http://www.nysora.com/files/suggest-articles-pdfs/LAST-and-US-Barrington-RAPM.pdf

Ultrasound Guidance Reduces the Risk of Local Anesthetic Systemic Toxicity Following Peripheral Nerve Blockade

https://rapm.bmj.com/content/rapm/34/2/134-170.full.pdf

Lower extremity regional anesthesia: essentials of our current understanding.

https://rapm.bmj.com/content/rapm/35/Suppl_1/S1.full.pdf

The ASRA evidence-based medicine assessment of ultrasound-guided regional anesthesia and pain medicine: Executive summary.

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.

An estimation of the minimum effective anesthetic volume of 2% lidocaine in ultrasound-guided axillary brachial plexus block.

Background: Use of ultrasound by anaesthesiologists performing regional blocks is rapidly gaining popularity. The aims of this review were to summarize and update accumulating evidence on ultrasound-guided nerve blocks, with an emphasis on the clinical relevance of the results and to critically appraise changing standards in regional anaesthesia.



Methods: A search of MEDLINE and EMBASE (1966 to 31 December 2007) was conducted using the following free terms: ‘ultrasound and regional anesthesia’, ‘ultrasound and peripheral block’ and ‘ultrasound and nerve and block’. These were combined with the MESH terms ‘nerve block’ and ‘ultrasonography’. The following limits were applied: studies with abstracts, only in humans, published in core clinical journals. Trial type: meta-analysis, randomized-controlled trial and clinical trial.



Results: When peripheral nerves are adequately imaged by ultrasound, the concomitant use of nerve stimulation offers no further advantage. However, several studies reported problems with obtaining satisfactory images in some patients. Ultrasound guidance significantly shortened the block performance time and/or reduced the number of needle passes to reach the target in all comparative studies. The occurrence of paraesthesia during block performance was also reduced, but not the incidence of short-lasting post-operative neuropraxia. The frequency of accidental vascular punctures may be lower, but the data are contradictory. Block onset time was significantly shortened. Block duration was longer in children, but not in adults. Ultrasound also allowed dose reduction of the local anaesthetic (LA).



Conclusions: Ultrasound guidance shortens the block performance time, reduces the number of needle passes and shortens the block onset time. Blocks may be performed using lower LA doses.

Ultrasound-guided peripheral nerve blocks : What are the benefits?

Background We tested the hypothesis that ultrasound guidance may reduce the minimum effective anaesthetic volume (MEAV50) of ropivacaine 0.5% required to block the femoral nerve compared with nerve stimulation guidance. Methods After standard premedication and sciatic nerve block were given, 60 patients undergoing knee arthroscopy were randomly allocated to receive a femoral nerve block with ropivacaine 0.5% using either nerve stimulation (group NS, n = 30) or ultrasound (group US, n = 30) guidance. The volume of the injected solution was varied for consecutive patients based on an up-and-down staircase method according to the response of the previous patient. The initial volume was 12 ml. A double-blinded observer evaluated the occurrence of complete loss of pinprick sensation in the femoral nerve distribution, with concomitant block of the quadriceps muscle: positive or negative responses within 30 min after the injection determined a 3 ml decrease or increase for the next patient, respectively. Results The mean ( sd ) MEAV50 for femoral nerve block was 15 (4) ml (95% CI, 7–23 ml) in group US and 26 (4) ml (95% CI, 19–33 ml) in group NS (P = 0.002). The effective dose in 95% of cases (ED95) calculated with probit transformation and logistic regression analysis was 22 ml (95% CI, 13–36 ml) in group US, and 41 ml (95% CI, fs 24–66 ml) in group NS. Conclusions Ultrasound guidance provided a 42% reduction in the MEAV of ropivacaine 0.5% required to block the femoral nerve as compared with the nerve stimulation guidance.

Effects of ultrasound guidance on the minimum effective anaesthetic volume required to block the femoral nerve

Purpose: The aim of this prospective, randomised, blind study was to compare the evolution of spinal block produced with 50 mg lidocaine 10 mg/ml and 10 mg ropivacaine 5 mg/ml for outpatient knee arthroscopy.



Methods: Thirty outpatients undergoing knee arthroscopy received 50 mg of lidocaine 10 mg/ml (n=15) or 10 mg of ropivacaine 5 mg/ml (n=15) intrathecally. The evolution of spinal block was recorded until home discharge, while the occurrence of transient neurologic symptoms (TNS) was evaluated through phone-call follow-ups.



Results: The median onset time was 15 (10–21) min with lidocaine and 24 (11–37) min with ropivacaine (P=0.109). Spinal lidocaine resulted in a faster resolution of sensory block [148 (130–167) min vs. 188 (146–231) (P=0.022)], unassisted ambulation with crutches [176 (144–208) min vs. 240 (179–302) min (P=0.014)], and voiding [208 (163–254) min vs. 293 (242–343) min (P=0.001)] than ropivacaine. Recovery of motor function required 113 (95–131) min with lidocaine and 135 (87–183) with ropivacaine (P=0.219). Six lidocaine patients reported TNS (40%) as compared with no patient receiving ropivacaine (0%) (P=0.005).



Conclusions: Spinal block produced with 10 mg ropivacaine 5 mg/ml is as effective as that produced by 50 mg of lidocaine 10 mg/ml. Recovery of unassisted ambulation and spontaneous voiding occurred earlier with lidocaine, but this was associated with a markedly higher incidence of TNS.

S. Leone

Papers

Effects of ultrasound guidance on the minimum effective anaesthetic volume required to block the femoral nerve

Intrathecal ropivacaine 5 mg/ml for outpatient knee arthroscopy : a comparison with lidocaine 10 mg/ml

Ultrasound guidance for axillary block: a prospective, randomized, observer-blinded comparison with nerve stimulation: 8AP2-2