Effective local anaesthetic volumes for sciatic nerve blockade: a clinical evaluation of the ED99

Ultrasound-Guided Lumbar Plexus-Sciatic Nerve Blocks Versus Epidurals for Orthopaedic Surgeries: A Study to Compare the Competency of Novice Anaesthesiology Residents in a High-Volume Level 1 Trauma Centre

INTRODUCTION

The relative merits of peripheral nerve blocks (PNB) over central neuraxial anaesthesia and the advantages of the above two techniques over general anaesthesia for surgical interventions of the lower limb are well established. The competency of anaesthetic trainees in a high-volume level 1 trauma centre in administering dual ultrasound and nerve stimulator-guided lumbar plexus-sciatic nerve block (DUNLuPS) vs. epidural anaesthesia (EA) was compared by reporting the adequacy of anaesthesia with the two techniques, time taken for the performance of block, time of onset of sensory block (TOSB), and time of onset of motor block (TOMB).

MATERIALS AND METHODS

This prospective, randomized, study enrolled 92 patients aged 18-80 years with lower limb fractures admitted in trauma triage and scheduled for surgery. The patients were randomly allocated equally into the EA group and the DUNLuPS group. A total of 20 anaesthesia trainees in the third year of residency with clinical experience of more than 15 independent lumbar plexus-sciatic nerve blocks were included in the study. A volume of 20 ml of 0.5% ropivacaine was administered in the lumbar plexus (Shamrock technique) but the volume used for sciatic nerve (subgluteal approach) was varied so that the cumulative dose did not exceed 3 mg/kg. For each block, the onset of nerve blockade was assessed every five minutes, and the assessments continued for an additional 30 minutes after the nerve blocks were finished.

RESULTS

Clinical characteristics and adequacy of anaesthesia were comparable, i.e., 95.65% and 93.47% success in the EA (n = 46) and DUNLuPS (n = 46) groups, respectively. Performance time was significantly more in the DUNLuPS group but followed by significantly less TOSB and TOMB. The time for the first analgesic request was 351.63 ± 148.70 minutes in the DUNLuPS group and 147.60 ± 52.65 minutes in the EA group (p < 0.0001).

CONCLUSION

Both EA and DUNLuPS provide effective and comparable intra-operative anaesthesia for orthopaedic lower limb surgeries (OLLS) when administered by residents with more than two years of experience (third year of residency) in ultrasound-guided regional nerve blocks in a high-volume level 1 trauma centre. Statistically significant differences in the block performance characteristics had no clinical advantage as it was compensated by the faster onset time in the DUNLuPS group. Post-operative pain management was better in the DUNLuPS group, so the practice and conduct of anaesthesia for trauma patients should focus on the establishment of "block rooms" and timely training of residents in the former so that the advantages can be extended to the patient population.

Interventional Radiology Regional Anesthesia Approaches for Intra- and Postprocedural Pain Control

Effective pain control enables procedural success and improved patient satisfaction in interventional radiology. Regional anesthesia techniques are now established for intraoperative and postoperative anesthesia during major surgery, and interventional radiologists (IRs) can readily apply these injections for intraprocedural nerve blocks that can reduce anesthetic requirements and ensure durable analgesia postprocedure. Moreover, IR is poised to advance this field with novel blocks unique to IR needs and by blocking deep plexi safely reachable with CT guidance (e.g., hepatic hilar plexus, aorticorenal plexus blocks). This report aims to provide a succinct IR-directed primer for image-guided nerve blocks usable in the interventional radiology suite.

Factors Associated With Minimum Effective Volume of Lidocaine 1.5% for Sciatic Nerve Blocks

OBJECTIVES

The objectives of this study were to investigate the correlations between the minimum effective volume (MEV) of lidocaine 1.5% for an ultrasound-guided popliteal sciatic nerve block and individual factors including the cross-sectional nerve area, sex, age, body mass index, and the depth of the sciatic nerve and to evaluate the safety of combined femoral and sciatic nerve blocks by monitoring the plasma concentration of local anesthetics.

