Brazilian Journal of Anesthesiology
https://bjan-sba.org/article/doi/10.1590/S0034-70942005000300002
Brazilian Journal of Anesthesiology
Scientific Article

Volume anestésico mínimo para bloqueio retrobulbar extraconal: comparação entre soluções a 0,5% de bupivacaína racêmica, de levobupivacaína e da mistura enantiomérica S75/R25 de bupivacaína

Minimum anesthetic volumes for extraconal retrobulbar block: comparison between 0.5% racemic bupivacaine, levobupivacaine and enantiomeric mixture S75/R25 bupivacaine

Luiz Fernando Soares; Ana Claudia de Melo Barros; Gustavo Paiva Almeida; Gustavo Luchi Boos; Getúlio Rodrigues de Oliveira Filho

http://dx.doi.org/10.1590/S0034-70942005000300002 Braz J Anesthesiol, vol.55, n3, p.263-268, 2005
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Resumo

JUSTIFICATIVA E OBJETIVOS: O volume anestésico mínimo (VAM) de um anestésico local é o volume efetivo para anestesia regional em 50% dos pacientes. O objetivo deste estudo foi calcular os volumes anestésicos mínimos das soluções a 0,5% de bupivacaína racêmica, de levobupivacaína e da mistura enantiomérica S75/R25 de bupivacaína para anestesia retrobulbar extraconal. MÉTODO: Foram estudadas duas séries de pacientes submetidos à extração de catarata. Na série 1, os pacientes receberam bupivacaína a 0,5% (n = 9) ou levobupivacaína a 0,5% (n = 11). Na série 2, os pacientes receberam bupivacaína racêmica a 0,5% (n = 11) ou a mistura enantiomérica S75/R25 de bupivacaína a 0,5% (n = 10). Os bloqueios foram realizados por injeção única ínfero-lateral. A mobilidade de cada músculo reto foi avaliada após 10 minutos como: 0 (ausente), 1 (diminuída) ou 2 (normal). A soma dos escores constituiu o escore total de mobilidade (ETM) do globo ocular. O volume inicial foi de 7,4 mL. Os volumes utilizados em pacientes subseqüentes corresponderam 0,1 unidade logarítmica maior (ETM > 2) ou menor (ETM < 2) que o logaritmo natural do volume precedente. Foram utilizadas as fórmulas de Massey e Dixon para cálculos dos VAM. RESULTADOS: Os volumes anestésicos mínimos da bupivacaína racêmica foram 6 mL e 6,2 mL, o da levobupivacaína foi 5,7 mL e o da mistura enantiomérica de bupivacaína S75/R25 foi 5,8 mL. Não houve diferença entre os grupos quanto aos volumes anestésicos efetivos. CONCLUSÕES: Volumes semelhantes de soluções a 0,5% de bupivacaína racêmica, levobupivacaína ou da mistura enantiomérica S75/R25 de bupivacaína são necessários para anestesia retrobulbar extraconal.

Palavras-chave

ANESTÉSICOS, Local, ANESTÉSICOS, Local, ANESTÉSICOS, Local, TÉCNICAS ANESTÉSICAS, Regional

Abstract

BACKGROUND AND OBJECTIVES: Minimum anesthetic volume (MAV) of local anesthetics corresponds to the effective volume for regional anesthesia in 50% of patients. In this study, MAV of 0.5% racemic bupivacaine, 0.5% levobupivacaine and enantiomeric S75/R25 bupivacaine were calculated and compared. METHODS: This study involved two series of patients undergoing cataract extraction. Series 1 patients received either 0.5% racemic bupivacaine (n = 9) or 0.5% levobupivacaine (n = 11). Series 2 patients received either 0.5% racemic bupivacaine (n = 11) or 0.5% enantiomeric S75/R25 bupivacaine (n = 10). Blockades were achieved by single-injection and inferior-lateral approach. Motility of each rectus muscle was assessed 10 minutes later as: 0 (absent), 1 (decreased) or 2 (normal). Total muscle scores represented total eye motility score (TMS). Local anesthetic volume administered to the first patient of each group was 7.4 mL. Subsequent patients received volumes corresponding to 0.1 higher natural logarithm unit (if TME > 2) or lower (if TME < 2) as compared to natural logarithm of preceding volume. Massey and Dixon's formulae were used for MAV calculations. RESULTS: MAVs of bupivacaine in both series were 6 mL and 6.2 mL, respectively. MAVs of levobupivacaine and enantiomeric S75/R25 bupivacaine were 5.7 mL and 5.8 mL, respectively. There were no differences between groups in effective anesthetic volumes. CONCLUSIONS: Similar volumes of 0.5% racemic bupivacaine, 0.5% levobupivacaine and enantiomeric S75/R25 bupivacaine are needed for extraconal retrobulbar anesthesia.

Keywords

ANESTHETICS, Local, ANESTHETICS, Local, ANESTHETICS, Local, ANESTHETIC TECHNIQUES, Regional

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