Cerebral haemodynamics in preterm infants after exposure to dexamethasone

Abstract

Aim-To determine changes in brain haemodynamics produced by dexamethasone; to evaluate the pathophysiological conditions involved in the eVect of dexamethasone. Methods-A prospective study was made of 12 ventilated preterm infants who received dexamethasone (0.25 mg/kg/12 hours) for ongoing chronic lung disease or extubation failure. Cerebral blood flow (CBF), absolute cerebral blood volume (CBV), and cerebral blood volume changes ( CBV) were estimated by near infrared spectroscopy, before and 10, 30, 60, 120, 180 and 240 minutes after the first, third, and fifth doses of dexamethasone. All patients were monitored continuously using pulse oximetry, transcutaneous blood gases, and blood pressure. Results-There were significant short term changes in CBV on each day of the study; CBV increased significantly at 240 minutes compared with values before the first dose, and from 120 minutes 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 progressively up to the fifth dose (significant differences between the first and fifth dose). The short term changes in CBF consisted of a significant increase 60 minutes after dexamethasone administration compared with the before and 10 minute values in every study. Blood pressure was significantly higher in the third and fifth doses than in the first dose. Blood pressure showed no short term changes. There was no correlation between CBF and blood pressure changes. TcPCO 2 (transcutaneous PCO 2 ) decreased significantly throughout the study period, with the average mean value in the fifth dose significantly lower than in the first dose. Nevertheless, no short term changes in TcPCO 2 were observed. Conclusions-Postnatal systemic dexamethasone administration produced significant changes in cerebral haemodynamics that seemed to be related to both a direct eVect on regional vessel walls and the cumulative eVect of dexamethasone. (Arch Dis Child Fetal Neonatal Ed 1998;79:F123-F128)

Dexamethasone Alters Vascular Reactivity by Enhancing COX-Related Vasodilatation in Fetal Ovine Carotids

“…In contrast, our fi nding differs from studies performed antenatally, which showed glucocorticoid-induced vasoconstriction after 24, 36, or 48 h of infusion [24,25] , highlighting differences in response between ante-and postnatal corticosteroid administration. As shown in fi gure 2 , we found that continued exposure to DEX for up to 4 h further decreased 5-HT efficacy, consistent with results by Pellicer et al [8] who reported signifi cant increases in cerebral blood fl ow and volume in infants after 4 h of exposure to DEX [8] . This data suggests that DEX treatment may alter cerebral circulation in unstable neonates, leading to either intracranial hemorrhage secondary to transient increases in cerebral blood fl ow or ischemia secondary to systemic hypotension.…”

“…The relaxant response was cumulative and immediate in nature and was seen at all bath concentrations investigated [22] . Our data also corresponds with clinical investigations performed postnatally which showed increases in cerebral blood fl ow velocity and decreases in resistance index in preterm infants after 60 min of DEX administration [8,23] . In contrast, our fi nding differs from studies performed antenatally, which showed glucocorticoid-induced vasoconstriction after 24, 36, or 48 h of infusion [24,25] , highlighting differences in response between ante-and postnatal corticosteroid administration.…”

“…While numerous studies, both in vivo and in vitro, have demonstrated that corticosteroids, such as DEX, can potentiate contractile responses to catecholamines [1,2] , other investigators demonstrate that DEX produces signifi cant relaxant effects [3][4][5] or no effects [6] on vascular tone. For instance, although postnatal DEX treatment was shown to increase cerebral blood fl ow in neonatal pigs [7] and decrease cerebral vascular resistance in preterm infants [8] , it was also shown to decrease pial arterial diameter and vasodilator prostanoids in neonatal pigs subjected to hyperventilation [9] . Overall, the contractile and relaxant effects of DEX have been shown to depend on age, species and artery type, dose and type of agonists utilized, presence of pathological condition, and the timing and duration of drug administration.…”

Cardiovascular Support for Low Birth Weight Infants and Cerebral Hemodynamics: A Randomized, Blinded, Clinical Trial

“…Analyses of the NIRS curves, including the quality check of raw data and rejection of measurements or calculations, were performed off-line with a custom-made computer program. 27,28 During the study, patients lay supine, with the head of the bed tilted 30°upward. The position of the head was either midline or turned 45°to the right or left.…”

“…A detailed description of the equipment can be found elsewhere. 27,28 Changes in O 2 Hb and RHb concentrations were calculated from changes in light absorption at each of these wavelengths and are given in micromolar units. A fixed pathlength factor of 4.4 was used to correct the path length of the light for the degree of scattering in brain tissue.…”