Published on 27/03/2015 by admin

Filed under Pediatrics

Last modified 27/03/2015

Print this page

rate 1 star rate 2 star rate 3 star rate 4 star rate 5 star
Your rating: none, Average: 0 (0 votes)

This article have been viewed 1444 times

Chapter 460 Polycythemia

Polycythemia exists when the red blood cell (RBC) count, hemoglobin level, and total RBC volume all exceed the upper limits of normal. In postpubertal individuals, an RBC mass > 25% above the mean normal value (based on body surface area), or a hematocrit level > 60 (in males) or > 56 (in females) indicate absolute erythrocytosis. A decrease in plasma volume, such as occurs in acute dehydration and burns, may result in a high hemoglobin value. These situations are more accurately designated as hemoconcentration or relative polycythemia because the RBC mass is not increased and normalization of the plasma volume restores hemoglobin to normal levels. Once the diagnosis of true polycythemia is made, sequential studies should be done to determine the underlying etiology (see imageFig. 460-1 on the Nelson Textbook of Pediatrics website at www.expertconsult.com).