Materials and Methods Study design and Population All infants and children admitted to Cairo University Children Hospital Medical PICU in the period from July 2010 through December 2010 were consecutively and prospectively enrolled excluding those with renal insufficiency. Sample size was determined using power analysis. Power was computed through the statistical package used and the value was 0.896 with alpha level = 0.05, power = 80%. After calculation, n = 68 and we have chosen 72 cases. The study was approved by Cairo University Ethics Committee and was conducted in accordance with the bylaws for human research. The study was explained and consents were obtained from all parents or legal guardians before enrollment. We had 4 drop out patients due to laboratory test availability (absent serum phosphorus level).