pain measurements were obtained from asymptomatic controls and patients with SCN entrapment at various time points after hydrodissection (with 1 mL of 50% dextrose, 4 mL of 1% lidocaine, and 5 mL of 1% normal saline) in the short-axis view.

RESULTS

Twenty sides of 10 formalin-fixed cadavers were dissected. The SCN locations on the iliac crest did not differ from the ultrasound findings in 30 asymptomatic volunteers. The average CSA of the SCN across different branches and sites ranged between 4.69-5.67 mm² and did not vary across different segments/branches or pain statuses. Initial treatment success was observed in 77.7% (n = 28) of 36 patients receiving hydrodissection due to SCN entrapment. A group with initial treatment success experienced symptom recurrence in 25% (n = 7) of cases, and those with recurrent pain had a higher prevalence of scoliosis than those without symptom recurrence.

CONCLUSIONS

Ultrasonography effectively localizes SCN branches on the iliac crest, whereby increased nerve CSA is not useful for diagnosis. Most patients benefit from ultrasound-guided dextrose hydrodissection; however, those with scoliosis may experience symptom recurrence and whether structured rehabilitation can reduce recurrence post-injection should be considered as one perspective in future research. Trial registration ClinicalTrials.gov (NCT04478344). Registered on 20 July 2020, https://clinicaltrials.gov/ct2/show/NCT04478344?cond=Superior+Cluneal+Nerve&cntry=TW&draw=2&rank=1 . Critical relevance statement Ultrasound imaging accurately locates SCN branches on the iliac crest, while enlargement of the CSA is not useful in diagnosing SCN entrapment; however, approximately 80% of SCN entrapment cases respond positively to ultrasound-guided dextrose hydrodissection.

An uncommon cause of nerve stimulator's malfunction during a dual guidance lumbar plexus block: A technical brief report and an algorithm for prevention of complications

Posterior Lumbar plexus block (PLPB) combined with an ipsilateral sacral plexus block is a valuable anaesthetic technique in patients undergoing hip fracture surgery. PLPB is performed through the acoustic window of the lumbar ultrasound trident and the position of the needle tip, before injection of LA, was confirmed by observing quadriceps femoris muscle contraction to peripheral nerve stimulation (i.e., dual guidance). We report an uncommon cause of nerve stimulator malfunction that might impair block performance and promote complications. We add an algorithm to limit the risk of complications.

The efficacy of maxillary and mandibular nerve blockade using electrical nerve stimulation for guidance

BACKGROUND

In oral and maxillofacial surgical procedures, sometimes conventional loco-regional anesthesia techniques could be insufficient in daily clinical practice. The aim of this study was to evaluate the efficacy of analgesia using electrical nerve stimulation (ENS) for maxillary or mandibular nerve blockade, in comparison with conventional loco-regional anesthesia techniques.

METHODS

The study comprised 52 patients who were attending the department for advanced surgery of the upper and lower jaw. Patients were randomly divided into 2 groups: ENS and Local group. The predictor variable was the anesthesia technique (ENS and Local groups). The outcome variables were patient assessed pain levels (VAS scores) and total anesthetic dose.

RESULTS

Both the administered anesthetic dose and patient-assessed pain levels were significantly lower in the ENS group than in the Local group, despite there being no difference in age, sex or any hemodynamic parameters between the groups.

CONCLUSIONS

Maxillary and mandibular nerve blockade is more efficient with ENS guidance, with lower amounts of anesthetic required, compared to conventional loco-regional anesthesia.

Treatment Outcome of Acute Sacral Nerve Stimulation in Functional Anorectal Pain

BACKGROUND

Sacral nerve stimulation (SNS) has revolutionized the management of certain intractable cases of fecal and urinary incontinence; however, the management of functional anorectal pain (FAP) has been addressed in only a few studies.

OBJECTIVE

The aim of this study was to evaluate the treatment effect of SNS in improving FAP symptoms.

METHODS

A total of 120 patients with FAP who had undergone temporary SNS probe placement were investigated at Qianfoshan Hospital between January 2014 and December 2016. Pre- and post-SNS treatment outcomes were assessed using the VAS, anorectal manometry, and the 36-item short-form health survey (SF-36) medical outcomes study instrument.

RESULTS

A total of 120 patients proceeded to insertion of an SNS probe at the S3 nerve root (2 Hz, 1.50 mA, 0.10 milliseconds). Of these, 75 patients were cured, 41 improved, and 4 had an ineffective outcome. The total effectiveness rate was 96.7% 1 year after treatment. There was a significant reduction in the median VAS score pre-SNS and post-SNS, from 8 to 3, respectively. Patients post-SNS had lower anal maximum contraction pressure and anal rest pressure than did patients pre-SNS. Compared with the pretreatment group, there were no substantial differences between anal longest contraction time and rectal rest pressure. In addition to general health, there was a substantial improvement in the remaining dimension scores of the SF-36.

