Effect of Lidocaine 2% Versus Bupivacaine 0.5% and 1 Versus 2 Dual Separate Injections on Onset and Duration of Ultrasound-Guided Wrist Blocks: A Blinded 2 × 2 Factorial Randomized Clinical Trial.

BACKGROUND: Local anesthetics are often selected or mixed to accomplish faster onset of anesthesia. However, with ultrasound guidance, local anesthetics are delivered with greater precision, which may shorten the onset time with all classes of local anesthetics. In this study, we compared onset time and duration of ultrasound-guided wrist blocks with a fast onset versus a longer lasting local anesthetic administered via single or dual (spatially separate) injections at the level of the midforearm. METHODS: In this randomized clinical trial, 36 subjects scheduled for carpal tunnel release were randomly assigned to receive ultrasound-guided median and ulnar nerve blocks with lidocaine 2% or bupivacaine 0.5% via single or dual injections (n = 9 in each group). Subjects fulfilled the study requirements. The main outcome variables were onset and duration of sensory blockade, which were tested separately in 2 (drug) × 2 (injection) analysis of variances (ANOVAs) with interaction terms. RESULTS: Sensory block onset time did not differ significantly between subjects given lidocaine 2% (9.2 ± 3.4 minutes) or bupivacaine 0.5% (9.5 ± 3.1 minutes) (P = .76; mean difference, -0.3 ± 1.1 minutes [95% confidence interval {CI}, -2.5 to 1.9]) or between the single- (9.6 ± 2.8 minutes) and dual- (9.1 ± 3.6 minutes) injection groups (P = .69; mean difference, -0.4 ± 1.1 minutes [95% CI, -1.8 to 2.6]). Sensory duration was longer for subjects in the bupivacaine 0.5% group (27.3 ± 11.6 hours) than for subjects in the lidocaine 2% group (8.4 ± 4.1 hours) (P < .001; 95% CI, 12.7-25.1). However, sensory duration in the single- (15.7 ± 12.5 hours) and dual- (19.4 ± 13.1 hours) injection groups did not differ significantly (P = .28; mean difference, -3.7 ± 4.3 hours [95% CI, -12.6 to 5.1]). CONCLUSIONS: No significant effect was found for onset time between lidocaine 2% and bupivacaine 0.5% used in ultrasound-guided wrist blocks. Dual injections did not shorten onset time. Since mean nerve block duration was longer with bupivacaine 0.5%, our results suggest that the selection of local anesthetic for the median and ulnar nerves at the level of the midforearm should be based on the desired duration of the block and not on its speed of onset.

Neurotoxicity of bupivacaine and liposome bupivacaine after sciatic nerve block in healthy and streptozotocin-induced diabetic mice.

BACKGROUND: Long-acting local anaesthetics (e.g. bupivacaine hydrochloride) or sustained-release formulations of bupivacaine (e.g. liposomal bupivacaine) may be neurotoxic when applied in the setting of diabetic neuropathy. The aim of the study was to assess neurotoxicity of bupivacaine and liposome bupivacaine in streptozotocin (STZ) - induced diabetic mice after sciatic nerve block. We used the reduction in fibre density and decreased myelination assessed by G-ratio (defined as axon diameter divided by large fibre diameter) as indicators of local anaesthetic neurotoxicity. RESULTS: Diabetic mice had higher plasma levels of glucose (P < 0.001) and significant differences in the tail flick and plantar test thermal latencies compared to healthy controls (P < 0.001). In both diabetic and nondiabetic mice, sciatic nerve block with 0.25% bupivacaine HCl resulted in a significantly greater G-ratio and an axon diameter compared to nerves treated with 1.3% liposome bupivacaine or saline (0.9% sodium chloride) (P < 0.01). Moreover, sciatic nerve block with 0.25% bupivacaine HCl resulted in lower fibre density and higher large fibre and axon diameters compared to the control (untreated) sciatic nerves in both STZ-induced diabetic (P < 0.05) and nondiabetic mice (P < 0.01). No evidence of acute or chronic inflammation was observed in any of the treatment groups. CONCLUSIONS: In our exploratory study the sciatic nerve block with bupivacaine HCl (7 mg/kg), but not liposome bupivacaine (35 mg/kg) or saline, resulted in histomorphometric indices of neurotoxicity. Histologic findings were similar in diabetic and healthy control mice.

