Abstract 1262 Poster Session I, Saturday, 5/1 (poster 99)

We determined the efficacy and safety of Tolazoline infusion in infants birth weight less than 750 gm with respiratory distress who developed severe hypoxemia, after ruling out any acute complication of mechanical ventilation and cardiovascular failure. Preterm infants (n=43) received Tolazoline infusion during 4 year-period. 3 infants were excluded secondary to incomplete data. Mean gestational age (GA) was 24 wk (22-34 wk) and mean birth weight (BW) was 581 gm (370-741 gm). All infants were on conventional ventilation and 33 infants received surfactant before initiation of Tolazoline infusion. Mean pre-treatment pH was 7.27±0.09 and mean PaCO2 was 44±13.6 torr with mean oxygen index (OI) of 34. Mean post-natal age at treatment was 7.9±4.6 hours. Dose of Tolazoline ranged from 0.25 to 2.0 mg/kg with an average dose of 0.5 mg/kg. A mixture of Tolazoline 1 mg/kg in 10 ml/kg of Plasmanate or normal saline was infused slowly at rate of 1 ml/min. 27 infants (67.5%) responsed; their OI decreased significantly to 9.5 post-treatment (p<0.001) without change in mean airway pressure. 52% of infants in this group exhibited dramatic response within 5 min. and 96% responsed within 30 min. 9 infants (33%) required repeated dose within 40 min. to 72 hours of the initial dose. No significant changes in blood pressure (BP) and heart rate (HR) were observed. There were no significant differences between responders and non-responders as to GA, BW, APGAR scores, admission arterial blood gas (ABG), pre-treatment ABG values, pre-treatment OI and ventilator settings. In non-responders (n=13), post-treatment HR droped from the baseline; mean HR decreased by 17 bpm.,p = 0.04 with no changes of BP, except for one infant, whose systolic BP decreased from 40 to 34 torr. 12/13 infants in non-response group died within the first week of life, from respiratory failure and air leak syndrome. Of the responders, only 5 infants died in the first week of life (p<.01).

We conclude that Tolazoline infusion is useful in management of extremely preterm infants with respiratory distress during early post-natal age. No serious side effects were observed. Decrease in HR after infusion may be an indicator of needing alternative therapies such as high frequency ventilation or nitric oxide inhalation.

Speculation: Prolonged elevated pulmonary artery pressure has been demonstrated in preterm infants with respiratory distress. Decreased pulmonary artery pressure after Tolazoline administration might improve pulmonary blood flow and decrease ventilation/perfusion mismatch, thus maintaining oxygenation in these infants and avoidance of barotrauma.