Anatomical study with clinical significance of communicating and visceral branching of the cervical and upper thoracic sympathetic trunk

Current advances in the management of the autonomic nervous system in various cardiovascular diseases, and in treatments for pain or sympathetic disturbances in the head, neck, or upper limbs, necessitate a thorough understanding of the anatomy of the cervicothoracic sympathetic trunk. Our objective was to enhance our understanding of the origin and distribution of communicating branches and visceral cervicothoracic sympathetic nerves in human fetuses. This was achieved through a comprehensive topographic systematization of the branching patterns observed in the cervical and upper thoracic ganglia, along with the distribution of communicating branches to each cervical spinal nerve. We conducted detailed sub-macroscopic dissections of the cervical and thoracic regions in 20 human fetuses (40 sides). The superior and cervicothoracic ganglia were identified as the cervical sympathetic ganglia that provided the most communicating branches on both sides. The middle and accessory cervical ganglia contributed the fewest branches, with no significant differences between the right and left sides. The cervicothoracic ganglion supplied sympathetic branches to the greatest number of spinal nerves, spanning from C5 to T2 . The distribution of communicating branches to spinal nerves was non-uniform. Notably, C3 , C4 , and C5 received the fewest branches, and more than half of the specimens showed no sympathetic connections. C1 and C2 received sympathetic connections exclusively from the superior ganglion. Spinal nerves that received more branches often did so from multiple ganglia. The vertebral nerve provided deep communicating branches primarily to C6 , with lesser contributions to C7 , C5 , and C8 . The vagus nerve stood out as the cranial nerve with the most direct sympathetic connections. The autonomic branching pattern and connections of the cervicothoracic sympathetic trunk are significantly variable in the fetus. A comprehensive understanding of the anatomy of the cervical and upper thoracic sympathetic trunk and its branches is valuable during autonomic interventions and neuromodulation. This knowledge is particularly relevant for addressing various autonomic cardiac diseases and for treating pain and vascular dysfunction in the head, neck, and upper limbs.

The size, number, and distribution of nerve endings around and within the human epiglottis, focusing on tracheal intubation maneuvers

The aim of this study was to examine the distribution of nerve endings in the mucosa, submucosa, and cartilage of the epiglottis and the vallecula area and to quantify them. The findings could inform the choice of laryngoscope blades for intubation procedures. Fourteen neck slices from seven unembalmed, cryopreserved human cadavers were analyzed. The slices were stained, and cross and longitudinal sections were obtained from each. The nerve endings and cartilage were identified. The primary metrics recorded were the number, area, and circumference of nerve endings located in the mucosa and submucosa of the pharyngeal and laryngeal sides of the epiglottis, epiglottis cartilage, and epiglottic vallecula zone. The length and thickness of the epiglottis and cartilage were also measured. The elastic cartilage of the epiglottis was primarily continuous; however, it contained several fragments. It was covered with dense collagen fibers and surrounded by adipose cells from the pharyngeal and laryngeal submucosa. Nerve endings were found within the submucosa of pharyngeal and laryngeal epiglottis and epiglottic vallecula. There were significantly more nerve endings on the posterior surface of the epiglottis than on the anterior surface. The epiglottic cartilage was twice the length of the epiglottis. The study demonstrated that the distribution of nerve endings in the epiglottis differed significantly between the posterior and anterior sides; there were considerably more in the former. The findings have implications for tracheal intubation and laryngoscope blade selection and design.

Innervation of the heart: Anatomical study with application to better understanding pathologies of the cardiac autonomics

Current advances in management of the cardiac neuroaxis in different cardiovascular diseases require a deeper knowledge of cardiac neuroanatomy. The aim of the study was to increase knowledge of the human fetal extrinsic cardiac nervous system. We achieved this by systematizing the origin and formation of the cardiac nerves, branches, and ganglia and their sympathetic/parasympathetic connections. Thirty human fetuses (60 sides) were subjected to detailed sub-macroscopic dissection of the cervical and thoracic regions. Cardiac accessory ganglia lying on a cardiac nerve or in conjunction with two or more (up to four) nerves before entering the mediastinal cardiac plexus were observed in 13 sides. Except for the superior cardiac nerve, the sympathetic cardiac nerves were individually variable and inconstant. In contrast, the cardiac branches of the vagus nerve appeared grossly more constant and invariable, although the individual cardiac branches varied in number and position of origin. Each cervical cardiac nerve or cardiac branch of the vagus nerve could be singular or multiple (up to six) and originated from the sympathetic trunk or the vagus nerve by one, two, or three roots. Sympathetic nerves arose from the cervical-thoracic ganglia or the interganglionic segment of the sympathetic trunk. Connections were found outside the cardiac plexus. Some cardiac nerves were connected to non-cardiac nerves, while others were connected to each other. Common sympathetic/parasympathetic cardiac nerve trunks were more frequent on right (70%) versus left sides (20%). The origin, frequency, and connections of the cardiac nerves and branches are highly variable in the fetus. Detailed knowledge of the normal neuroanatomy of the heart could be useful during cardiac neuromodulation procedures and in better understanding nervous pathologies of the heart.

