Brian D O'Donnell

The Analgesic Efficacy of Transversus Abdominis Plane Block After Abdominal Surgery: A Prospective Randomized Controlled Trial

BACKGROUND:The transversus abdominis plane (TAP) block is a novel approach for blocking the abdominal wall neural afferents via the bilateral lumbar triangles of Petit. We evaluated its analgesic efficacy in patients during the first 24 postoperative hours after abdominal surgery, in a randomized, controlled, double-blind clinical trial. METHODS:Thirty-two adults undergoing large bowel resection via a midline abdominal incision were randomized to receive standard care, including patient-controlled morphine analgesia and regular nonsteroidal antiinflammatory drugs and acetaminophen (n = 16), or to undergo TAP block (n = 16) in addition to standard care (n = 16). After induction of anesthesia, 20 mL of 0.375% levobupivacaine was deposited into the transversus abdominis neuro-fascial plane via the bilateral lumbar triangles of Petit. Each patient was assessed by a blinded investigator in the postanesthesia care unit and at 2, 4, 6, and 24 h postoperatively. RESULTS:The TAP block reduced visual analog scale pain scores (TAP versus control, mean ± sd) on emergence (1 ± 1.4 vs 6.6 ± 2.8, P < 0.05), and at all postoperative time points, including at 24 h (1.7 ± 1.7 vs 3.1 ± 1.5, P < 0.05). Morphine requirements in the first 24 postoperative hours were also reduced (21.9 ± 8.9 mg vs 80.4 ± 19.2 mg, P < 0.05). There were no complications attributable to the TAP block. All TAP patients reported high levels of satisfaction with their postoperative analgesic regimen. CONCLUSIONS:The TAP block provided highly effective postoperative analgesia in the first 24 postoperative hours after major abdominal surgery.

Transversus abdominis plane block: a cadaveric and radiological evaluation.

Background and Objectives: The abdominal wall is a significant source of pain after abdominal surgery. Anterior abdominal wall analgesia may assist in improving postoperative analgesia. We have recently described a novel approach to block the abdominal wall neural afferents via the bilateral lumbar triangles of Petit, which we have termed a transversus abdominis plane block. The clinical efficacy of the transversus abdominis plane block has recently been demonstrated in a randomized controlled clinical trial of adults undergoing abdominal surgery. Methods: After institutional review board approval, anatomic studies were conducted to determine the deposition and spread of methylene blue injected into the transversus abdominis plane via the triangles of Petit. Computerized tomographic and magnetic resonance imaging studies were then conducted in volunteers to ascertain the deposition and time course of spread of solution within the transversus abdominis fascial plane in vivo. Results: Cadaveric studies demonstrated that the injection of methylene blue via the triangle of Petit using the “double pop” technique results in reliable deposition into the transversus abdominis plane. In volunteers, the injection of local anesthetic and contrast produced a reliable sensory block, and demonstrated deposition throughout the transversus abdominis plane. The sensory block produced by lidocaine 0.5% extended from T7 to L1, and receded over 4 to 6 hours, and this finding was supported by magnetic resonance imaging studies that showed a gradual reduction in contrast in the transversus abdominis plane over time. Conclusions: These findings define the anatomic characteristics of the transversus abdominis plane block, and underline the clinical potential of this novel block.

An Estimation of the Minimum Effective Anesthetic Volume of 2% Lidocaine in Ultrasound-guided Axillary Brachial Plexus Block

Background:Ultrasound guidance facilitates precise needle and injectate placement, increasing axillary block success rates, reducing onset times, and permitting local anesthetic dose reduction. The minimum effective volume of local anesthetic in ultrasound-guided axillary brachial plexus block is unknown. The authors performed a study to estimate the minimum effective anesthetic volume of 2% lidocaine with 1:200,000 epinephrine (2% LidoEpi) in ultrasound-guided axillary brachial plexus block. Methods:After ethical approval and informed consent, patients undergoing hand surgery of less than 90 min duration were recruited. A step-up/step-down study model was used with nonprobability sequential dosing based on the outcome of the previous patient. The starting dose of 2% LidoEpi was 4 ml per nerve. Block failure resulted in a dose increase of 0.5 ml; block success in a reduction of 0.5 ml. A blinded assistant assessed sensory and motor blockade at 5-min intervals up to 30 min. Block performance time and duration were measured. Two predetermined stopping points were used; a minimum of five consecutive block success/failures and five consecutive successful blocks at 1 ml per nerve. Results:The study was terminated when five consecutive patients had successful blocks using 1 ml of 2% LidoEpi per nerve (overall group n = 11). All five patients had surgical anesthesia within 10 min. The mean (SD) block performance time was 445 (100) s, and block duration was 190 min (range 120-310 min). All surgical procedures were performed under regional anesthesia with anxiolytic sedation provided in 3 of 11 cases. Conclusion:Successful ultrasound-guided axillary brachial plexus block may be performed with 1 ml per nerve of 2% LidoEpi.

