Thoracic epidural puncture guided by an acoustic signal: clinical results:

Primary failure of thoracic epidural analgesia: revisited

Primary failure of thoracic epidural analgesia (TEA) remains an important clinical problem, whose incidence can exceed 20% in teaching centers. Since loss-of-resistance (LOR) constitutes the most popular method to identify the thoracic epidural space, the etiology of primary TEA failure can often be attributed to LOR's low specificity. Interspinous ligamentous cysts, non-fused ligamenta flava, paravertebral muscles, intermuscular planes, and thoracic paravertebral spaces can all result in non-epidural LORs. Fluoroscopy, epidural waveform analysis, electrical stimulation, and ultrasonography have been proposed as confirmatory modalities for LOR.The current evidence derived from randomized trials suggests that fluoroscopy, epidural waveform analysis, and possibly electrical stimulation, could decrease the primary TEA failure to 2%. In contrast, preprocedural ultrasound scanning provides no incremental benefit when compared with conventional LOR. In the hands of experienced operators, real-time ultrasound guidance of the epidural needle has been demonstrated to provide comparable efficacy and efficiency to fluoroscopy.Further research is required to determine the most cost-effective confirmatory modality as well as the best adjuncts for novice operators and for patients with challenging anatomy. Moreover, future trials should elucidate if fluoroscopy and electrical stimulation could potentially decrease the secondary failure rate of TEA, and if a combination of confirmatory modalities could outperform individual ones.

Eyes on the needle: Identification and confirmation of the epidural space

Epidural catheters are used to provide effective intraoperative and postoperative analgesia. Standard epidural catheterization techniques rely on palpation of surface anatomy and the experience of the anesthesiologist. Failure to correctly place an epidural catheter can lead to inadequate analgesia and serious complications, such as dural puncture headache. Exciting new devices and techniques are being developed for identification of the epidural space and confirmation of catheter entry. This article reviews and describes the recent research findings. The devices and techniques are categorized into three sections: devices that modify the loss of resistance technique; visual confirmation using the epidural needle; and confirmation of placement of the epidural catheter.

Localization of epidural space: A review of available technologies

Although epidural analgesia is widely used for pain relief, it is associated with a significant failure rate. Loss of resistance technique, tactile feedback from the needle, and surface landmarks are traditionally used to guide the epidural needle tip into the epidural space (EDS). The aim of this narrative review is to critically appraise new and emerging technologies for identification of EDS and their potential role in the future. The PubMed, Cochrane Central Register of Controlled Clinical Studies, and Web of Science databases were searched using predecided search strategies, yielding 1048 results. After careful review of abstracts and full texts, 42 articles were selected to be included. Newer techniques for localization of EDS can be broadly classified into techniques that (1) guide the needle to the EDS, (2) identify needle entry into the EDS, and (3) confirm catheter location in EDS. An ideal method should be easy to learn and perform, easily reproducible with high sensitivity and specificity, identifies inadvertent intrathecal and intravascular catheter placements with ease, feasible in perioperative setting and have a cost-benefit advantage. Though none of them in their current stages of development qualify as an ideal method, many show tremendous potential. Some techniques are useful in patients with difficult spinal anatomy and infants, and thus are complementary to traditional methods. In addition to improving the existing technology, future research should aim at proving the superiority of these techniques over traditional methods, specifically regarding successful EDS localization, better safety profile, and a favorable cost-benefit ratio.

Clinical Practice of Epidural Puncture in Dogs and Cats Assisted by a Commercial Acoustic Puncture Assist Device-Epidural Locator: Preliminary Results

The objective of this study was to compare an Acoustic Puncture Assist Device-Epidural Locator (APAD-EL) with the "pop sensation" (POP) and "lack of resistance" (LOR) commonly used to confirm penetration of the ligamentum flavum and to ensure correct epidural placement in dogs and cats. We recruited 38 dogs and cats undergoing surgery and receiving epidural analgesia. Two anesthetists performed epidural puncture using the POP and LOR signs. Simultaneously, APAD-EL was used to collect visual and acoustic confirmation during advancement and placement of the needle tip for post hoc evaluation. A positive APAD-EL sign consists of a sudden pressure drop at the needle tip visible on a display and a concomitant pitch change of an acoustic signal. Failure to record a sudden pressure drop is considered a negative APAD sign. Descriptive statistics were used. In 32 patients with positive POP and LOR, the APAD was also positive. In one patient, POP was positive with a negative LOR and APAD result. Five patients had negative POP but positive LOR. Four patients had APAD positive and one (a dog) APAD negative. The study results showed that the APAD-EL information supports the subjective signs of correct needle placement suggested by positive POP and LOR experienced by trained anesthetists. The technique can be useful to assist difficult epidural puncture and as a training and teaching tool.

