CEREBRAL HEMODYNAMICS IN PRETERM INFANTS AFTER EXPOSURE TO DEXAMETHASONE

Aim-To determine changes in brain haemodynamics produced by dexamethas one; to evaluate the pathophysiological conditions involved in the eff ect of dexamethasone. Methods-A prospective study was made of 12 venti lated preterm infants who received dexamethasone (0.25 mg/kg/12 hours) for ongoing chronic lung disease or extubation failure. Cerebral bloo d flow (CEF), absolute cerebral blood volume (CBV), and cerebral blood volume changes (Delta CBV) were estimated by near infrared spectrosco py, before and 10, 30, 60, 120, 180 and 240 minutes after the first, t hird, and fifth doses of dexamethasone. All patients were monitored co ntinuously using pulse oximetry; transcutaneous blood gases, and blood pressure. Results-There were significant short term changes in Delta CBV on each day of the study; Delta CBV increased significantly at 240 minutes compared with values before the first dose, and from 120 minu tes onward during the third and fifth doses. However, mean CBV values averaged over 240 minutes after the first, third, and fifth doses did not vary. Mean CBF values averaged over 240 minutes increased progress ively up to the fifth dose (significant differences between the first and fifth dose). The short term changes in CBF consisted of a signific ant increase 60 minutes after dexamethasone administration compared wi th the before and 10 minute values in every study Blood pressure was s ignificantly higher in the third and fifth doses than in the first dos e. Blood pressure showed no short term changes. There was no correlati on between CBF and blood pressure changes. TcPCO2 (transcutaneous PCO2 ) decreased significantly throughout the study period, with the averag e mean value in the fifth dose significantly lower than in the first d ose. Nevertheless, no short term changes in TcPCO2 were observed. Conc lusions-Postnatal systemic dexamethasone administration produced signi ficant changes in cerebral haemodynamics that seemed to be related to both a direct effect on regional vessel walls and the cumulative effec t of dexamethasone.