Forearm vascular tone and reactivity during lumbar epidural anesthesia.

Forearm vascular tone and sympathetic reactivity were investigated in ten unpremedicated patients during two levels of epidural sensory blockade, neither of which levels was high enough to block cardiac sympathetic pathways. An 8-MHz pulsed Doppler blood flowmeter was used to determine brachial artery diameter and flow characteristics. Measurements were made before and during sympathetic stimulation induced by a contralateral isometric handgrip. The lower level of sensory blockade (T11) in the absence of sympathetic stimulation was associated with decreases in right atrial pressure, brachial artery diameter (3.9 +/- 0.2 vs 4.2 +/- 0.2 mm, P less than 0.05) and brachial blood flow (42 +/- 5 vs 66 +/- 7 ml.min-1, p less than 0.001), whereas forearm vascular resistance increased significantly (2.2 +/- 0.3 vs 1.5 +/- 0.2 mm Hg.ml-1.min-1, P less than 0.01). Neither heart rate nor mean arterial pressure changed. At the higher level of blockade (T7), right atrial pressure and systemic arterial pressure decreased further without change in heart rate. Brachial artery diameter (3.8 +/- 0.2 mm) remained unchanged while brachial blood flow additionally decreased (30 +/- 3 ml.min, P less than 0.05), and forearm vascular resistances further increased (3.0 +/- 0.2 mm Hg.ml-1.min-1, P less than 0.01). Changes in heart rate and in mean arterial pressure associated with isometric exercise were similar before and during epidural anesthesia at both levels of epidural blockade.(ABSTRACT TRUNCATED AT 250 WORDS)