Neonatal pulmonary hypertension during extracorporeal membrane oxygenation

This prospective study was designed to monitor severe pulmonary hypertension during extra corporeal membrane oxygenation using echo Doppler variables.

All neonates treated with extracorporeal membrane oxygenation also have severe pulmonary hypertension. A study which monitors the reaction of the pre-existing pulmonary hypertension during extracorporeal oxygenation by frequent sampling of those variables related to pulmonary pressure is still lacking. Such a study is necessary to analyze the complex haemodynamic changes in patients undergoing extracorporeal membrane oxygenation.

In 29 neonates, we estimated pulmonary arterial pressure using peakflow velocity of regurgitation across the tricuspid- and pulmonary valve, peakflow velocity of shunting across persistent arterial ductus, and systolic time intervals of the right ventricle. Correlation between the several estimations of pulmonary arterial pressure were analysed with the Spearman correlation coefficient.

Systolic pulmonary arterial pressure measured by the velocity of tricuspid regurgitation illustrated severe pulmonary hypertension prior to extra corporeal membrane oxygenation (mean 63 mmHg, sd 20). Similar levels for the systolic pulmonary arterial pressure could be derived (mean 73 mmHg, sd 17) from ductal shunting. A fair correlation of 0.76 (p< 0.002) could be demonstrated. Pulmonary hypertension responded well and quickly to treatment by extra corporeal membrane oxygenation, with reductions within 24 hours to mean systolic levels of 35 mmHg, sd 23. This very early reaction has not previously been demonstrated and could be of importance in defining parameters for weaning from cardiopulmonary bypass. Diastolic pulmonary arterial pressure was investigated because of its relation to vascular resistance. It proved more difficult to measure because of the low incidence of pulmonary regurgitation. Derived diastolic pressures did not show any good correlations.

Pulmonary hypertension is well documented prior to extra corporeal membrane oxygenation and response very quickly to the institution of treatment. Ultra sound techniques are indicated at the bedside, and prove useful in monitoring pulmonary blood pressure during the procedure.