Human lumbar sympathetic blockade: An anatomical study to address potential block failure

The lumbar sympathetic block is often used to treat complex regional pain syndrome, but it seems to have a high failure rate. This study seeks anatomical explanations for this apparent failure in order to refine our block procedure. Two simulated sympathetic trunk blocks were carried out on four fresh, cryopreserved unembalmed human cadavers under fluoroscopic control at the L2 vertebral body level, followed by two further simulated blocks at the L4 vertebral body level on the other side. Dye was injected, and the areas were dissected following a specific protocol. We then describe the anatomy and the spread of the dye compared to the spread of the contrast medium on fluoroscopy. The ganglia were differently located at different vertebral levels, and differed among the cadavers. Following this anatomical clarification, we now prefer to perform lumbar sympathetic blocks at the fourth lumbar vertebra level, using an extraforaminal approach at the caudal end of ​​the vertebra, avoiding the anterolateral margin of the vertebral body at the midpoint.

Microscopy of Structures Surrounding Typical Acupoints Used in Clinical Practice and Electron Microscopic Evaluation of Acupuncture Needles

Background and objectives Although the general functionality and structures of acupoints have been studied, there has been little insight into their underlying morphology and physical characteristics. We describe the microanatomical structures surrounding acupoints, the electron microscopic appearance of the needles, and the physical effects of acupuncture needling on the fascia. We injected heparinized blood solution through thin needles at seven known and commonly used "sweat acupoints" in eight fresh, unembalmed, cryopreserved human cadavers to mark the needle positions, and later, during histological examination, to identify them. After the solution was injected, samples were dissected and prepared for histological examination. We examined 350 cross-sections of five different paraffin wax sections from each acupoint microscopically. Acupuncture needles were photographed and superimposed on the cross-sectioned tissues at similar magnifications. Needles were also examined under a scanning electron microscope to judge the roughness or smoothness of their surfaces. A greater conglomeration of nerve endings surrounded the acupoints than in tissues more than 1-3 cm distant from them. Nerve endings and blood vessels were in close contact with a complex network of membranes formed by interlacing collagen fibers, and were always enclosed within those collagen membranes. Nerve endings were found within hypodermis, muscles, or both. Scanning electron microscopy demonstrated the three-dimensional shapes and sizes of the needles, and the degree of roughness or smoothness of their polished external surfaces. We demonstrate a delicate arrangement of nerve endings and blood vessels enclosed within complex collagen membrane networks at acupoints within the hypodermis and muscle. This arrangement could explain why needling is an essential step in the acupuncture process that provides favorable outcomes in clinical practice.

Spinal arachnoid sleeves and their possible causative role in cauda equina syndrome and transient radicular irritation syndrome

INTRODUCTION

We have previously described arachnoid sleeves around cauda equina nerve roots, but at that time we did not determine whether injections could be performed within those sleeves. The purpose of this observational study was to establish whether the entire distal orifice of a spinal needle can be accommodated within an arachnoid sleeve.

MATERIALS AND METHODS

We carefully dissected the entire dural sacs off four fresh cadavers, opened them by longitudinal incision, and immersed them in saline. Under direct vision, we penetrated the cauda equina roots nerves traveling almost vertically downward at 30 locations each with a 27- and a 25-G pencil-point needle (60 punctures total). We captured the images with a stereoscopic camera.

RESULTS

The nerve root offered no noticeable resistance to needle entry. Although the arachnoid sleeves could not be identified with the naked eye, they were translucent but visible under microscopy. In 21 of 30 attempts with a 27-gauge needle, and in 20 of 30 attempts with a 25-gauge needle, the distal orifice of the spinal needle was completely within the arachnoid sleeve.

CONCLUSION

It seems possible to accommodate the distal orifice of a 25- or a 27-gauge pencil-point spinal needle completely within the space of the arachnoid sleeve. An injection within this sleeve could potentially lead to a neurological syndrome, as we have previously proposed.

Case series of fluoroscopic findings and 3D reconstruction of human spinal MRIs of the space of Okada

OBJECTIVE

To better understand the unexpected spread of contrast medium observed by conventional fluoroscopic X-ray images during standard neuraxial techniques used in the treatment of pain. The support of 3D reconstruction of MRI images of structures within the lumbar spine was used to better understand the space of Okada.

