Abstract
Racemic bupivacaine has been the local anaesthetic of choice in regional blocks due to quality and duration of anesthesia. However its cardiovascular toxicity has been a source of concern and research has been made for lesser impact drugs. One choice is its levogyre isomer, levobupivacaine, apparently less cardiotoxic due a lower affinity to the heart sodium channels. In Brazil, a drug containing 75% of levogyre isomer and 25% of dextrogyre isomer, called enantiomeric excess mixture, is available. This study intends to evaluate haemodynamic effects of the intravascular injection of a toxic dose of both agents in swine. Large White pigs were anaesthetized with thiopental, intubated and placed on mechanical ventilation. Haemodynamic monitoring was performed with an invasive blood pressure and Swan-Ganz catheter on a pulmonary artery. After a 30 minute rest period, animals were randomly divided in two groups and the intoxication was performed on a double-blind method with 4 mg.kg-1 of one of the drugs. Haemodynamic parameters were then evaluated at 1, 5, 10, 15, 20 and 30 minutes. The enantiomeric excess mixture caused greater haemodynamic effects than the racemic bupivacaine. These results diverge from those found in humans with levogyre isomer but are similar to recent results reported in animals. Care should be taken when extrapolating data obtained in swine to humans and further research is necessary. When high doses are injected in swine, the enantiomeric excess mixture was more toxic than the racemic bupivacaine.
Highlights
Racemic bupivacaine has been the local anaesthetic of choice in regional blocks due to quality and duration of anesthesia
After a 30 minute rest period, animals were randomly divided in two groups and the intoxication was performed on a double-blind method with 4 mg.kg[1] of one of the drugs
The enantiomeric excess mixture caused greater haemodynamic effects than the racemic bupivacaine. These results diverge from those found in humans with levogyre isomer but are similar to recent results reported in animals
Summary
ARTUR UDELSMANN*, SÍLVIA ELAINE RODOLFO DE SÁ LORENA, SAMIRA UBAID GIRIOLI, WILLIAM ADALBERTO SILVA, ANA CRISTINA DE MORAES Trabalho realizado no Laboratório de Anestesia Experimental do Núcleo de Medicina e Cirurgia Experimental da FCM / UNICAMPm, Campinas, SP. Os animais foram aleatoriamente, em duplocego, divididos em dois grupos: grupo bupivacaína (B) e grupo mistura enantiomérica (E), e neles foi praticada injeção endovenosa de uma dose tóxica de 4 mg/kg do anestésico local[13] correspondente, sem o conhecimento do experimentador; 9. Em consonância ao demonstrado por outros autores, também em animais, comparando levobupivacaína, bupivacaína racêmica, ropivacaína, e que encontraram toxicidade semelhante[19] ou mesmo maior[20,21] da levobupivacaína, nossos resultados mostraram uma maior repercussão hemodinâmica da mistura enantiomérica e, em menor grau, da bupivacaína racêmica num modelo suíno de intoxicação aguda, como a que acontece por ocasião de injeção intravenosa acidental na prática de uma anestesia loco-regional. CONCLUSÃO Este trabalho mostrou, em suínos, que a mistura enantiomérica é mais cardiotóxica do que a bupivacaína racêmica, quando grandes doses são injetadas por via endovenosa, como acidentalmente acontece durante anestesias loco-regionais
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