Roemer V M
International Institute of Foeto-Maternal Medicine Detmold e. V., Detmold, Germany.
Z Geburtshilfe Neonatol. 2007 Dec;211(6):224-9. doi: 10.1055/s-2007-981337.
Foetal hypoxia may lead to multi-organ failure and cerebral injury. Usually this process is accompanied by severe metabolic acidosis. The base excess (BE) determined in umbilical artery (UA) blood is the most appropriate parameter to evaluate metabolic acidosis. The correct determination of BE therefore is of paramount importance both for the jeopardised foetus and the obstetrician in litigation. In blood, BE is dependent on the oxygen saturation [sO2 (%)] of haemoglobin (cHb). Due to the normally low foetal pO2 values in UA blood (median: ca. 18 mmHg) sO2 is low as well; therefore computational correction of BE to - by definition - 100 % oxygen saturation seems to be mandatory. This paper presents an analysis of this complex problem in obstetrics.
pH, pCO2, pO2 and cHb were measured in UA blood of 6 302 term infants delivered spontaneously using equipments from Radiometer (Copenhagen). BE was computed according to the equation of Siggaard-Andersen actually used in many blood-gas analysers. sO2 (%) was computed for HbF using the algorithm of Ruiz et al. . The numerical correction of BE was achieved with an equation given again by Siggaard-Andersen . APGAR indices after 1 minute were used.
Median BE in UA was - 4.6 and the mean was - 4.9 +/- 3.0 mmol / L, respectively. Correction of BE (BEoxy.) to the actual (calculated) oxygen saturation (%) leads (always) to lower values: a median BE (oxy.) in UA of - 7.4 and a mean of - 7.6 +/- 3.2 mmol / L, respectively. There is no correlation between BE and sO2 in UA blood: r = 0.0078, p = 0.532, n = 6 302 (mean oxygen saturation: 27.7 +/- 18.3 % ). The median cHb amounted to 15.2 and the mean to 15.0 +/- 2.6 g %, respectively. The median delta-BE,UA(BE - BEoxy.) amounts to 2.74 mmol / L; the maximum delta-BE reached 5.2 mmol / L in this sample. Correction of BE to 100 % oxygen saturation based on the (calculated) real oxygen saturation (%) leads to significantly (p = 0.0099) higher correlations with the APGAR index (1 min) and pCO2 in UA (p << 10 (-4)) as well.
Correction of BE in UA, i. e., correction of BE to 100 % oxygen saturation using the (calculated) actual oxygen saturation (%) of the blood sample is mandatory in perinatal medicine. Correction uniformly leads to lower BE values (median: 2.7 mmol / L) and significantly higher correlation coefficients with important clinical variables (e. g., the APGAR index).
胎儿缺氧可能导致多器官功能衰竭和脑损伤。通常这个过程伴有严重的代谢性酸中毒。脐动脉（UA）血中测得的碱剩余（BE）是评估代谢性酸中毒最合适的参数。因此，准确测定BE对于处于危险中的胎儿以及面临诉讼的产科医生都至关重要。在血液中，BE取决于血红蛋白（cHb）的氧饱和度[sO2（%）]。由于UA血中胎儿的pO2值通常较低（中位数：约18 mmHg），sO2也较低；因此，按照定义将BE计算校正至100%氧饱和度似乎是必要的。本文对产科中的这一复杂问题进行了分析。
使用Radiometer（哥本哈根）的设备，对6302例足月自然分娩婴儿的UA血进行pH、pCO2、pO2和cHb测定。BE根据许多血气分析仪实际使用的Siggaard-Andersen方程计算。使用Ruiz等人的算法计算HbF的sO2（%）。BE的数值校正通过Siggaard-Andersen再次给出的方程实现。使用1分钟后的阿氏评分指数。
UA中的BE中位数为 - 4.6，平均值为 - 4.9±3.0 mmol/L。将BE（BEoxy.）校正至实际（计算）氧饱和度（%）会（总是）导致较低的值：UA中的BE（oxy.）中位数为 - 7.4，平均值为 - 7.6±3.2 mmol/L。UA血中BE与sO2之间无相关性：r = 0.0078，p = 0.532，n = 6302（平均氧饱和度：27.7±18.3%）。cHb中位数为15.2，平均值为15.0±2.6 g%。UA中δ-BE（BE - BEoxy.）的中位数为2.74 mmol/L；该样本中δ-BE的最大值达到5.2 mmol/L。基于（计算）实际氧饱和度（%）将BE校正至100%氧饱和度，与1分钟时的阿氏评分指数（p = 0.0099）以及UA中的pCO2（p << 10⁻⁴）也具有显著更高的相关性。
围产医学中必须对UA中的BE进行校正，即使用血样的（计算）实际氧饱和度（%）将BE校正至100%氧饱和度。校正后BE值通常会降低（中位数：2.7 mmol/L），并且与重要临床变量（如阿氏评分指数）的相关系数显著更高。
