FETAL BLOOD FLOW DURING INTRATHECAL ANAESTHESIA FOR ELECTIVE CAESAREAN SECTION

Fetal aortic and umbilical blood flows were studied in 15 mothersbefore and during spinal (intrathecal) anaesthesia for electiveCaesarean section, using a method combining real-time ultrasonographyand a pulsed Doppler technique. Spinal anaesthesia with 0.5%bupivacaine hydrochloride 2.5ml in 8% glucose monohydrate solutionwas administered after preloading with 2 litre of lactated Ringer'ssolution. Simultaneously with the subarachnoid injection, aninfusion i. v. of ephedrine 50 mg in 500 ml normal saline wasinitiated. Maternal heart rate and systolic arterial pressureremained stable during the spinal anaesthesia, but diastolicarterial pressure decreased (P<0.05). Fetal heart rate increased(P<0.05) 30 min after the introduction of the spinal anaesthesia,but blood flows in the fetal descending aorta and umbilicalvein were unaffected. The pulsatility index of the fetal bloodvelocity decreased (P<0.05) both in the fetal aorta and inthe umbilical artery 30 min after induction of the spinal anaesthesia,indicating a possible decrease in the placental vascular resistance.We conclude that, when normotension is maintained in the motherwith a preload infusion and an infusion of ephedrine, spinalanaesthesia for Caesarean section has no harmful effect on thefetal circulation.