18 - Obstetrical anaesthesia

Summary

Neuraxial analgesia (epidural, and combined spinal–epidural techniques) effectively relieves labour pain. Whether or not these modalities affect progress of labour has been controversial. This chapter discusses the effect of neuraxial analgesia on caesarean section rates, instrumental delivery rates and the duration of labour. There is strong, homogeneous evidence to show that neuraxial analgesia does not increase the caesarean section rate. There is also strong, consistent evidence to show that there is an increase in the incidence of instrumental vaginal delivery in patients who have neuraxial analgesia. Further, there appears to be a dose–response relationship – parturients exposed to high concentrations of local anaesthetic are at higher risk for instrumental vaginal delivery than those exposed to low concentrations. While there appears to be a prolongation of the second stage of labour with neuraxial analgesia, these results are inconsistent and dependent on the obstetric protocol at a particular institution. In conclusion, neuraxial analgesia does not cause an increased incidence of caesarean section but may increase the incidence of instrumental vaginal delivery. This effect can be reduced by reducing the concentration of local anaesthetic. The effect on the length of first and second stage of labour is variable but is likely clinically unimportant.

Introduction

Since the introduction of anaesthesia to obstetric practice by James Young Simpson in 1847, there have been controversies concerning its use.