Nerve Catheter Research Articles

Development of a Mobile Ultrasound-Guided Peripheral Nerve Block and Catheter Service

Ultrasound guidance is associated with improved efficiency and success of peripheral nerve blockade and a decreased incidence of vascular puncture, making these interventions safer. Patients with peripheral nerve blocks report decreased pain and increased satisfaction scores. We present the development of a mobile ultrasound-guided block service that allows for the safe and efficient placement of nerve blocks and perineural catheters at the nontraditional location of the patient's bedside and in the emergency department.

Functional Role of Diverse Changes in Sympathetic Nerve Activity in Regulating Arterial Pressure during REM Sleep

This study aimed to investigate whether REM sleep evoked diverse changes in sympathetic outflows and, if so, to elucidate why REM sleep evokes diverse changes in sympathetic outflows. Male Wistar rats were chronically implanted with electrodes to measure renal (RSNA) and lumbar sympathetic nerve activity (LSNA), electroencephalogram, electromyogram, and electrocardiogram, and catheters to measure systemic arterial and central venous pressure; these parameters were measured simultaneously and continuously during the sleep-awake cycle in the same rat. REM sleep resulted in a step reduction in RNSA by 36.1% ± 2.7% (P < 0.05), while LSNA increased in a step manner by 15.3% ± 2% (P < 0.05) relative to the NREM level. Systemic arterial pressure increased gradually (P < 0.05), while heart rate decreased in a step manner (P < 0.05) during REM sleep. In contrast to REM sleep, RSNA, LSNA, systemic arterial pressure, and heart rate increased in a unidirectional manner associated with increases in physical activity levels in the order from NREM sleep, quiet awake, moving, and grooming state. Thus, the relationship between RSNA vs. LSNA and systemic arterial pressure vs. heart rate observed during REM sleep was dissociated compared with that obtained during the other behavioral states. It is suggested that the diverse changes in sympathetic outflows during REM sleep may be needed to increase systemic arterial pressure by balancing vascular resistance between muscles and vegetative organs without depending on the heart.

Taking the nervousness out of nerve catheter removal: smart phone to the rescue

Taking the nervousness out of nerve catheter removal: smart phone to the rescue

Brachial Plexus Entrapment of Interscalene Nerve Catheter after Uncomplicated Ultrasound-Guided Placement

We report on the case of an entrapped interscalene nerve catheter in a 46-year-old male undergoing left shoulder arthroscopic lysis of adhesions for a frozen shoulder. The catheter was placed under ultrasound guidance without any apparent complications. The continuous interscalene nerve block was successfully used as the primary anesthetic and for postoperative pain management. Upon attempted catheter removal, the patient experienced severe pain and paresthesias. Fluoroscopy revealed possible brachial plexus involvement, and surgery was performed to extract the catheter, which had become hooked and entrapped around the C5 nerve root and sheath.

Spinal or epidural analgesia for cancer pain: The Ottawa Hospital experience.

e19701 Background: Cancer pain is occasionally intractable, resistant to opioid and associated with increased mortality and long hospitalizations. Invasive nerve blocks and catheters are perceived ...

Tips and tricks to facilitate ultrasound‐guided placement of peripheral nerve catheters in children

