Gruber E M, Jonas R A, Newburger J W, Zurakowski D, Hansen D D, Laussen P C
Department of Anesthesiology, Harvard Medical School, Boston, Massachusetts, USA.
Anesth Analg. 1999 Aug;89(2):322-7. doi: 10.1097/00000539-199908000-00014.
Varying degrees of hemodilution are used during deep hypothermic cardiopulmonary bypass. However, the optimal hematocrit (Hct) level to ensure adequate oxygen delivery without impairing microcirculatory flow is not known. In this prospective, randomized study, cerebral blood flow velocity in the middle cerebral artery was measured using transcranial Doppler sonography in 35 neonates and infants undergoing surgery with deep hypothermic cardiopulmonary bypass. Patients were randomized to low Hct (aiming for 20%) or high Hct (aiming for 30%) during cooling on cardiopulmonary bypass (CPB). Systolic (V(s)), mean (Vm), and diastolic (Vd) cerebral blood flow velocity, as well as pulsatility index (PI = [V(s) - Vd]/Vm) and resistance index (RI = [V(s) - Vd]/V(s)) were recorded at six time points: postinduction, at cannulation, after 10 min cooling on CPB, rewarmed to 35 degrees C on CPB, immediately off CPB, and at skin closure. Vm was significantly lower in the high Hct group compared with that in the low Hct group during cooling (P < 0.01). Postinduction, the high Hct group demonstrated significantly lower Vd immediately off CPB (P < 0.01) and significantly lower Vm and V(s) at skin closure (P < 0.001). We conclude that there is an inverse relation between hematocrit and cerebral blood flow velocity during deep hypothermic cardiopulmonary bypass in neonates and infants.
There is an inverse relation between hematocrit and cerebral blood flow velocity during deep hypothermic cardiopulmonary bypass in neonates and infants. Further studies correlating Hct and cerebral blood flow velocity with cerebral metabolic rate and neurologic outcome are necessary to determine the optimal Hct during deep hypothermic cardiopulmonary bypass.
在深度低温体外循环期间会采用不同程度的血液稀释。然而，在不损害微循环血流的情况下确保充足氧输送的最佳血细胞比容（Hct）水平尚不清楚。在这项前瞻性随机研究中，对35例接受深度低温体外循环手术的新生儿和婴儿，使用经颅多普勒超声测量大脑中动脉的脑血流速度。在体外循环（CPB）降温期间，将患者随机分为低血细胞比容组（目标值为20%）或高血细胞比容组（目标值为30%）。记录六个时间点的收缩期（V(s)）、平均（Vm）和舒张期（Vd）脑血流速度，以及搏动指数（PI = [V(s) - Vd]/Vm）和阻力指数（RI = [V(s) - Vd]/V(s)）：诱导后、插管时、CPB降温10分钟后、CPB复温至35℃时、CPB结束即刻以及皮肤缝合时。在降温期间，高血细胞比容组的Vm显著低于低血细胞比容组（P < 0.01）。诱导后，高血细胞比容组在CPB结束即刻的Vd显著降低（P < 0.01），在皮肤缝合时的Vm和V(s)显著降低（P < 0.001）。我们得出结论，在新生儿和婴儿深度低温体外循环期间，血细胞比容与脑血流速度呈负相关。
在新生儿和婴儿深度低温体外循环期间，血细胞比容与脑血流速度呈负相关。有必要进一步开展将血细胞比容和脑血流速度与脑代谢率及神经学转归相关联的研究，以确定深度低温体外循环期间的最佳血细胞比容。
