Thursday, April 14, 2011

Hepatitis C; Understanding the Basic Metabolic Profile (BMP)

Understanding the Basic Metabolic Profile (BMP)

The Basic Metabolic Profile (BMP) is a group of tests that examine blood chemistry, that is, the components of blood excluding red and white blood cells and platelets.

The tests which make up a BMP may vary slightly between labs or institutions, but generally they will provide the physician with information about serum electrolytes, blood sugar and kidney function.

The tests described in this article include:




Carbon Dioxide



Blood Urea Nitrogen (BUN)


Anion Gap

The normal range for serum sodium in the adult is 135 to 148 mEq/L.

Sodium (Na) aids in the regulation of the body's fluid balance, and along with potassium, maintains the electrical potential in the body that allows nerves to operate properly.

The fluids containing sodium are found almost entirely in extracellular (outside the cell) spaces, such as blood vessels. Sodium levels are maintained by the ingestion of sodium in food, and it is excreted through sweat, urine and feces.
Common causes of decreased serum sodium (hyponatremia) include:

Decreased sodium intake / increased sodium loss

Excess water ingestion



Administration of diuretics

Kidney disease

Addison’s disease

Edema and/or ascites.
Common causes of increased sodium (hypernatremia) include:

Increased sodium intake / decreased sodium loss

Excessive free water loss, such as sweating, burns

Diabetes insipidus

Osmotic diuresis.

The normal range for serum potassium in the adult is 3.5 to 5.5 mEq/L.

Potassium (K), as opposed to sodium, is found almost entirely inside the cells of the body. Proper levels of potassium are critical to the normal function of muscles, including the heart.

Abnormal levels of potassium can cause severe irregularities in the heart's rhythm and ability to contract. Potassium is ingested in the diet and is excreted in urine.

Common causes of decreased potassium (hypokalemia) include:

Diuretic use without potassium replacement

Administration of IV fluids without potassium

Alcoholic cirrhosis


Crohn's disease

Cushing's syndrome.
Common causes of increased potassium (hyperkalemia) include:

Kidney disease or failure

Rapid administration of IV fluids containing potassium

Burns and crushing injuries, trauma

Myocardial infarction (heart attack)

Addison's disease.

The normal range for serum chloride in the adult is 95 to 105 mEq/L.

Chloride (Cl) works with sodium to maintain the balance of fluids in the body, and aids in the regulation of the acid / base balance. It is an anion (negatively charged particle) found mainly in extracellular spaces.

Chloride abnormalities can cause increased nervous system irritability, exaggerated reflex responses, decreased respiration, weakness, stupor and coma.

Alterations in chloride levels are unusual, but are found in association with other electrolyte imbalances.

Common causes of deceased chloride (hypochloremia) include:

Vomiting, diarrhea, or gastrointestinal suctioning

Administration of diuretics

Administration of IV fluids without electrolyte replacement.
Common causes in increased chloride (hyperchloriemia) include:


Acid/base imbalances

Administration of medications containing chloride.
Carbon Dioxide

The normal range for serum carbon dioxide in the adult is 23 to 30 mEq/L or 23 to 30 mmol/L.

Carbon dioxide (CO2) is an anion (negatively charged ion) that assists in acid / base balance and helps maintain the electrical neutrality of fluids both inside and outside cells.

In solution, carbon dioxide (CO2) combines with water (H2O) to form carbonic acid (H 2CO3). Higher levels of CO2 in the blood create an acidic condition (acidosis), and low levels create an alkaline condition (alkalosis).

Levels of CO2 are regulated by the kidneys and CO2 is expelled by the lungs during respiration.

Alterations in the concentration of this electrolyte do not occur in isolation; that is, abnormalities in CO2 are always related to a co-existing disease or condition.

Common causes of increased serum carbon dioxide (acidosis) include:

Diseases / conditions that decrease respiration


Congestive heart failure

Uncontrolled diabetes


Kidney disease / failure


Certain medications and poisons.
Common causes of decreased serum carbon dioxide (alkalosis) include:

Diseases / conditions that increase respiration (hyperventilation)

Fluid losses from the GI tract (vomiting, suctioning)

Administration of diuretics

Administration of steroids

Cushing's disease

Salicylate intoxication

Excessive administration of medications containing bicarbonate.

The normal range for serum calcium in the adult is 9 to 10.5 mg/dL, or 2.25 to 2.75 mmol/L.

Calcium (Ca) is found primarily in the body in the form of bones and teeth; however, about 10% is found in the blood, in the form of a cation (positively charged ion) that plays an important role in the function of nerves and coagulation of blood.

When levels of serum calcium are low, the body produces hormones that remove calcium from bone to supplement serum calcium.

Because serum calcium plays an important role in nerve function, alterations in calcium levels can cause serious symptoms. These include decreased or exaggerated muscle tone, abnormal reflexes, severe gastrointestinal problems, such as nausea, vomiting, cramping and constipation, and disorders of the central nervous system, like lethargy, depression, convulsions and coma.

In extreme cases, pathological bone fractures can occur as a result of prolonged calcium loss.