To describe an approach to facilitate ultrasound (US)-guided placement of peripheral nerve catheters in children. Continuous peripheral nerve blocks (CPNB) provide excellent surgical anesthesia and postoperative analgesia. However, catheters can be difficult to place, especially in children. Ten US-guided peripheral nerve catheters were placed and placement difficulties encountered were recorded. Four series of 15 consecutive US-guided CPNB were then performed, adding in each series one possible solution to each of the troubles previously encountered. Finally, all maneuvers were employed in the placement of 15 US-guided CPNB in children 3-10 years old and then followed clinically. Initial difficulties encountered were as follows: (i) introducing the catheter, (ii) catheter tip visualization, (iii) length of catheter to be introduced, and (iv) catheter fixation and appropriate long-lasting dressing. The proposed facilitating procedure that addresses each of these difficulties is as follows: (i) three-hand technique: an assistant's hand holds the US transducer, the proceduralist anesthetist slightly withdraws and rotates the needle tip with one hand and advances the catheter with the other, (ii) needle visualization in long axis (LAX) whenever possible with catheter placed inside the needle and US guidance of spread of local anesthetic (LA) through the catheter, (iii) catheter advanced until resistance is found or up to a maximum of 5 cm, and (iv) subcutaneous tunneling of the catheter, Dermabond glue, and careful transparent dressing. All catheters in the last series were 100% effective during surgery and provided complete analgesia for ≥3 days without complications. Continuous peripheral nerve blocks in children should be placed under US guidance in LAX whenever possible, with a three-hand technique and slightly withdrawing or rotating the needle tip to introduce the catheter, administering LA through the catheter, and performing subcutaneous tunneling and careful dressing.

Did Continuous Femoral and Sciatic Nerve Block Obscure the Diagnosis or Delay the Treatment of Acute Lower Leg Compartment Syndrome? A Case Report

We report a case of acute lower extremity compartment syndrome that was diagnosed despite continuous regional analgesia with 0.2% ropivacaine via femoral and sciatic nerve catheters. Academic tertiary care center. Report of a clinical case. A 15-year-old boy with adolescent Blount's disease underwent elective distal femur and proximal tibia osteotomy with external fixation and stabilization of his right leg. The patient's anesthetic and analgesic management included general anesthesia with adjunctive regional anesthesia via continuous femoral and sciatic nerve blocks with 0.2% ropivacaine-each block initially infused at 10 mL per hour. On the first postoperative day, the patient reported no pain (0/10 on the visual analog scale, where 0 is no pain and 10 is the worst pain imaginable). However, on the second postoperative day, the patient reported severe pain despite effective blocks and oral opioid analgesic modalities. Compartment syndrome was diagnosed and treated with decompressive fasciotomy; tissue loss resulted. Despite concerns of masking pain that may be secondary to compartment syndrome, this case demonstrates that compartment syndrome can be diagnosed in the presence of effective regional anesthesia. Careful clinical evaluation coupled with a high index of suspicion is essential in the timely diagnosis and effective treatment of compartment syndrome.

Two continuous femoral nerve block strategies after TKA

The purposes of this study were to compare the pain score, systemic opioid consumption, and range of motion (ROM) between the group where the use of continuous femoral nerve block (CFNB) was discontinued on postoperative day 3 (POD 3) and the group where it was discontinued on POD 7 within an established clinical pathway for postoperative recovery after total knee arthroplasty (TKA) and to assess the treatment-related side effects and complications, as well as the functional status of these two groups of patients at 2 years after surgery. This prospective, randomized, double-blinded trial compared the analgesic efficacy and the functional outcomes between group A (n = 30) where continuous femoral nerve block was performed until POD 3 (discontinued prior to the initiation of range of motion (ROM) exercises) and group B (n = 33), where the continuous femoral nerve block was performed until POD 7 (discontinued during the ROM exercise) after TKA. The resting pain scores of group B were lower than those of group A but there was no significant difference between the two groups (n.s., P = 0.387). However, the peak pain scores during ROM exercise, beginning on POD3 through to POD14, were significantly lower in group B than in group A (P = 0.001). The cumulative morphine IV-PCA requirements through the POD 2 were similar in the two groups (n.s., P = 0.811). However, the cumulative oral oxycodone consumption during hospitalization was significantly lower in group B than in group A, P < 0.0001. Group B showed significantly greater satisfaction with their method of analgesia than group A (P = 0.001). Group A scored 2.0 (2.0-3.0), whereas group B scored 1.0 (1.0-2.0). At 2 years, there was no significant difference in the functional outcomes (the knee flexion and extension angle, the Knee Society Score, and WOMAC pain, stiffness, and function scale). The study group who received 7-day continuous femoral nerve block after TKA showed superior analgesia and higher patient satisfaction during the hospital stay than those given 3-day continuous femoral nerve block. Despite the additional time, effort and cost to place and manage continuous femoral nerve catheters, the 7-day continuous femoral nerve block can be recommended as an effective and safe regional component of a multimodal analgesia strategy after TKA.

