A STUDY OF PLASMA PK1' IN WOMEN IN LABOUR

Summary: Recent work has suggested that the term pK1′ in the Henderson-Hasselbalch equation may show wider variation than has been thought, and it seemed possible that the generally accepted values might not apply to women in labour. pK1′ was therefore determined experimentally in twenty volunteers in normal labour using arterialized venous blood. pH was measured by the glass electrode, Pco2 by the carbon dioxide electrode and Cco2 by the manometric apparatus of Van Slyke. The value so obtained was 6.106 at 38°C (with a standard deviation of 0.011). This was identical with the value obtained from ten non-pregnant controls and accords well with the value generally accepted as normal. This finding demonstrates the validity of the use of such nomograms as those of Siggaard-Andersen (1962a, 1963) and incidentally confirms the existence of a metabolic acidosis during labour. © 1969 John Sherratt and Son Ltd.