Prangmalee Leurcharusmee

A Multicenter Randomized Comparison Between Intravenous and Perineural Dexamethasone for Ultrasound-Guided Infraclavicular Block.

Background and Objectives This multicenter, randomized trial compared intravenous (IV) and perineural (PN) dexamethasone for ultrasound (US)-guided infraclavicular brachial plexus block. Our research hypothesis was both modalities would result in similar durations of motor block. Methods One hundred fifty patients undergoing upper limb surgery with US-guided infraclavicular block were randomly allocated to receive IV or PN dexamethasone (5 mg). The local anesthetic agent (35 mL of lidocaine 1%-bupivacaine 0.25% with epinephrine 5 &mgr;g/mL) was identical in all subjects. Patients and operators were blinded to the nature of IV and PN injectates. During the performance of the block, the performance time, number of needle passes, procedural pain, and complications (vascular puncture, paresthesia) were recorded. Subsequently, a blinded observer assessed the success rate (defined as a minimal sensorimotor composite score of 14 of 16 points at 30 minutes), onset time as well as the incidence of surgical anesthesia (defined as the ability to complete surgery without local infiltration, supplemental blocks, IV opioids, or general anesthesia). Postoperatively (at 24 hours), the blinded observer contacted patients with successful blocks to enquire about the duration of motor block, sensory block, and postoperative analgesia. The main outcome variable was the duration of motor block. Results No intergroup differences were observed in terms of technical execution (performance time/number of needle passes/procedural pain/complications), onset time, success rate, and surgical anesthesia. However, compared to its IV counterpart, PN dexamethasone provided 19% to 22% longer durations for motor block (15.7 ± 6.2 vs 12.9 ± 5.5 hours; P = 0.009), sensory block (16.8 ± 4.4 vs 13.9 ± 5.4 hours; P = 0.002), and postoperative analgesia (22.1 ± 8.5 vs 18.6 ± 6.7 hours; P = 0.014). Conclusions Compared with its IV counterpart, PN dexamethasone (5 mg) provides a longer duration of motor block, sensory block, and postoperative analgesia for US-guided infraclavicular block. Future dose-finding studies are required to elucidate the optimal dose of dexamethasone.

A Randomized Comparison Between Conventional and Waveform-Confirmed Loss of Resistance for Thoracic Epidural Blocks.

Background and Objectives Epidural waveform analysis (EWA) provides a simple confirmatory adjunct for loss of resistance (LOR): when the needle tip is correctly positioned inside the epidural space, pressure measurement results in a pulsatile waveform. In this randomized trial, we compared conventional and EWA-confirmed LOR in 2 teaching centers. Our research hypothesis was that EWA-confirmed LOR would decrease the failure rate of thoracic epidural blocks. Methods One hundred patients undergoing thoracic epidural blocks for thoracic surgery, abdominal surgery, or rib fractures were randomized to conventional LOR or EWA-LOR. The operator was allowed as many attempts as necessary to achieve a satisfactory LOR (by feel) in the conventional group. In the EWA-LOR group, LOR was confirmed by connecting the epidural needle to a pressure transducer using a rigid extension tubing. Positive waveforms indicated that the needle tip was positioned inside the epidural space. The operator was allowed a maximum of 3 different intervertebral levels to obtain a positive waveform. If waveforms were still absent at the third level, the operator simply accepted LOR as the technical end point. However, the patient was retained in the EWA-LOR group (intent-to-treat analysis). After achieving a satisfactory tactile LOR (conventional group), positive waveforms (EWA-LOR group), or a third intervertebral level with LOR but no waveform (EWA-LOR group), the operator administered a 4-mL test dose of lidocaine 2% with epinephrine 5 &mgr;g/mL. Fifteen minutes after the test dose, a blinded investigator assessed the patient for sensory block to ice. Results Compared with LOR, EWA-LOR resulted in a lower rate of primary failure (2% vs 24%; P = 0.002). Subgroup analysis based on experience level reveals that EWA-LOR outperformed conventional LOR for novice (P = 0.001) but not expert operators. The performance time was longer in the EWA-LOR group (11.2 ± 6.2 vs 8.0 ± 4.6 minutes; P = 0.006). Both groups were comparable in terms of operators level of expertise, depth of the epidural space, approach, and LOR medium. In the EWA-LOR group, operators obtained a pulsatile waveform with the first level attempted in 60% of patients. However, 40% of subjects required performance at a second or third level. Conclusions Compared with its conventional counterpart, EWA-confirmed LOR results in a lower failure rate for thoracic epidural blocks (2% vs 24%) in our teaching centers. Confirmatory EWA provides significant benefits for inexperienced operators.

Reliability of Waveform Analysis as an Adjunct to Loss of Resistance for Thoracic Epidural Blocks.