METHODS

Lumbar facet joint and epidural corticosteroid injections in five patients under fluoroscopic guidance with loss of resistance to air or saline to identify the facet joints or epidural space. Next, in a retrospective study, the authors examined the retrodural space of Okada and the neighboring tissues with 3D reconstruction of spinal MRIs of seven patients without any demonstrable spinal pathology to better understand the characteristics of the space of Okada.

RESULTS

Contrast medium spread to the ipsilateral and contralateral sides was observed in five patients. The contralateral spread was thought to be through the retrodural space of Okada, which is a potential space between the anterior surface of the vertebral lamina and the posterior surface of the ligamentum flavum. It facilitates communication between the contralateral articular facet joints of the spine.

CONCLUSIONS

This study provides new evidence for the existence of the space of Okada where an unexpected contralateral spread occurred following facet joint and attempted epidural injection. The 3D reconstructions of MRIs may help us better understand the nature of the retrodural space of Okada and its clinical implications.

The Posterior Lumbar Epidural Space: Three-Dimensional Reconstruction of High-Resolution MRI: Real and Potential Epidural Spaces and Their Content In Vivo

OBJECTIVE

Our aim was to study the posterior lumbar epidural space with 3D reconstructions of magnetic resonance images (MRIs) and to compare and validate the findings with targeted anatomic microdissections.

DESIGN

We performed 3D reconstructions of high-resolution MRIs from seven patients and normal-resolution MRIs commonly used in clinical practice from 196 other random patients. We then dissected and photographed the lumbar spine areas of four fresh cadavers.

RESULTS

From the 3D reconstructions of the MRIs, we verified that the distribution of the posterior fat pad had an irregular shape that resembled a truncated pyramid. It spanned between the superior margin of the lamina of the caudad vertebra and beyond the inferior margin to almost halfway underneath the cephalad lamina of the cranial vertebra, and it was not longitudinally or circumferentially continuous. The 3D reconstructions of the high-definition MRI also consistently revealed a prelaminar fibrous body that was not seen in most of the usually used low-definition MRI reconstructions. Targeted microdissections confirmed the 3D reconstruction findings and also showed the prelaminar tissue body to be fibrous, crossing from side to side anterior to the cephalad half of each lamina, and spanning from the dural sac to the laminae.

CONCLUSIONS

Three-dimensional reconstructions and targeted microdissection revealed the unique appearance of posterior fat pads and a prelaminar fibrous body. The exact consistency, presence, prevalence with age, presence in other regions, and function of this body are unknown and require further research.

Early Experience with Bilateral Continuous Femoral Nerve Block and Single-Injection Spinal Anesthesia for Bilateral Total Knee Arthroplasty: A Case Series

Objective

Total knee arthroplasty (TKA) is a commonly performed surgery in the United States, with demand for unilateral and simultaneous bilateral TKAs (BTKAs) expected to increase significantly over the coming decades. This study reports the authors' early experience in a consecutive series of simultaneous BTKAs performed under regional anesthesia and mild sedation.

Methods

In this retrospective case series, the authors examined all simultaneous BTKAs performed over two years by a single surgeon. Only patients receiving bilateral continuous femoral nerve blockade (CFNB) and single-injection sciatic nerve blockade in combination with single-injection subarachnoid block were included in the study. Of the 32 patients who underwent BTKAs during this period, 25 met the inclusion criteria. The patient's anesthesia records, physician notes, nursing notes, pharmacy records, and physical therapy records were then reviewed systematically to create a database of information.

Results

Only one of 25 patients required conversion to general anesthesia during surgery. There were no major perioperative complications. The average Defense and Veterans Pain Rating Scale score immediately postoperation was 0.6/10, and the average daily score remained below 3.5/10 throughout the hospital stay. The use of bilateral CFNB did not prevent patients from ambulating during physiotherapy.

Conclusions

This early retrospective case series suggests that it is feasible to effectively manage the postoperative pain associated with BTKA with staged bilateral CFNB and single-injection sciatic nerve blockage in combination with single-injection subarachnoid block as the sole anesthetic technique without negatively influencing early ambulation.

Acute pain medicine in anesthesiology

The American Academy of Pain Medicine and the American Society for Regional Anesthesia have recently focused on the evolving practice of acute pain medicine. There is increasing recognition that the scope and practice of acute pain therapies must extend beyond the subacute pain phase to include pre-pain and pre-intervention risk stratification, resident and fellow education in regional anesthesia and multimodal analgesia, as well as a deeper understanding of the pathophysiologic mechanisms that are integral to the variability observed among individual responses to nociception. Acute pain medicine is also being established as a vital component of successful systems-level acute pain management programs, inpatient cost containment, and patient satisfaction scores. In this review, we discuss the evolution and practice of acute pain medicine and we aim to facilitate further discussion on the evolution and advancement of this field as a subspecialty of anesthesiology.

