Acute changes in vasoactive lipid mediators in experimental hyaline membrane disease

Endothelial release of the arachidonate derivative PGI2 may be increased in response to cyclic lung stretching. We therefore sought to determine if the stable metabolite of PGI2, 6-keto-PGF1 alpha, would be found in increased quantities in primates ventilated with conventional mechanical ventilation (CMV) compared to treatment with high frequency oscillatory ventilation (HFOV). We also sought to determine if other membrane-derived vasoactive substances such as LTC4, PAF and TXB2 would be elevated in plasma and lung tissue of animals developing hyaline membrane disease (HMD) and if the levels would correlate with the severity of the respiratory distress. Twenty prematurely delivered monkeys were treated with either CMV or HFOV from the first breath after Cesarean delivery until sacrifice at 6 h of age. We found a significant increase from birth to 5 min and from 5 min to 5 h in 6-keto-PGF1 alpha, and a significant increase from 5 min to 5 h in TXB2. We found a significant decline from cord blood to 5 min of LTC4, without further change by 5 h. PAF was present in all plasma samples but showed no upward or downward trend. There was no difference in the 5-h plasma level or in the lung homogenate level of any of the lipid mediators between the two types of assisted ventilation. There was no correlation between any lipid mediator level and severity of the HMD, as measured by gas exchange, radiographic or histologic criteria, when assessed by each ventilator group alone or with both groups combined. We conclude that the immediate postnatal increases in TXB2 and PGI2 and decrease in LTC4 are not altered substantially by use of HFOV.