Effect of hyperventilation on total calcium, ionized calcium, and serum phosphorus in neonates.

The effect of alkalosis (pH greater than 7.55) on total calcium, ionized calcium, and serum phosphorus was studied in seven infants with persistent pulmonary hypertension (PPH) before, during, and after hyperventilation. Hyperventilation-induced alkalosis resulted in marked decreases in total calcium, phosphorus, and ionized calcium. There was an inverse correlation between plasma Ca+2 and pH; a 0.1-unit increase in blood pH decreased Ca+2 by 0.42 mg/dl. Two of the study infants had ionized calcium concentrations less than 2.5 mg/dl during hyperventilation. These disturbing changes in total calcium, ionized calcium, and serum phosphorus could have potentially detrimental effects on neonates with PPH.