Extended release bupivacaine formulations for postoperative analgesia: an update.

PURPOSE OF REVIEW: New formulations of local anesthetics with sustained release and longer duration of action are being developed to improve patient outcomes following surgery. This review summarizes the efficacy and safety of the three most recently developed extended-release formulations of the local anesthetic, bupivacaine. RECENT FINDINGS: Bupivacaine liposome injectable suspension (EXPAREL) encapsulates bupivacaine in biodegradable liposomes. It is currently the only extended-release formulation of bupivacaine approved by the FDA for infiltration of the tissues during surgery and for interscalene nerve block analgesia following shoulder surgery. SABER-Bupivacaine and HTX-011, are extended-release bupivacaine products in active development. Available data suggest relative safety and efficacy of all three formulations, although more data are needed to define their indications and dosing. SUMMARY: Extended-release bupivacaine formulations are promising alternatives to prolong duration of analgesia. To date, only EXPAREL has been approved by the FDA for tissue infiltration during surgery and for interscalene nerve block.

A Prospective Randomized Study to Evaluate a New Learning Tool for Ultrasound-Guided Regional Anesthesia.

Objective: To evaluate the effectiveness of a new learning tool for needle insertion accuracy skills during a simulated ultrasound-guided regional anesthesia procedure. Methods: Thirty participants were included in this randomized controlled study. After viewing a prerecorded video of a single, discreet, ultrasound-guided regional anesthesia task, all participants performed the same task three consecutive times (pretest), and needle insertion accuracy skills in a phantom model were recorded as baseline. All participants were then randomized into two groups, experimental and control. The experimental group practiced the task using the new tool, designed with two video cameras, a monitor, and an ultrasound machine where the images from the ultrasound and video of hand movements are viewed simultaneously on the monitor. The control group practiced the task without using the new tool. After the practice session, both groups repeated the same task and were evaluated in the same manner as in the pretest. Results: Participants in both group groups had similar baseline characteristics with respect to previous experience with ultrasound-guided regional anesthesia procedures. The experimental group had significantly better needle insertion accuracy scores ( P < 0.01) than the control group. Using the new learning tool, inexperienced participants had better needle insertion accuracy scores ( P < 0.01) compared with experienced participants. Conclusions: This study demonstrates that the use of this new learning tool results in short-term improvement in hand-eye, motor, and basic needle insertion skills during a simulated ultrasound-guided regional anesthesia procedure vs traditional practice methods. Skill improvement was greater in novices compared with experienced participants.

Liposome Bupivacaine Femoral Nerve Block for Postsurgical Analgesia after Total Knee Arthroplasty.

BACKGROUND: The authors evaluated the efficacy of liposome bupivacaine in a femoral nerve block (FNB) after total knee arthroplasty. METHODS: Part 1: subjects received FNB with 20 ml liposome bupivacaine (67, 133, or 266 mg) or placebo. Part 2: subjects were randomized to FNB with liposome bupivacaine 266 mg or placebo. The primary outcome measure was area under the curve of the numeric rating scale score for pain intensity at rest through 72 h (AUC NRS-R0-72) with imputed scores after rescue medication. RESULTS: In part 1, FNB with liposome bupivacaine 266 mg (n = 24) resulted in analgesia similar to that obtained with 133 mg and was chosen for part 2. In part 2, least-squares mean (standard error) AUC NRS-R0-72 was lower with liposome bupivacaine 266 mg (n = 92) than with placebo (n = 91; 419 [17] vs. 516 [17]; P < 0.0001). This outcome remained unchanged in a post hoc analysis without score imputation (221 [12] vs. 282 [12]; P = 0.0005). Least-squares mean AUC NRS-R with imputed scores was lower with liposome bupivacaine during each 24-h interval (0 to 24, 24 to 48, and 48 to 72 h) after surgery; AUC NRS-R without imputed scores was lower during the 0- to 24-h and 24- to 48-h intervals. The liposome bupivacaine group had lower mean total opioid use (76 vs. 103 mg morphine; P = 0.0016). Pain was sufficiently severe to require second-step rescue with opioids via intravenously administered patient-controlled analgesia in 92% of liposome bupivacaine patients and 81% of placebo patients. With patient-controlled analgesia and other forms of rescue analgesia, mean NRS scores with activity were moderate in both liposome bupivacaine and placebo groups throughout the part 2 study period. Incidence of adverse events was similar between the groups (part 1: 90 vs. 96%; part 2: 96 vs. 96%, respectively). CONCLUSION: FNB with liposome bupivacaine (266 mg) resulted in modestly lower pain scores and reduced opioid requirements after surgery, with an adverse event profile similar to placebo.