Ultrasound-Guided Axillary Brachial Plexus Block with 20 Milliliters Local Anesthetic Mixture Versus General Anesthesia for Upper Limb Trauma Surgery: An Observer-Blinded, Prospective, Randomized, Controlled Trial

OBJECTIVE: We performed a randomized, controlled trial comparing low-dose ultrasound-guided axillary block with general anesthesia evaluating anesthetic and perioperative analgesic outcomes. METHODS: Patients were randomized to either ultrasound-guided axillary block or general anesthesia. Ultrasound-guided axillary block was performed using a needle-out-of-plane approach. Up to 5 mL of local anesthetic injectate (equal parts 2% lidocaine with 1:200,000 epinephrine and 0.5% bupivacaine with 7.5 mg/mL clonidine) was injected after identifying the median, ulnar, radial, and musculocutaneous nerves. A maximum of 20 mL local anesthetic injectate was used. General anesthesia was standardized to include induction with fentanyl and propofol, maintenance with sevoflurane in an oxygen/nitrous oxide mixture. Pain scores were measured in the recovery room and at 2, 6, 24, 48 h, and 7 days. Ability to bypass the recovery room and time to achieve hospital discharge criteria were also assessed. RESULTS: All ultrasound-guided axillary block patients achieved satisfactory anesthesia. The ultrasound-guided axillary block group had lower visual analog scale pain scores in the recovery room (0.3 [1.3] vs 55.8 [36.5], P < 0.001), and visual rating scale pain scores at 2 h (0.3 [1.3] vs 45 [29.6], P < 0.001), and at 6 h (1.1 [2.7] vs 4 [2.8], P < 0.01). All ultrasound-guided axillary block patients bypassed the recovery room and attained earlier hospital discharge criteria (30 min vs 120 min 30/240 P < 0.0001 median [range]). CONCLUSIONS: Ultrasound-guided axillary brachial plexus block with 20 mL local anesthetic mixture provided satisfactory anesthesia and superior analgesia after upper limb trauma surgery when compared with general anesthesia.

A Clinical Evaluation of Block Characteristics Using One Milliliter 2% Lidocaine in Ultrasound-Guided Axillary Brachial Plexus Block

We report onset and duration of ultrasound-guided axillary brachial plexus block using 1 mL of 2% lidocaine with 1:200,000 epinephrine per nerve (total local anesthetic volume 4 mL). Block performance time, block onset time, duration of surgery, and block duration were measured. Seventeen consecutive patients were recruited. The mean (SD) block performance and onset times were 271 (67.9) seconds and 9.7 (3.7) minutes, respectively. Block duration was 160.8 (30.7) minutes. All operations were performed using regional anesthesia alone. The duration of anesthesia obtained is sufficient for most ambulatory hand surgery.

Proactive error analysis of ultrasound-guided axillary brachial plexus block performance.

Background: Detailed description of the tasks anesthetists undertake during the performance of a complex procedure, such as ultrasound-guided peripheral nerve blockade, allows elements that are vulnerable to human error to be identified. We have applied 3 task analysis tools to one such procedure, namely, ultrasound-guided axillary brachial plexus blockade, with the intention that the results may form a basis to enhance training and performance of the procedure. Methods: A hierarchical task analysis of the procedure was performed with subsequent analysis using systematic human error reduction and prediction approach (SHERPA). Failure modes, effects, and criticality analysis was applied to the output of our SHERPA analysis to provide a definitive hierarchy to the error analysis. Results: Hierarchical task analysis identified 256 tasks associated with the performance of ultrasound-guided axillary brachial plexus blockade. Two hundred twelve proposed errors were analyzed using SHERPA. Failure modes, effects, and criticality analysis methodology was applied to the output of SHERPA analysis to prioritize 20 errors. Conclusions: This study presents a formal analysis of (i) the specific tasks that might be associated with the safe and effective performance of the procedure and (ii) the most critical errors likely to occur as trainees learn to perform the procedure. Potential applications of these data include curricular development and the design of tools to teach and assess block performance.

