Alan J. R. Macfarlane

Is circumferential injection advantageous for ultrasound-guided popliteal sciatic nerve block?: A proof-of-concept study.

Background: Ultrasound (US) guidance, in some instances, can increase the success rate and reduce the onset and procedure times for peripheral nerve blockade compared with traditional nerve localization techniques. The presumptive mechanism for these benefits is the ability to accurately inject local anesthetic circumferentially around the target nerve. We aimed to determine whether ensuring circumferential spread of local anesthetic is advantageous for US-guided popliteal sciatic nerve block. Methods: Sixty-four adult patients undergoing US-guided popliteal sciatic block for elective foot and ankle surgery were randomly assigned to 1 of 2 groups, circumferential or single-location injection. Using a short-axis nerve view and out-of-plane needle approach, the needle tip was advanced to the posterior external surface of the sciatic nerve. A 30-mL local anesthetic admixture (1:1 lidocaine 2%/bupivacaine 0.5% with 1:200,000 epinephrine) was injected either entirely at this location (single location) or incrementally at multiple locations to ensure circumferential spread around the sciatic nerve (circumferential). Sensory and motor functions were assessed by a blinded observer at predetermined intervals. The primary outcome was sensory block defined as loss of sensation to pinprick in the distribution of both tibial and common peroneal nerves at 30 mins after injection. Results: Sensory block was achieved in 94% of patients in the circumferential injection group compared with 69% in the single-location injection group (P = 0.010). There were no differences detected in block performance time, pain during block performance, or block-related complications between groups. Conclusions Ultrasound-guided circumferential injection of local anesthetic around the sciatic nerve at the popliteal fossa can improve the rate of sensory block without an increase in block procedure time or block-related complications compared with a single-location injection technique.

Needle to nerve proximity: what do the animal studies tell us?

Recent animal studies have provided insight and understanding, as well as promising clinical tools, to help identify needle-to-nerve contact and potentially hazardous intraneural injection. This narrative review describes and summarizes the contemporary animal studies primarily relating to indicators of needle-to-nerve contact and intraneural injection. Resultant nerve injury, whenever sought, is discussed.

Ultrasound-guided versus anatomic landmark-guided ankle blocks: a 6-year retrospective review.

Background and Objectives: Ultrasound-guided (USG) ankle block has been described; however, its clinical efficacy compared with conventional anatomic landmark-guided (ALG) techniques remains undetermined. Methods: We performed a 6-year retrospective cohort study of all ankle blocks performed for foot surgery and extracted demographic, intraoperative, and postoperative outcome data. We divided blocks into 2 groups for comparison, depending on whether they were performed using an ALG technique or a USG technique. Results: We identified 655 patients who received unilateral ankle block and 58 patients who received bilateral ankle block; we analyzed these separately. Trainees performed most blocks (approximately 80%). In patients receiving unilateral ankle block, successful surgical anesthesia was more likely in the USG group (84% versus 66%, P < 0.001). Patients in the ALG group were more likely to require supplemental local anesthesia (10% versus 5%, P = 0.04), unplanned general anesthesia (17% versus 7%, P = 0.001), or supplemental fentanyl (18% versus 9%, P = 0.002). Postanesthetic care unit pain scores were similar between groups. However, patients in the ALG group were more likely to receive intravenous opioids (21% versus 12%, P = 0.01), and they received a higher mean opioid dose (10.6 versus 8.7 mg intravenous morphine, ALG versus USG, P = 0.022). In patients receiving bilateral ankle block, successful surgical anesthesia was also more likely in the USG group (84% versus 57%); however, this was not statistically significant because of the small sample size. Conclusions: This study demonstrates that the USG technique of ankle block improves clinical efficacy compared with a conventional ALG technique, particularly in the hands of less-experienced practitioners.