Distribution of Injectate and Sensory-Motor Blockade After Adductor Canal Block.

BACKGROUND: The analgesic efficacy reported for the adductor canal block may be related to the spread of local anesthetic outside the adductor canal. METHODS: Fifteen patients undergoing knee surgery received ultrasound-guided injections of local anesthetic at the level of the adductor hiatus. Sensory-motor block and spread of contrast solution were assessed. RESULTS: Sensation was rated as "markedly diminished" or "absent" in the saphenous nerve distribution and "slightly diminished" in the sciatic nerve territory without motor deficits. Contrast solution was found in the popliteal fossa. CONCLUSIONS: The spread of injectate to the popliteal fossa may contribute to the analgesic efficacy of adductor canal block.

Interfascial Spread of Injectate After Adductor Canal Injection in Fresh Human Cadavers.

The adductor canal block has become a common analgesic technique in patients undergoing knee arthroplasty. Dispersion of local anesthetic outside the adductor canal through interfascial layers and blockade of smaller nerves that confer innervation to the knee could contribute to the analgesic efficacy of the adductor canal block. We studied the diffusion of local anesthetic mixed with dye after injection into the adductor canal in fresh human cadavers. In all 8 legs, injectate was found in the popliteal fossa in contact with the sciatic nerve and/or popliteal blood vessels. Interfascial spread patterns were identified.

The Disposition of Radiocontrast in the Interscalene Space in Healthy Volunteers.

BACKGROUND: We measured the spread of radiocontrast in the interscalene space after injection under low (<15 psi) and high (>20 psi) pressures. METHODS: Nine healthy volunteers received ultrasound-guided injections of 10 mL radio-opaque NaCl 0.9% in both interscalene spaces. Spread of injectate as assessed by computed tomography scan and discomfort on injection were recorded. RESULTS: Under both opening pressure conditions, injectate contacted 3 brachial plexus roots and spilled over the surface of the anterior and/or middle scalene muscles underneath the cervical fascia. CONCLUSIONS: Regardless of injection pressure, the interscalene space was filled with 10 mL of radiocontrast injectate.

Minimal current intensity to elicit an evoked motor response cannot discern between needle-nerve contact and intraneural needle insertion.

