FOETAL AND MATERNAL PLASMA LEVELS OF MEPIVACAINE AND FOETAL ACID-BASE BALANCE AND HEART RATE AFTER PARACERVICAL BLOCK DURING LABOUR

Mepivacaine concentrations were estimated simultaneously inmaternal venous plasma and foetal capillary plasma in elevenobstetrical cases after paracervical blockade (PCB) with 200–400mg of mepivacaine without adrenaline. 400 mg of mepivacainefor PCB produced a clearly higher maternal mepivacaine levelthan 200 mg of mepivacaine. Foetal mepivacaine levels paralleledor were lower than the corresponding maternal levels in allexcept one case immediately after PCB. The possible causes ofa higher foetal than maternal mepivacaine level after PCB arediscussed. A significantly greater mean pH decrease (–0.115pH units) was found in the group with foetal bradycardia observedimmediately after PCB than in the group with no bradycardia(–0.040 pH units). A relationship between the fall infoetal pH and the foetal plasma concentration of mepivacaineafter PCB was suggested by the relatively high correlation coefficient(r= –0.65) between the mavimai values of these two parameters.