A Survey of Acute Pain Service Structure and Function in United States Hospitals

Although the number of U.S. hospitals offering an acute pain service (APS) is increasing, the typical structure remains unknown. This survey was undertaken to describe the structure and function of the APS in U.S. hospitals only. We contacted 200 non-teaching and 101 teaching U.S. hospitals. The person in charge of postoperative pain management completed and returned the survey. Seventy-four percent of responding hospitals had an organized APS. An APS was significantly more formally organized in academic/teaching hospitals when compared to non-teaching hospitals. Pain assessments included “pain at rest” (97%), “pain on activity” (63%), and reassessment after pain therapy intervention (88.8%). Responding hospitals utilized postoperative pain protocols significantly more commonly in teaching hospitals when compared to non-teaching and VA hospitals. Intravenous patient controlled analgesia (IV-PCA) was managed most commonly by surgeons (75%), while epidural analgesia and peripheral nerve block infusions were exclusively managed by anesthesiologists. For improved analgesia, 62% allowed RNs to adjust the IV-PCA settings within set parameters, 43% allowed RN adjustment of epidural infusion rates, and 21% allowed RN adjustment of peripheral nerve catheter local anesthetic infusion rates.

Levobupivacain und Ropivacain zur kontinuierlichen Nervenblockade des N. femoralis nach Rekonstruktion des vorderen Kreuzbandes

Levobupivacaine and ropivacaine are both used for continuous femoral analgesia after anterior cruciate ligament reconstruction; however it is unknown whether both drugs are equally effective regarding pain control, preservation of mobility and patient satisfaction. In this randomized, placebo-controlled trial 84patients undergoing anterior cruciate ligament (ACL) reconstruction with quadruple hamstring tendons were studied. For postoperative pain therapy levobupivacaine 0.125%, ropivacaine 0.2% or placebo control with NaCl 0.9% at a rate of 6ml/h were used for 48h using a femoral nerve catheter. All patients also received an i.v. patient-controlled analgesia (IVPCA) pump with piritramide. Patient satisfaction was significantly higher and night rest was better in both treatment groups compared to the placebo group but there appeared to be no major differences between the two local anesthetics. Opioid consumption was significantly higher in the placebo group compared to the levobupivacaine group but not the ropivacaine group. The pain scores showed a trend towards higher scores in the placebo group throughout but the difference only reached statistical significance on postoperative day1. No statistical significant differences in motor block were found between the three groups. Postoperative analgesia for ACL reconstruction during the first 48h using femoral block with a continuous infusion of levobupivacaine 0.125% or ropivacaine 0.2% in combination with an IVPCA is similarly effective and better than a placebo. Both studied drugs seem to be equally appropriate for this purpose.

Bilateral Brachial Plexus Home Going Catheters After Digital Amputation for Patient With Upper Extremity Digital Gangrene

Peripheral nerve catheter placement is used to control surgical pain. Performing bilateral brachial plexus block with catheters is not frequently performed; and in our case sending patient home with bilateral brachial plexus catheters has not been reported up to our knowledge. Our patient is a 57 years old male patient presented with bilateral upper extremity digital gangrene on digits 2 through 4 on both sides with no thumb involvement. The plan was to do the surgery under sequential axillary blocks. On the day of surgery a right axillary brachial plexus block was performed under ultrasound guidance using 20 ml of 0.75% ropivacaine. Patient was taken to the OR and the right fingers amputation was carried out under mild sedation without problems. Left axillary brachial plexus block was then done as the surgeon was closing the right side, two hours after the first block was performed. The left axillary block was done also under ultrasound using 20 ml of 2% mepivacaine. The brachial plexus blocks were performed in a sequential manner. Surgery was unremarkable, and patient was transferred to post anesthetic care unit in stable condition. Over that first postoperative night, the patient complained of severe pain at the surgical sites with minimal pain relief with parentral opioids. We placed bilateral brachial plexus catheters (right axillary and left infra-clavicular brachial plexus catheters). Ropivacaine 0.2% infusion was started at 7 ml per hour basal rate only with no boluses on each side. The patient was discharged home with the catheters in place after receiving the appropriate education. On discharge both catheters were connected to a single ON-Q (I-flow Corporation, Lake Forest, CA) ball pump with a 750 ml reservoir using a Y connection and were set to deliver a fixed rate of 7 ml for each catheter. The brachial plexus catheters were removed by the patient on day 5 after surgery without any difficulty. Patient's postoperative course was otherwise unremarkable. We concluded that home going catheters are very effective in pain control postoperatively and they shorten the period of hospital stay.KeywordsBrachial plexus; Home going catheters; Post-operative pain

