Regional Anesthesia for Pediatric Ophthalmic Surgery: A Review of the Literature.

Ophthalmic pediatric regional anesthesia has been widely described, but infrequently used. This review summarizes the available evidence supporting the use of conduction anesthesia in pediatric ophthalmic surgery. Key anatomic differences in axial length, intraocular pressure, and available orbital space between young children and adults impact conduct of ophthalmic regional anesthesia. The eye is near adult size at birth and completes its growth rapidly while the orbit does not. This results in significantly diminished extraocular orbital volumes for local anesthetic deposition. Needle-based blocks are categorized by relation of the needle to the extraocular muscle cone (ie, intraconal or extraconal) and in the cannula-based block, by description of the potential space deep to the Tenon capsule. In children, blocks are placed after induction of anesthesia by a pediatric anesthesiologist or ophthalmologist, via anatomic landmarks or under ultrasonography. Ocular conduction anesthesia confers several advantages for eye surgery including analgesia, akinesia, ablation of the oculocardiac reflex, and reduction of postoperative nausea and vomiting. Short (16 mm), blunt-tip needles are preferred because of altered globe-to-orbit ratios in children. Soft-tip cannulae of varying length have been demonstrated as safe in sub-Tenon blockade. Ultrasound technology facilitates direct, real-time visualization of needle position and local anesthetic spread and reduces inadvertent intraconal needle placement. The developing eye is vulnerable to thermal and mechanical insults, so ocular-rated transducers are mandated. The adjuvant hyaluronidase improves ocular akinesia, decreases local anesthetic dosage requirements, and improves initial block success; meanwhile, dexmedetomidine increases local anesthetic potency and prolongs duration of analgesia without an increase in adverse events. Intraconal blockade is a relative contraindication in neonates and infants, retinoblastoma surgery, and in the presence of posterior staphylomas and buphthalmos. Specific considerations include pertinent pediatric ophthalmologic topics, block placement in the syndromic child, and potential adverse effects associated with each technique. Recommendations based on our experience at a busy academic ophthalmologic tertiary referral center are provided.

An initial evaluation of the effect of a novel regional block needle with tip-tracking technology on the novice performance of cadaveric ultrasound-guided sciatic nerve block.

Visibility of the needle tip is difficult to maintain during ultrasound-guided nerve block. A new needle has been developed that incorporates a piezo element 2-2.3 mm from the tip, activated by ultrasound. The electrical signal manifests as a coloured circle surrounding the needle tip, and allows real-time tracking. We hypothesised that novice regional anaesthetists would perform nerve block better with the tracker turned on rather than off. Our primary objective was to evaluate the new needle by measuring the performance of novice anaesthetists conducting simulated sciatic block on the soft embalmed Thiel cadaver. Training consisted of a lecture, scanning in volunteers and practice on cadavers. Testing entailed scanning the sciatic nerve of a cadaver and conducting 20 in-plane sciatic blocks in the mid-to-upper thigh region. Subjects were randomised equally, in groups of five, according to the sequence: tracker on/off/on/off; or tracker off/on/off/on. Video recordings were assessed by six raters for steps performed correctly and errors committed. Eight subjects were recruited and 160 videos were analysed. Using the tracking needle, five correct steps improved and one error reduced. The benefits included: better identification of the needle tip before advancing the needle, OR (95%CI) 3.4 (1.6-7.7; p < 0.001); better alignment of the needle to the transducer, 3.1 (1.3-8.7; p = 0.009); and better visibility of the needle tip 3.0 (1.4-7.3; p = 0.005). In conclusion, use of the tracker needle improved the sciatic block performance of novices on the soft embalmed cadaver.

Ultrasound-Guided Regional Anaesthesia: Visualising the Nerve and Needle.