Effect of regional versus local anaesthesia on outcome after arteriovenous fistula creation: a randomised controlled trial

BACKGROUND Arteriovenous fistulae are the optimum form of vascular access in end-stage renal failure. However, they have a high early failure rate. Regional compared with local anaesthesia results in greater vasodilatation and increases short-term blood flow. This study investigated whether regional compared with local anaesthesia improved medium-term arteriovenous fistula patency. METHODS This observer-blinded, randomised controlled trial was done at three university hospitals in Glasgow, UK. Adults undergoing primary radiocephalic or brachiocephalic arteriovenous fistula creation were randomly assigned (1:1; in blocks of eight) using a computer-generated allocation system to receive either local anaesthesia (0·5% L-bupivacaine and 1% lidocaine injected subcutaneously) or regional (brachial plexus block [BPB]) anaesthesia (0·5% L-bupivacaine and 1·5% lidocaine with epinephrine). Patients were excluded if they were coagulopathic, had no suitable vessels, or had a previous failed ipsilateral fistula. The primary endpoint was arteriovenous fistula patency at 3 months. We analysed the data on an intention-to-treat basis. This study was registered with ClinicalTrials.gov (NCT01706354) and is complete. FINDINGS Between Feb 6, 2013, and Dec 4, 2015, 163 patients were assessed for eligibility and 126 patients were randomly assigned to local anaesthesia (n=63) or BPB (n=63). All patients completed follow-up on an intention-to-treat basis. Primary patency at 3 months was higher in the BPB group than the local anaesthesia group (53 [84%] of 63 patients vs 39 [62%] of 63; odds ratio [OR] 3·3 [95% CI 1·4-7·6], p=0·005) and was greater in radiocephalic fistulae (20 [77%] of 26 patients vs 12 [48%] of 25; OR 3·6 [1·4-3·6], p=0·03). There were no significant adverse events related to the procedure. INTERPRETATION Compared with local anaesthesia, BPB significantly improved 3 month primary patency rates for arteriovenous fistulae. FUNDING Regional Anaesthesia UK, Darlindas Charity for Renal Research.

Practical knobology for ultrasound-guided regional anesthesia.

This article provides an instructive review of the essential functions universal to modern ultrasound machines in use for regional anesthesia practice. An understanding of machine knobology is integral to performing safe and successful ultrasound-guided regional anesthesia.

The Requisites of Needle-to-Nerve Proximity for Ultrasound-Guided Regional Anesthesia: A Scoping Review of the Evidence.

This scoping review examines the literature to determine whether the position of the needle tip relative to the target nerve is accurately and reliably detected during ultrasound (US)–guided regional anesthesia. The requisites for successful and safe needle tip positioning relative to the target nerve include accurate and reliable needle presentation by the machine, needle interpretation by the operator, nerve presentation by the machine, and nerve interpretation by the operator. Failure to visualize the needle tip is a common occurrence, frequently prompting operators to use needle and probe maneuvers, which are not necessarily based on evidence. Needle tip interpretation often relies on surrogate indicators that have not been validated. The acoustic resolution of modern portable US machines limits the extent to which nerve microanatomy can be reliably presented. Finally, our interpretation of the sonographic end points for local anesthetic injection that best balance success and safety for US-guided regional anesthesia continues to evolve. Whats New In order to determine whether or not the position of the needle tip relative to the target nerve is accurately and reliably detected during US-guided regional anesthesia, the available literature is reviewed and interpreted to address the following 4 questions: Is the presentation of needle tip by the ultrasound machine accurate and reliable? Is the interpretation of the needle tip image by the operator accurate and reliable? Is the presentation of the nerve by the ultrasound machine accurate and reliable? Is the interpretation of the nerve image by the operator accurate and reliable?

Does regional compared to local anaesthesia influence outcome after arteriovenous fistula creation