BACKGROUND: The ability of an evoked motor response (EMR) with nerve stimulation to detect intraneural needle placement reliably at low current intensity has recently been challenged. In this study, we hypothesized that current intensity is higher in needle-nerve contact than in intraneural needle placement. METHODS: Brachial plexus nerves were exposed surgically in 6 anesthetized pigs. An insulated needle connected to a nerve stimulator was placed either with 1 mm distance to the nerve (control position), adjacent to nerve epineurium (needle-nerve contact position), or inside the nerve (intraneural position). Three pulse duration settings were applied in random fashion (0.1, 0.3, or 1.0 milliseconds) at each needle position. Starting at 0.0 mA, electrical current was increased until a minimal threshold current resulting in a specific EMR was observed. Fifty threshold current measurements were scheduled for each needle position-pulse duration setting. RESULTS: Four hundred-fifty threshold currents in 50 peripheral nerves were measured. Threshold current intensities (mA) to elicit EMR showed small differences between the needle-nerve contact position [median (25th-75th percentiles); 0.1 milliseconds: 0.12 (0.08-0.18) mA; 0.3 milliseconds: 0.10 (0.06-0.12) mA; 1.0 milliseconds: 0.06 (0.04-0.10) mA] and the intraneural position (0.1 milliseconds: 0.12 [0.10-0.16] mA; 0.3 milliseconds: 0.08 [0.06-0.10] mA; 1.0 milliseconds: 0.06 [0.06-0.08] mA) that are neither statistically significant nor clinically relevant. Regardless of the pulse duration that was applied, the 98.33% confidence interval revealed a difference of at most 0.02 mA. However, threshold current intensities to elicit EMR were lower for the needle-nerve contact position than for the control position (0.1 milliseconds: 0.28 [0.26-0.32] mA; 0.3 milliseconds: 0.20 [0.16-0.22] mA; 1.0 milliseconds: 0.12 [0.10-0.14] mA). CONCLUSIONS: The confidence interval for differences suggests minimal current intensity to elicit a motor response that cannot reliably discern between a needle-nerve contact from intraneural needle placement. In addition, an EMR at threshold currents <0.2 mA (irrespective of the applied pulse duration) indicates intraneural needle placement or needle-nerve contact.

Intraneural and perineural inflammatory changes in piglets after injection of ultrasound gel, endotoxin, 0.9% NaCl, or needle insertion without injection.

BACKGROUND: Ultrasound gel nerve inflammation has been reported. We evaluated the extent and nature of inflammation after gel injection with endotoxin (positive), saline, or dry needle puncture (negative) controls after peripheral blocks in piglets. METHODS: Selected nerves of 12 piglets were localized by landmarks and nerve stimulator. Forty-eight hours after injection, specimens were examined for immunohistochemical cell differentiation/quantification and cytokine expression by using quantitative polymerase chain reaction. RESULTS: Both gel and endotoxin injections resulted in a significantly higher density of inflammatory cells (lymphocytes/granulocytes) as compared with needle insertions and/or saline injections (both P < 0.001). Cytokines were not detected in any of the specimens. CONCLUSIONS: Perineural gel injections cause significant inflammation. The lack of cytokines suggests injectate-related changes rather than mechanical trauma.

Pericapsular nerve group block: a 3D CT scan imaging study to determine the spread of injectate.

BACKGROUND: Current understanding of the mechanism of action of the pericapsular nerve group (PENG) block is primarily based on cadaver studies. We performed an imaging study in patients undergoing hip surgery to enhance the understanding of the analgesic mechanisms following a PENG block. MATERIALS AND METHODS: 10 patients scheduled for hip surgery received an ultrasound-guided PENG block with 18 mL of 0.5% ropivacaine mixed with 2 mL of a contrast agent. After completion of the block, a high-resolution CT scan was performed to obtain a three-dimensional reconstruction of the injectate's dispersion. RESULTS: The CT imaging revealed that injectate was mainly confined to the epimysium of the iliacus and the psoas muscle, with a minor spread to the hip capsule. Contrast dye was detected within the iliacus and/or the psoas muscle in all patients. No observed spread to either the subpectineal plane or the obturator foramen was detected. CONCLUSION: Our study suggests that the analgesic effect of the PENG block may be related to the block of the branches of the femoral nerve traveling within the iliopsoas muscle without a spread pattern commensurate with the block of the obturator nerve. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov Registry (NCT06062134).

Effective volume of ropivacaine 0.75% through a catheter required for interscalene brachial plexus blockade.

