All issues > Volume 34(3); 1991

Original Article

J Korean Pediatr Soc. 1991;34(3):303-310. Published online March 31, 1991.

Serum ionized Ca measured with new ion-selected electrode and Q-oTc interval in newborn infants.

Beom Joo Kim¹, Chang Hee Han¹, Heng Mi Kim¹, Doo Hong Ahn¹

¹Department of Pediatrics, School of Medicine Kyungpook National University, Taegu, Korea

Received: December 28, 1990;  Accepted: February 20, 1991.

Abstract

The reliability of electrocardiographic detection of serum ionized Ca level was studied in 13 preterm and 32 full term infants. The concentration of ionized Ca was measured with a new ion-selected electrode, NOVA SP4 (NOVA Biomedical, Waltham, MA USA). The Q-oTc interval correlated with total Ca (r=o.553, p<0.01) and ionized Ca (r= -0.435, p< 0.01) but the Q-Tc interval did not correlate with total and ionized Ca. The concentration of ionized Ca correlated with total Ca (r=0.455, p<0.01) but the predictive values of ionized Ca were poor. When the hypocalcemia was defined as ionized Ca<3.0 mg/dl, 91% of hypocalcemic infants revealed prolonged Q-oTc interval. Ionized Ca was low in 42% of cases when the Q-oTc interval was prolonged and in 2% when the Q-oTc interval was normal. When the hypocalcemia was defined as ionized Ca<3.5mg/dl, 69% of hypocalcemic infants revealed prolonged Q-oTc interval. Ionized Ca was low in 46% of cases when the Q-oTc interval was prolonged and in 10% when the Q-oTc interval was normal. The Q-oTc interval permits reliable screening test for ionized Ca<3.0 mg/dl but not for ionized Ca<3.5 mg/dl.

Keywords :Ionized Ca;Q-oTc interval