Background The epidural space is most commonly identified with loss of resistance (LOR). Although sensitive, LOR lacks specificity, as cysts in interspinous ligaments, gaps in ligamentum flavum, paravertebral muscles, thoracic paravertebral spaces, and intermuscular planes can yield nonepidural LOR. Epidural waveform analysis (EWA) provides a simple confirmatory adjunct for LOR. When the needle is correctly positioned inside the epidural space, measurement of the pressure at its tip results in a pulsatile waveform. In this observational study, we set out to assess the sensitivity, specificity, as well as positive and negative predictive values of EWA for thoracic epidural blocks. Methods We enrolled a convenience sample of 160 patients undergoing thoracic epidural blocks for thoracic surgery, abdominal surgery, or rib fractures. The choice of patient position (sitting or lateral decubitus), approach (midline or paramedian), and LOR medium (air or normal saline) was left to the operator (attending anesthesiologist, fellow, or resident). After obtaining a satisfactory LOR, the operator injected 5 mL of normal saline through the epidural needle. A sterile tubing, connected to a pressure transducer, was attached to the needle to measure the pressure at the needle tip. A 4-mL bolus of lidocaine 2% with epinephrine 5 &mgr;g/mL was then administered and, after 10 minutes, the patient was assessed for sensory blockade to ice. Results The failure rate (incorrect identification of the epidural space with LOR) was 23.1%. Of these 37 failed epidural blocks, 27 provided no sensory anesthesia at 10 minutes. In 10 subjects, the operator was unable to thread the catheter through the needle. When compared with the ice test, the sensitivity, specificity, and positive and negative predictive values of EWA were 91.1%, 83.8%, 94.9%, and 73.8%, respectively. Conclusions Epidural waveform analysis (with pressure transduction through the needle) provides a simple adjunct to LOR for thoracic epidural blocks. Although its use was devoid of complications, further confirmatory studies are required before its routine implementation in clinical practice.

A Randomized Comparison Between Single- and Triple-Injection Subparaneural Popliteal Sciatic Nerve Block.

Background and Objectives This prospective randomized trial compared ultrasound-guided single-injection (SI) and triple-injection (TI) subparaneural popliteal sciatic nerve block. We hypothesized that multiple injections are not required when local anesthetic (LA) is deposited under the paraneurium because the latter entraps LA molecules, ensuring circumferential spread around the nerve. Therefore, in addition to comparable success rates, we also expected similar total anesthesia-related times (sum of performance and onset times) and designed this study as an equivalency trial. Methods Ultrasound-guided subparaneural posterior popliteal sciatic nerve block was carried out in 100 patients. In the SI group, LA was deposited at a single location between the tibial and peroneal nerves. In the TI group, LA was injected between the tibial and peroneal divisions, medial to the tibial nerve, and lateral to the common peroneal nerve. The total LA volume (15 mL) and mixture (lidocaine 1%–bupivacaine 0.25%–epinephrine 5 &mgr;g/mL) were identical in all subjects. The performance time, number of needle passes, and adverse events (paresthesia, neural edema) were recorded by the (nonblinded) investigator supervising the block. A blinded observer evaluated the success rate (sensorimotor composite score ≥6/8 points at 30 minutes) as well as the onset time and contacted patients 7 days after the surgery to inquire about persistent numbness or motor deficit. Results Both techniques provided comparable success rates (92%) and total anesthesia-related times (17.1–19.7 minutes). Expectedly, the SI group required fewer needle passes (1 vs 3; P < 0.001) and a shorter needling time (3.0 ± 2.3 minutes vs 4.0 ± 2.3 minutes; P = 0.025). The TI group displayed a shorter onset time (12.5 ± 7.9 minutes vs 15.8 ± 7.9 minutes; P = 0.027). The performance time, procedural discomfort, and incidence of paresthesia (14%–20%) were similar between the 2 groups. Sonographic neural swelling was detected in 2 subjects in the SI group. In both cases, the needle was carefully withdrawn and the injection was completed uneventfully. Follow-up of the 100 subjects 1 week after surgery revealed no residual numbness or motor deficit. Conclusions Ultrasound-guided SI and TI subparaneural popliteal sciatic nerve blocks result in comparable success rates and total anesthesia-related times. Expectedly, the SI technique requires fewer needle passes.

How Should Beginners Learn Ultrasound In-Plane Needle Techniques? A Randomized Comparison between Directed- and Self-Learning

Background: With ultrasound (US) guidance, the in-plane (IP) technique allows operators to track the needle in real time during its advancement towards the target nerve. While mastery of the IP technique is instrumental to the success (and safety) of peripheral nerve blocks, the optimal learning strategy for beginners has not been elucidated. In this randomized trial, using phantom gel models, we compared control-, self- and directed-learning for the acquisition of IP needle skills. We hypothesized that, compared to the 2 other groups, directed-learning would require a shorter performance time and fewer needle passes to complete the post-test. Methods: Thirty novice operators (experience level<30 US-guided procedures in the 6 months prior to the study) were randomized to 1of 3 groups. In the control group, subjects underwent pre- and post-testing with no training in between. In the self-learning group, subjects underwent 1 hour of independent learning (needling of a practice phantom model) between the pre- and post-tests. In the directed-learning group, 1 hour of learning through coaching and feedback was provided between the pre- and post-tests. Pre-tests and post-tests, which were identical, consisted of needling sonographic targets of varying sizes and depths, which were embedded in a test phantom model. The primary outcomes encompassed performance time and number of needle passes; secondary outcomes included the presence or frequency of 8 quality-compromising behaviors. All study variables were assessed by a blinded observer. Results: Compared to the pre-tests, post-test performance times improved similarly in all 3 groups. However only subjects randomized to directed-learning showed a reduction in the number of needle passes as well as improvement in several quality-compromising behaviors. Conclusion: A directed-learning session, integrating coaching and feedback, is pedagogically more productive than self-learning for beginners aiming to acquire US IP technique. Further trials are required to determine the IP technique learning curve for novice operators.