Looking at Labs Hemoglobin level Background Clinical alert • Increased Hb levels are found in: Hemoglobin (Hb), the main An Hb value less than 5.0 g/dL ° polycythemia vera component of erythrocytes (red (50 g/L) can lead to heart failure ° heart failure blood cells [RBCs]), serves as the and death. A value greater than ° chronic obstructive pulmonary vehicle for the transportation 20 g/dL (200 g/L) can lead to disease of oxygen and carbon dioxide. obstruction of the capillaries as a • Variation in Hb levels: It is composed of amino acids result of hemoconcentration. ° occurs after transfusions, that form a single protein called hemorrhages, burns. (Hb and globin, and a compound called Clinical implications HCT are both high during heme, which contains iron atoms • Decreased Hb levels are found and immediately after hemor- and the red pigment porphyrin. in anemia states (a condition in rhage.) It is the iron pigment that com- which there is a reduction of Hb, ° The Hb and HCT provide bines readily with oxygen and hematocrit [HCT], or RBC val- valuable information in an gives blood its characteristic red ues). The Hb must be evaluated emergency if they are inter- color. Each gram of Hb can carry along with the RBC count and preted not in an isolated fash- 1.34 mL of oxygen per 100 mL HCT. ion but in conjunction with of blood. The oxygen-combining ° iron deficiency, thalassemia, other pertinent lab data. capacity of the blood is directly pernicious anemia, hemoglo- ° Hb variants can cause varia- proportional to the Hb concentra- binopathies tion in measured Hb: tion rather than to the RBC count ° liver disease, hypothyroidism methemoglobin because some RBCs contain more ° hemorrhage (chronic or acute) sickle cell hemoglobin Hb than others. Therefore, Hb ° hemolytic anemia caused by: fetal hemoglobin determinations are important in transfusions of incompatible deoxyhemoglobin. the evaluation of anemia. blood The Hb determination is part reactions to chemicals or Clinical implications of of a complete blood cell count. drugs polycythemia It is used to screen for disease reactions to infectious agents Polycythemia is the term used to associated with anemia, to deter- reactions to physical agents describe an abnormal increase in mine the severity of anemia, to (severe burns, artificial heat the number of RBCs. Although monitor the response to treat- valves) there are several tests to directly ment for anemia, and to evaluate ° various systemic diseases, determine the RBC mass, these polycythemia. Hb also serves as including: tests are expensive and some- an important buffer in the extra- Hodgkin disease what cumbersome. For screen- cellular fluid. leukemia ing purposes, we rely on the lymphoma HCT and Hb to evaluate polycy- Normal findings systemic lupus erythemato- themia indirectly. Polycythemias • Women: 12.0 to 16.0 g/dL or sus are classified as follows: 120 to 160 g/L carcinomatosis • Relative polycythemia: an • Men: 14.0 to 17.4 g/dL or 140 to sarcoidosis increase in Hb, HCT, or RBC 174 g/L. renal cortical necrosis count caused by a decrease in 34 l Nursing2020CriticalCare l Volume 15, Number 4 www.nursingcriticalcare.com Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved. the plasma volume (dehydration, Clinical implications of ° hemorrhagic: acute blood spurious erythrocytosis from anemia loss stress or smoking) Anemias are classified as follows: ° hemolytic: a premature, accel- • Absolute or true polycythemia. • hypoproliferative anemias (inad- erated destruction of RBCs ° primary (polycythemia vera) equate production of RBCs) immune hemolysis ° secondary ° marrow aplasia hemoglobinopathies appropriate (an appropriate ° myelophthisic anemia toxic hemolysis (physical– bone marrow response to ° anemia with blood dyscrasias chemical) physiologic conditions) ° anemia of chronic disease traumatic or microangiopath- – high altitude ° anemia with organ failure ic hemolysis – cardiopulmonary disorder • maturation defect anemias hypersplenism – increased affinity for oxygen ° cytoplasmic: hypochromic enzymopathies inappropriate (an overpro- anemias parasitic infections duction of RBCs not neces- ° nuclear: megaloblastic anemias ° dilutional anemias sary to deliver oxygen to the ° combined: myelodysplastic pregnancy tissues) syndromes splenomegaly. ■ – renal tumor or cyst • hyperproliferative anemias – hepatoma (decreased Hb or HCT despite an – cerebellar hemangioblastoma increased production of RBCs) DOI-10.1097/01.CCN.0000660408.76985.53 www.nursingcriticalcare.com July l Nursing2020CriticalCare l 35 Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved..