Response to a Valsalva manoeuvre before and after epidural block.

In pregnant patients at term the cardiovascular response to a Valsalva manoeuvre has been evaluated in the lateral and supine positions, before and after epidural block (T8-S5). There was no difference in the pattern of response under these four conditions. After epidural block, there was a tendency to a greater degree of hypotension and a slower recovery. In labour such repeated hypotension could account for the increase in fetal acidosis when the second stage of labour is conducted in the supine position.