Regional anaesthesia and uterine blood flow.

Sufficient placental blood flow is mandatory for the well-being of the fetus. The delicate balance between uterine perfusion pressure and uterine vascular resistance can be critically disturbed during epidural anaesthesia. Maternal hypotension is common when extensive block for Caesarean Section is used. If hypotension as well as aortocaval compression is avoided and sufficient preload (Ringer's lactate) is used intervillous blood flow (IBF) will not significantly change. Ephedrine given to prevent or treat maternal hypotension will not adversely effect IBF. Lumbar epidural analgesia used for pain relief during labor (10 ml dose of local anaesthetic (1.a.] will significantly (p less than 0.05) improve IBF in healthy parturients. Epinephrine (less than or equal to 50 micrograms), added to the local anaesthetic, will not decrease IBF. IBF can be severely reduced in pregnancy-induced hypertension (PIH) since the fetus is chronically asphyxiated it is crucial to avoid any further decrease in IBF. Extensive sympathetic blockade (T8) using epidural analgesia (10 ml dose of 1.a.) has been shown to significantly (p less than 0.01) improve IBF in parturients with PIH by decreasing uteroplacental vascular resistance.