Extradural analgesia in labour. A comparison of 2-chloroprocaine hydrochloride and bupivacaine hydrochloride.

Chloroprocaine hydrochloride 2% and bupivacaine hydrochloride 0.375% in 10-ml doses of plain solutions were studied in a randomised blind manner as the agents for continuous lumbar extradural analgesia in labour. Twenty-four patients were assessed for the speed of onset, duration of action, degree of motor blockade, dermatomal spread, arterial hypotension, and the incidence of unblocked segments. Chloroprocaine showed a quicker onset time and a shorter duration of action than bupivacaine. Chloroprocaine exhibited more marked motor blockade and a lower incidence of unblocked segments. The dermatomal spread and effect on arterial pressure were similar in both groups.