Epidural ropivacaine hydrochloride during labour: protein binding, placental transfer and neonatal outcome

This study was undertaken: (i) to quantify the effects of labour and epidur al analgesia on plasma alpha (1)-acid glycoprotein concentration, (ii) to e xamine the effects of changes in plasma oil-acid glycoprotein concentration on plasma protein binding and placental transfer of ropivacaine, and (iii) to examine the association between umbilical venous ropivacaine concentrat ion and neurobehavioural function in the neonate. Multiparous patients unde rgoing induction of labour received a continuous epidural infusion of 0.1% ropivacaine following an epidural bolus. A significant association was demo nstrated between maternal plasma cll-acid glycoprotein concentration and 1/ free fraction of ropivacaine 60 min after starting ropivacaine administrati on (r(2) = 0.77) but not at delivery. No significant correlation was demons trable between maternal unbound ropivacaine concentration and either neonat al (cord) ropivacaine concentration or UV/MV (a measure of placental transf er). Thirty minutes after delivery, 9/10 neonates had neurological and adap tive capacity scores <35, whereas only three infants had scores <35 at 2 h. All scores exceeded 35 16 h after delivery. No association between mean (S D) umbilical venous ropivacaine concentration [0.09 (0.08) mg.l(-1)] and ne urological and adaptive capacity scores was demonstrated.