BACKGROUND: Ultrasound guidance during peripheral nerve blocks has allowed for reduction in dose and volume of local anesthetic required to accomplish successful blockade using multiple injections through a needle. The authors undertook this study to determine the minimal effective volume required to accomplish successful interscalene brachial plexus block (ISB) through the catheter. METHODS: After obtaining institutional ethics committee approval and written informed consent, patients aged 18-75 yr and scheduled for arthroscopic shoulder surgery under ISB were enrolled. All patients using a step-up/step-down method and the starting dose of 15 ml of 0.75% ropivacaine received an ultrasound-guided ISB catheter. The injection volume was increased or decreased by 1 ml in case of block failure or block success, respectively. RESULTS: The authors found that the proportion of patients with successful blockade increased sharply from approximately 57% at 6 ml to 100% by 7 ml, indicating that a small increase in volume of ropivacaine 0.75% markedly affects the success rate. A total of 12 ISB with injection volume less than 7 ml resulted in successful anesthesia within 30 min, yielding an ED95 of 7 ml (95% CI 6.8-7.2) ropivacaine 0.75%. For the group as a whole, the median (min-max) sensory block onset time was 5 (5-20) min, the median (min-max) motor blocks for the biceps and the deltoid muscles were 7.5 (5-15) min and 10 (5-15) min, respectively. The median (min-max) block duration was 8.9 (3-15) h. CONCLUSIONS: An injection of a minimum of 7 ml of ropivacaine 0.75% through the catheter is required for success rate and timely onset of surgical anesthesia with ISB.

Case report: ultrasound-guided continuous thoracic paravertebral block for outpatient acute pain management of multilevel unilateral rib fractures.

A 61-year-old man with multiple unilateral rib fractures (T3-T8) gained the ability to breathe deeply and to ambulate after ultrasound-guided continuous thoracic paravertebral block and was discharged home after being observed for 15 hours after the block. The ultrasound guidance was helpful in determining the site of rib fractures and the optimal level for catheter placement. This report also discusses the management of analgesia using continuous paravertebral block in an outpatient with trauma.

Continuous interscalene block in patients having outpatient rotator cuff repair surgery: a prospective randomized trial.

BACKGROUND: We performed this randomized trial to compare the recovery profile of patients receiving single injection (SISB) and continuous interscalene brachial plexus block (CISB) or general anesthesia (GA) for arthroscopic rotator cuff repair surgery through the first postoperative week. Our primary hypothesis was that the highest pain numeric rating scale (NRS) (worst pain score) at the end of the study week would be lower for patients in the CISB group than for patients in the SISB or GA groups. METHODS: Seventy-one patients scheduled for elective outpatient arthroscopic rotator cuff repair were enrolled. CISB patients received 20 mL of 0.5% ropivacaine as a bolus through a catheter, whereas SISB patients received the same injection volume through a needle. CISB patients received an infusion of 0.2% ropivacaine at 5 mL/h with a patient-controlled bolus of 5 mL hourly for 48 hours. GA-only patients received a standardized general anesthetic. Postoperative highest NRS pain scores through the first postoperative week, time-to-first pain, analgesic consumption, fast-tracked postoperative anesthesia care unit (PACU) bypass rate, length of PACU stay, time-to-discharge home, total hours of sleep, and related adverse effects were recorded in the PACU and at home on postoperative days 1, 2, 3, and 7. RESULTS: No patient in the CISB or SISB groups reported a NRS ≥1 or required analgesics while in the PACU. While most patients in the CISB and SISB groups were fast-tracked to PACU discharge, no patient in the GA group was fast-tracked (Χ P = 0.003). Length of stay in the PACU was significantly shorter for the CISB and SISB groups than for the GA group (20 ± 31, 30 ± 42, and 165 ± 118 minutes, respectively (CISB vs GA, P < 0.001; SISB vs GA, P <0.001), and time-to-discharge home was significantly shorter when compared with the GA group. Time to first pain report was longer in the CISB group. Mean NRS scores were lower for patients in the CISB group than in the SISB and GA groups on postoperative days 1 and 2, and use of narcotics (doses ≥1) was lower until postoperative day 3. Patients who received CISB slept significantly longer than patients who received SISB or GA (P < 0.01) during the first 48 hours postoperatively. By the end of the study week, 26% of patients in the CISB group, 83% in the SISB group, and 58% of GA patients reported NRS ≥4 (both P-values ≤ 0.05). CONCLUSION: The analgesic benefits of CISB found in the PACU and immediately after discharge extend through the intermediate recovery period ending on postoperative day 7.

