The effects of morphine on the resistance and capacitance vessels of the peripheral circulation

The Cardiovascular Effects of Morphine THE PERIPHERAL CAPACITANCE AND RESISTANCE VESSELS IN HUMAN SUBJECTS

“…Measurements were made between the 3rd and 6th min of head-up tilt. Similar studies were performed [15][16][17][18][19][20] min after the intravenous administration of morphine.…”

“…Although it has been suggested that morphine causes an adrenal release of catecholamines, this could not be responsible for the observed initial venoconstrictor effect of morphine (16,36). Since the hand was isolated from the circulation, the venoconstriction could not have been from a direct effect of the drug on the veins or secondary to a humoral blood-borne mediator.…”

“…Although respiratory depression is acknowledged as an important side effect of the drug, the unstressed human cardiovascular system appears to be little affected by the usual clinical doses of morphine (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18). While much research has been done on the circulatory effects of morphine, there still exists considerable uncertainty regarding its precise mechanism of action.…”

“…Morphine might alter any portion of the reflex arc from peripheral mechanoreceptor perception of hypotension through central nervous system integration to the usual effector responses of tachycardia, peripheral arteriolar constriction, and possibly venoconstriction. It has been suggested by animal studies that morphine does produce a venodilation that leads to a peripheral pooling of blood, and that this is the mechanism by which morphine improves pulmonary edema (2,16,18). Further, numerous studies have been done on the effects of morphine on the peripheral resistance vessels; however, considerable conflict still exists regarding the direction, magnitude, and mechanism of the response (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19).…”

Reversal by acupuncture of cardiovascular depression induced with morphine during halothane anaesthesia in dogs

“…1. [3][4][5][6][7] The inhibition of peripheral venous constriction by morphine has been used to explain the clinical usefulness of this drug in patients with acute pulmonary oedema, s Contradictorily, other investigators have concluded that morphine may improve ventricular performance by causing sympathoadrenal discharge 9 in spite of biphasic depressor responses, bradycardia and decreased respiratory rate. 3,1~…”