Regional anaesthesia involves targeting specific peripheral nerves with local anaesthetic. It facilitates the delivery of anaesthesia and analgesia to an increasingly complex, elderly and co-morbid patient population. Regional anaesthesia practice has been transformed by the use of ultrasound, which confers advantages such as accuracy of needle placement, visualisation of local anaesthetic spread, avoidance of intraneural injection and the ability to accommodate for anatomical variation.An US beam is generated by the application of electrical current to an array of piezoelectric crystals, causing vibration and consequential production of high-frequency sound waves. The sound energy is reflected at tissue interfaces, detected by the piezoelectric crystals in the ultrasound probe, and most frequently displayed as a 2D image.Optimising image acquisition involves selection of the appropriate US frequency: this represents a trade-off between image resolution (better with high frequency) and tissue penetration/beam attenuation (better with low frequency). Altering alignment, rotation and tilt of the probe is often required to optimise the view as nerves are best visualised when the ultrasound beam is directly perpendicular to their fibres. Adjusting the focus, depth, and gain (brightness) of the image display can also help in this matter.Three key challenges exist in regional anaesthesia; image optimisation, image interpretation (nerve visualisation) and needle visualisation. There are characteristic sonographic appearances of the nerve structures for peripheral nerve blocks, as discussed in this chapter, and the above techniques can be used to enhance their appearance. Much research has been done, and is ongoing, with the aim of improving needle visualisation; this is also reviewed. Image interpretation requires the application of anatomical knowledge and understanding of the typical sonographic appearance of different tissues (as well as the needle). Years of practice are required to attain expertise, although it is hoped that continuing advances in nerve and needle visualisation, as described in this chapter, will expedite that process.

Anesthesia management for low-grade glioma awake surgery: a European Low-Grade Glioma Network survey.

BACKGROUND: Awake surgery has become a key treatment of diffuse low-grade gliomas (DLGG) and is divided in three main phases: opening, tumor resection - during which the patient needs to be fully awake - and closure. The anesthetic management of awake neurosurgery is a challenge, and there are currently no guidelines. OBJECTIVE: The objective of the survey was to explore differences and commonalities regarding the anesthetic management of awake DLGG surgery within the European Low-Grade Glioma Network (ELGGN) centers. METHODS: A form that contained 14 questions about the anesthetic management was sent to 28 centers in May 2015. RESULTS: Twenty centers responded. During the opening and closing non-awake periods, 56% of teams chose general anesthesia with mechanical ventilation for at least one period (asleep-awake-asleep, SAS protocol), and 44% monitored anesthesia care including sedation without mechanical ventilation (MAC protocol). In case of SAS, all the teams chose intravenous anesthesia, 82% used laryngeal mask instead of endotracheal intubation during the opening sequence, and 71% during closure. Local and regional anesthesia was practiced by all the teams. The most frequently reported cause of pain was dural and cerebral vessels manipulation (77%). Pain management was mostly based on paracetamol (70%) and remifentanil (55%). CONCLUSION: Our survey showed that there was an equivalent proportion of centers using SAS or MAC protocols in the anesthetic management of awake surgery in ELGGN centers. The advantages and disadvantages of each anesthesia protocol were reviewed.

A Prototype Patient-Maintained Propofol Sedation System Using Target Controlled Infusion for Primary Lower-Limb Arthroplasty.

Each year, many operations in the UK are performed with the patient awake, without the use of general anaesthesia. These include joint replacement procedures, and in order to reduce patient anxiety, the supervising anaesthetist delivers the sedative propofol intravenously using a target-controlled infusion (TCI) device. However, it is clinically challenging to judge the required effect-site concentration of sedative for an individual patient, resulting in patient care issues related to over or under-sedation. To improve the process, patient-maintained propofol sedation (PMPS), where the patient can request an increase in concentration through a hand-held button, has been considered as an alternative. However, due to the proprietary nature of modern TCI pumps, the majority of PMPS research has been conducted using prototypes in research studies. In this work, a PMPS system is presented that effectively converts a standard infusion pump into a TCI device using a laptop with TCI software. Functionally, the system delivers sedation analogous to a modern TCI pump, with the differences in propofol consumption and dosage within the tolerance of clinically approved devices. Therefore, the Medicines and Healthcare products Regulatory Agency (MHRA) has approved the system as a safe alternative to anaesthetist-controlled TCI procedures. It represents a step forward in the consideration of PMPS as a sedation method as viable alternative, allowing further assessment in clinical trials.

