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[Cerebrovascular circulation in premature infants in relation to theophylline therapy]
Insights
Theophylline (Euphyllin) reduces cerebral blood flow in preterm infants by constricting brain vessels. This effect, observed in Doppler studies, is considered a tolerable risk for neonatal brain circulation.
Area of Science:
- Neonatal Medicine
- Pharmacology
- Neuroscience
Background:
- Theophylline (Euphyllin) is used in preterm infants.
- Its effects on intracerebral circulation require detailed investigation.
Purpose of the Study:
- To assess the impact of intravenous theophylline on cerebral blood flow velocity in preterm infants.
- To determine the relationship between theophylline dosage and changes in cerebral circulation.
Main Methods:
- Transfontanellar pulsed Doppler ultrasonography was used to measure blood flow velocity.
- Measurements were taken in the internal carotid artery, internal jugular vein, and anterior cerebral artery.
- Theophylline was administered intravenously at 6 mg/kg and 1.5 mg/kg to preterm infants.
Main Results:
- A 6 mg/kg dose of theophylline decreased mean peak velocity (Vmax) by 25% in the internal carotid artery, 26% in the internal jugular vein, and 17% in the anterior cerebral artery.
- A 1.5 mg/kg dose showed a 10% decrease in Vmax in the internal carotid artery.
- Theophylline-induced reduction in cerebral blood flow is attributed to decreased pCO2 and direct vasoconstriction.
Conclusions:
- Theophylline administration leads to a reduction in cerebral blood flow velocity in preterm infants.
- The observed effects on neonatal cerebral circulation are considered a tolerable risk given physiological variability and the brain's ischemic threshold.
Abstract:
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.