METHODS

Forty patients received combined single-shot femoral and continuous sciatic nerve blocks. The femoral nerve block was performed with an in-plane technique and 15 mL of lidocaine 1.5%. A continuous peripheral nerve block annular tube was positioned between the tibial and peroneal nerves inside the paraneural sheath. Thirty minutes after the femoral nerve block, a loading dose of 5 mL of lidocaine 1.5% was given to block the sciatic nerve after obtaining the maximum compound muscle action potential (CMAP) amplitude using nerve conduction studies. Additional lidocaine 1.5% was pumped at a rate of 30 mL/h through the indwelling annular tube if, after 8 minutes, the CMAP amplitude was still present. The CMAP amplitude monitored by the nerve conduction studies and pinprick tests were recorded every 2 minutes after the administration of lidocaine 1.5%. When the CMAP amplitude decreased to nearly 0 mV, this MEV was recorded. The influences of the cross-sectional area of the sciatic nerve, sex, age, body mass index, and the depth of the sciatic nerve on the MEV were analyzed using stepwise multiple linear regression. Blood samples were collected from 10 patients to evaluate the safety of combined femoral and sciatic nerve blocks by ultra-performance liquid chromatography-tandem mass spectrometry. Blood was drawn at 0 minutes before femoral nerve injection; 0 minutes before sciatic nerve injection; 8 minutes after sciatic nerve injection; and 0, 10, 20, 30, 45, 60, 75, 90, and 120 minutes after the pumping of lidocaine 1.5% stopped.

RESULTS

A significant correlation was found between the MEV of lidocaine 1.5% and the cross-sectional area of the sciatic nerve (r=0.459), with a regression equation of the MEV (mL)=5.969+0.095×(the cross-sectional area of the sciatic nerve). The coefficient of determination was 0.211 (P<0.05). The MEV of lidocaine 1.5% for complete sciatic nerve blocks ranged from 7 to 15 mL. The maximum concentrations of lidocaine, monoethylglycinexylidide, and glycinexylidide were 1672.9 (227.6), 265.7 (32.7), and 42.2 (22.4) ng/mL, respectively.

CONCLUSIONS

There is a positive correlation between the cross-sectional area of the sciatic nerve and the MEV. The regression equation can help to predict the MEV of lidocaine 1.5% for popliteal sciatic nerve blocks. The maximum concentrations of lidocaine and its metabolites did not approach toxic threshold limits in this study.

Lower extremity regional anesthesia: essentials of our current understanding

The advent of ultrasound guidance has led to a renewed interest in regional anesthesia of the lower limb. In keeping with the American Society of Regional Anesthesia and Pain Medicine's ongoing commitment to provide intensive evidence-based education, this article presents a complete update of the 2005 comprehensive review on lower extremity peripheral nerve blocks. The current review article strives to (1) summarize the pertinent anatomy of the lumbar and sacral plexuses, (2) discuss the optimal approaches and techniques for lower limb regional anesthesia, (3) present evidence to guide the selection of pharmacological agents and adjuvants, (4) describe potential complications associated with lower extremity nerve blocks, and (5) identify informational gaps pertaining to outcomes, which warrant further investigation.

Monitoring regional blockade

This review attempts to draw on the published literature to address three practical clinical questions. First, what means of testing the degree of regional blockade pre-operatively are available, and can eventual success or failure be determined soon after injection? Second, is it possible to predict if a block inserted after the induction of general anaesthesia will be effective when the patient wakes? Third, what features, and what duration, should cause concern when a block does not resolve as expected after surgery? Although the relevant literature is limited, we recommend testing of multiple sensory modalities before surgery commences; temperature and thermographic changes may offer additional early warning of success or failure. There are a number of existing methods of assessing nociception under general anaesthesia, but none has yet been applied to gauge the onset of a regional block. Finally, criteria for further investigation and neurological referral when block symptoms persist postoperatively are presented.

Ultrasound-Guided Subgluteal Sciatic Nerve Perineural Injection: Report on Safety and Efficacy at a Single Institution

OBJECTIVES

To determine the safety and efficacy of ultrasound (US)-guided subgluteal sciatic nerve injections.

METHODS

A retrospective chart review of US-guided subgluteal sciatic nerve injections at our institution was performed.