Prolonged Catheter Use and Infection in Regional Anesthesia: A Retrospective Registry Analysis.

BACKGROUND: Prolonged catheter use is controversial because of the risk of catheter-related infection, but the extent to which the risk increases over time remains unknown. We thus assessed the time-dependence of catheter-related infection risk up to 15 days. METHODS: Our analysis was based on the German Network for Regional Anesthesia, which includes 25 centers. We considered 44,555 patients who had surgery between 2007 and 2014 and had continuous regional anesthesia as well as complete covariable details. Cox regression analysis was performed and adjusted for confounding covariables to examine the relationship between catheter duration and probability of infection-free catheter use. RESULTS: After adjustment for confounding factors, the probability of infection-free catheter use decreases with each day of peripheral and epidural catheter use. In peripheral catheters, it was 99% at day 4 of catheter duration, 96% at day 7, and 73% at day 15. In epidural catheters, it was 99% at day 4 of catheter duration, 95% at day 7, and 73% at day 15. Only 31 patients (0.07%) had severe infections that prompted surgical intervention. Among these were five catheters that initially had only mild or moderate signs of infection and were left in situ; all progressed to severe infections. CONCLUSIONS: Infection risk in catheter use increases over time, especially after four days. Infected catheters should be removed as soon as practical. VISUAL ABSTRACT: An online visual overview is available for this article at http://links.lww.com/ALN/B683.

Effect of Beam Steering on Echogenic and Nonechogenic Needle Visibility at 40°, 50°, and 60° Needle Insertion Angles.

Currently, there is little understanding of the role of echogenic needles and beam steering at moderate angles of needle insertion. The ultrasound images of the echogenic and nonechogenic needles inserted into pork at 40°, 50°, and 60° were scored by anesthesiologists on a scale of 0-10. The effect of different levels of beam steer was also explored. At 40°, steep beam steering improves visualization of both nonechogenic and echogenic needles to an equal, satisfactory level. At 50° and 60°, visualization of nonechogenic needles is poor, whereas visibility of an echogenic needle was adequate and may be improved with steep beam steering.

The Effect of High-Frequency, Structured Expert Feedback on the Learning Curves of Basic Interventional Ultrasound Skills Applied to Regional Anesthesia.

BACKGROUND: Proficiency in needle-to-ultrasound beam alignment and accurate approach to structures are pivotal for ultrasound-guided regional anesthesia. This study evaluated the effects of high-frequency, structured expert feedback on simulation training of such abilities. METHODS: Forty-two subjects randomly allocated as controls or intervention participated in two 25-trial experiments. Experiment 1 consisted of inserting a needle into a bovine muscular phantom parallel to the ultrasound beam while maintaining full imaging of the needle. In experiment 2, the needle aimed to contact a target inside the phantom. Intervention subjects received structured feedback between trials. Controls received a global critique after completing the trials. The slopes of the learning curves derived from the sequences of successes and failures were compared. Change-point analyses identified the start and the end of learning in trial sequences. The number of trials associated with learning, the number of technical errors, and the duration of training sessions were compared between intervention and controls. RESULTS: In experiment 1, learning curves departed from 73% (controls) and 76% (intervention) success rates; slopes (standard error) were 0.79% (0.02%) and 0.71% (0.04), respectively, with mean absolute difference of 0.18% (95% confidence interval [CI], 0.17%-0.19%; P = 0). Intervention subjects' learning curves were shorter and steeper than those of controls. In experiment 2, the learning curves departed from 43% (controls) and 80% (intervention) success rates; slopes (standard error) were 1.06% (0.02%) and 0.42% (0.03%), respectively, with a mean difference of 0.65% (95% CI, 0.64%-0.66%; P = 0). Feedback was associated with a greater number of trials associated with learning in both experiment 1 (mean difference, 1.55 trials; 95% CI, 0.15-3 trials; P = 0) and experiment 2 (mean difference, 4.25 trials; 95% CI, 1.47-7.03 trials; P = 0) and a lower number of technical errors per trial in experiments 1 (mean difference, 0.19; 95% CI, 0.07-0.30; P = .02) and 2 (mean difference, 0.58; 95% CI, 0.45-0.70; P = 0), but longer training sessions in both experiments 1 (mean difference, 9.2 minutes; 95% CI, 4.15-14.24 minutes; P = .01) and 2 (mean difference, 7.4 minutes; 95% CI, 1.17-13.59 minutes; P = .02). CONCLUSIONS: High-frequency, structured expert feedback compared favorably to self-directed learning, being associated with shorter learning curves, smaller number of technical errors, and longer duration of in-training improvement, but increased duration of the training sessions.