BackgroundAn arteriovenous fistula is the optimal form of vascular access in patients with end-stage renal failure requiring haemodialysis. Unfortunately, approximately one-third of fistulae fail at an early stage. Different anaesthetic techniques can influence factors associated with fistula success, such as intraoperative blood flow and venous diameter. A regional anaesthetic brachial plexus block results in vasodilatation and improved short- and long-term fistula flow compared to the infiltration of local anaesthetic alone. This, however, has not yet been shown in a large trial to influence long-term fistula patency, the ultimate clinical measure of success.The aim of this study is to compare whether a regional anaesthetic block, compared to local anaesthetic infiltration, can improve long-term fistula patency.MethodsThis study is an observer-blinded, randomised controlled trial. Patients scheduled to undergo creation of either brachial or radial arteriovenous fistulae will receive a study information sheet, and consent will be obtained in keeping with the Declaration of Helsinki. Patients will be randomised to receive either: (i) an ultrasound guided brachial plexus block using lignocaine with adrenaline and levobupivicaine, or (ii) local anaesthetic infiltration with lignocaine and levobupivicaine.A total of 126 patients will be recruited. The primary outcome is fistula primary patency at three months. Secondary outcomes include primary patency at 1 and 12 months, secondary patency and fistula flow at 1, 3 and 12 months, flow on first haemodialysis, procedural pain, patient satisfaction, change in cephalic vein diameter pre- and post-anaesthetic, change in radial or brachial artery flow pre- and post-anaesthetic, alteration of the surgical plan after anaesthesia as guided by vascular mapping with ultrasound, and fistula infection requiring antibiotics.ConclusionsNo large randomised controlled trial has examined the influence of brachial plexus block compared with local anaesthetic infiltration on the long-term patency of arteriovenous fistulae. If the performance of brachial plexus block increases fistulae patency, this will have significant clinical and financial benefits as the number of patients able to commence haemodialysis when planned should increase, and the number of “redo” or revision procedures should be reduced.Trial registrationThis study has been approved by the West of Scotland Research Ethics Committee 5 (reference no. 12/WS/0199) and is registered with the ClinicalTrials.gov database (reference no. NCT01706354).

A randomised, controlled, double blind, non‐inferiority trial of ultrasound‐guided fascia iliaca block vs. spinal morphine for analgesia after primary hip arthroplasty

We performed a single centre, double blind, randomised, controlled, non‐inferiority study comparing ultrasound‐guided fascia iliaca block with spinal morphine for the primary outcome of 24‐h postoperative morphine consumption in patients undergoing primary total hip arthroplasty under spinal anaesthesia with levobupivacaine. One hundred and eight patients were randomly allocated to receive either ultrasound‐guided fascia iliaca block with 2 mg.kg−1 levobupivacaine (fascia iliaca group) or spinal morphine 100 μg plus a sham ultrasound‐guided fascia iliaca block using saline (spinal morphine group). The pre‐defined non‐inferiority margin was a median difference between the groups of 10 mg in cumulative intravenous morphine use in the first 24 h postoperatively. Patients in the fascia iliaca group received 25 mg more intravenous morphine than patients in the spinal morphine group (95% CI 9.0–30.5 mg, p < 0.001). Ultrasound‐guided fascia iliaca block was significantly worse than spinal morphine in the provision of analgesia in the first 24 h after total hip arthroplasty. No increase in side‐effects was noted in the spinal morphine group but the study was not powered to investigate all secondary outcomes.

Continuous interscalene block for open shoulder surgery.

bidity or sequelae in the patient population studied. The protocol and informed consent were approved by the IRB of the University of Pennsylvania. The protocol underwent review at the highest levels of the health system, including the Chief Safety Officer and the chair of the Committee on Medical Ethics. The protocol explicitly stated that a single adverse event leading to tracheal intubation would halt the study pending review by the Chairman of Anesthesiology and Critical Care. The risks and benefits of the study including the risk of hypoxia were explained to all patients by the principal investigator. The principal investigator met regularly with the Data Safety Monitor and filed Adverse Event reports in a timely fashion. There was no outside funding utilized in the study. We and the IRB believe that every attempt was made to conduct the study ethically, but welcome suggestions on how we could improve. We do not represent our protocol as a recipe for standard clinical practice. It is a single piece of evidence in an effort to devise a safe practice of sedation for colonoscopy that permits anesthesiologists to maintain involvement in a clinical area that is rapidly slipping irretrievably from our grasp.

Essential Knobology for Ultrasound-Guided Regional Anesthesia and Interventional Pain Management

The safety and efficacy of ultrasound (US)-guided nerve blockade relies heavily upon a comprehensive understanding of machine “knobology” [1–3]. Despite differences in appearance and layout, all US machines share the same basic operative functions that users must appreciate in order to optimize the image. While modern US machines offer an abundance of features, the basic functions that all operators should be familiar with are frequency and probe selection, depth, gain, time gain compensation (TGC), focus, preprogrammed presets, color Doppler, power Doppler, compound imaging, tissue harmonic imaging (THI) (on some models), and image freeze and acquisition. Once the physical principles of US are understood, it becomes clear that creating the “best” image is often a series of trade-offs between improving one function at the expense of another. Each of the aforementioned functions is presented in turn below, following the sequence we use when performing any US-guided intervention.