OBJECTIVE To assess in children with a transcranial Doppler the effect on cerebral blood flow velocities of desflurane, whose cerebral vasodilator effects have been studied in animals and in adults with intracranial lesions. METHODS Prospective clinical study. METHODS Ten healthy children, mean age: 3.4 yr, ASA physical class 1, undergoing minor urologic surgery, were included in this study. METHODS Induction was obtained with atropine 10 micrograms.kg-1, fentanyl 3 micrograms.kg-1 and propofol 3 mg.kg-1. Endotracheal intubation was facilitated by atracurium 0.3 mg.kg-1. Mechanical ventilation, with a 50% air/oxygen mixture was adjusted to achieve an end-tidal CO2 (PETCO2) level of 38 +/- 2 mmHg. Monitoring included measurement of mean arterial blood pressure (MAP), heart rate, PETCO2, SpO2 and end-tidal desflurane concentrations (FETDes). Mean blood flow velocities (Vmean) were measured in the middle cerebral artery using a bi-directional 2 MHz TCD system (EME-TC 2000 S). A first TCD measurement followed intubation (T1). Thereafter, desflurane was adjusted to 1 MAC. Six other TCDs were recorded each minute until FETDes reached the inspired fraction (T2-T7). Thereafter, CO2 reactivity was assessed with a hypocapnia test, induced by hyperventilation. Measures were done at T8 (PETCO2: 33 +/- 1 mmHg), T9 (PETCO2: 29 +/- 1 mmHg), and T10 (initial PETCO2: 38 +/- 1 mmHg). All these measurements were made before starting surgery. Analysis of variance (ANOVA) was used to analyse the data (P < 0.05 was considered as significant). RESULTS The Vmean and heart rate increased significantly with increasing concentrations of desflurane (Vmean from 68 +/- 27 to 106 +/- 30 cm.s-1 and heart rate from 109 +/- 17 to 136 +/- 15 b.min-1 between T1 and T7). During hypocapnia, Vmean decreased to 68 +/- 23 cm.s-1 at T9, and returned to normal values with PETCO2 at 38 mmHg at T10. SpO2 remained unchanged. Mean arterial pressure was stable from T1 to T7, but decreased significantly at T9 and T10. CONCLUSIONS Desflurane elicits a dose-dependent increase in cerebral blood flow velocities and heart rate, but does not change mean arterial pressure, suggesting that its cerebrovascular action is independent of its systemic vascular action. CO2 reactivity is maintained at one MAC. The results in children are similar to those seen in adults.