Walker Joshua L, Gelfond Jonathan, Zarzabal Lee Ann, Darling Edward
University of Texas Health Science Center at San Antonio, Division of Surgery, Department of Cardiothoracic Surgery, San Antonio, Texas 78229, USA.
Perfusion. 2009 Sep;24(5):333-9. doi: 10.1177/0267659109354790. Epub 2009 Nov 30.
Recirculation (R), the shunting of arterial blood back into to the venous lumen, commonly occurs during veno-venous extracorporeal membrane oxygenation (VV-ECMO) and renders the monitoring of the venous line oxygen saturation no longer reflective of patient mixed venous oxygen saturation (S(V)O(2)). Previously, we failed to prove the hypothesis that, once R is known, it is possible to calculate the S(V)O(2) of a patient on VV-ECMO. We hypothesize that we can calculate S(V)O(2) during VV-ECMO if we account for and add an additional correction factor to our model for dissolved oxygen content. Therefore, the purpose of this study is to derive a more accurate model that will allow clinicians to determine S(V)O(2) during VV-ECMO when ultrasound dilution is being used to quantify R.
Using an extracorporeal circuit primed with fresh porcine blood, two stocks of blood were produced; (1) arterial blood (AB), and (2) venous blood (VB). To mimic recirculation, the AB and VB were mixed together in precise ratios using syringes and a stopcock manifold. Six paired stock AB/VB sets were prepared. Two sets were mixed at 20% R increments and 4 sets were mixed at 10% R increments. The partial pressure of oxygen (pO(2) ) and oxygen (O(2)) saturation of the stock blood and resultant mixed blood was determined. The original model was modified by modeling the residual errors with linear regression.
When using the original model, as the partial pressure of arterial oxygen (P(a)O( 2)) of the stock AB increased, the calculated S(V)O(2) was higher than actual, especially at higher R levels. An iteration of the original model incorporating the P(a)O(2) level (low, medium, high) and R was derived to fit the data.
The original model using R and circuit saturations for the calculation of S(V)O( 2) in VV-ECMO patients is an oversimplification that fails to consider the influence of the high pO(2) of arterial blood during therapy. In the future, further improvements in this model will allow clinicians accurately to calculate S(V)O(2) in conjunction with recirculation measurements.
再循环（R），即动脉血分流回静脉腔，在静脉 - 静脉体外膜肺氧合（VV - ECMO）期间普遍发生，这使得监测静脉管路氧饱和度不再能反映患者的混合静脉氧饱和度（S(V)O(2)）。此前，我们未能证明这一假设，即一旦知道R值，就可以计算接受VV - ECMO治疗患者的S(V)O(2)。我们假设，如果在溶解氧含量模型中考虑并添加一个额外的校正因子，我们就能在VV - ECMO期间计算S(V)O(2)。因此，本研究的目的是推导一个更准确的模型，使临床医生在使用超声稀释法量化R时能够确定VV - ECMO期间的S(V)O(2)。
使用用新鲜猪血预充的体外循环回路，制备两种血样；（1）动脉血（AB）和（2）静脉血（VB）。为模拟再循环，使用注射器和旋塞歧管将AB和VB按精确比例混合在一起。制备了六对AB/VB血样组。两组以20%的R增量混合，四组以10%的R增量混合。测定储备血样和混合后血样的氧分压（pO(2)）和氧（O(2)）饱和度。通过线性回归对残差进行建模，对原始模型进行修改。
使用原始模型时，随着储备AB血样的动脉血氧分压（P(a)O(2)）升高，计算出的S(V)O(2)高于实际值，尤其是在较高R水平时。推导了一个结合P(a)O(2)水平（低、中、高）和R的原始模型迭代版本以拟合数据。
在VV - ECMO患者中使用R和回路饱和度来计算S(V)O(2)的原始模型过于简化，未考虑治疗期间动脉血高pO(2)的影响。未来，对该模型的进一步改进将使临床医生能够结合再循环测量准确计算S(V)O(2)。