Peripheral nerve blocks for outpatient surgery: evidence-based indications.

PURPOSE OF REVIEW: There has been an increasing use of peripheral nerve blocks (PNBs) in ambulatory surgery. Several recent reports have contributed to our understanding of the optimal PNB technique for specific surgical procedures in this setting. In this review, we have summarized the available literature on indications of PNBs for outpatient surgery of the upper extremity. RECENT FINDINGS: Although many of the recent studies focus on technical aspects of PNBs, few center on evidence-based indications or their utility in the ambulatory setting. The available literature suggests that although multiple techniques have been reported for outpatient shoulder surgery, interscalene brachial plexus block (ISBPB) is currently the most preferred technique. Supraclavicular, infraclavicular, and axillary brachial plexus blocks, however, are all commonly used and effective PNBs for outpatient surgery and analgesia of the arm, forearm, and hand. SUMMARY: ISBPB is currently the most beneficial PNB for outpatient shoulder surgery. Supraclavicular block functionally can be considered an alternative to the traditional ISBPB; however, additional studies are required before routine use can be recommended. Although the review identified several reports with benefits of one PNB technique over the others, the existing literature suggests that many of these techniques may be interchangeable with regards to procedures of the distal upper extremity. Future studies are indicated to help standardize the techniques, selection, and postoperative management of PNBs for specific surgical indications.

The effect of spinal versus general anaesthesia on perioperative muscle weakness in patients having bilateral total hip arthroplasty: a single center randomized clinical trial.

BACKGROUND: Perioperative neuro-endocrine stress response may contribute to acquired muscle weakness. Regional anaesthesia has been reported to improve the outcome of patients having total hip arthroplasty. In this study, it was hypothesized that spinal anaesthesia (SA) decreases the perioperative neuro-endocrine stress response and perioperatively acquired muscle weakness (PAMW), as compared to general anaesthesia (GA). METHODS: Fifty subjects undergoing bilateral total hip arthroplasty (THA) were randomly allocated to receive a standardized SA (n = 25) or GA (n = 25). Handgrip strength was assessed preoperatively, on the first postoperative day (primary endpoint) and on day 7 and 28. Respiratory muscle strength was measured by maximal inspiratory pressure (MIP). Stress response was assessed by measuring levels of Adrenocorticotropic hormone (ACTH), cortisol and interleukin-6 (IL-6). RESULTS: Handgrip strength postoperatively (day 1) decreased by 5.4 ± 15.9% in the SA group, versus 15.2 ± 11.7% in the GA group (p = 0.02). The handgrip strength returned to baseline at day 7 and did not differ between groups at day 28. MIP increased postoperatively in patients randomized to SA by 11.7 ± 48.3%, whereas it decreased in GA by 12.2 ± 19.9% (p = 0.04). On day 7, MIP increased in both groups, but more in the SA (49.0 ± 47.8%) than in the GA group (14.2 ± 32.1%) (p = 0.006). Postoperatively, the levels of ACTH, cortisol and IL-6 increased in the GA, but not in the SA group (p < 0.004). CONCLUSION: In patients having bilateral THA, SA preserved the postoperative respiratory and peripheral muscle strength and attenuated the neuro-endocrine and inflammatory responses. TRIAL REGISTRATION: clinicaltrials.gov NCT03600454.

A novel infrapatellar approach of ultrasound-guided intra-articular injection of the knee from both lateral and medial side: a case series.

Knee osteoarthritis (OA) is common. Ultrasound-guided intra-articular injection (UGIAI) using the superolateral approach is currently the gold standard for treating knee OA, but it is not 100% accurate, especially in patients with no knee effusion. Herein, we present a case series of chronic knee OA treated with a novel infrapatellar approach to UGIAI. Five patients with chronic grade 2-3 knee OA, who had failed on conservative treatments and had no effusion but presented with osteochondral lesions over the femoral condyle, were treated with UGIAI with different injectates using the novel infrapatellar approach. The first patient was initially treated using the traditional superolateral approach, but the injectate was not delivered intra-articularly and became trapped in the pre-femoral fat pad. The trapped injectate was aspirated in the same session due to interference with knee extension, and the injection was repeated using the novel infrapatellar approach. All patients who received the UGIAI using the infrapatellar approach had the injectates successfully delivered intra-articularly, as confirmed with dynamic ultrasound scanning. Their Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain, stiffness, and function scores significantly improved 1 and 4 weeks post-injection. UGIAI of the knee using a novel infrapatellar approach is readily learned and may improve accuracy of UGIAI, even for patients with no effusion.

