Combined spinal-epidural analgesia is effective in labour analgesia. Nitric oxide may play important roles in pregnancy and labour and is probably affected by labour pain. The aim of the present study was to explore the alteration in serum levels of nitric oxide metabolites, i.e. nitrate and nitrite, during labour with or without combined spinal-epidural analgesia.

Fifty pregnant women were recruited at the cervical dilatation of 3∼4 cm, 25 received combined spinal-epidural analgesia and 25 served as control. Twenty in the combined spinal-epidural analgesia group and 19 in the control group finished data collection and were included in the analysis. Blood samples were taken at study entry, full cervical dilation and 2 h after delivery. Total serum level of nitrite and nitrate was measured with enzymatic conversion and followed by Griess reaction. Visual analogue pain scores and mean blood pressure were monitored.

After analgesia, pain score and mean blood pressure were significantly lower in the combined spinal-epidural analgesia group than in the control group (P < 0.05). Serum levels of nitric oxide metabolites were not significantly different at study entry (P > 0.05) but significantly different at full cervical dilation and 2 h after delivery (P < 0.05 for both) between the control group and the combined spinal-epidural analgesia group. Serum levels of nitric oxide metabolites decreased significantly at full cervical dilation and 2 h after delivery compared with study entry in the control group (P < 0.05) and this decrease was almost abolished in the combined spinal-epidural analgesia group (P > 0.05).

Combined spinal-epidural analgesia provided effective analgesia and abolished the decrease in nitric oxide metabolites during active labour.