INTRODUCTION: Arterial hypotension in the first 72 hours of age is observed in 20-40% in sick preterm newborns with a birth weight < 1500g. The two main causes are hypovolemia and cardiac dysfunction. Conventional therapy includes IV administration of iso-oncotic albumin, although in half of the patients this is not effective and inotropes. The objective of this study was to investigate if dopamine is better than dobutamine in the treatment of hypotension in newborns <1500g.

METHODS: Prospective, randomized study. All hypotensive infants with a birth weight between 1000 to 1500g were included in the study. Arterial hypotension was defined according to current criteria in relation to birth weight and postnatal age. We did not include infants with a maternal history of bleeding, infants with tight nuchal cords, hydrops fetalis or acute bleeding. Infants were divided into two groups after an initial an IV bolus of iso-oncotic albumin. Infants in Group A received dopamine and those in group B dobutamine. The initial dose of dopamine or dobutamine was 2.5 mcg/kg/min, with increases every 20 min, if necessary, to a maximum dose of 10 mcg/kg/min. Treatment failure was considered when there was no satisfactory response in 2 hours and then the infant was switched-over to the other inotropic agent. Data were compared with paired and non-paired student tests. The success rate was measured with X2.

RESULTS: 48 preterm infants were studied, 24 in each group. Both groups were similar in birth weight, gestational age, initial pH and blood pressure. All babies were receiving mechanical ventilation at the time of the study. Dopamine was successful in 87% and Dobutamine in 66% of the cases (p>0.05). In Group A there was a significant response (p <0.001) starting at 5mcg/kg/min, in relation to basal blood pressure and to the value obtained with a 2.5 mcg/kg/min dose. In Group B the only significant difference to the basal value was with a 10 mcg/kg/min dose (p <0.01). When dopamine failed and was switched to dobutamine, the success rate was 33%. When dobutamine failed, the success rate with dopamine, was 87.5%. There were no differences in heart rate any of the groups.

DISCUSSION: The initial dose for both drugs when used for hypotension should be at least 5mcg/kg/min. Since the success rate is higher with dopamine, and because switching dobutamine for dopamine had better results according to our study, dopamine should be the drug of choice in hypotensive infants < 1500g.