Local Anesthetic-Induced Neurotoxicity.

This review summarizes current knowledge concerning incidence, risk factors, and mechanisms of perioperative nerve injury, with focus on local anesthetic-induced neurotoxicity. Perioperative nerve injury is a complex phenomenon and can be caused by a number of clinical factors. Anesthetic risk factors for perioperative nerve injury include regional block technique, patient risk factors, and local anesthetic-induced neurotoxicity. Surgery can lead to nerve damage by use of tourniquets or by direct mechanical stress on nerves, such as traction, transection, compression, contusion, ischemia, and stretching. Current literature suggests that the majority of perioperative nerve injuries are unrelated to regional anesthesia. Besides the blockade of sodium channels which is responsible for the anesthetic effect, systemic local anesthetics can have a positive influence on the inflammatory response and the hemostatic system in the perioperative period. However, next to these beneficial effects, local anesthetics exhibit time and dose-dependent toxicity to a variety of tissues, including nerves. There is equivocal experimental evidence that the toxicity varies among local anesthetics. Even though the precise order of events during local anesthetic-induced neurotoxicity is not clear, possible cellular mechanisms have been identified. These include the intrinsic caspase-pathway, PI3K-pathway, and MAPK-pathways. Further research will need to determine whether these pathways are non-specifically activated by local anesthetics, or whether there is a single common precipitating factor.

Day surgery regional anesthesia in children: safety and improving outcomes, do they make a difference?

PURPOSE OF REVIEW: The objective of this review is to provide an overview of recent developments in pediatric regional anesthesia and elucidate outcomes as it relates to patient safety and overall satisfaction. RECENT FINDINGS: Since the inception of the Pediatric Regional Anesthesia Network database, the acquisition of data has enabled the pediatric anesthesiologist to extrapolate results and translate them into useful outcomes. Despite the growing trend to provide regional anesthesia in the pediatric population, there continues to be a paucity of available research studies to evaluate outcomes of various regional nerve blocks. This review serves as a conduit to explore the most recent data available, in each regional anesthetic technique, as it relates to outcomes such as analgesia, patient safety and satisfaction. SUMMARY: Despite the limited number of randomized controlled trials evaluating the safety of individual regional anesthetic techniques, the growing body of data, such as presented in the Pediatric Regional Anesthesia Network database, suggests a high degree of safety in performing various regional anesthetic modalities. Modern medicine should continue to embrace the use of regional anesthesia, particularly in the ambulatory setting, to reduce perioperative pain and improve patient outcomes.

Clinical and microbiological evaluation of epidural and regional anaesthesia catheters in injured UK military personnel.