Complications of peripheral nerve blocks

Complications of peripheral nerve blocks are fortunately rare, but can be devastating for both the patient and the anaesthesiologist. This review will concentrate on current knowledge about peripheral nerve injury secondary to nerve blocks, complications from continuous peripheral nerve catheter techniques, and local anaesthetic systemic toxicity.

Mayo Clinic Atlas of Regional Anesthesia and Ultrasound-guided Nerve Blockade.

Veterans Affairs Palo Alto Health Care System, Regional Anesthesia and Perioperative Analgesia Service, Palo Alto, California. tedward.kim@va.govBy James R. Hebl, M.D., Robert L. Lennon, D.O., Editors, Adam K. Jacob, M.D., Hugh M. Smith, M.D., Ph.D., Associate Editors, John V. Hagen, Illustrator. New York, Oxford University Press, 2010. Pages: 488. Price: $125.00.The application of ultrasonography to obtain real-time visualization of nerves, vessels, needles, and spread of local anesthetic has recently challenged the traditional methods of performing peripheral nerve blocks (PNB) and has prompted numerous studies to compare their efficiency, efficacy, and safety. Regardless of the method employed, a solid foundation of neuroanatomy is a prerequisite for regional anesthesia. Successful placement of an ultrasound-guided PNB also requires an understanding of ultrasound equipment, principles of sound wave propagation, and scanning techniques to correlate relevant anatomy to its corresponding sonoanatomy. Because of the relatively rapid and recent introduction of ultrasound to regional anesthesia, few currently available textbooks focus on ultrasound-guided nerve-block techniques. The Mayo Clinic Atlas of Regional Anesthesia and Ultrasound-Guided Nerve Blockade is a refreshing book that truly lives up to its name as an atlas and provides a concise, informative review of ultrasound-guided regional anesthesia.The purpose of this book is to be a practical guide to regional anesthesia for residents and practicing anesthesiologists, an overview of ultrasound-guided regional anesthesia, and a review of fundamental principles of ultrasound-guided PNB. The section on ultrasound-guided regional anesthesia consists of three chapters dedicated entirely to the principles of ultrasonography and the application of ultrasound to regional anesthesia, including clear explanations of sound wave propagation and tissue densities, probe selection, and image optimization with changes in frequency, depth, gain, and probe movements (sliding, angling, rotating, tilting, and pressure). These chapters also describe the advantages and disadvantages of in-plane and out-of-plane approaches; use of hydrodissection to avoid nerve trauma from needle contact; employment of color Doppler ultrasound for detecting fluid movement during injection; and common errors, particularly intraneural and intravascular injection. Each chapter in the section on upper extremity and peripheral nerve-block techniques consists of a brief summary of clinical indications for each nerve block; a review of pertinent anatomy; recommendations on patient positioning; description of nerve stimulation technique; and an in-depth explanation of ultrasound-guided techniques, including an evaluation of in-plane and out-of-plane approaches. Each chapter in this section concludes with a discussion of side effects and potential complications. When applicable, the technique of continuous peripheral nerve catheters is also outlined. These focused and succinct explanations, combined with ample images, enable the reader to quickly gain an understanding of basic ultrasound principles and become familiar with various ultrasound-guided techniques.The use of ultrasonography requires correct interpretation of ultrasound images, and this book, aptly titled an atlas, strikes a perfect balance between text and illustration. The study of sonoanatomy is greatly facilitated by detailed and enlarged anatomical illustrations that are juxtaposed with their corresponding ultrasound images on the same page, allowing readers to easily correlate vessels, tendon, muscle, fascia, bone, and nerve. Drawings of patient positioning, probe orientation, and needle introduction also serve as a guide for readers to improve ultrasound image visualization and ergonomics, especially for those new to ultrasound-guided techniques. In addition, the inclusion of nerve stimulation techniques, with supplemental illustrations of relevant anatomy and surface landmarks, can be helpful for those who choose to employ both nerve stimulation and ultrasound-guided techniques.One of the exciting aspects of ultrasound-guided regional anesthesia is the potential for new applications and techniques. With the time lapse inherent in the creation and publication of a textbook, it is unlikely that a single book can keep up with the rapid progress of ultrasound application to regional anesthesia. This book does not include descriptions of all potential ultrasound-guided PNB techniques (e.g. , paravertebral and posterior lumbar plexus blocks), but, although it is not a comprehensive review, it accomplishes its purpose to provide the necessary groundwork for ultrasound-guided PNB. As novel ultrasound-guided PNB techniques are developed, the challenge remains for the clinician to stay informed of the latest innovations.Although many questions about ultrasound-guided regional anesthesia techniques remain, the application of ultrasonography has revolutionized the practice of regional anesthesia in a relatively short time and is here to stay. The Mayo Clinic Atlas of Regional Anesthesia and Ultrasound-Guided Nerve Blockade effectively summarizes the available ultrasound-guided PNB techniques to date and makes a timely entrance as an excellent resource for residents and clinicians. Indeed, the common adage, “a picture is worth a thousand words,” applies seamlessly to this atlas.Veterans Affairs Palo Alto Health Care System, Regional Anesthesia and Perioperative Analgesia Service, Palo Alto, California. tedward.kim@va.gov

