Perivascular Axillary Block V: Blockade following 60 ml of Mepivacaine 1 % Injected as a Bolus or as 30 + 30 ml with a 20-min Interval

Perivascular axillary blockade was performed on 60 patients with the aid of a catheter technique. The patients were randomly allocated to two groups. All patients received the same dose of local anaesthetic: 60 ml of mepivacaine 1% with adrenaline, but one group received the dose as a bolus injection, whereas the other group received the dose as fractional injections of 30 + 30 ml with an interval of 20 min. Blood concentrations of mepivacaine were measured up to 90 min after injection of local anaesthetic. Sensory and motor blockade were evaluated 20, 30 and 40 min after injection. Forty minutes after the last injection of local anaesthetic, there was no difference between the blockades of the two groups, except for the sensory blockade of the lower lateral cutaneous nerve of the arm, in which the frequency of analgesia was 90% after bolus injection and 63% after fractional injections. There was no difference in blood concentrations of mepivacaine between the two groups. None of the 60 patients showed any sign of systemic toxic reactions. Fractional injection of local anaesthetic in perivascular axillary blockade does not offer any advantage over bolus injection with regard to the resulting blockade.     

Perivascular Axillary Block IV: Blockade Following 40, 50 or 60 ml of Mepivacaine 1 % with Adrenaline

Perivascular axillary blockade was performed on 90 patients with the aid of a catheter technique. The patients were randomly allocated to receive either 40, 50 or 60 ml of 1% mepivacaine with adrenaline 1:200,000. Blood concentrations of mepivacaine were measured up to 90 min after injection in seven, eight and ten of the patients from the three groups. Sensory and motor blockade was evaluated 20, 30 and 40 min after injection. All groups showed the same temporal development of the blockade, i.e. improval of the blockade during the period from 20 to 40 min after injection, but no difference was found in the sensory or motor blockade between the three groups. However, a further analysis of the incomplete blockades showed a better quality of the sensory blockade in the groups given 50 and 60 ml than in the group given 40 ml. None of the 90 patients showed any signs of systemic toxic reactions. The mean peak values of blood concentrations were 0.5-1.0 microgram/ml higher in the groups given 50 ml and 60 ml than in the group given 40 ml. On the basis of the present and two previous investigations on the dose response in perivascular axillary blockade, a dose of 50 ml 1% mepivacaine with adrenaline or another equivalent drug with vasoconstrictor is recommended.     

Comparison of transarterial and multiple nerve stimulation techniques for axillary block using a high dose of mepivacaine with adrenaline

BACKGROUND: High-dose transarterial (TA) technique results in high effectiveness of the axillary block. The technique is fast and simple, but does not produce a satisfactory success rate when using the manufacturer's recommended dose of mepivacaine. The multiple nerve stimulation (MNS) technique requires more time and experience. This double-blind study compared effectiveness, safety and the time used to obtain an effective analgesia in 101 patients, having an axillary block by either TA or MNS techniques. METHODS: Mepivacaine with adrenaline (MEPA), 850 mg, was used for the initial block. Five millilitres of 1% solution was injected subcutaneously. In the TA group, 20 mL of 2% solution was injected deep to, and 20 mL superficial to the axillary artery. In the MNS group, four terminal motor nerves were electrolocated in the axilla, and injected with 10 mL each. Analgesia was assessed every 10 min and, when needed, supplemented after 30 min. The block was effective when analgesia was present in all sensory nerve areas distal to the elbow. RESULTS: The MNS group required median 11 min for block performance compared with 8 min for the TA group (P < 0.001). Latency of the initial block was shorter and the frequency of supplemental analgesia lower in the MNS group (median 10 min and 6%) than in the TA group (30 min and 36%, respectively), P < 0.001. All incomplete blocks were successfully supplemented. However, the total time to obtain an effective block was shorter in the MNS group (23 min) than in the TA group (37 min), P < 0.001. Two patients in each group had signs and symptoms of systemic toxicity, the most serious being atrial fibrillation and temporary loss of consciousness in a cardiovascularly medicated patient. The local adverse effects (intravascular injections and haematomas) were fewer in the MNS group, P < 0.001. CONCLUSION: The MNS technique of axillary block by four injections of 10 mL of 2% MEPA produces faster and more extensive block than the TA technique by two injections of 20 mL. Therefore, the MNS technique requires fewer supplementary blocks and results in faster patient readiness for surgery. However, high doses of MEPA may result in dangerous systemic toxic reactions.     

