Alexandre Takeda

Determination of the minimum effective volume of 0.5% bupivacaine for ultrasound-guided axillary brachial plexus block

BACKGROUND AND OBJECTIVE The use of ultrasound for needle correct placement and local anesthetic spread monitoring helped to reduce the volume of local anesthetic required for peripheral nerve blocks. There are few studies of the minimum effective volume of local anesthetic for axillary brachial plexus block. The aim of this study was to determine the minimum effective volume (VE90) of 0.5% bupivacaine with epinephrine (1:200,000) for ultrasound guided ABPB. METHOD Massey and Dixons up-and-down method was used to calculate the minimum effective volume. The initial dose was 5 mL per nerve (radial, median, ulnar, and musculocutaneous). In case of blockade failure, the volume was increased to 0.5 mL per nerve. A successful blockade resulted in decreased volume of 0.5 mL per nerve to the next patient. Successful blockade was defined as a motor block ≤2, according to the modified Bromage scale; lack of thermal sensitivity; and response to pinprick. The achievement of five cases of failure followed by success cases was defined as criterion to complete the study. RESULTS 19 patients were included in the study. The minimum effective volume (VE90) of 0.5% bupivacaine with 1:200,000 epinephrine was 1.56 mL (95% CI, 0.99-3.5) per nerve. CONCLUSION This study is in agreement with some other studies, which show that it is possible to achieve surgical anesthesia with low volumes of local anesthetic for ultrasound-guided peripheral nerve blocks.

Malignant hyperthermia in Brazil: analysis of hotline activity in 2009

BACKGROUND AND OBJECTIVES Malignant hyperthermia (MH) is a pharmacogenetic disease that causes abnormal hypermetabolic reaction to halogenated anesthetics and/or depolarizing muscle relaxants. In Brazil, there is a hotline telephone service for MH since 1991, available 24 hours a day in São Paulo. This article analyzes the activity of the Brazilian hotline service for MH in 2009. METHODS Prospective analysis of all phone calls made to the Brazilian hotline service for MH from January to December 2009. RESULTS Twenty-two phone calls were received: 21 from the South/Southeast region of Brazil and one from the North region. Fifteen calls were requests for general information about MH. Seven were about suspected MH acute episodes, two of which were not considered as MH. In five episodes compatible with MH, all patients received halogenated volatile anesthetics (2, isoflurane; 3, sevoflurane) and one also used succinylcholine; there were four men and one woman, with a mean age of 18 years (2-27). The problems described in the five MH episodes were tachycardia (5), increased expired carbon dioxide (4), hyperthermia (3), acidemia (1), rhabdomyolysis (1), and myoglobinuria (1). One patient received dantrolene. All five patients with MH episodes were follow-up in the intensive care unit and recovered without sequelae. Susceptibility to MH was later confirmed in two patients by in vitro muscle contracture test. CONCLUSIONS The number of calls per year in the Brazilian hotline service for MH is still low. The characteristics of MH episode were similar to those reported in other countries. The knowledge of MH in Brazil needs to be increased.

Minimum effective concentration of bupivacaine for axillary brachial plexus block guided by ultrasound

INTRODUCTION The use of ultrasound in regional anesthesia allows reducing the dose of local anesthetic used for peripheral nerve block. The present study was performed to determine the minimum effective concentration (MEC90) of bupivacaine for axillary brachial plexus block. METHODS Patients undergoing hand surgery were recruited. To estimate the MEC90, a sequential up-down biased coin method of allocation was used. The bupivacaine dose was 5 mL for each nerve (radial, ulnar, median, and musculocutaneous). The initial concentration was 0.35%. This concentration was changed by 0.05% depending on the previous block; a blockade failure resulted in increased concentration for the next patient; in case of success, the next patient could receive or reduction (0.1 probability) or the same concentration (0.9 probability). Surgical anesthesia was defined as driving force ≤ 2 according to the modified Bromage scale, lack of thermal sensitivity and response to pinprick. Postoperative analgesia was assessed in the recovery room with numeric pain scale and the amount of drugs used within 4h after the blockade. RESULTS MEC90 was 0.241% [R(2): 0.978, confidence interval: 0.20-0.34%]. No patient, with successful block, reported pain after 4h. CONCLUSION This study demonstrated that ultrasound guided axillary brachial plexus block can be performed with the use of low concentration of local anesthetics, increasing the safety of the procedure. Further studies should be conducted to assess blockade duration at low concentrations.

