Summary
The effect of tolazoline was assessed in 29 hypoxic neonates. Tolazoline was given in a bolus starting at 1 mg/kg and repeated or infused for 5–134 hours. A “good clinical response,” defined as a rise in Pao2 of more than 20 mm Hg, was obtained in 23 (79%), 20 of this group were weaned from the respirator, and three died. Six infants did not respond initially and four died. Failure to respond to tolazoline or to be weaned from the ventilator was usually associated with severe additional pathology.
Urine output (>1 ml/kg/h) was adequate in most neonates during therapy. In those with preexisting oliguria (<1 ml/kg/h), output improved during therapy. Blood pressure monitoring showed a fall in blood pressure in 19 patients during tolazoline administration, but true hypotension only occurred in four; in seven there was no fall and in three there was a rise in blood pressure.
Echocardiography was performed prior to therapy in 19 patients and repeated in 12 patients after 24 h. Additional “tracking” was performed at 10 min, 1 h, and 4 h in seven patients. Prior to therapy, right ventricular dysfunction was demonstrated by abnormal right ventricular systolic time intervals (RVSTIs) in 17 of the patients tested. A rapid improvement was evident during therapy especially with “tracking.” Left ventricular dysfunction, assessed by left ventricular systolic time intervals (LVSTIs), ejection fraction (EF), shortening fraction (SF), and velocity of circumferential fiber shortening (VCF), was also evident prior to therapy and improved, though more gradually than the RVSTIs.
Tolazoline was therefore effective in neonatal hypoxia and improved cardiac dysfunction. A critical review of side effects and complications showed that (a) oliguria may precede therapy and renal impairment usually diminished, and (b) true hypotension was less of a problem than previously reported. As perfusion depends directly on blood pressure and inversely on vascular resistance, the systemic effect of tolazoline was to improve perfusion as a consequence of the fall in vascular resistance which improved ventricular function. We wish to introduce the hypothesis that afterload reduction is an additional therapeutic mechanism of tolazoline in neonatal hypoxemia.
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Sandor, G.G.S., Macnab, A.J., Akesode, F.A. et al. Clinical and echocardiographic evidence suggesting afterload reduction as a mechanism of action of tolazoline in neonatal hypoxemia. Pediatr Cardiol 5, 93–99 (1984). https://doi.org/10.1007/BF02424957
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DOI: https://doi.org/10.1007/BF02424957