An unusual toxic reaction to axillary block by mepivacaine with adrenaline

An increase in blood pressure, accompanied by atrial fibrillation, agitation, incomprehensible shouts and loss of consciousness, was observed in an elderly, ASA classification group II, cardio-vascularly medicated male, 12 min after performance of axillary block with mepivacaine 850 mg containing adrenaline 0.225 mg, for correction of Dupuytren's contracture. After intravenous administration of labetalol, metoprolol and midazolam the patient's condition improved, and 15 min later he woke up. The block was successful and surgery was conducted as scheduled despite persisting atrial fibrillation. Postoperatively, the patient refused DC cardioversion and was treated medically. Both the temporal relationship of events and the response to treatment suggest that a rapid systemic absorption of mepivacaine with adrenaline and/or interaction of these drugs with the patient's cardiovascular medications were responsible for the perioperative complications.     

Comparison of transarterial and multiple nerve stimulation techniques for an initial axillary block by 45 mL of mepivacaine 1% with adrenaline

Background : The single-injection axillary block is rapidly performed but gives unpredictable results. Axillary block by multiple nerve stimulation technique (MNS) gives better results, but takes longer to perform. Transarterial (TA) injections of high doses of local anaesthetics are very successful. This double-blind study compared both block effectiveness and anaesthesiologic time consumption in 100 patients, having an axillary block by either TA or MNS techniques. Methods : 45 mL of 1% mepivacaine with adrenaline 5 μg/mL was used in each patient. Five mL was injected subcutaneously. In the TA group, 20 mL was injected deep to, and 20 mL superficial to the axillary artery. In the MNS group, four terminal motor nerves were electrolocated in the axilla, and injected with 10 mL each. Analgesia was assessed every 10 min and when needed supplemented after 30 min. The block was considered successful when analgesia was present in all sensory nerve areas distal to the elbow. Results : MNS group required 10δ2 min (meanδ1 SD) for the initial block performance compared with 7δ2 min for TA group, P<0.001. Latency of the initial block was shorter and the frequency of supplemental analgesia lower in the MNS group (mean 17 min and 12%), than in the TA group (25 min and 38%, respectively), P<0.001. All incomplete blocks were successfully supplemented by electrolocating the unblocked nerves. However, the total time to obtain 100% success rate was shorter in the MNS group (30 min), than in the TA group (38 min), P<0.001. The adverse effects (accidental intravascular injections and axillary haematomas) were fewer in the MNS group. Conclusion : In the hands of anaesthetists experienced in nerve electrolocation, the MNS technique of an initial axillary block by four separate injections of 10 mL of mepivacaine produces faster and more extensive block than the TA technique by two separate injections of 20 mL. Hence, the MNS technique requires fewer supplementary blocks and results in faster patient readiness for surgery than the TA technique.     

Perivascular Axillary Block III: Blockade Following 40 ml of 0.5%, 1% or 1.5% Mepivacaine with Adrenaline

Perivascular axillary blockade was performed on 90 patients with the aid of a catheter technique. All blockades were performed by the same anaesthetist, who practised perivascular axillary blockade three or four times a day. The patients were randomly allocated to three groups. The injected volume of local anaesthetic was constant in each group: 40 ml mepivacaine with adrenaline. The concentration and, consequently, the amount (mg) were variable factors: 1/2% (200 mg), 1% (400 mg) and 1 1/2% (600 mg). Sensory and motor blockade were tested 30 min after each injection. All three groups showed a high incidence of analgesia (70%-100%) in all cutaneous segments, and none of the blockades showed total failure of the sensory blockade. The lowest incidence of sensory blockade was found in the areas innervated by the axillary, the radial and the musculocutaneous nerves, but no difference was found between the groups. However, the motor blockade was found to improve with increasing concentration of local anaesthetic solution.     

