TY - CHAP M1 - Book, Section TI - Polycythemia: On Call A1 - Gomella, Tricia Lacy A1 - Eyal, Fabien G. A1 - Bany-Mohammed, Fayez PY - 2020 T2 - Gomella's Neonatology: Management, Procedures, On-Call Problems, Diseases, and Drugs, 8e AB - The hematocrit (Hct) is 68% in a newborn. Polycythemia is an increase in total erythrocyte mass empirically defined as a venous Hct >2 standard deviations above the normal value for postnatal and gestational age. An infant who has a peripheral venous Hct >65% or a hemoglobin >22 g/dL is considered polycythemic. Polycythemia occurs in 1% to 5% of healthy newborns (1%–2% at sea level and 5% at high altitude) and is rare in premature infants 14.6 centipoise (shear rate of 11.5 seconds) and is also defined as 2 standard deviations greater than the norm. Viscosity rises linearly until the Hct reaches 60% but increases exponentially when it reaches 70%. SN - PB - McGraw-Hill Education CY - New York, NY Y2 - 2024/03/28 UR - accesspediatrics.mhmedical.com/content.aspx?aid=1168357002 ER -