Choudhury Minati, Kiran Usha, Choudhary Shiv Kumar, Airan Balram
Department of Cardiac Anaesthesia, Cardiothoracic and Sciences Center, All India Institute of Medical Sciences, New Delhi, India.
J Cardiothorac Vasc Anesth. 2006 Apr;20(2):196-201. doi: 10.1053/j.jvca.2005.11.008.
This study estimated the arterial-to-end-tidal carbon dioxide tension difference (deltaPaCO2-PE'CO2) in children with congenital heart disease; evaluated whether hyperventilation can reduce this difference; and analyzed the relationship between the difference and the oxygen saturation (SaO2) and hemoglobin level.
Prospective clinical study.
Tertiary health care center.
One hundred patients scheduled for correction of their underlying cardiac defect with either right-to-left or left-to-right intracardiac shunts were divided into 4 groups (n = 25 each): (1) N1, cyanotic with severe pulmonary artery hypertension; (2) N2, cyanotic with normal or decreased pulmonary artery pressure (PAP); (3) N3, acyanotic with normal or mild increases in PAP and severe increases in pulmonary blood flow (PBF); and (4) N4, acyanotic with normal PAP and normal or mild increase in PBF.
All the patients received the same anesthetic regimen. The initial settings for tidal volume, respiratory rate, and inspiratory-to-expiratory (I:E) ratio were 10 mL/kg, 15 to 30 breath/min, and inspired time 40% of the total respiratory period with a 10% end-inspiratory pause. After the measurement of oxygen saturation, PO2, Hb, and deltaPaCO2-PE'CO2, all the children were hyperventilated (tidal volume: 14-15 mL/kg, respiratory rate: 5-6 breaths/min more than the initial rate, I:E ratio: same) to observe its effects on the deltaPaCO2-PE'CO2.
The deltaPaCO2-PE'CO2, when predicted from the oxygen saturation, hemoglobin concentration, and PaO2, was found to be greater than the observed value in the first 3 groups (p < 0.001); whereas in group N4 these 2 values were comparable. It was also found that the gradient was higher when there was a decrease in SaO2 and an increase in the hemoglobin level. After hyperventilation, in groups N1 and N3, deltaPaCO2-PE'CO2 was decreased when compared with their baseline values; this reduction was not as much as predicted (p = 0.363 and 0.236, respectively). However, in groups N2 and N4 posthyperventilation, the deltaPaCO2-PE'27 CO2 was decreased significantly below their baseline measurements. These decreases were as much predicted.
The deltaPaCO2-end-tidal carbon dioxide (PE'CO2) can be increased both in cyanotic and acyanotic children. Increased PAP is as important as increased PBF or right-to-left shunting in producing disorders in carbon dioxide homeostasis. Hyperventilation is of little use in reducing deltaPaCO2-PE'CO2 in children with high PAPs and pulmonary hyperperfusion.
本研究估算先天性心脏病患儿的动脉血与呼气末二氧化碳分压差值（ΔPaCO₂ - PetCO₂）；评估过度通气是否能降低该差值；并分析该差值与血氧饱和度（SaO₂）及血红蛋白水平之间的关系。
前瞻性临床研究。
三级医疗保健中心。
100例计划接受心内右向左或左向右分流的心脏缺陷矫正手术的患者被分为4组（每组n = 25）：（1）N1组，青紫型伴严重肺动脉高压；（2）N2组，青紫型伴正常或降低的肺动脉压（PAP）；（3）N3组，非青紫型伴正常或轻度升高的PAP及严重增加的肺血流量（PBF）；（4）N4组，非青紫型伴正常PAP及正常或轻度增加的PBF。
所有患者接受相同的麻醉方案。潮气量、呼吸频率及吸气与呼气（I:E）比值的初始设置分别为10 mL/kg、15至30次/分钟，吸气时间为总呼吸周期的40%，呼气末暂停10%。在测量血氧饱和度、PO₂、Hb及ΔPaCO₂ - PetCO₂后，所有儿童进行过度通气（潮气量：14 - 15 mL/kg，呼吸频率：比初始频率多5 - 6次/分钟，I:E比值不变），以观察其对ΔPaCO₂ - PetCO₂的影响。
根据血氧饱和度、血红蛋白浓度及PaO₂预测的ΔPaCO₂ - PetCO₂在前三组中高于实测值（p < 0.001）；而在N4组中这两个值相当。还发现当SaO₂降低且血红蛋白水平升高时，该梯度更高。过度通气后，N1组和N3组的ΔPaCO₂ - PetCO₂与基线值相比降低；但降低幅度未达预期（分别为p = 0.363和0.236）。然而，在N2组和N4组过度通气后，ΔPaCO₂ - PetCO₂显著低于其基线测量值。这些降低幅度与预期相符。
青紫型和非青紫型儿童的ΔPaCO₂ - 呼气末二氧化碳（PetCO₂）均可升高。在导致二氧化碳内环境稳态紊乱方面，升高的PAP与增加的PBF或右向左分流同样重要。对于PAP高且肺血流灌注过多的儿童，过度通气在降低ΔPaCO₂ - PetCO₂方面作用不大。