The Episure Autodetect syringe, a loss-of-resistance technique for locating the epidural space, used in pediatric patients

INTRODUCTION

The Episure Autodetect syringe, a spring-loaded syringe, is a loss-of-resistance syringe with an internal compression that applies constant pressure on the plunger. As the principle of loss-of-resistance is the same for adult and for pediatric patients, the Episure Autodetect syringe should be able to identify correctly the epidural space also in pediatric patients.

METHODS

A retrospective review was carried out for all pediatric patients, in which the Episure Autodetect syringe was used for locating the epidural space between 2007 and 2011 in our department.

RESULTS

In 17 pediatric patients (9 months-14 years, 7.5-43 kg weight), the Episure syringe was used. In all 17 patients, the epidural space was correctly identified using the spring-loaded syringe as evidenced by satisfactory analgesia. No accidental dural punctures or false loss-of-resistances were observed.

CONCLUSION

The spring-loaded Episure Autodetect syringe might be a potentially useful loss-of-resistance syringe for identification of the epidural space in pediatric patients.

Needle-tissue interaction forces--a survey of experimental data

The development of needles, needle-insertion simulators, and needle-wielding robots for use in a clinical environment depends on a thorough understanding of the mechanics of needle-tissue interaction. It stands to reason that the forces arising from this interaction are influenced by numerous factors, such as needle type, insertion speed, and tissue characteristics. However, exactly how these factors influence the force is not clear. For this reason, the influence of various factors on needle insertion-force was investigated by searching literature for experimental data. This resulted in a comprehensive overview of experimental insertion-force data available in the literature, grouped by factor for quick reference. In total, 99 papers presenting such force data were found, with typical peak forces in the order of 1-10N. The data suggest, for example, that higher velocity tends to decrease puncture force and increase friction. Furthermore, increased needle diameter was found to increase peak forces, and conical needles were found to create higher peak forces than beveled needles. However, many questions remain open for investigation, especially those concerning the influence of tissue characteristics.

The use of a sound-enabled device to measure pressure during insertion of an epidural catheter in women in labour

The insertion of an epidural catheter for labour analgesia may be challenging. This observational study compared pressures during insertion of an epidural catheter in pregnant (n = 35) and non-pregnant (n = 10) women, using an acoustic device for locating the epidural space that also records and stores pressure data during the procedure. In both groups, we compared the maximum pressure just before loss of resistance, the pressure in the epidural space and the pressure in the inserted epidural catheter. Maximum pressure just before loss of resistance in the pregnant women was significantly lower compared with the non-pregnant women. Pressures in the epidural space and with the disposable tubing connected to the inserted epidural catheter were greater in pregnant women than in non-pregnant women. The results support the hypothesis that physiological changes in the third trimester of pregnancy are the reason why epidural catheters are more difficult to insert in women in labour.

How to teach regional anesthesia

PURPOSE OF REVIEW

The demand for peripheral nerve blocks and neuroaxial blocks from both patients and surgeons has increased over the last few years. This change in attitude towards regional anesthesia is prompted by the insight that adequate perioperative pain management leads to earlier ambulation, shorter hospital stay, reduced cost and increased patient satisfaction. To avoid serious complications of these techniques structured residency programs need to be available.

RECENT FINDINGS

Until 2004, the Residency Review Committee for Anesthesiology in the United States required a minimum of 50 epidurals, 40 spinals and 40 peripheral nerve blocks during residency. Similarly, the German Society for Anesthesia and Intensive Care required 100 neuroaxial blocks and 50 peripheral nerve blocks. In 2004 the American Society of Regional Anesthesia and Pain Medicine endorsed standardized guidelines for regional anesthesia fellowships which regulate the administrative, equipment and educational demands.

SUMMARY

This review introduces the reader to the different teaching methods available, including cadaver workshops, three-dimensional videoclips, video filming, ultrasound guidance and acoustic assist devices as well as demonstrating their advantages and disadvantages. Moreover, an overview is given of future residency training programs, which integrate administrative, material and educative demands as well as the teaching means into the daily clinical routine.