Plasma Ultrafiltrable Calcium in Respiratory Alkalosis and Acidosis

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Abstract
Dogs were subjected to either 30 minutes of respiratory alkalosis produced by overventilating with a positive pressure pump, or to 30 minutes of respiratory acidosis produced by inhalation of 30% CO2 in O2. Total plasma calcium concentration and ultrafiltrable calcium concentrations were determined on arterial blood samples drawn before, during and following the experimental procedure. In agreement with theory, ultrafiltrable calcium concentration decreased slightly during hyperventilation and increased during respiratory acidosis. A rebound increase in the level of ultrafiltrable calcium in the recovery phase following hyperventilation and a similar but inverse rebound following respiratory acidosis was observed in every case. It is postulated that these changes may be due to concomitant changes in plasma phosphate concentration. Total proteins and fractionated proteins did not show consistent changes in these experiments which could account for the changes observed in the ultrafiltrable calcium concentration. The significant changes in ultrafiltrable calcium concentration observed in these experiments would not be apparent if only total calcium concentration were determined since total plasma calcium concentration changed very little or not at all.