Effects of dopexamine, dobutamine or dopamine on prolactin and thyreotropin serum concentrations in high-risk surgical patients

Objectives. Catecholamines are often used for optimisation of cardiac index and oxygen delivery in high-risk surgical patients; however, infusions of dopamine and dopexamine are associated with dose-dependent hypophysiotropic and thyreotropic properties. The objective was to compare endocrine effects of equipotent inotropic doses of dopexamine, dobutamine and dopamine on prolactin and thyreotropin release perioperatively. Design. A prospective, randomised, blinded clinical trial. Setting. Adult surgical intensive care unit in a university hospital. Patients. Thirty male patients (ASA III) undergoing elective major abdominal surgery. Interventions. Patients were randomised to receive dopexamine (DX, n=10), dobutamine (DO, n=10) or dopamine (DA, n=10) on the first postoperative day for 8 h. Measurements and results. All patients received a catecholamine infusion in doses adjusted to increase cardiac index by 35% within the first hour. Blood samples were obtained and prolactin and thyreotropin serum concentrations were determined by radioimmunoassays. Mean doses of dopexamine, dobutamine and dopamine used were 0.73+/-0.27, 4.06+/-1.95 and 5.0+/-1.84 mug kg(-1)min(-1), respectively. Cardiac index was increased by 36% (DX group), 38% (DO group) and 38% (DA group). Alterations of oxygen delivery and oxygen consumption were not significantly different between the study groups. Dopexamine and dobutamine had no hypophysiotropic effects. In contrast, dopamine suppressed prolactin and thyreotropin secretion with a maximal effect after 4 h. After dopamine withdrawal, a rebound release of prolactin and thyreotropin was observed. Conclusions. In high-risk surgical patients dopexamine or dobutamine produced fewer effects on prolactin and thyreotropin serum concentrations in comparison with DA when used in equivalent dosages.