Use of epidural and peripheral nerve blocks at the end of life in children and young adults with cancer: the collaboration between a pain service and a palliative care service

Clinicians may avoid continuous pain blocks in pediatric cancer patients at the end of life for fear of complications or of interfering with the desired location of death. To examine the impact of epidural or peripheral nerve catheters on pain control in children and young adults with cancer within the last 3 months of life. We retrospectively reviewed the medical records to assess pain scores, systemic opioid requirements, and impact on death at the preferred location. Ten patients (4.4-21.3 years of age), nine with solid tumors, one with lymphoma, had 14 devices (11 epidural, 3 peripheral nerve catheters) for a range of 3-81 days. Twelve of 13 catheters provided improvement by at least one of three criteria: improved mean pain scores at 24 h (8 of 13) and decreased opioid requirement at 24 h in nine cases and at day 5 in nine cases. Eight patients died in their preferred setting. Six patients had catheters (five epidural, one peripheral) until death, including two who died at home. In some cases, typical contraindications for indwelling catheters (spinal metastasis, vertebral fracture, thrombocytopenia, fever) were superseded by palliative care needs. We found no bleeding, infectious, or neurological complications. Our findings suggest that continuous catheter-delivered pain blockade at the end of life contributes to analgesia, moderates opioid requirements, and usually does not preclude death at the preferred location.

Complications of peripheral nerve catheter removal at home: case series of five ambulatory interscalene blocks

The placement of continuous peripheral nerve catheters on an ambulatory basis is increasing and is routine at our institution. There are few reports of complications associated with peripheral nerve catheter removal in the literature. Described herein is a case series of five patients where complications related to catheter withdrawal were observed. A stimulating catheter with a stainless steel coil surrounded by polyurethane (19-G, 60-cm) exhibited shearing when removal proved difficult in five patients. In four cases, catheter removal by the patients was not possible, requiring them to return to hospital for management. No long-term sequelae were observed in any patient. There can be various causes for difficulty with catheter removal, such as a technical aspect of catheter placement, catheter design, tissue reaction at the catheter site, or a combination thereof. The majority of complications related to outpatient perineural catheters can be handled over the telephone, but our case series may highlight a potential management dilemma in placing continuous stimulating perineural catheters on an ambulatory basis.