Concentração mínima efetiva de bupivacaína para o bloqueio do plexo braquial via axilar guiado por ultrassom

INTRODUCTION The use of ultrasound in regional anesthesia allows reducing the dose of local anesthetic used for peripheral nerve block. The present study was performed to determine the minimum effective concentration (MEC90) of bupivacaine for axillary brachial plexus block (ABPB). METHODS Patients undergoing hand surgery were recruited. To estimate the MEC90, a sequential up-down biased coin method of allocation was used. The bupivacaine dose was 5mL for each nerve (radial, ulnar, median, and musculocutaneous). The initial concentration was 0.35%. This concentration was changed by 0.05% depending on the previous block: a blockade failure resulted in increased concentration for the next patient; in case of success, the next patient could receive or reduction (0.1 probability) or the same concentration (0.9 probability). Surgical anesthesia was defined as driving force ≤ 2 according to the modified Bromage scale, lack of thermal sensitivity and response to pinprick. Postoperative analgesia was assessed in the recovery room with numeric pain scale and the amount of drugs used within 4hours after the blockade. RESULTS MEC90 was 0.241% [R2: 0.978, confidence interval: 0.20%-0.34%]. No successful block patient reported pain after 4hours. CONCLUSION This study demonstrated that ultrasound guided ABPB can be performed with the use of low concentration of local anesthetics, increasing the safety of the procedure. Further studies should be conducted to assess blockade duration at low concentrations.

Estudo prospectivo randomizado de três diferentes técnicas para o bloqueio do plexo braquial via axilar guiado por ultrassom

INTRODUCTION Randomized prospective study comparing two perivascular techniques with the perineural technique for ultrasound-guided axillary brachial plexus block (US-ABPB). The primary objective was to verify if these perivascular techniques are noninferior to the perineural technique. METHOD 240 patients were randomized to receive the techniques: below the artery (BA), around the artery (AA) or perineural (PN). The anesthetic volume used was 40mL of 0.375% bupivacaine. All patients received a musculocutaneous nerve blockade with 10mL. In BA technique, 30mL were injected below the axillary artery. In AA technique, 7.5mL were injected at 4 points around the artery. In PN technique, the median, ulnar, and radial nerves were anesthetized with 10mL per nerve. RESULTS Confidence interval analysis showed that the perivascular techniques studied were not inferior to the perineural technique. The time to perform the blockade was shorter for the BA technique (300.4±78.4sec, 396.5±117.1sec, 487.6±172.6sec, respectively). The PN technique showed a lower latency time (PN - 655.3±348.9sec; BA -1044±389.5sec; AA-932.9±314.5sec), and less total time for the procedure (PN-1132±395.8sec; BA -1346.2±413.4sec; AA 1329.5±344.4sec). BA technique had a higher incidence of vascular puncture (BA - 22.5%; AA - 16.3%; PN - 5%). CONCLUSION The perivascular techniques are viable alternatives to perineural technique for US-ABPB. There is a higher incidence of vascular puncture associated with the BA technique.

Efeitos farmacocinéticos e clínicos de duas concentrações de bupivacaína no bloqueio do plexo braquial via axilar

INTRODUCTION The risk of systemic bupivacaine toxicity is a persistent problem, which makes its pharmacokinetic study fundamental for regional anesthesia safety. There is little evidence of its influence on plasma peak at different concentrations. The present study compares two bupivacaine concentrations to establish how the concentration affects this drug plasma peak in axillary brachial plexus block. Postoperative latency and analgesia were also compared. METHODS 30 patients were randomized. In the 0.25% Group, 0.25% bupivacaine (10mL) was injected per nerve. In the 0.5% Group, 0.5% bupivacaine (5mL) was injected per nerve. Peripheral blood samples were collected during the first 2hours after the blockade. For sample analyses, high performance liquid chromatography mass spectrometry was used. RESULTS Plasma peak occurred 45minutes after the blockade, with no difference between groups at the assessed time-points. Plasma peak was 933.97 ± 328.03 ng.mL-1 (mean ± SD) in 0.25% Group and 1022.79 ± 253.81 ng.mL-1 in 0.5% Group (p = 0.414). Latency was lower in 0.5% Group than in 0.25% Group (10.67 ± 3.71 × 17.33min ± 5.30, respectively, p = 0.004). No patient had pain within the first 4hours after the blockade. CONCLUSION For axillary brachial plexus block, there was no difference in bupivacaine plasma peak despite the use of different concentrations with the same local anesthetic mass. The concentration inversely influenced latency.

