Horner's syndrome during epidural anaesthesia for elective caesarean section

Twenty ml of three per cent chloroprocaine solution was injected into the lumbar epidural space of a parturient for anaesthesia for elective caesarean section. Ten minutes after injection of the anaesthetic, the patient developed Horner's syndrome on the left side. The anaesthetic level was C7 on the affected side. Thirty minutes after the bolus dose of chloroprocaine the signs disappeared, at which time the patient received a reinforcing dose of 10 ml of chloroprocaine three per cent. The Horner's complex reappeared in eight minutes and persisted for 20 minutes. While Horner's syndrome is not uncommon in women in labour receiving lumbar epidural anaesthesia, it is virtually unknown in patients who are not in labour. The mechanism for the appearance of the syndrome in this case is unclear. The most likely explanation is that only a small amount of local anaesthetic was necessary to produce the syndrome and the subsequent bolus of anaesthetic followed pathways opened by the original dose, since a much smaller amount of anaesthetic was necessary to reproduce the syndrome.