RESULTS

Of 221 US-guided subgluteal sciatic nerve injections, 100% achieved technical success, with no postprocedure complications. Sixty-eight percent of patients with follow-up reported symptom relief. Most patients with no relief had suboptimal preprocedure screening.

CONCLUSIONS

With appropriate screening, our technique of US-guided subgluteal sciatic nerve injection is safe and effective.

Ultrasound-Guided Popliteal Sciatic Block Provides Adequate Analgesia During Urgent Endovascular Treatment of Critical Limb Ischemia with Resting Pain

PURPOSE

To demonstrate feasibility and safety of ultrasound-guided popliteal sciatic nerve block for providing analgesia during urgent endovascular treatment of critical limb ischemia with resting pain.

MATERIALS AND METHODS

Ultrasound-guided popliteal sciatic blocks were performed by an interventional radiologist in angiography suite immediately prior to commencement of urgent endovascular treatment of 30 critical limb ischemia patients. Subjective pain levels prior to and following sciatic block were assessed using the visual analog scale (VAS). Need for any supplemental anxiolytics or analgesics during treatment was recorded. Post-procedural evaluation of patient and operator satisfaction levels regarding the intervention was also documented.

RESULTS

Ultrasound-guided sciatic block provided adequate analgesia in all patients; VAS scores were 0 (no pain) in 87% and 1-3 (mild to annoying pain) in 13%. Two patients required anxiolytic premedication. Additional analgesia was not required during course of endovascular treatment of any patients. Time necessary to perform sciatic block ranged 3-9 (mean 5.9 ± 1.3) min. Median number of needle attempts was 1 (range 1-3). Onset of satisfactory block ranged from 5 to 20 min (mean 9.4 ± 2.6 min). Mean treatment time was 102.2 ± 36.7 min, and balloon time was 22.4 ± 6.1 min. Patient and operator satisfaction with pain control were very good in all cases. There were no procedure-related complications.

CONCLUSIONS

Ultrasound-guided popliteal sciatic block is a feasible and safe alternative for providing adequate analgesia during urgent endovascular treatment of critical limb ischemia with resting pain.

LEVEL OF EVIDENCE

Level 4, case series.

Minimum effective local anesthetic volume for surgical anesthesia by subparaneural, ultrasound-guided popliteal sciatic nerve block: A prospective dose-finding study

Because of its rapid onset time, recent years have seen an increase in the use of ultrasound (US)-guided popliteal sciatic nerve block (PSNB) via subparaneural injection for induction of surgical anesthesia. Moreover, in below-knee surgery, combined blocks, as opposed to sciatic nerve block alone, have become more common. These combined blocks often require a large volume of local anesthetic (LA), thus increasing the risk of local-anesthetic systemic toxicity (LAST). Thus, to decrease the risk of LAST, it is important to know the minimum effective volume (MEV) required for an adequate block. We, therefore, aimed to determine the MEV of ropivacaine 0.75% for induction of surgical anesthesia by the method of US-guided popliteal sciatic nerve block via subparaneural injection.Thirty patients underwent a US-guided PSNB with ropivacaine 0.75% at a 20-mL starting volume. Using a step-up/step-down method, we determined injection volumes for consecutive patients from the preceding patient's outcome. When an effective block was achieved within 40 minutes after injection, the next patient's volume was decreased by 2 mL. If the block failed, the next patient's volume was increased by 2 mL. The sensory and motor blockade was graded according to a 4-point scale. The block was considered a success if a combination of anesthesia and paresis (a score of 3 for both the sensory and motor nerves) was achieved within 40 minutes. The primary outcome measure was the MEV resulting in a successful subparaneural block of the sciatic nerve in 50% of patients (MEV50). Additionally, the data were processed with a probit regression analysis to determine the volume required to produce a complete sciatic nerve block in 90% of subjects (ED90).The MEV50 of 0.75% ropivacaine is 6.14 mL (95% confidence interval, 4.33-7.94 mL). The ED90 by probit analysis for a subparaneural injection was 8.9 mL (95% CI, 7.09-21.75 mL).The 6.14-mL MEV50 of ropivacaine 0.75% represents a 71% reduction in volume compared with neurostimulation techniques and a 14.7% reduction in volume compared with US-guided PSNB using the alternative perineural injection technique.