The effect of smoking upon blood flow in the sympathectomized limb.

The effect of smoking upon the blood flow of a sympathectomized limb was examined in 19 patients. Sympathectomy was found to abolish the peripheral vasoconstriction produced by smoking. The constriction, therefore, is mediated by sympathetic vasomotor fibers and not by humoral agents such as adrenaline or posterior pituitary hormone. There is no difference in the response of patients sympathectomized for thromboangiitis obliterans, arteriosclerosis or severe vasospasm. The relation between the vasoconstrictor effect of smoking and the action of tobacco in thromboangiitis obliterans is discussed. T HE PERIPHERAL vasoconstriction produced by smoking has been known for many years. Most investigatorsl-5 have found this constriction due to the action of the absorbed nicotine; and not, as some have claimed, 6,7 the result of sympathetic reflexes initated by the breathing pattern of smoking or by the irritation of the smoke itself. GoetzO reported that the constriction at the very onset of smoking is of such reflex origin, while the more marked decrease in blood flow which follows is due to the sympathomimetic action of the absorbed nicotine. Nicotine in the amount inhaled from one or two cigarettes acts as a general synaptic stimulant. As such, in theory, it could produce peripheral vasoconstriction by four known mechanisms: (1) by the excitation of central vasomotor centers, (2) by a direct stimulation of sympathetic ganglia, (3) by an increased production of adrenaline, and (4) by the liberation of posterior pituitary hormone. The first two of these mechanisms require an intact sympathetic nerve supply to the blood vessels. The third and fourth are humoral and should not be abolished by sympathectomy. Rather, Sponsored by the Veterans Administration and published with the approval of the Chief Medical Director. The statements and conclusions published by the authors are a result of their own study and do not necessarily reflect the opinion or l)olicy of the Veterans Administration. 850 sympathectomy has been said to increase the sensitivity of blood vessels to the vasocon-strictor effects of adrenaline,9 10 although this is questionable.1' About 50 milliunits of posterior pituitary hormone are said to be liberated by the smoking of one or two cigarettes.'2 This is the equivalent in man of the amount found to decrease coronary blood flow in the dog. It seemed possible that it should also produce peripheral vasoconstriction. The present experiments were conducted to answer the question-does the vasoconstrictor response to smoking persist after sympathec-tomy, i.e., is its mechanism …