Use of machine-learning classifiers to predict requests for preoperative acute pain service consultation

OBJECTIVE

  The purpose of this project was to determine whether machine-learning classifiers could predict which patients would require a preoperative acute pain service (APS) consultation.

DESIGN

  Retrospective cohort.

SETTING

  University teaching hospital.

SUBJECTS

  The records of 9,860 surgical patients posted between January 1 and June 30, 2010 were reviewed.

OUTCOME MEASURES

  Request for APS consultation. A cohort of machine-learning classifiers was compared according to its ability or inability to classify surgical cases as requiring a request for a preoperative APS consultation. Classifiers were then optimized utilizing ensemble techniques. Computational efficiency was measured with the central processing unit processing times required for model training. Classifiers were tested using the full feature set, as well as the reduced feature set that was optimized using a merit-based dimensional reduction strategy.

RESULTS

  Machine-learning classifiers correctly predicted preoperative requests for APS consultations in 92.3% (95% confidence intervals [CI], 91.8-92.8) of all surgical cases. Bayesian methods yielded the highest area under the receiver operating curve (0.87, 95% CI 0.84-0.89) and lowest training times (0.0018 seconds, 95% CI, 0.0017-0.0019 for the NaiveBayesUpdateable algorithm). An ensemble of high-performing machine-learning classifiers did not yield a higher area under the receiver operating curve than its component classifiers. Dimensional reduction decreased the computational requirements for multiple classifiers, but did not adversely affect classification performance.

CONCLUSIONS

  Using historical data, machine-learning classifiers can predict which surgical cases should prompt a preoperative request for an APS consultation. Dimensional reduction improved computational efficiency and preserved predictive performance.

Social network analysis and quantification of a prototypical acute pain medicine and regional anesthesia service

OBJECTIVE

The objective of this study was to quantify the network complexity, information flow, and effect of critical-node failures on a prototypical regional anesthesia and perioperative pain medicine (RAPPM) service using social network analysis.

DESIGN

Pilot cross-sectional investigation.

SETTING

This study was conducted at a prototypical single-center, multi-location academic anesthesiology department with an active RAPPM service.

INTERVENTIONS

We constructed an empirically derived prototypical social network representative of a large academic RAPPM service.

OUTCOME MEASURES

The primary objective was measurement of network complexity via network size, structure, and information flow metrics. The secondary objective identified, via network simulation, those nodes whose deletion via single, two-level, or three-level node failures would result in the greatest network fragmentation. Exploratory analyses measured the impact of nodal failures on the resulting network complexity.

RESULTS

The baseline network consisted of 84 nodes and 208 edges with a low density of 0.03 and high Krackhardt hierarchy of 0.787. Nodes exhibited low average total degree centrality (mean ± standard deviation [SD]) of 0.03 ± 0.034 and mean eigenvector centrality of 0.164 ± 0.182. The RAPPM resident-on-call was identified as the critical node in a single-node failure, with the resulting network fragmentation increasing from 0 to 0.52 upon node failure. A two-level failure involved both the RAPPM resident-on-call as well as the RAPPM attending-on-call, with the resulting fragmentation expanding to 0.772. A three-level node failure included the RAPPM resident-on-call, the main block-room attending, and block room fellow with fragmentation increasing to 0.814.

CONCLUSIONS

The RAPPM service entails considerable network complexity and increased hierarchy, but low centrality. The network is at considerable fragmentation risk from even single-node failure.

Applied sonoanatomy of the posterior triangle of the neck

The posterior triangle of the neck is an area of the body frequently visited by regional anesthesiologists, acute and chronic pain physicians, surgeons of all disciplines, and diagnosticians. It houses the entire brachial plexus from the roots to the divisions, the scalene muscles, the cervical sympathetic ganglions, the major blood vessels to and from the brain, the neuroforamina and various other structures of more or less importance to these physicians. Ultrasound (US) offers a handy visual tool for these structures to be viewed in real time and, therefore, its popularity and the need to understand it. We will discuss pertinent clinical anatomy of the neck and offer a basic visual explanation of the often-difficult two-dimensional (2-D) images seen with US.

Unintended epidural placement of a thoracic paravertebral catheter in a patient with severe chest trauma

OBJECTIVE

Severe pain can lead to ventilatory compromise in patients with multiple rib fractures. Regional anesthetic techniques, including continuous thoracic paravertebral and thoracic epidural blocks, can be useful in reducing this pain and subsequent morbidity due to respiratory compromise. Thoracic paravertebral block can result in significant complications. Presumed epidural spread of injected medication has been described with thoracic paravertebral block. High-quality radiographic images of an attempted placement of a thoracic paravertebral catheter in the epidural space have not been reported. We present these images to highlight the occurrence of this complication.