The effects of intrathecal morphine on urinary bladder function and recovery in patients having a cesarean delivery - A randomized clinical trial.

INTRODUCTION: Spinal anesthesia with intrathecal morphine (ITM) is a common anesthesia technique for cesarean delivery. The hypothesis was that the addition of ITM will delay micturition in women undergoing cesarean delivery. METHODS: Fifty-six ASA physical status I and II women scheduled to undergo elective cesarean delivery under spinal anesthesia were randomized to the PSM group (50 mg prilocaine + 2.5 mcg sufentanil + 100 mcg morphine; n = 30) or PS group (50 mg prilocaine + 2.5 mcg sufentanil; n = 24). The patients in the PS group received a bilateral transverse abdominal plane (TAP) block. The primary outcome was the effect of ITM on the time to micturition and the secondary outcome was the need for bladder re-catheterization. RESULTS: The time to first urge to urinate (8 [6-10] hours in the PSM group versus 6 [4-6] hours in the PS group) and the time to first micturition (10 [8-12] hours in the PSM group versus 6 [6-8] hours in the PS group) were significantly (p < 0.001) prolonged in the PSM group. Two patients in the PSM group met the 800 mL criterium for urinary catheterization after 6 and 8 h respectively. CONCLUSION: This study is the first randomized trial to demonstrate that the addition of ITM to the standardized mixture of prilocaine and sufentanil significantly delayed micturition.

The presence of transverse cervical and dorsal scapular arteries at three ultrasound probe positions commonly used in supraclavicular brachial plexus blockade.

BACKGROUND: Ultrasound-guided supraclavicular brachial plexus block carries a risk for puncture of vascular structures. In this study, we determined the frequency with which the transverse cervical artery (TCA) and the dorsal scapular artery (DSA) are detected by ultrasound evaluation at 3 probe positions during supraclavicular block. METHODS: Ultrasound examinations of the supraclavicular region were performed in 53 healthy adult volunteers. Ultrasound images of the supraclavicular region were acquired at 3 probe positions: position A (the brachial plexus and the subclavian artery both lying on the first rib); position B (the brachial plexus on the first rib; the artery on the pleura); and position C (the brachial plexus between the anterior and middle scalene muscles). The primary outcome variables were the frequencies with which TCA and DSA were detected by 2-dimensional and color Doppler imaging at 3 specified probe positions. RESULTS: One hundred six supraclavicular regions were examined in 53 subjects. The subclavian artery was detected in all subjects. TCA was more often detected than DSA, 94 (88.7%, 95% confidence interval [CI] 80.7%-93.8%) and 36 (34%, 95% CI 25.3%-43.9%) of 106 scans, respectively (McNemar P value <0.001). TCA was detected in 2 (1.9%, 95% CI 0.3%-7.3%), 31 (29.2%, 95% CI 20.9%-38.9%), and 61 (57.5%, 95% CI 47.5%-66.9%) of scans at probe positions A, B, and C, respectively, whereas DSA was detected in 3 (2.8%, 95% CI 0.7%-8.6%), 23 (21.7%, 95% CI 14.5%-30.9%), and 10 (9.4%, 95% CI 4.8%-17.0%) of scans at probe positions A, B, and C, respectively. Thus, the TCA and DSA were less likely to be present with probe position A (all P < 0.001). CONCLUSION: TCA was more often detected than DSA in the vicinity of the brachial plexus in the supraclavicular region. Both TCA and DSA were least likely to be present in probe position A. Color Doppler, particularly for probe position A, may help to reduce the risk for inadvertent vascular puncture during ultrasound-guided supraclavicular block.