Background: Intraventricular and germinal matrix hemorrhage (IVH) is still a common neurological complication of the premature infants due to functional and structural vulnerable vessels in this area of the brain. However, term infants undergoing corrective cardiac surgery within the neonatal period are subjected to various physiological extremes and possible alteration of cerebral and cardiovascular hemodynamics during and after surgery predisposing to vascular injury and development of IVH. The objective of the study was to elucidate the relationship between the change in cerebral hemodynamics and subsequent occurrence of IVH in a homogeneous group of term infants undergoing an uniform procedure of corrective cardiac surgery involving hypothermic cardiopulmonary bypass (CPB).

Methods: In 21 neonates with complete d-transposition of great arteries (d-TGA) (age 8±3.4 days, weight 3338±320 g) undergoing primary arterial switch operation serial ultrasonography of the brain and doppler measurements of cerebral blood flow velocity (CBFV) in the anterior cerebral artery and internal carotid artery were performed 24 hours before and after surgery at the following postoperative hours (0.5, 1, 2, 4, 8, 24, 48, 72, 96, 120, 144). The resistance index (RI: maximal systolic flow velocity - enddiastolic flow velocity / maximal systolic flow velocity) was used as qualitative parameter of cerebrovascular resistance. Cardiac surgery was performed using full-fow CPB (120-150 ml/min/kg) and moderate hypothermia(rectal temp. 20-24 C°) without circulatory arrest. Intraoperative management of acide-base status was used according to the alpha-stat method.

Results: Moderate IVH grade I-III was diagnosed in 9 infants (2 grade 1, 4 grade II, 3 grade III) within the first 24 hours postoperatively. After surgery Infants with IVH had significantly increased enddiastolic flow velocities resulting in a significantly lower RI than those without IVH(p<0,01) prior to the detection of IVH. There was no significant difference in gestational age, mean arterial blood pressure and paCO2 between the IVH and non-IVH group. However, during this period infants with IVH had significantly lower central venous blood saturation (p<0.05) and higher epinephrine infusion rate (p<0.01) indicating transient low cardiac output. After the occurrence of IVH the RI was significantly increased for further 48 hours. 2 infants with IVH III developed internal hydrocephalus.

Conclusion: The significantly lower RI may indicate vasodilation and impairment of autoregulation in the IVH group after cardiac surgery by means of CPB. The immediate postoperative period in these hemodynamicaly unstable infants should be considered as a critical vulnerable phase for cerebral injury.