Abstract
Pudendal block with 20 ml of 1 per cent lidocaine (200 mg) with and without epinephrine was used in 24 patients for pain relief during the second stage of labour. The addition of epinephrine improved the quality and prolonged the duration of the anasthe-sia. Measurable amounts of lidocaine were detected in maternal venous And foetal scalp blood within 5 minutes after the injection with peak levels within 10-20 minutes. Lidocaine with epinephrine gave lower maternal and foetal levels than plain lidocaine. The peak levels were about 30 per cent lower in maternal and about 20 per cent lower in foetal blood when epinephrine was added to the solution injected. The lidocaine levels in foetal blood were lower than the corresponding concentrations in maternal blood. They were always far below levels reported to be toxic. No correlation existed between maternal or foetal blood lidocaine concentrations and acid-base changes in maternal or foetal blood. A slight but transient decline in the uterine activity was sometimes observed. This tendency was more pronounced when lidocaine with epinephrine was used. The mean duration of the second stage was longer in the anaesthetized patients than in a control group, probably more due to the abolishment of the bearing down reflex than to the slightly affected uterine activity. A prolongation of the second stage of labour was found to give a significantly increased tendency to foetal aci-dosis in the anaesthetized as well as in the control group. The one minute Apgar scores were, however, normal. Adverse effects on the foetus due to a second stage prolonged by pudenda] block may be minimized by liberal use of episotomy, proper instruction, and coaching.