The hemodynamic effects of dobutamine infusion in the chronically instrumented newborn piglet

Objective: To determine the systemic, pulmonary, mesenteric, and renal hemo dynamic effects of short and prolonged infusions of dobutamine, Design: Prospective randomized unblinded study, Setting: University research laboratory., Subjects: Thirteen newborn (1-3 days old) piglets. Interventions: Piglets were instrumented and studied 48 hrs later. Fifteen- minute infusions of dobutamine at 5, 10, 20 and 50 mu g/kg.min were randoml y given with 15-min rests between the doses. After a l-hr hiatus, a dose of 10 mu g/kg.min was continuously administered for 2 hrs, Measurements and Main Results: Systemic and pulmonary arterial pressures, c ardiac index (thermodilution), and superior mesenteric and renal artery flo ws were measured. Vascular resistance values were calculated. Main Results: Fifteen minute infusions: Dobutamine dose dependently increas ed cardiac index with tachycardia but not stroke volume (from 187 +/- 43 to 238 +/- 51 mL/kg.min at baseline and 50 mu g/kg.min, respectively, p < .05 ; values expressed as mean +/- so). Systemic, but not pulmonary, vascular r esistance decreased, resulting:in a significant decrease in systemic to pul monary arterial pressure ratio (from 3.8 +/- 0.8 at baseline to 3.2 +/- 1.0 at 50 mu g/kg.min). Superior mesenteric and renal flows were not affected. Two-hour infusion at 10 mu g/kg.min: Cardiac index progressively increased from 173 +/- 34 to 240 +/- 58 mL/kg.min at baseline and 120 mins, respecti vely (p < .05), The initial tachycardia was transient, and stroke volume wa s significantly increased at 60 mins and thereafter. Although systemic and pulmonary vascular resistance values fell simultaneously, systemic to pulmo nary arterial pressure ratio decreased significantly to 3.4 +/- 0.9 at 120 mins from 3.9 +/- 0.7 at baseline. Superior mesenteric and renal artery flo ws increased significantly with vasodilation after 60 mins, Conclusions: Short Infusions of dobutamine dose dependently increase cardia c output due to tachycardia, without significant effect on mesenteric and r enal blood flows. Prolonged infusion of dobutamine at 10 mu g/kg.min progre ssively increases cardiac output and stroke Volume with transient tachycard ia, and increases mesenteric and renal blood flows. Caution is required in the treatment of critically ill neonates with dobutamine, which could also reduce systemic to pulmonary arterial pressure ratio.