SETTINGS AND PATIENTS

In this case, we report an attempted placement of a thoracic paravertebral catheter that passed into the epidural space. High-fidelity, three-dimensional computer tomography images and the management of the unintended epidural catheterization are presented.

RESULTS AND CONCLUSIONS

In the setting of severe chest trauma, the potential risk of unintended placement of an intended thoracic paravertebral catheter in the epidural space is graphically illustrated as a potential risk of this procedure.

Neurogenic thoracic outlet syndrome: A case report and review of the literature

Neurogenic thoracic outlet syndrome (NTOS) is an oft-overlooked and obscure cause of shoulder pain, which regularly presents to the office of shoulder surgeons and pain specialist. With this paper we present an otherwise healthy young female patient with typical NTOS. She first received repeated conservative treatments with 60 units of botulinium toxin injected into the anterior scalene muscle at three-month intervals, which providing excellent results of symptom-free periods. Later a trans-axillary first rib resection provided semi-permanent relief. The patient was followed for 10 years after which time the symptoms reappeared. We review the literature and elaborate on the anatomy, sonoanatomy, etiology and characteristics, symptoms, diagnostic criteria and treatment modalities of NTOS. Patients with NTOS often get operated upon - even if just a diagnostic arthroscopy, and an interscalene or other brachial plexus block may be performed. This might put the patient in jeopardy of permanent nerve injury, and the purpose of this review is to minimize or prevent this.

New trends in regional anesthesia for shoulder surgery: Avoiding devastating complications

Surgeons and patients are often reluctant to support regional anesthesia (RA) for shoulder and other orthopedic surgeries. This is because of the sometimes true but usually incorrectly perceived "slowing down" of operating room turnover time and the perceived potential for added morbidity. Recently, severe devastating and permanent nerve injury complications have surfaced, and this article attempts to clarify the modern place of RA for shoulder surgery and the prevention of these complications. A philosophical approach to anesthesiology and regional anesthesiology is offered, while a fresh appreciation for the well-described and often forgotten microanatomy of the brachial plexus is revisited to explain and avoid some of the devastating complications of RA for shoulder surgery.

Dysphagia following anterior cervical arthrodesis is associated with continuous, strong retraction of the esophagus

BACKGROUND

The prevalence of dysphagia after anterior cervical decompression and arthrodesis is estimated to be 50% within one month and 21% at twelve months. However, its exact etiology is not well understood. The objective of the present study was to explore the relationship between intraoperative intra-esophageal pressure due to surgical retraction, esophageal mucosal blood flow at the level of surgery, and postoperative dysphagia. Our hypothesis was that sustained elevated pressure on the esophagus during anterior cervical arthrodesis is associated with postoperative dysphagia.

METHODS

Seventeen selected patients scheduled for anterior cervical arthrodesis were studied. Throughout the procedure, intraluminal pressure in the upper esophageal sphincter was measured (mm Hg) with a custom-made manometer probe and mucosal perfusion was measured at the level of surgery with a laser Doppler flowmeter. The type of retraction chosen by the surgeon was noted. Postoperatively, the patients were specifically evaluated for dysphagia on the first postoperative day and at six weeks, three months, and six months postoperatively with use of the M.D. Anderson Dysphagia Inventory.

RESULTS

Four of the eleven patients who had dynamic retraction and five of the six patients who had static retraction during surgery had postoperative dysphagia. In the group of patients with dysphagia, the average M.D. Anderson Dysphagia Inventory score decreased from 93.8 +/- 12.1 preoperatively to 67.7 +/- 11.4 on the first postoperative day (p < 0.001). The patients with dysphagia had a significantly higher average intraluminal pressure (60.8 +/- 54.3 compared with 54.4 +/- 51.8 mm Hg; p < 0.0001) as well as significantly lower average mucosal perfusion (26.1 +/- 18.1 compared with 40.8 +/- 26.2 tissue perfusion units; p < 0.0001) in comparison with the asymptomatic patients.

CONCLUSIONS

Patients with dysphagia following anterior cervical arthrodesis were exposed to higher intraoperative esophageal pressure and decreased esophageal mucosal blood flow during surgical retraction as compared with patients without dysphagia. In this small series, dynamic retraction seemed to be associated with a lower prevalence of postoperative dysphagia.

Epidural spread after continuous cervical paravertebral block: a case report

BACKGROUND AND OBJECTIVE

This report illustrates epidural spread after continuous cervical paravertebral block (CCPVB). By fluoroscopy, it also explains the mechanism of the complication.