Ultrasound-guided peripheral nerve blocks in anticoagulated patients - case series

BACKGROUND AND OBJECTIVES The advent of ultrasound has brought many benefits to peripheral nerve blocks. It includes both safety and effectiveness, given the possibility of visualizing the neurovascular structures and the needle during the procedure. Despite these benefits, there is no consensus in the literature on the use of this technique in anticoagulated patients or with other coagulation disorders. Moreover, peripheral blocks vary in depth, spreadability, and possibility of local compression. However, few societies take it into account when drawing up its recommendations, establishing a single recommendation for performing peripheral blocks, regardless of the route used. The objective of this series is to expand the discussion on peripheral nerve block in anticoagulated patients. CASE REPORTS This series reports 9 cases of superficial peripheral nerve blocks guided by ultrasound in patients with primary or secondary dyscrasias. All blocks were performed by experienced anesthesiologists in the management of ultrasound, and there was no bruising or neurological injuries in the cases. CONCLUSIONS This case series support the discussion on conducting surface peripheral nerve blocks and easy local knowledge as the axillary, interscalene, femoral, saphenous or popliteal in anticoagulated patients, on dual antiaggregation therapy and/or with other coagulation disorders, provided that guided by ultrasound and performed by an anesthesiologist with extensive experience in guided nerve blocks. However, larger series should be performed to prove the safety of the technique for these patients.

Hipertermia maligna no Brasil: análise da atividade do hotline em 2009

JUSTIFICATIVA E OBJETIVOS: Hipertermia maligna (HM) e doenca farmacogenetica, com reacao hipermetabolica anormal a anestesicos halogenados e/ou relaxantes musculares despolarizantes. Desde 1991 ha um servico hotline de atendimento telefonico para HM no Brasil, disponivel 24 horas por dia, em Sao Paulo. Este artigo analisa a atividade do servico brasileiro de hotline para HM em 2009. METODOS: Analise prospectiva de todas chamadas telefonicas paria maligna (HM) e doenca farmacogenetica, com reacao hipermetabolica anormal a anestesicos halogenados e/ou relaxantes musculares despolarizantes. Desde 1991 ha um servico hotline de atendimento telefonico para HM no Brasil, disponivel 24 horas por dia, em Sao Paulo. Este art go analisa a at vidade do servico brasileiro de hotline para HM em 2009a o servico brasileiro de hotline para HM, de janeiro a dezembro de 2009. RESULTADOS: Foram recebidas 22 ligacoes; 21 provenientes do Sul-Sudeste do Brasil e uma do Norte. Quinze eram pedidos de informacoes gerais sobre HM. Sete foram suspeitas de crises agudas de HM, das quais duas nao foram consideradas como HM. Nas cinco crises compativeis com HM, todos os pacientes receberam anestesicos inalatorios halogenados (2 isoflurano, 3 sevoflurano) e um usou tambem succinilcolina; havia quatro homens e uma mulher, com media de idade de 18 anos (2-27). Problemas descritos nas cinco crises de HM: taquicardia (cinco), aumento do gas carbonico expirado (quatro), hipertermia (tres), acidemia (um), rabdomiolise (um) e mioglobinuria (um). Um paciente recebeu dantrolene. Todos os cinco pacientes com crises de HM foram seguidos em unidade de terapia intensiva e recuperaram-se sem sequelas. A suscetibilidade a HM foi posteriormente confirmada em dois pacientes por meio do teste de contratura muscular in vitro. CONCLUSOES: O numero de chamadas por ano no servico brasileiro de hotline para HM ainda e reduzido. As caracteristicas das crises foram similares as descritas em outros paises. E preciso aumentar o conhecimento sobre HM no Brasil.