Postoperative efficacies of femoral nerve catheters sited using ultrasound combined with neurostimulation compared with neurostimulation alone for total knee arthroplasty

Neurostimulation is commonly used to perform femoral nerve block. Ultrasound can be used to identify nerve structures and guide needle placement. The aim of this study was to compare postoperative analgesic efficiency when femoral nerve catheters were sited using ultrasound (in-plane approach) combined with neurostimulation or neurostimulation alone, for total knee arthroplasty. Ninety-three patients were enrolled in this prospective, randomized, blind study to receive a continuous femoral nerve block performed using conventional neurostimulation or ultrasound guidance combined with neurostimulation. The primary endpoint was the postoperative 48 h total local anaesthetic consumption. Other outcomes included visual analogue scale scores at rest, after 12, 24 and 48 h; total oral opioid dose; onset time of femoral block; procedural time; knee flexion and complications. Results are expressed with medians (25-75th percentiles), mean ± SD and n (%), as appropriate. The onset time of sensory and motor block was faster in the ultrasound group [11 (6-17) min] than in the conventional group [16 (11-23) min, P = 0.009]. Total local anaesthetic dose was reduced [299 ± 45 vs. 333 ± 48 ml, (difference = 34.0 ml, 95% confidence interval 15.6-52.5 ml), P = 0.0003] and the time to the first analgesic request was lengthened [11 (7-13) vs. 7 (4-12) h, P = 0.034] in the ultrasound group. Visual analogue scale scores at 12, 24 and 48 h were lower in the ultrasound group as well as visual analogue scale scores during knee flexion at 48 h [14.5 (11.0-23.0) vs. 28.5 (21.0-43.5) mm, P < 0.0001]. Total oral morphine doses were 20 (0-40) vs. 40 (20-60) mg (P = 0.0065). Durations of hospital stay were comparable in both groups. Continuous perineural femoral catheter placement using ultrasound combined with neurostimulation and an in-plane approach reduces total doses of local anaesthetic, morphine consumption and improves postoperative pain management by comparison with neurostimulation alone.

An Introductory Curriculum for Ultrasound-Guided Regional Anesthesia: A Learner's Guide.

