Effect of local anesthetic concentration, dose and volume on the duration of single-injection ultrasound-guided axillary brachial plexus block with mepivacaine: a randomized controlled trial.

BACKGROUND: In what way volume, concentration and dose affect block duration is controversial. The purpose of the present study is to investigate the effect of dose, volume and concentration of mepivacaine on the duration of sensory and motor blockade in ultrasound-guided single shot axillary brachial plexus blockade. METHODS: In this parallel group randomized trial conducted in the Sint Maartenskliniek Nijmegen, 45 adult patients undergoing minor orthopaedic forearm, wrist or hand surgery were randomized to 3 groups. Group A: 20 mL mepivacaine 1.5 %, Group B: 30 mL mepivacaine 1 % and Group C: 30 mL mepivacaine 1.5 %. Randomization was computer-generated, with allocation concealment by opaque sequentially numbered sealed envelopes. Patients and observers were blinded to group allocation. PRIMARY OUTCOME MEASURE: duration of sensory block. RESULTS: Forty-five patients were randomized, four patients were excluded and replaced, and 15 patients in each group were included in the analysis. Mean (95 % CI) sensory and motor block duration was 256 (230-282) and 254 (226-282) minutes in Group A, 226 (209-243) and 220 (200-240) minutes in Group B and 270 (249-291) and 264 (244-284) minutes in Group C. Duration of sensory and motor block duration differed significantly between groups (p = 0.012 and p = 0.016 respectively). Post-hoc analysis showed a significantly reduced sensory and motor block duration in Group B when compared to Group C of 44 min. No local anesthetic systemic toxicity was reported. CONCLUSIONS: When using mepivacaine for axillary brachial plexus block, a higher dose and concentration was associated with a longer duration of sensory and motor blockade, but not a higher volume. TRIAL REGISTRATION: The Netherlands National Trial Register NTR3648 . Registered October 3, 2012.

The effects of adding epinephrine to ropivacaine for popliteal nerve block on the duration of postoperative analgesia: a randomized controlled trial.

BACKGROUND: Duration of peripheral nerve blocks depends on multiple factors. Both technique and type of local anesthetic used, either with or without adjuncts, may result in different duration times of the block. The purpose of the present study was to compare the duration of postoperative analgesia of 30 mL ropivacaine 0.75 % with or without epinephrine for popliteal sciatic nerve block. METHODS: Thirty-eight patients were included to receive ultrasound guided continuous popliteal nerve block with ropivacaine 0.75 % either without (ROPI) or with epinephrine 5 µg/mL (ROPI-EPI) for ankle fusion, subtalar fusion, or a combination of both. The primary outcome parameter was the duration of postoperative analgesia as reflected by the time to first request for postoperative analgesia (TTFR) through the popliteal nerve catheter. Secondary outcome measures included the onset of sensory and motor block and NRS score for pain at rest and during movement. RESULTS: Thirty patients, 15 in each group, were studied. Eight patients were withdrawn because of specific withdrawal criteria described in the protocol and replaced according to their group allocation. Median [interquartile range] TTFR was 463 [300-1197] min and 830 [397-1128] min for the ROPI vs ROPI-EPI group respectively. Hodges Lehman median difference between groups was 71 min (95 % CI -415 - 473 min). There was no difference in any clinical outcome measure between the groups. CONCLUSION: The results of this study did not show any significant increase in the duration of postoperative analgesia by adding epinephrine to ropivacaine for popliteal nerve block. This may be due to the intrinsic vasoconstrictive properties of ropivacaine. The absence of a significant difference can also be the result of a type II error caused by a large variation in the individual TTFR. TRIAL REGISTRATION: Trial register.nl identifier: NTR3330 , keyword TTFR.

Pharmacokinetics of 450 mg ropivacaine with and without epinephrine for combined femoral and sciatic nerve block in lower extremity surgery. A pilot study.

AIMS: No pharmacokinetic data exist on doses of ropivacaine larger than 300 mg for peripheral nerve block in man, although in clinical practice higher doses are frequently used. The purpose of the present study was to describe the pharmacokinetic profile in serum of 450 mg ropivacaine with and without epinephrine in patients undergoing anterior cruciate ligament reconstruction. METHODS: Twelve patients were randomly allocated to receive a single shot combined sciatic/femoral nerve block with 60 ml of either ropivacaine 0.75% alone (group R, n = 6) or ropivacaine 0.75% plus epinephrine 5 µg ml(-1) (group RE, n = 6). Venous blood samples for total and free ropivacaine serum concentrations were obtained during 48 h following block placement. Pharmacokinetic parameters were calculated using a non-compartmental approach. RESULTS: Results are given as mean (SD) for group R vs. group RE (95% CI of the difference). Total Cmax was 2.81 (0.94) µg ml(-1) vs. 2.16 (0.21) µg ml(-1) (95% CI -0.23, 1.53). tmax was 1.17 (0.30) h vs. 1.67 (0.94) h (95% CI -1.40, 0.40). The highest free ropivacaine concentration per patient was 0.16 (0.08) µg ml(-1) vs. 0.12 (0.04) µg ml(-1) (95% CI -0.04, 0.12). t(1/2) was 6.82 (2.26) h vs. 5.48 (1.69) h (95% CI -1.23, 3.91). AUC was 28.35 (5.92) µg ml(-1) h vs. 29.12 (7.34) µg ml(-1) h (95% CI -9.35, 7.81). CONCLUSIONS: Free serum concentrations of ropivacaine with and without epinephrine remained well below the assumed threshold of 0.56 µg ml(-1) for systemic toxicity. Changes in pharmacokinetics with epinephrine co-administration did not reach statistical significance.

Effect of local anesthetic volume (15 vs 40 mL) on the duration of ultrasound-guided single shot axillary brachial plexus block: a prospective randomized, observer-blinded trial.

BACKGROUND AND OBJECTIVES: One of the advantages of ultrasound-guided peripheral nerve block is that visualization of local anesthetic spread allows for a reduction in dose. However, little is known about the effect of dose reduction on sensory and motor block duration. The purpose of the present study was to compare the duration of sensory and motor axillary brachial plexus block (ABPB) with 15 or 40 mL mepivacaine 1.5%. METHODS: Thirty patients were randomly allocated to receive ultrasound-guided ABPB with either 15 (group 15 mL, n = 15) or 40 mL (group 40 mL, n = 15) mepivacaine 1.5%. Onset, efficacy, and duration of sensory and motor block were compared. RESULTS: Two patients in group 15 mL needed an additional rescue block before surgery and were excluded from subsequent analysis. The overall median duration of sensory and motor block was significantly shorter in group 15 mL (225 [148-265] mins vs 271 [210-401] mins and 217 [144-250] mins vs 269 [210-401] mins, respectively; P < 0.01). Duration of sensory and motor block of individual nerves was significantly shorter in group 15 mL (20%-40% reduction for sensory and 18%-37% for motor block). Time to first request of postoperative analgesia was also significantly reduced in group 15 mL (163 [SD, 39] vs 235 [SD, 59] mins, respectively, P < 0.05). There were no differences in the other block characteristics. CONCLUSIONS: In ABPB with mepivacaine 1.5%, reducing the dose from 40 mL to 15 mL (62.5%) shortens the overall duration of sensory and motor block by approximately 17% to 19%, reduces sensory and motor block duration of individual nerves by 18% to 40%, and decreases the time to first request of postoperative analgesia by approximately 30%.