Diurnal Variations in the Acid-Base Balance of Blood

Abstract

Rune, S. J. & Lassen, N. A. Diurnal variations in the acid/base blance of blood. Scand. J. clin. Lab. Invest 22, 151-156, 1968.

Frequent measurements were made of pH and P_co2 in arterial blood samples from five subjects over many hours in the awake and sleeping state. Calculation of the concentration of non-volatile acid (i.e. ‘base-excess’, ‘buffer-base’ or ‘standard bicarbonate’) showed that the diurnal variations are dominated by those induced by secretion of gastric acid and pancreatic bicarbonate after ingestion of food. Expressed as change in the ‘base-excess’, a post-prandial alkaline tide lasting several hours and amounting to 1 to 2 mEq/l was found in subjects with normal gastric secretory capacity of acid. Otherwise no significant variation was found, either in day-time or during the night. No systematic post-prandial change in P_co2 was seen, but during sleep an increase was a constant finding. As a consequence of this variation also the pH of arterial blood is subject to variations during day and night. In the post-prandial period and during sleep, the pH undergoes a systematic change, being higher after meals and lower during sleep.

Key Words:

• Acid-base balance
• diurnal variation
• arterial pH
• arterial P_co2
• gastric acid secretion