Treatment of severe persistent pulmonary hypertension of the newborn with magnesium sulphate.

Eight of nine newborn infants with severe persistent pulmonary hypertension of the newborn (PPHN), and a predicted mortality of 100%, and one infant with a predicted mortality greater than 94% based on alveolar-arterial oxygen tension difference [A-a)DO2) were treated with magnesium sulphate (MgSO4) as a life saving therapy after they failed to improve with conventional treatment. Magnesium at high serum concentrations decreases pulmonary pressures and is a muscle relaxant and sedative. Diluted MgSO4.7H2O solution (200 mg/kg) was given intravenously over 20-30 minutes. No changes in the treatment were made after MgSO4. Mean serum magnesium concentration was maintained between 2.88 and 5.67 mmol/l by continuous intravenous infusion (six infants). Baseline arterial oxygen tension (PaO2) and haemoglobin oxygen saturation had mean (SD) values of 4.66 (1.8) kPa and 60.4 (29.7)% respectively, which started to increase one hour after MgSO4 infusion, and increased significantly at six hours to 12.04 (7.07) kPa and 91.8 (10.88)% respectively. Arterial carbon dioxide tension (PaCO2) decreased and pH increased significantly after one hour compared with the baseline value. PaO2 increases are probably secondary to a decrease in pulmonary vascular resistance and pressure, decrease in a right to left shunt, better ventilation:perfusion ratio, and PaCO2 decrease and pH rise. Seven infants survived (77.8%). These results demonstrate the beneficial effect of magnesium in the management of PPHN when other accepted treatment fails, is contraindicated, or not available.