[Cerebrovascular circulation in premature infants in relation to theophylline therapy].

The impact of 6 mg/kg resp. 1.5 mg/kg i.v. administered Euphyllin (containing ca. 80% theophylline and ca. 20% ethylenediamine) on intracerebral circulation was investigated in 20 (gestational age 25-37 weeks) resp. 10 preterms (26-33 weeks). For that purpose blood flow velocity was measured in three intracerebral vessels (Internal carotid artery, internal jugular vein, and anterior cerebral artery) by transfontanellar pulsed Doppler ultrasonography before, 2 min after and 6 min after the drug was given. Vmax (mean peak velocity) decreased by 25% in the internal carotid artery, by 26% in the internal jugular vein, and by 17% in the anterior cerebral artery. With 1.5 mg/kg a decrease could only be evaluated in the internal carotid artery (by 10%). The reduction of cerebral blood flow induced by theophylline is due to both the simultaneous decrease of pCO2 (by 3 mmHg in our study) and a direct vasoconstrictive effect of the drug on the cerebral resistance vessels. Effects of theophylline on systemic circulation are not responsible for its influence on cerebral circulation. Regarding the physiological variability and ischemic threshold of the human brain the impact of theophylline on neonatal cerebral circulation must be estimated as a tolerable risk.