CASE REPORT

A healthy 22-year-old male developed bilateral upper-extremity motor weakness immediately after placement of a continuous cervical paravertebral block for postoperative pain control after shoulder stabilization surgery. The tip of the stimulating catheter was demonstrated in the C7 neuroforamen. Contrast injected through the catheter demonstrated epidural spread. The contralateral block resolved after 4 hours and the patient suffered no respiratory embarrassment or other untoward sequelae.

CONCLUSION

Continuous cervical paravertebral block is a relatively new, but generally well-accepted, modality for postoperative pain control after major surgery to the upper limb. Epidural spread is recognized as a complication. In this particular case, medial placement of the catheter was possibly caused by unintentional medial direction of the bevel of the Tuohy needle. Meticulous attention to the direction of the needle bevel and early recognition and management of adverse events are mandatory. The same principles may apply for continuous thoracic, lumbar, and sacral paravertebral blocks.

A Method to Estimate the Depth of the Sciatic Nerve During Subgluteal Block by Using Thigh Diameter as a Guide

BACKGROUND AND OBJECTIVE

The subgluteal approach is common for sciatic nerve block. Although the surface landmarks are clear, the depth of this nerve at this level is difficult to judge. The purpose of this study is to establish a method of estimating the sciatic nerve depth using the anteroposterior (AP) diameter of the thigh as a marker.

METHODS

The study was undertaken in 2 phases. Phase 1 entailed review of 100 magnetic resonance images (MRIs) of the pelvis and proximal lower extremity of patients. Measurements were taken of the AP diameter of the thigh at the midpoint of the lesser trochanter and then compared with distances of the sciatic nerves from the skin of the posterior aspect of the thigh at the same level. Phase 2 involved enrolling 40 patients undergoing lower-extremity surgery for whom subgluteal sciatic nerve blocks were indicated. The AP diameters of the thighs were measured from the subgluteal groove to the inguinal groove with the patient in the supine position. Placing the patient in the lateral position, the subgluteal sciatic block was then performed by using a stimulating needle. The distances from the skin at which the sciatic nerves were actually found, as estimated by maximum motor response to stimulus, were noted.

RESULTS

Phase 1 showed a mean AP diameter of 18.94 cm +/- 2.61 cm (mean +/- standard deviation [SD]), mean nerve depth of 6.51 cm +/- 1.46 cm (mean +/- SD), and a linear regression slope of 0.48. Phase 2 showed a mean AP diameter of 16.28 cm +/- 2.73 cm (mean +/- SD), a mean nerve depth of 6.99 cm +/- 1.39 cm (mean +/- SD), and a linear regression slope of 0.43. The thigh diameters differed (P < .001) between the groups, but there was no difference in the depth to the sciatic nerve between the 2 groups (P = .07).

CONCLUSIONS

Comparing phase 1 and phase 2 datasets shows the slopes of linear regression lines are nearly parallel. The clinical data from phase 2 verify the anatomical data collected in phase 1 and show that the sciatic nerve depth to AP diameter ratio is 0.43 or the depth of the sciatic nerve is approximately 43% of thigh diameter if the patient is positioned in the lateral decubitus position.

Electrical nerve stimulation using a stimulating catheter: what is the lower limit?

OBJECTIVES

To minimize the risk of intraneural injection when performing nerve blocks, some authors caution against injecting through a needle placed with motor responses observed at nerve stimulator output settings of 0.3 mA or less. We present a case of placing a continuous cervical paravertebral catheter with brisk motor response while stimulating the catheter at 0.05 mA, with no adverse sequelae.

CASE REPORT

A 56-year-old man scheduled for rotator cuff repair received a continuous cervical paravertebral block for intraoperative and postoperative pain control. A stimulating catheter was used for the block. During catheter placement, nerve stimulator output was decreased to 0.05 mA at 300 micros and the motor response remained brisk. The patient was not significantly sedated and experienced no pain during placement or with injection of 40 mL of 0.5% ropivacaine through the catheter. Narcotic drugs were not required during surgery, and the block provided excellent postoperative pain control. Catheter position was evaluated by fluoroscopy to further identify the catheter's relationship to the brachial plexus. The nerve trunks of C5 and C6 were clearly visible after 1 mL of iohexol (Omnipaque) was injected through the catheter. The catheter was removed the following day. At the follow-up visit 2 weeks later, the patient's neurological examination remained unremarkable.

CONCLUSION

We present a single case of successful placement of a stimulating catheter with no neurological injury even when motor response occurred at very low nerve stimulator output settings.

