Correlation between QoTc and serum as well as ionised calcium in sick neonates

Abstract

Background: Hypocalcemia is a frequently observed clinical and laboratory abnormality in neonates with risk factors such as prematurity, infant of diabetic mothers and perinatal asphyxia. Hypocalcemia can be asymptomatic or can cause apnoea, seizures, jitteriness, stridor, cardiac abnormalities. Clinically as calcium levels are maintained within narrow ranges. It is therefore imperative to measure and correct any deficit at the earliest. Unfortunately, total serum calcium level correlates poorly with ionized calcium level. Measurement of ionized calcium is both time consuming and expensive and therefore the need for more rapid, inexpensive and non-invasive method for screening at risk-neonates. Serum calcium levels are known to affect the duration of the QoTc interval. Therefore establishing a good correlation between serum/ionized calcium levels and QoTc will validate ECG as a reliable marker of hypocalcemia. Objective was to find correlation between QoTc interval and serum calcium levels in sick neonates.Methods: Total 730 infants were for serum total calcium and ionized calcium levels. Off these 142 infants with hypocalcemia, 29 infants were excluded based on exclusion criteria. The remaining 113 neonates were subjected to three cycles of ECG measurement before correction of calcium and were taken as cases. QoTc intervals were measured and were correlated with corresponding serum total calcium and ionized calcium levels.Results: In this study, a moderate negative or downhill correlation was found between total serum calcium QoT (r = -0.694 and p = <0.001) and QoTc (r = -0.680 and p = <0.001). The ionized calcium levels were found to have strong negative or downhill correlation with QoT (r = -0.837 and p = <0.001), QoTc (r = -0.819 and p = <0.001). All these correlations were found to be statistically significant with p<0.05.Conclusions: QoTc interval can be used as a surrogate marker for blood total or ionized calcium levels.