This is the fourth article in a series on monitoring laboratory values. This month's column discusses the importance of monitoring glucose, hemoglobin (Hg), hematocrit (Hct), and iron. Refer to the table in the December 2008 issue as a quick reference tool.1

GLUCOSE

Glucose is formed from dietary carbohydrates and is stored in the liver and muscles as glycogen. Fasting blood glucose level gives the best indication of overall glucose hemostasis.

Insulin causes the transport of glucose to the cells for storage as glycogen. Glucagon stimulates conversion of glycogen to glucose for use by the cells as energy. Hypoglycemia results from malnutrition, cirrhosis, alcoholism, and excess insulin. Malnutrition leads to decreased wound healing. Patients with diabetes mellitus, burns, crush injuries, renal failure, and steroids have elevated levels of serum glucose. Chronically elevated glucose levels lead to decreased wound healing by inhibiting oxygen and nutrient perfusion via microvascular damage. It also affects polymorphonuclear lymphocytes causing decreased chemotaxis, diapedesis, and phagocytosis, leading to a decreased ability to fight infection. Finally, it is a risk factor for the development of arterial and neuropathic ulcers in patients with diabetes mellitus.

The normal glucose level ranges from 70 to 120 mg/dL. For the patient with a wound and diabetes, blood glucose levels should be checked before every meal with a glucometer if necessary.

HEMOGLOBIN

Hemoglobin is a protein found in blood, which gives blood its red color. Hg is composed of a protein globin envelope and heme, which binds and transports oxygen through the use of iron. Any deficiency of vitamins, minerals, and amino acids will cause a decreased production of Hg.

The lower the Hg, the less oxygen is transported to tissues, and the less capacity wounds have to heal properly. Oxygen plays a role in enzymatic and cellular metabolic reactions necessary for cell growth and proliferation. Decreased levels of Hg result from anemia, cirrhosis, hemorrhage, renal disease, volume overload, and certain medications (penicillin, tetracycline, aspirin, sulfonamides, indomethacin, vitamin A). Artificially low levels of Hg occur when blood is drawn from the same arm that is receiving intravenous fluids. True decreased Hg level is a risk factor for pressure ulcer formation. Elevated Hg results from dehydration, polycythemia, severe burns, high altitudes, and gentamicin use.

The normal Hg level varies for men and women. For men, the normal level ranges from 13 to 18 g/dL; for women, the level ranges from 12 to 16 g/dL. For the patient with a wound, the Hg level should be evaluated monthly.

HEMATOCRIT

Hematocrit is the volume of packed red blood cells in 100 mL of blood. It represents the concentration of red cells in blood.

Decreased Hct is associated with blood loss, anemia, malignancies, protein malnutrition, liver and renal disease, lupus and rheumatoid arthritis, antineoplastic agents, and penicillin. Elevated levels result from dehydration, diarrhea, polycythemia, and burns. As with Hg, artificially low levels may occur if blood is drawn from the same arm that is receiving intravenous fluids.

The normal Hct level varies for men and women. For men, the normal Hct level ranges from 42% to 52%. For women, this range is 37% to 48%. For the patient with a wound, the Hct level should be checked monthly.

IRON

Iron is the most abundant trace element in the body. It is absorbed from the duodenum and upper jejunum. It transports oxygen within the heme component of Hg. Iron is transported as transferrin to bone marrow for Hg synthesis and stored as ferritin. Total iron-binding capacity (TIBC) measures the amount of iron that can bind to transferrin for transport.

Iron and Hg go hand-in-hand. Therefore, decreased iron leads to decreased oxygen transport to tissues and subsequent decreased wound healing. Iron also aids in the oxidation of glucose to energy and acts as a cofactor for lysyl and prolyl oxidase involved in collagen synthesis. Iron deficiency causes decreased production of myeloperoxidase and catalase, which results in the inhibition of intracellular bacterial killing. Decreased levels of iron occur in anemia, malignancies, malnutrition, blood loss, burns, and steroid use.

Low serum iron in conjunction with high transferrin and TIBC indicates iron deficiency anemia. Low serum iron, transferrin, and TIBC are suggestive of chronic disease, cancers, and infections.

Increased iron also impairs immunity and can cause susceptibility to tumor formation. Elevated levels of iron can be found in hemochromatosis, anemia, liver damage, and oral contraceptive use.

The normal adult iron level ranges from 50 to 150 [mu]g/dL. For a patient with a wound, iron levels should be checked monthly.

Source: Hess CT. Clinical Guide: Skin & Wound Care. 5th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2005.

Reference