At the cords, the pinkie towards: Interpreting infraclavicular motor responses to neurostimulation

Identification of elicited muscle twitches while performing infraclavicular block of the brachial plexus is often confusing but is critical for success of the block. An easily defined endpoint when evaluating these motor responses to neurostimulation is essential, as it is necessary to block the appropriate cord or cords. In addition to an extensive review of the motor and sensory neuroanatomy of the upper extremity, we describe an easy method to learn and remember the motor response to stimulation of each of the cords of the brachial plexus. If the arm is positioned in the anatomical position, the 5th digit (pinkie) moves laterally (pronation of the forearm) when the lateral cord is stimulated, posteriorly (extension) when the posterior cord is stimulated, and medially (flexion) when the medial cord is stimulated. The pinkie thus moves "toward" the cord that is stimulated.

Early experience with continuous cervical paravertebral block using a stimulating catheter

BACKGROUND AND OBJECTIVES

This study reports our early experience with continuous cervical paravertebral block (CCPVB) using a stimulating catheter for the management of acute pain after shoulder surgery.

METHODS

This prospective observational study presents 256 CCPVB for pain relief after 14 different shoulder operations. Surgery was performed under general anesthesia and blocks were placed prior to induction of general anesthesia (n = 81 [32%]), after induction of general anesthesia (n = 116 [45%]), or postoperatively in the recovery room (n = 59 [23%]). A bolus dose of 30 mL of 0.5% ropivacaine was followed by an infusion of 0.1 mL/kg/h of 0.2% ropivacaine. Patient- or nurse-initiated bolus doses of 10 mL of the same drug were used for breakthrough pain and rescue analgesics were available. Postoperative pain, patient satisfaction, and motor function in different parts of the upper limb were evaluated immediately after surgery (time 0), and then 6, 12, 24, 48, 60 hours, and 14 days postoperatively.

RESULTS

An average of 2 (range 1-7) attempts were needed to advance the catheter while still stimulating the nerve. Average postoperative pain ranged from 0.27 +/- 1.04 cm to 0.78 +/- 1.56 cm (mean +/- SD) on a visual analog scale (VAS) (0-10 cm) for the first 48 hours and 3.8 +/- 2.1 cm and 3.5 +/- 2.4 cm at 60 hours and 14 days, respectively. Patient satisfaction on a VAS of 0 to 5 was 4.19 +/- 1.1, 4.28 +/- 1.01, and 4.69 +/- 1.05 at times 0, 6 hours, and 14 days, respectively. Motor function returned to normal in the fingers within 24 hours and in the shoulder within 60 hours. Complications included Horner's syndrome (40%), dyspnea (8%), superficial skin infection (5%), posterior neck pain (22%), subclavian artery puncture (1%), contralateral epidural spread (4%), and 8% of the patients complained of an unpleasant "dead feeling" of the arm. Ninety-one percent of patients would request CCPVB again for future shoulder surgery. There was no evidence of nerve damage.

An indication for continuous cervical paravertebral block (posterior approach to the interscalene space)

We present a patient who required perioperative analgesia with continuous nerve block for shoulder disarticulation, for whom the only approach possible to the brachial plexus was from posterior. A 51-yr-old woman was suffering from intractable upper extremity pain and dysfunction as a result of severe lymphedema after metastatic spread of breast cancer to the axilla. Her pain was poorly controlled despite aggressive treatment with oral, systemic, and intrathecal opiates. She presented for amputation of her arm as a last resort for management of pain. In order to provide optimal postoperative analgesia, continuous peripheral nerve block was selected in consultation with the patient, and due to anatomic disfigurement and tumor invasion, a continuous cervical paravertebral block was placed preoperatively and shoulder disarticulation was performed using a combined regional/general anesthesia technique. The patient had an uneventful recovery without pain for the 6 postoperative days that the catheter was in place and 0.25% bupivacaine was infused at 5 mL/h. Because of anatomic considerations, which precluded the use of all other approaches to the brachial plexus, the posterior cervical paravertebral approach provided an effective means of pain control in this difficult clinical situation.

Surface mapping of peripheral nerves in children with a nerve stimulator

Defining anatomical landmarks may be difficult in the growing child. With the aid of a peripheral nerve stimulator, the path of many superficial peripheral nerves can be 'mapped' prior to skin penetration by stimulating the motor component of the peripheral nerve percutaneously with a 2-3.5 mA output. The required current will vary and is dependent upon the depth of the nerve and the moistness of the overlying skin. This 'nerve mapping technique' has proved particularly useful for brachial plexus, axillary, ulna and median nerve blocks in the upper limb and femoral and popliteal nerve blocks in the lower limb. It is a useful teaching tool and improves the success rate of peripheral nerve blocks in children of all ages.

