Foetal bradycardia during caudal analgesia: A discussion of possible causative factors

A 31-year-old female had caudal analgesia during labour, using 0.5% bupivacaine. Nine minutes after the block, the foetus developed severe bradycardia which lasted for 9 min but recovered spontaneously. Thereafter the foetal heart rate was within the normal range until the end of labour when variable decreases in rate occurred, suggesting cord compression. At the time of delivery there was a knot of the umbilical cord which was also forming a loop around the neck of the baby. There was no abnormality of the Apgar scores or blood-gases in the baby; the plasma bupivacaine concentrations in both mother and child were within the expected range. The possible causative factors for this bradycardia are explained.