What is the venous hematocrit level at which you will diagnose polycythemia in a newborn?
Definition of polycythemia: a. Venous haematocrit of over 65%. b. Venous haematocrit of over 64% at 2 hours age. c. An umbilical venous or aerial haematocrit over 63% or more. The mean venous haematocrit of term infants is 53 in cord blood, 60 at 2 hours of age, 57 at 6 hours of age and 52 at 12-18 hours of age. As the haematocrit increases, there is increased viscosity and decreased blood flow. When haematocrit increases to more than 60% there is a fall in O2 transpo. Definition of hyperviscosity: Viscosity greater than 14.6 centipose at a shear rate of 11.55 as measured by a viscometer. (normal is 1.4-1.8 centipoise).
55%
60%
65%
70%