Department of Obstetrics and Gynecology, Texas Children's Hospital, Baylor College of Medicine, Houston, Texas.
Department of Pathology, Texas Children's Hospital, Baylor College of Medicine, Houston, Texas.
Am J Perinatol. 2019 Dec;36(14):1481-1484. doi: 10.1055/s-0039-1677800. Epub 2019 Jan 23.
The calculation of HCO and base excess in current blood gas analysis is based on the Siggaard-Andersen equation. One of the constants in this equation is dependent on the known buffering capacity of hemoglobin A. We sought to investigate differences in buffering capacity between adult hemoglobin A and fetal hemoglobin F as a potential explanation for the observed poor correlation between calculated base excess in umbilical cord blood and newborn outcomes. Such differences would influence a key constant in the Van Slyke/Siggaard-Andersen equation used to calculate HCO and base excess and could be an explanation of these observations.
This was a prospective observational study. We analyzed umbilical cord blood bicarbonate levels both as calculated values from a traditional blood gas analyzer and as measured values in 20 women giving birth at term. Since the calculated value is dependent upon the concentration and known buffering capacity of hemoglobin A, significant differences in these two analyses would imply differences in the buffering capacity of hemoglobins A and F.
The mean calculated HCO value was 25 mEq/L (25.3 ± 1.9) compared with a mean measured value of 25 mEq/L (24.6 ± 1.7) over a range of pH levels of 7.16 to 7.42. This difference was not significant ( = 0.07).
The buffering capacity of hemoglobin F, for clinical purposes, is not different than that of hemoglobin A and is not an explanation for the recognized poor correlation between base excess and neonatal outcome.
目前血液气体分析中 HCO 和碱剩余的计算基于 Siggaard-Andersen 方程。该方程中的一个常数取决于已知的血红蛋白 A 的缓冲能力。我们试图研究成人血红蛋白 A 和胎儿血红蛋白 F 之间缓冲能力的差异，这可能是解释在脐带血中计算的碱剩余与新生儿结局之间观察到的不良相关性的原因。这种差异会影响用于计算 HCO 和碱剩余的 Van Slyke/Siggaard-Andersen 方程中的关键常数，并且可能是这些观察结果的解释。
这是一项前瞻性观察性研究。我们分析了 20 名足月分娩妇女的脐带血碳酸氢盐水平，既有传统血液气体分析仪计算的值，也有实际测量的值。由于计算值取决于血红蛋白 A 的浓度和已知的缓冲能力，如果这两种分析存在显著差异，则意味着血红蛋白 A 和 F 的缓冲能力存在差异。
平均计算的 HCO 值为 25 mEq/L（25.3±1.9），而在 pH 值范围为 7.16 至 7.42 时，平均实测值为 25 mEq/L（24.6±1.7）。这一差异无统计学意义（ = 0.07）。
在临床实践中，血红蛋白 F 的缓冲能力与血红蛋白 A 没有区别，并且不能解释碱剩余与新生儿结局之间公认的不良相关性。