Northwestern University Feinberg School of Medicine, Chicago, Illinois.bachung@northwestern.eduAn Introductory Curriculum for Ultrasound-Guided Regional Anesthesia: A Learner's Guide. Edited by Brian A. Pollard, B.Sc., M.D., Med., F.R.C.P.C., and Vincent W. S. Chan, M.D., F.R.C.P.C. Toronto, University of Toronto Press UTPRINT, 2009. Pages: 81. Price: $109.00.The burgeoning use of ultrasound imaging to guide the performance of regional anesthesia has breathed new life into an already dynamic and compelling field. The anesthesia residents at my institution have minimal interest in using anatomic landmarks and nerve stimulation alone for guidance in peripheral nerve blocks. It is now all about the ultrasound. As a result, there is a considerable demand for quality resources on ultrasound-guided regional anesthesia for primary learning as well as for reference. This text is well-designed to help meet this need on an introductory level. Its target audience will likely extend from trainees at the beginning of their anesthesia careers to well-seasoned practitioners of regional anesthesia who are only recently incorporating ultrasound imaging as guidance for their peripheral nerve blocks.The text is divided into five sections. The first lays the foundation required for the practice of ultrasound-guided regional anesthesia, a basic science understanding of ultrasound. Because the physics of ultrasound can be tedious and not particularly useful in clinical practice, the authors do not delve deeply into how an electric current will cause a physical transition of a piezoelectrical crystal, for example. Rather, they describe why higher transducer frequencies provide excellent image resolution within superficial tissues and why this is not the case at greater tissue depths. Emphasis on this type of knowledge has direct clinical applications to the attainment of high quality images, and, by extension, successful blocks.Real-time ultrasound imaging elevates a blurry canvas of whites, blacks, and grays to form a cinematic movie showing anatomic structures, and, like holding a camera, one controls the image by guiding the transducer. The authors discuss practical techniques for manipulating the transducer, such as sliding and tilting, to improve the attainment, interpretation, and overall quality of the images. Their favored practice target is one's own forearms, which have a wealth of structures to examine.Included in the first section is a discussion on the use of needles in conjunction with an ultrasound transducer. Using the two in combination is a skill to be gained in its own right. The emphasis on this is critical for the successful and safe execution of regional anesthesia with ultrasound guidance. One useful pearl is for the practitioner to avoid “chasing” the needle while using the in-plane technique but to strive always to guide the needle to the target in the existing optimal image.Only after this introduction are we ready to explore the blocks themselves. The next three sections describe ultrasound-guided nerve blocks in order of increasing complexity. Forearm blocks are discussed along with single-shot femoral nerve blocks as part of the introductory or beginner blocks. The intermediate blocks include the different approaches to target the brachial plexus and sciatic nerve. The final section on peripheral blocks includes a discussion on indwelling peripheral nerve catheters. The fifth, and final, section of the text focuses on ultrasound-assisted neuraxial blocks. The authors make the distinction between “assisted” and “guided,” as these techniques are used mainly to help establish landmarks and depth. True ultrasound guidance depends on real-time images.The recommendations at the end of each chapter are helpful for those wanting or needing further depth in the subject material. The bullet points at the conclusion of each chapter provide a distillation of the most important concepts. The images and illustrations are of high quality and occupy nearly as much real estate as the written text, which is fitting for a book on image guidance. The cross-sectional magnetic resonance images are particularly helpful for those trying to grapple with 2D images in planes they may not be used to visualizing. The book repeatedly highlights the continued need for a solid understanding of anatomy, whether or not ultrasound is employed.In terms of critique, I will return again to a subject that was a rite of passage for all physicians: physics. Although the discussion that relates to ultrasound energy was made brief by intent, it was still not exceptionally clear. However, this is probably because the subject of ultrasound physics itself is not particularly suited to brevity and thus becomes a bit of an impossible task for an introductory guide. Overall, An Introductory Curriculum for Ultrasound-Guided Regional Anesthesia: A Learner's Guide is an easy-to-read, informative text. With an efficiency of words, it remains meaty enough to start feeding the scholarly appetite for ultrasound-guided regional anesthesia and will likely spur further study as well as hands-on practice.Northwestern University Feinberg School of Medicine, Chicago, Illinois.bachung@northwestern.edu

The threshold elicited motor response via an in situ femoral nerve catheter predicts analgesia following total knee replacement

BackgroundContinuous femoral nerve blocks are a part of the multimodal perioperative anesthetic regimen following total knee replacement. Elicitation of a quadriceps muscle contraction (QC) at placement is desirable. We prospectively evaluated the relationship between elicited motor response and threshold current with block success in situ femoral nerve catheters after total knee replacement.MethodsAfter Institutional Review Board approval and written informed consent, 100 adults aged ≥18 years, undergoing total knee replacement were studied. The threshold current for an elicited motor response (QC or sartorius muscle contraction [SC]) was recorded during needle insertion, after femoral nerve catheter advancement, and prior to local anesthetic administration on the first postoperative day. Patients were assessed for pinprick sensory anesthesia of the femoral nerve distribution by an observer unaware of the current threshold or evoked motor response at 5-minute intervals for 30 minutes. A successful block was considered a lack of pinprick sensation within 30 minutes.ResultsNinety patients completed the study. A QC was obtained at needle insertion in 89 and maintained following catheter advancement in 77 subjects. Prior to drug administration a QC was obtained in 66 patients, 13 demonstrated an SC, and 11 had no motor response. QC prior to drug administration had a sensitivity of 0.85 (95% confidence intervals [CI]: 0.75 to 0.92) and a specificity of 0.55 (95% CI: 0.37 to 0.72) for complete femoral nerve block. The specificity of a QC prior to drug administration was greater than at catheter placement (P = 0.006). Compared to the threshold current at catheter placement, 27 patients had a decrease, 60 had an increase, and 3 exhibited no change in the threshold current prior to drug administration (P < 0.01). The median interquartile range (IQR) threshold current in patients that achieved a complete block was 0.56 (0.29 to 0.80) mA compared with 1.1 mA (0.41 to 2.75) mA for incomplete blocks (P < 0.01). The area under the receiver operator characteristics curve for current threshold prior to local anesthetic administration (0.74) was greater than at catheter placement (0.45) (P < 0.001). The intersection of sensitivity and specificity for the minimal threshold current prior to local anesthetic injection was 0.84 mA.ConclusionThe elicited motor response and current threshold from a stimulating femoral catheter measured prior to local anesthetic injection is an important determinant of the success of femoral nerve block following bolus administration.