CONCLUSION

The effect of SNS in treating FAP was positive, and the improvement of symptoms was substantial and worthy of clinical promotion.

High-reliability microcontroller nerve stimulator for assistance in regional anaesthesia procedures

In the last decades, the use of nerve stimulators to aid in regional anaesthesia has been shown to benefit the patient since it allows a better location of the nerve plexus, leading to correct positioning of the needle through which the anaesthetic is applied. However, most of the nerve stimulators available in the market for this purpose do not have the minimum recommended features for a good stimulator, and this can lead to risks to the patient. Thus, this study aims to develop an equipment, using embedded electronics, which meets all the characteristics, for a successful blockade. The system is made of modules for generation and overall control of the current pulse and the patient and user interfaces. The results show that the designed system fits into required specifications for a good and reliable nerve stimulator. Linearity proved satisfactory, ensuring accuracy in electrical current amplitude for a wide range of body impedances. Field tests have proven very successful. The anaesthesiologist that used the system reported that, in all cases, plexus blocking was achieved with higher quality, faster anaesthetic diffusion and without needed of an additional dose when compared with same procedure without the use of the device.

Electrical nerve stimulation method for intraoperative localization of the inferior alveolar nerve within the mandible: a pilot study in rabbits

The efficacy of the electrical nerve stimulation method for localizing the inferior alveolar nerve (IAN) within the mandibular bone was evaluated. Six New Zealand rabbits were used (both sides of the mandible). The IAN was stimulated through the mandibular bone and compound action potentials (CAPs) were recorded proximally from the main trunk of the nerve. Stimulation current pulse widths were set at 0.05, 0.1, 0.3, 0.5, and 1ms. The minimum current magnitude that generated a CAP with a criterion level (300mV peak-to-peak amplitude) was measured in the range of 0.05-5mA. Correlations between the distance of the IAN from the active electrode site and the minimum current magnitudes were studied for each pulse width. The correlation coefficients were 0.678, 0.807, 0.893, 0.851, and 0.890 for the pulse widths of 0.05, 0.1, 0.3, 0.5, and 1ms, respectively. The minimum current producing the criterion CAP response in the IAN was significantly (P<0.0001 for all pulse widths) and highly correlated with the distance between the stimulation site and the nerve. The results suggest that electrical nerve stimulation is a promising method that can be used for the localization of the IAN, especially during mandibular implant surgery.

[Localization of peripheral nerves. Success and safety with electrical nerve stimulation]

Peripheral electrical nerve stimulation is one of the standard applications in peripheral regional anesthesia in addition to the ultrasound technique. Among other findings, the visualization of needle and nerve during ultrasound-guided blockade caused a change in clinical practice of peripheral nerve stimulation in the last decade. In the present article old and new aspects of principles and clinical practice of the nerve stimulation technique are presented and summarized in a total clinical concept in order to achieve safe and successful peripheral regional anesthesia using electrical peripheral nerve stimulation.

Peripheral nerve stimulation in regional anesthesia

Peripheral nerve stimulation has a long history in regional anesthesia. Despite the advent of ultrasound-guided peripheral nerve blockade, nerve stimulation remains a popular technique used alone or, now, in combination with ultrasound-guided techniques. In light of this evolving utility of nerve stimulation, this is an appropriate time to review the basic concepts and knowledge base of this historically important tool. Electrical nerve stimulation facilitates nerve localization, using threshold current as a surrogate for needle-to-nerve distance. Preferential activation of motor nerves is possible because motor nerve fibers are more readily activated with a shorter duration of current compared with sensory nerves. The association between current and needle-to-nerve distance predicts that less current is needed to evoke a motor response as the needle moves closer to the nerve. Thus, an elicited motor response at or below 0.5 mA is considered a common end point for successful neural blockade. However, current magnitude is neither 100% sensitive nor specific. Independent of technical ability, both the biological environment and the equipment used impact the current-distance relationship. Thus, successful electrical nerve stimulation is dependent on an anesthesiologist with a solid foundation in anatomy and a thorough understanding of electrophysiology.

Défaut de circuit électrique et neurostimulation: cas cliniques et procédure de prévention

Functionality of the nerve stimulator and integrity of the electrical circuit should be verified and confirmed before performing peripheral nerve blockade. The clinical cases reported here demonstrate that electrical disconnection or malfunction during nerve localization can unpredictably occur and a checklist is described to prevent the unknown electrical circuit failure.