What causes decreased blood flow back to the mother's heart during maternal hypotension after regional analgesia?

Decreased blood flow back to the mother's heart during maternal hypotension following regional analgesia is primarily caused by pooled blood in the lower extremities. When regional analgesia, such as an epidural or spinal block, is administered, it results in the vasodilation of the lower body due to the blockade of sympathetic nerves. This vasodilation causes blood vessels in the lower extremities to widen, leading to blood pooling in those areas instead of returning to the heart.

As a result of this blood pooling, the effective circulating blood volume returning to the heart decreases, which can lead to hypotension. The inability of blood to return efficiently impacts cardiac preload and can subsequently reduce cardiac output, contributing to a further drop in blood pressure. Managing maternal hypotension involves measures such as positioning the woman to encourage venous return and administering intravenous fluids to counteract the pooling effect and stabilize blood pressure.