Background and objective: To prevent neurological complications, low-flow antegrade cerebral perfusion (ACP) is used during repair of complex congenital heart defects. To overcome technical problems, continuous monitoring of cerebral blood flow and oxygenation is mandatory. The aim of the study was to evaluate the effect of different ACP flow rates on cerebral oxygen saturation obtained by near infrared spectroscopy.
Methods: Ten consecutive neonates undergoing Norwood stage I were included. In addition to near infrared spectroscopy (Invos 5100; Somanetics Corp., USA) on both hemispheres, mean arterial pressure and transcranial Doppler flow velocity were measured continuously and arterial and jugular venous oxygen saturation intermittently. Cerebral oxygen extraction ratio was calculated. Measurement points were obtained after starting bypass, during ACP with flow rates of 30, 20 and 10 mL kg−1 min−1 and immediately after ACP. ANOVA and Tukey–Kramer multiple comparison test were used for statistics.
Results: The near infrared spectroscopy signal could be obtained in all children at all measurement points, whereas transcranial Doppler failed in 1 neonate at a flow rate of 30 mL kg−1 min−1, in 3 neonates at 20 mL kg−1 min−1 and in 4 neonates at 10 mL kg−1 min−1. With the reduction of flow there was a significant decrease of cerebral oxygen saturation on both hemispheres (right: 78 ± 8 to 72 ± 9 and 66 ± 8, P < 0.001; left: 71 ± 7 to 65 ± 7 and 60 ± 7, P < 0.001), of jugular venous oxygen saturation (94 ± 6 to 89 ± 13 and 83 ± 15, P < 0.001) and a significant increase in oxygen extraction ratio (9.1 ± 8 to 14.8 ± 14 and 21 ± 16, P < 0.001) respectively, for 30, 20, 10 mL kg−1 min−1.
Conclusion: Near infrared spectroscopy reliably detects flow alterations during ACP with profound hypothermia.