A comparison of 0.5% ropivacaine and 1% mepivacaine for sciatic nerve block in the popliteal fossa

BACKGROUND: The purpose of this study was to compare anesthetic efficacy and postoperative analgesia of 0.5% ropivacaine and 1% mepivacaine for sciatic nerve block in the popliteal fossa (popliteal block). METHODS: A prospective, double-blind study was carried out in 58 adult patients scheduled for outpatient foot or ankle surgery. They were randomized to receive popliteal block with 40 ml of either 0.5% ropivacaine (group R) or 1% mepivacaine (group M). An atraumatic, Teflon-coated needle connected to a neurostimulator was used to make a single puncture using a posterior approach. The times to onset of sensory and motor block, and the need for intraoperative sedation were recorded. Before discharge, patients were asked to document the time to first analgesic use, time to return of full sensation in the foot, and their evaluation of the technique. RESULTS: Onset time (mean+/-standard deviation, 95% confidence interval) of both sensory block (6.5+/-5.1 min, 4.47-8.49, in group R and 6.2+/-3.7 min, 4.83-7.69, in group M) and motor block (6.6+/-4.4 min, 4.81-8.23, in group R and 7.9+/-4.1 min, 6.29-9.53, in group M) was similar in both groups. Postoperative analgesia lasted longer in group R (15.2+/-5.1 h, 13.25-17.21) than in group M (5.7+/-1.8 h, 5.01-6.41; P<0.001). Duration of sensory block was longer in group R (20.7+/-6.2 h, 18.51-23.01) than in group M (6.5+/-1.7 h, 5.86-7.16; P<0.001). Acceptance of the anesthetic procedure was similar in both groups. CONCLUSION: In this study we demonstrated that both 0.5% ropivacaine and 1% mepivacaine for popliteal block produced rapid, effective and safe anesthesia but postoperative analgesia was more long-lasting with ropivacaine.     

Epinephrine as an adjuvant to amino-amide local anesthetics does not prolong their duration of action in infraorbital nerve block in the rat

The effects of epinephrine as an adjuvant to local anesthetics were studied in the rat infraorbital nerve block (IONB) model, using solutions of 0.5% prilocaine, 0.5% mepivacaine, 0.125% bupivacaine or 0.125% ropivacaine in 50 mmol/l tris-hydroxymethylaminomethane (THAM) tested both without and with epinephrine (EPI) added at 2, 4, 8 or 16 micrograms/ml. Solutions of THAM and EPI in normal saline did not induce IONB. THAM-buffered solutions of bupivacaine induced IONB of longer duration than bicarbonate-buffered solutions. Intensity of block during onset was increased only when EPI at 2 and 16 micrograms/ml was included in bupivacaine solutions. The duration of block induced by prilocaine, bupivacaine and ropivacaine was not significantly prolonged by addition of EPI at any of the concentrations tested. Only at a concentration of 16 micrograms/ml did EPI significantly prolong the duration of mepivacaine-induced block (+48%). Low concentrations of EPI in solutions of bupivacaine and ropivacaine significantly reduced their duration of action by up to 22% and 57%, respectively. It is concluded that the duration of action of local anesthetics in buffered solutions is only moderately affected by the inclusion of EPI, the effects differing only slightly from one to another. The efficacy of EPI as an adjuvant would seem to be governed by factors affecting the local disposition of the main drugs, such as non-specific binding, buffering of solutions and tissue pH.