Continuous interscalene block for ambulatory shoulder surgery

Management of acute post-operative pain due to shoulder surgery may be successfully and consistently achieved in ambulatory patients by using continuous interscalene block. This chapter outlines the anterior and posterior approaches to the proximal brachial plexus and describes a method of precisely placing a catheter along the brachial plexus by stimulating the plexus through the needle used for placing the catheter as well as through the catheter itself. A technique for securing the catheter by subcutaneous tunneling to prevent dislodgement is also described. Suggested drugs and dosages for initial boluses, continuous infusions and patient controlled interscalene analgesia are discussed. Sedation for block placement, and special precautions, are outlined.

A comparison of propofol and remifentanil for sedation and limitation of movement during periretrobulbar block

STUDY OBJECTIVES

To compare clinical conditions in patients sedated with propofol or remifentanil during combined peri-bulbar and retrobulbar block (PRBB) for cataract surgery.

DESIGN

Prospective, randomized, double-blind study.

SETTING

Private clinic.

PATIENTS

106 ASA physical status I and II patients scheduled for cataract surgery.

INTERVENTIONS

Patients were randomized to receive either 0.5 mg/kg propofol (Group P) or 0.3 microg/kg remifentanil (Group R) as an intravenous (IV) bolus 1 minute prior to PRBB. At the same time, patients in both groups also received 0.5 to 1 mg midazolam IV. Movement of the hands, arms, head, and eyes were counted during each stage of the procedure by an observer who was blinded to the sedation used. Heart rate (HR), blood pressure (BP), respiratory rate (RR), expiratory CO(2) (PECO(2)), and hemoglobin oxygen saturation (SaO(2)) were recorded every minute for 10 minutes after the PRBB. Anesthetic complications, recall, and the pain experienced with the block and surgery were compared between the two groups. Means and variance of the results were compared with one-way analysis of variance and Fisher's exact test.

MEASUREMENTS AND MAIN RESULTS

Movements of the hands, arms, and head were significantly greater in Group P during all stages of the block. Almost no movements were recorded in the remifentanil group. Immediately after the PRBB (1 to 6 min), HRs were higher in Group P (73 +/- 11 bpm vs. 67 +/- 10 bpm; p = 0.0075), whereas the RRs were slower in Group R for the period 1 to 5 minutes after the PRBB (16 +/- 5 breaths/min vs.14 +/- 4 breaths/min; p = 0.0206). At these times, the mean PECO(2) was higher in Group R (36 +/- 7 mmHgvs. 32 +/- 9 mmHg; p = 0.0125). Nineteen patients in the propofol group sneezed during the medial peribulbar injection compared with none in the remifentanil group. Anesthetic and surgical complications were unremarkable and similar for the two groups.

CONCLUSIONS

Respiratory depression with remifentanil was mild and not clinically significant. Remifentanil sedation for this application was superior to sedation with propofol.

Effects of cerebrospinal fluid loss and epidural blood patch on cerebral blood flow in swine

BACKGROUND AND OBJECTIVES

The purpose of this study was to test the hypothesis that loss of cerebrospinal fluid (CSF) causes cerebral vasodilatation, which is reversible with peridural injection of autologous blood.

METHODS

Ten pigs were anesthetized with an infusion of propofol and remifentanil and mechanically ventilated to normocapnia with air and oxygen (60%). Cisternal puncture was performed and increments of 1 mL of cerebrospinal fluid were aspirated. After each milliliter was removed, hemodynamic and respiratory variables and cerebral blood flow (CBF) were measured, the latter with a transdural laser Doppler flowmeter (BLF 21; Transonic Systems Inc, Ithaca, NY) through a cranial burr hole. After 9 mL of CSF had been removed, 10 mL autologous blood was injected into the lumbar epidural space, and the CBF and other variables were measured immediately and 5 minutes thereafter. Ten milliliters of autologous blood was then injected subdurally and the measurements repeated. Data were analyzed for significant differences from the baseline and previous values by repeated analysis of variance.

RESULTS

CBF increased from 44.7 +/- 7.97 tissue perfusion units (TPU) (mean +/- SEM) at baseline to 75.3 +/- 13.53 TPU after removal of the first 7 mL of CSF (P < .0001). Following injection of 10 mL of blood into the epidural space, CBF immediately decreased to 47.6 +/- 9.18 TPU. After subdural injection of blood, the CBF decreased further to 20 +/- 3.77 TPU.

CONCLUSIONS

The increase in CBF probably represents cerebral vasodilatation. The immediate return of CBF to baseline values after epidural injections of blood, and to lower values after subdural injections of blood, was probably due to vasoconstriction. The data suggest that postdural puncture headache, and its successful treatment with epidural blood patch, can probably be ascribed to cerebrovascular dynamics.