INTRODUCTION: The adoption of regional and epidural analgesia in UK military personnel injured in action during Op HERRICK increased from 2008, in line with structural and environmental developments in the UK medical treatment facility. Historically, there have been concerns that invasive analgesic techniques could carry an increased risk of infection, due to the mechanism of injury and the environmental conditions in which the injuries were sustained. Consequently, the epidural and continuous peripheral nerve blockade (CPNB) catheters that were inserted in UK military personnel during a 33-month period of Op HERRICK were clinically and microbiologically examined, after subsequent admission to the University Hospitals Birmingham (UHB) NHS Trust. METHODS: Data on epidural and CPNB insertions were collected via the specialist pain service at UHB over the study period, including de novo and replacement insertions performed in both Afghanistan and the UK. Patients were regularly reviewed and relevant clinical concerns were documented in patients' case notes as necessary. The anatomical site, duration of placement and the results of microbiological culture of the epidural and CPNB catheter tips were all recorded. RESULTS: Overall, 236 catheters were assessed, of which 151 catheter tips (64%) were cultured (85 epidural, 66 CPNB). Of these, 48 grew bacteria (34% of cultured epidurals and 29% of cultured CPNB). There was no difference between the colonisation rates of epidurals inserted in Afghanistan and the UK. Only one infection related to a misplaced epidural catheter was confirmed. CONCLUSIONS: With the exception of the epidural (34%) and proximal sciatic (42%) catheters, these figures, in a military cohort characterised by significant injury scores, are consistent with those reported for civilian surgical patients. The results strongly support the expansion of regional analgesia during Op HERRICK from 2008 onwards. The outcomes suggest a possible translation into civilian major trauma practice.

The effect of needle dimensions and infusion rates on injection pressures in regional anaesthesia needles: a bench-top study.

Animal studies have shown that injection pressures > 75 kPa indicate probable intrafascicular needle tip position. This study describes the flow/pressure characteristics of seven common needle systems. A syringe pump delivered flow rates of 5, 6.67, 10, 13.3, 15 and 20 ml.min(-1) through these needle systems, while keeping the needle tips open to atmosphere. A pressure transducer connected between the syringe and needle provided a real-time graphical display for analysis. Mean plateau pressures increased linearly with flow and with decreasing needle diameter (2.7-92 kPa). Flow rates > 17 ml.min(-1) and needle sizes 22 G and smaller produced mean plateau pressures > 75 kPa. Pressure monitors upstream from the needle may produce false-positive alarms at high flow rates due to needle resistance, and unreliable readings due to non-laminar flow. We recommend injection rates ≤ 15 ml.min(-1) (0.25 ml.s(-1) ) to reduce the effect of factors upstream from the needle tip as a cause of high pressure readings.

An improvised pressure gauge for regional nerve blockade/anesthesia injections: an initial study.

High injection pressure is one of the warning signs of intraneural injection, with animal models suggesting pressures higher than 69 or 176 kPa as high risk, and is normally detected subjectively and inaccurately. We describe a system improvised from common clinical components that uses Boyle's law to objectively measure injection pressure. The objectives of the study were to (1) Validate our improvised pressure gauge (IPG) by comparing the injection pressure as calculated by Boyle's law against the measured pressure and (2) Use the IPG to measure the range of injection pressures by two groups of anesthetic professionals using the "syringe feel" technique. Our IPG system consists of an extended 1 ml syringe attached to a 3-way stopcock, inserted between the syringe containing the local anesthetic injectate and the needle. The IPG was validated against a pressure calibration reference. 20 anesthesiologists and 20 anesthetic assistants were recruited to apply pressure to the 20 ml syringe in vitro while blinded to the attached IPG. The pressures were measured on three separate occasions for each participant. There was good agreement (<8 percent difference) between the measured and theoretical pressure values. Anesthesiologists exceeded the threshold of 69 kPa in 18 of a total of 60 attempts whereas anesthetic assistants exceeded the threshold in 30 attempts out of 60 attempts. Anesthetic assistants exerted a higher overall pressure of 80 kPa compared to 51 kPa for anesthesiologists-this was statistically significant (p = 0.027). Our improvised system is easily and rapidly assembled from common clinical equipment and shows promise as a monitor for inadvertent intraneural injection.

A pilot in vitro evaluation of the "air test" for perineural catheter tip localization by a novice regional anesthesiologist.

