Evaluation of Neurogenic Control of Blood Pressure

The contribution of sympathetic constrictor impulses to arteriolar tone is now recognized as playing an important though sometimes variable role in the maintenance of increased peripheral resistance in some patients with hypertension. However, lack of a clear understanding of the exact nature of autonomic influences and of their importance in relation to other pressor factors has complicated the development and evaluation of therapeutic measures for hypertension which have as their aim the modification of the "neurogenic component." 3 Results obtained after surgical sympathectomy have seemed encouraging in certain patients, discouraging in others. It has become apparent that operative results are inconsistent and that the most striking inconsistency is the effect on the blood pressure. Difficult, too, is the choice of patients who may be expected to benefit from this type of treatment; no satisfactory method of selection has yet been suggested. This study was undertaken in an effort to evaluate the nature of autonomic influences on blood pressure level as indicated by observations and comparisons of the responses to autonomic blockade with tetraethylammonium chloride 4 (TEAC) and spinal anesthesia to high thoracic levels.