Effects of Regional Blockade on Materno-Fetal Physiology

# Pain relief leads to a reduction in serum catecholamines by decreasing physical stress or by denervating the adrenal medulla with subsequent enhancement of uterine blood flow.
# Hypotension occurring secondary to central blockade decreases uterine blood flow as uterine perfusion pressure is dependent on maternal mean arterial pressure with minimum capacity for autoregulation.
# Avoidance of maternal hypotension prevents any derangement of umbilical artery blood flow .
# Aortocaval compression is compensated for by sympathetic hyperactivity. Regional blockade may diminish this reflex but on the other hand venous dilatation of vertebral and paraspinous veins draining into the azygous compensates for minor degree of aortocaval compression. Provided prolonged hypotension is avoided, improved foetal outcomes with epidurals are known to occur secondary to improved placental haemodynamics.
# Reduced perioperative blood loss is associated with regional anesthesia (e.g. for placenta previa) . This has been attributed to avoidance of inhalational agents (all have uterine relaxant effects to a varying degree) and reduced pelvic venous plexuses pressures due to venodilatation.
# Early ambulation is another documented benefit of regional techniques which is caused by both direct effects (avoidance of depressant effects of general anesthesia) and indirect causes (elimination of stress response by the pre-emptive effect of regional blockades).
# Pain scores postoperatively are much lower postoperatively when a regional technique is used. This is reflected as a decrease in opioid requirements which leads to better somatosensory profiles for the mother and baby .
# Avoidance of general anesthetic effects on the baby is reflected as less postpartum interventions and early feeding. This is of particular value when a long predelivery phase (e.g. patients who had previous CS) is expected.
# Epidural improves incoordinate uterine activity unless severe hypotension ensues .