The "air test" is used clinically to infer perineural catheter location and has been recently evaluated for use by experts. However, its utility for practitioners with less experience is unknown. We tested the hypothesis that the air test, when performed by a novice regional anesthesiologist, will improve assessment of perineural catheter tip position in a validated porcine-bovine model and determined the test's positive and negative predictive values, sensitivity, and specificity for a novice. In contrast to the results of the expert study, the air test did not improve the novice's assessment of perineural catheter tip location over chance.

Differences in tip visibility and nerve block parameters between two echogenic needles during a simulation study with inexperienced anesthesia trainees.

Needle tip visualization during ultrasound-guided regional anesthesia (UGRA) is necessary for safety and efficacy. However, disruption of the image of the needle tip driven toward the target is a general problem, especially for beginners. The purpose of this study was to compare performance parameters between using the Sonoplex and Stimuplex D-Plus echogenic needles in a simulated ultrasound-guided interventional task by inexperienced anaesthesia residents. After a standardized training session, 28 anesthesiology residents performed simulated nerve blocks in a beef phantom with each needle. All ultrasound images were digitally stored for analysis. The absolute time the needle tip was in view, total procedure time, and angle of needle insertion were subsequently measured objectively by two single investigators. The procedures that used the Sonoplex echogenic needle had significantly better tip visibility and shorter total procedure time at insertion angles between 42° and 64° relative to the phantom surface. We have demonstrated that inexperienced users who used the Sonoplex echogenic needle were able to complete the procedure more quickly. Needles with improved visibility would be a very useful addition to UGRA for inexperienced users.

NRFit connectors in regional anaesthesia: avoiding medication errors.

The continuous development of medicine in most fields requires physicians to apply the latest methods and technology to ensure patients' safety. In the field of anesthesiology we are pioneers in the application of measures that guarantee the security of our patients, making possible the greatest reduction in mortality seen among all other specialties. This objective has been achieved thanks to the introduction of changes such as the one presented in this review article. The specific NRFit® connections for neuraxial and other regional anesthesia applications prevent wrong route medication errors to occur. These medication errors have been related to a high morbidity and mortality rate. This article reviews this new technology based in our own two-year experience at Hospital Universitario Príncipe de Asturias (Alcalá de Henares, Madrid) as well as a literature review using PubMed, UpToDate and ClinicalKey.

Needle echogenicity in sonographically guided regional anesthesia: blinded comparison of 4 enhanced needles and validation of visual criteria for evaluation.

OBJECTIVES: Needle visualization is important for sonographically guided regional anesthesia procedures. Needle characteristics that improve needle visualization are therefore important to anesthesiologists. This study compared several echogenic needle designs by defining characteristics of needle echogenicity and assessing regional anesthesiologist preferences for these characteristics across various needle angles. METHODS: Twelve blinded regional anesthesiologists graded 5 randomized block needles (1 nonechogenic control and 4 echogenic) on 4 predefined characteristics (overall brightness of the needle, overall clarity of the needle, brightness of the needle tip, and clarity of the needle tip). In-plane needle images in a gel phantom were obtained at 4 needle angles (15°, 30°, 45°, and 60°). Participants rated specific needle characteristics for each needle at each angle and then ranked their overall needle preferences. RESULTS: Significant differences in all 4 needle characteristics were found across needle types (P< .01). Clarity of the needle tip was significantly associated with overall needle rank (P = .009). Other needle visualization characteristics were not significantly correlated with needle rank. The SonoPlex Stim needle (Pajunk Medical Systems, Tucker, GA) was rated highest in all 4 predefined needle characteristics as well as overall needle rank. CONCLUSIONS: This study shows that anesthesiologists prefer certain visual characteristics of needles used in sonographically guided regional anesthesia procedures. Specifically, needle tip clarity most closely predicted clinician needle preferences. These results support the idea that all echogenic needle designs do not uniformly enhance needle visualization. Further studies are needed to determine whether needles with superior tip clarity predict not only clinician preferences but also improved sonographically guided regional anesthetic outcomes.