Vasopressin deficiency and pressor hypersensitivity in hemodynamically unstable organ donors

Background - Solid organ donors often develop hypotension due to vasodilation, and recently we observed that a variety of vasodilatory states are characterized by vasopressin deficiency and hypersensitivity. Thus, we investigated the prevalence of vasopressin deficiency in hypotensive solid organ donors without clinical evidence of diabetes insipidus; we also investigated the vasopressor effect of vasopressin replacement in hypotensive donors. Methods and Results - Fifty organ donors were evaluated for hemodynamic instability, (mean arterial pressure [MAP]≤70 mm Hg despite the use of catecholamine vasopressors), and in those unstable donors who were not already receiving exogenous vasopressin, low-dose vasopressin was administered as a continuous infusion (0.04 to 0.1 U/min). MAP, catecholamine requirements, serum vasopressin, and serum osmolality were obtained before and after vasopressin administration. Ten patients meeting the enrollment criteria received vasopressin and MAP increased from 72.2±3.5 to 89.8±4.2 mm Hg, (P<0.05), allowing for complete discontinuation of catecholamine pressors in 4 (40%) patients and a decrement in pressor dose in 4 (40%). Plasma vasopressin levels (2.9±0.8 pg/mL) were low for the degree of hypotension. Conclusions - Hemodynamically unstable organ donors without clinically apparent diabetes insipidus display a defect in the baroreflex- mediated secretion of vasopressin. In these patients, low-dose vasopressin significantly increases blood pressure with a pressor response sufficient to reduce catecholamine administration.