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Blood Tests

Blood may be tested on a regular basis while patients are in the intensive care setting. Results from these tests may be used either to help with diagnosis or to follow the progress of organ dysfunction during the patients illness.

The principle tests of kidney function are the BUN (Blood urea nitrogen) and the creatinine. Normally, the BUN level is less than 20 mg/dl and the creatinine level is less than 1.2 mg/dl. Elevations of these lab values above normal usually signify kidney dysfunction although occasionally other processes (such as intestinal bleeding) can elevate the BUN. Levels of creatinine greater than about 2.0 mg/dl signify moderate kidney impairment and levels above about 5.0 mg/dl signify severe impairment. Severe kidney dysfunction can cause other problems with the patients blood chemistry tests including elevation of the potassium level, low sodium level, low calcium level, or high phosphorous level as well of symptoms related to fluid and toxin accumulation which include itchiness, loss of appetite, swelling, altered state of consciousness or shortness of breath. The decision to start dialysis (kidney replacement therapy) is made only partially based on both these laboratory values and patients symptoms.

The principle tests of liver function include the bilirubin, alkaline phosphatase, SGPT (also called the ALT), SGOT (also called the AST), LDH and GGT. Elevations of these tests can occur in disorders causing direct liver injury such as hepatitis, drug reactions, or disorders of the flow of bile from the liver and gall bladder to the intestinal system.

Common tests of coagulation (the ability of the blood to clot) are the prothrombin time (PT), partial thromboplastin time (PTT), and platelet count. Less commonly used tests of coagulation include the fibrinogen level, the level of fibrin split products (FSP) and the bleeding time. If a patient is on anticoagulation therapy (such as heparin or warfarin) or if the patient has a significant disorder of coagulation, the physician may note elevations of the PT, PTT, FSP and bleeding time or may note a decrease in the platelet count or fibrinogen levels. The complete blood count (CBC) measures the number of the principle blood cells in the circulation - the white blood cells (WBC), the red blood cells (RBC), and the platelets (see above). The concentration of hemoglobin (the principle molecule in the RBC that carries oxygen) and hematocrit (HCT, the percent volume of blood that is occupied by RBC's) are calculated. Elevation in the WBC count usually indicates either infection or medical "stress". A low WBC may indicate overwhelming infection or a problem with the bone marrow's ability to make new WBC's. A low RBC count, hemoglobin level or HCT indicates anemia. Anemia can be caused by blood loss, bone marrow dysfunction or increased destruction of circulating RBC's.

Many other blood tests are available in the intensive care unit setting. These include drug level monitoring, serologies (which look for a immune response to a disease or an infection), blood typing (for patients that might need blood transfusions), and cardiac enzymes (which look for evidence of injury to the heart which may be seen after myocardial infarction {heart attack}).

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