A case of liver trauma with a blunt regional anesthesia needle while performing transversus abdominis plane block.

To the Editor: We read with interest the study by Bloc et al. regarding spread of injectate associated with radial or median nerve type motor response during infraclavicular brachial plexus block by ultrasound evaluation.1 They demonstrated that, compared with median nerve type motor response, injection performed after a radial nerve type motor response promoted reproducible and remarkable ultrasound spread characteristics associated with complete sensory block of the 3 cords at 30 minutes. The reason they have cited is that the posterior cord is the nerve structure in the most external and deepest position at the infraclavicular region. However, we do not agree with this explanation. Though brachial plexus is associated with at least 29 anatomical variations, the most common relation at the infraclavicular region is the lateral cord being most superior and anterior, followed by posterior cord which is lateral and between the lateral and medial cord, and medial cord which is the deepest at this location. Lecamwasam et al. demonstrated similar results as the above authors, that is, stimulation of posterior cord predicted successful infraclavicular block in their study. However, they cited a different reason for this result. They inferred that localizing the posterior cord places the needle centrally in the infraclavicular region and thus assures an even spread of local anesthetic both above and below the posterior cord ensuring a more complete block of all 3 cords. Thus we believe that the reason for a better block would not be because the posterior cord is located deepest at the infraclavicular region, but because of even spread of local anesthetic around it. The reason why quality diffusion of local anesthetic was most dense posteriorly, though present in all 3 zones, could be because of gravity.

Local anesthetic dose and volume used in ultrasound-guided peripheral nerve blockade.

In 1978, Drs La Grange, Foster, and Pretorius were the first to describe the use of Doppler ultrasound to identify the third part of the subclavian artery during the performance of supraclavicular brachial plexus block. In their report, they described vascular echolocation using an auditory signal from Doppler ultrasound, and declared the resultant brachial plexus block highly successful and safer than conventional approaches. Three years later in 1981, Drs Abramowitz and Cohen described the first use of Doppler ultrasound to identify the axillary artery, thereby aiding in the performance of an axillary brachial plexus block for upper limb surgery. Despite the availability of B-mode ultrasound imaging, visual guidance was not used at this point in the evolution of ultrasound-assisted peripheral nerve block, favoring auditory signals received from hand-held Doppler ultrasound. It was not until 1989 that images of local anesthetic spread around the axillary brachial plexus were reported. This report heralded an era of ultrasonographic visualization of neural structures and perineural local anesthetics in the performance of peripheral nerve block.

Construct validity of a novel assessment tool for ultrasound-guided axillary brachial plexus block.

The purpose of this study was to examine the construct validity and reliability of a novel metrics‐based assessment tool, previously developed for ultrasound‐guided axillary brachial plexus block. Five expert and eight novice anaesthetists performed a total of 18 ultrasound‐guided axillary brachial plexus blocks on the same number of patients. A trained investigator video‐taped procedures according to a pre‐defined protocol. Two trained consultant anaesthetists independently scored the videos using the assessment tool. Compared with novices, experts completed more steps (mean 41.0 vs. 33.1, p = 0.001), had fewer procedural errors (2.8 vs. 7.9, p < 0.0001), had fewer critical errors (0.8 vs. 1.3, p = 0.030), and fewer total errors (3.5 vs. 9.1, p < 0.0001). The mean inter‐rater reliability for scoring of experts’ performance was 0.91, for novices’ performance was 0.84, and for all performance combined (n = 18) was 0.88. This assessment tool is valid, and discriminates reliably between expert and novice performance for placement of ultrasound‐guided axillary brachial plexus blocks.

Nerve localization techniques for peripheral nerve block and possible future directions

Ultrasound guidance is now a standard nerve localization technique for peripheral nerve block (PNB). Ultrasonography allows simultaneous visualization of the target nerve, needle, local anesthetic injectate, and surrounding anatomical structures. Accurate deposition of local anesthetic next to the nerve is essential to the success of the nerve block procedure. Due to limitations in the visibility of both needle tip and nerve surface, the precise relationship between needle tip and target nerve is unknown at the moment of injection. Importantly, nerve injury may result both from an inappropriately placed needle tip and inappropriately placed local anesthetic. The relationship between the block needle tip and target nerve is of paramount importance to the safe conduct of peripheral nerve block.