Estudo comparativo entre bupivacaína racêmica (S50-R50) a 0,125% e bupivacaína em excesso enantiomérico de 50% (S75-R25) a 0,125% e 0,25% em anestesia peridural para analgesia de parto

Abstract

Continuous epidural block is used for relief of labor pain and it is associated with a low incidence of complications. Studies with the levorotatory isomer of local anesthetics demonstrated that they are safer regarding the cardiotoxicity. The objective of this study was to compare analgesia and motor blockade of 0.125% bupivacaine (S50-R50) and 0.125% and 0.25% 50% enantiomeric excess bupivacaine (S75-R25) in continuous epidural block for labor analgesia. Seventy-five patients in labor participated in this randomized, double-blind study after signing an informed consent. Patients were divided in three groups: GI - 0.125% bupivacaine (S50-R50); GII - 0.125% bupivacaine (S75-R25) and GIII - 0.25% bupivacaine (S75-R25). The latency of analgesia, levels of sensorial blockade, volume of local anesthetic, duration of labor and analgesia, frequency of instrumental delivery, Apgar scores, or pH of umbilical cord blood showed no statistically significant differences. The length of time until the first rescue dose was greater and pain scores at 45 minutes were also greater in the 0.25% bupivacaine (S75-R25) group. The intensity of the motor blockade was greater in the 0.125% bupivacaine (S50-R50) group. The motor blockade was less intense with bupivacaine (S75-R25) regardless the concentration, resulting in analgesia of better quality without interfering with the evolution of labor or the vitality of newborns.