Efficacy and safety of tolazoline for treatment of severe hypoxemia in extremely preterm infants

Objective. To determine the efficacy of tolazoline as a rescue treatment for hypoxemia in preterm infants with respiratory distress syndrome. Methods. Retrospective chart review on case series of infants weighing <750 g at birth who received tolazoline during a severe hypoxemic episode while receiving maximal ventilator support for respiratory distress syndrome. A slow bolus infusion of low dose tolazoline (0.5 mg-2 mg/kg) mixed with plasmanate or normal saline (10 mL/kg) was administered. Outcome measures evaluated included an increase in Pao₂ ≥20 mm Hg from pretreatment value and an increase in oxygen saturation to ≥90%. Results. Forty-three infants with a mean gestational age and birth weight of 24 weeks and 581 g, respectively, received tolazoline. All infants were mechanically ventilated and required a fraction of inspired oxygen of 1.0. Oxygenation improved in 72% (31/43) of infants with a tolazoline dose of 0.5 to 1.0 mg/kg. Of those who responded, Pao₂ values (mean ± standard deviation) pretolazoline and posttolazoline were 32 ± 7.5 mm Hg and 156 ± 114.9 mm Hg, respectively. In all responders, oxygen saturation increased to ≥90% within 30 minutes of tolazoline administration. Improvement in pH, pCO₂, oxygenation index, and mean airway pressure was also noted. Among nonresponders, pH decreased and pCO₂ increased after tolazoline. Minimal change in blood pressure was noted in both responders and nonresponders. Heart rate decreased by 19 beats per minute among nonresponders compared with an increase of 3 beats per minute in those who responded to tolazoline. Conclusion. Tolazoline is an effective treatment of severe resistant hypoxemia in preterm infants who are already on vigorous ventilatory support.