Differential control of renal and lumbar sympathetic nerve activity during freezing behavior in conscious rats

The present study was designed to document changes in sympathetic nerve activity and cardiovascular function when conscious rats were challenged with a noise stressor to induce freezing behavior. The potential contribution of the arterial baroreceptors in regulating sympathetic nerve activity and cardiovascular adjustments during the freezing behavior was then examined. Wistar male rats were assigned to sham-operated (SO) and sinoaortic-denervated (SAD) groups and instrumented chronically with electrodes for measurements of renal (RSNA) and lumbar (LSNA) sympathetic nerve activity, electroencephalogram, electromyogram, and electrocardiogram and catheters for measurements of systemic arterial and central venous pressure. Both SO and SAD rats were exposed to 90 dB of white noise for 10 min, causing freezing behavior in both groups. In SO rats, freezing behavior was associated with an immediate and significant (P < 0.05) increase in RSNA, no changes in LSNA or mean arterial pressure, and a significant (P < 0.05) decrease in heart rate. SAD attenuated the magnitude of the immediate increase in RSNA and had no influence on the response in LSNA during freezing behavior compared with SO rats. Moreover, in SAD rats, mean arterial pressure increased significantly (P < 0.05) while heart rate did not change during the freezing behavior. These data indicate that freezing behavior evokes regionally different changes in sympathetic outflows, which may be involved in generating the patterned responses of cardiovascular function to stressful or threatening sensory stimulation. Moreover, it is suggested that the arterial baroreceptors are involved in generating the differential changes in RSNA and LSNA and thus the patterned changes in cardiovascular functions observed during freezing behavior in conscious rats.

Long-Term Ambulatory Continuous Nerve Blocks for Terminally Ill Patients: A Case Series

Intolerable side effects and dissatisfactory pain control with traditional analgesics prompted the utilization of long-term, ambulatory, continuous peripheral nerve blocks (CPNBs) in terminally ill patients for palliative care. Case series. Continuous peripheral nerve catheters were placed in terminally ill patients in an ambulatory setting. The patients were managed at their homes, with nursing services available to manage the infusions and provide routine monitoring and care. This is a case series of patients with severe peripheral pain and a terminal diagnosis in whom the goals of care were aimed at palliation. All three cases had an unfavorable coagulation status; case 2 had a prior pneumonectomy on the contralateral side and a large tumor on the ipsilateral lung of the continuous brachial plexus block. Interventions included CPNBs, with infusion of local anesthetic. Specific techniques used include cervical paravertebral block and lumbar paravertebral block. After infusion and titration of local anesthetic doses, oral opioid medication was significantly reduced, which resulted in an improved quality of life. The nerve blocks did not hasten death in any of the patients despite their coexisting conditions. CPNBs are a reasonably effective modality to decrease opioid usage when side effects are undesirable for end-of-life care. The risk of unfavorable coagulation status, poor lung function, and risk of infection was outweighed by the benefit in this patient population.