Common causes of decreased serum calcium (hypocalcemia) include:

Diseases of the small intestine, interfering with calcium absorption

Excessive protein intake

Administration of blood with citrate

Common causes of increased serum calcium (hypercalcemia) include:

Prolonged immobilization


Diseases involving the breakdown of bone

Excessive ingestion of vitamin D

Kidney diseases / failure.

The normal range for serum glucose in the adult is 70 to 110 mg/dL.

Glucose (Glu) is a form of sugar that circulates in the blood to provide metabolic fuel for all body processes. Carbohydrates and sugars are ingested through food, broken down and absorbed in the small intestine, and are stored in the liver in the form of glucose.

The most common cause of abnormal blood sugar levels is Diabetes Mellitus, a disease in which serum glucose is consistently elevated as a result of decreased or absent insulin production, insulin resistance, or both.

The physical consequences of persistently elevated serum glucose / diabetes are many, and affect almost every body system.

The symptoms of decreased levels of serum glucose (hypoglycemia) can include sweating, anxiety, rapid pulse, and headache. If serum glucose drops to below 50 mg/dL, the patient may have loss of consciousness, and perhaps convulsions.

Common causes of increased serum glucose (hyperglycemia) include:

Diabetes Mellitus

Administration of certain steroids and hormones

Administration of total parenteral nutrition

Administration of diuretics

Diseases of the pancreas.
Decreased serum glucose (hypoglycemia) is not common, but causes may include:

Administration of insulin or other hypoglycemic medication


Exposure to severe cold


Prolonged fever

Diseases of the pancreas

Decreases in pituitary or adrenocortical function.
Blood Urea Nitrogen

The normal range for blood urea nitrogen in the adult is 4 to 22 mg/dL.

Blood urea nitrogen (BUN) is a waste product of protein metabolism. It is produced by the liver and excreted in the urine.

Abnormal elevations of BUN are most commonly caused by diseases of the kidney, prostate, and urinary tract, and the patient may have symptoms characteristic of fluid overload: decreased urine output, weight gain, edema, and distended neck veins. The skin may be yellowed and easily bruised, and the patient's mental state may be affected.

Decreased BUN is uncommon, but common causes may include:

Liver failure, inhibiting protein metabolism

Negative nitrogen balance (when protein breakdown exceeds protein intake)



Prolonged IV therapy in patients receiving inadequate oral nutrition

Common causes of increased blood urea nitrogen (azotemia) include:

Kidney diseases / failure

Diseases decreasing the ability to excrete urine

Increased protein metabolism

Breakdown of muscle tissue (starvation, anorexia nervosa)




Gastrointestinal bleeding

Administration of corticosteroids

Administration of tetracyclines


The normal range for serum creatinine in the adult is 0.6 to 1.2 mg/dL. The ideal BUN:creatinine ratio is 20:1.

Creatinine (Cr) is a nitrogen-based waste product that is produced as a result of protein metabolism in muscle tissue. Creatinine is produced at a very steady rate and is not subject to rapid fluctuations. It is excreted by the kidneys.

Creatinine and BUN both measure kidney function, but in slightly different ways. It is clinically useful to evaluate the ratio of BUN to creatinine when conducting a diagnostic assessment.

Dehydration and protein breakdown can cause elevation in BUN, but may affect serum creatinine only slightly or not at all. However, if both BUN and serum creatinine are elevated, this strongly suggests the presence of primary kidney disease.

Common causes of increased serum creatinine include:

Kidney diseases / failure

Administration of diuretics, sulfonamides, chloramphenicol, ascorbic acid

Use of marijuana

Diet high in red meat.
Decreased serum creatinine is rare, but has been associated with muscular dystrophy.

Anion Gap

The normal range for anion gap is 12 to 18 mmol/L; however, newer, more sensitive test equipment may have a reference range of -4 to 7 mmol/L.

The anion gap is a figure calculated by subtracting the number of anions (chloride and bicarbonate, the negatively charged electrolytes) from the cations (sodium and potassium, the positively charged electrolytes).

The remainder, the "gap," is composed of unmeasured electrolytes, organic ions, and plasma proteins.

An increased anion gap indicates that presence of an excess of the unmeasured anions which can occur when surplus hydrogen ions have been introduced into the body.

Surplus hydrogen ions can shift the pH (the measure of acid / base balance) of the body towards an acid state, or acidosis.

Common causes of an increased anion gap include condition or diseases that induce acidosis, such as:

Diabetic ketoacidosis

Lactic acidosis

Kidney failure associated with increased BUN

Various drug or chemical toxicities.
Summary of Normal Ranges (Adult)

Sodium: 135 to 148 mEq/L

Potassium: 3.5 to 5.5 mEq/L

Chloride: 95 to 105 mEq/L

Carbon Dioxide: 23 to 30 mEq/L or 23 to 30 mmol/L

Calcium: 9 to 10.5 mg/dL, or 2.25 to 2.75 mmol/L

Glucose: 70 to 110 mg/dL

BUN: 4 to 22 mg/dL

Creatinine: 0.6 to 1.2 mg/dL

BUN / Creatinine ratio: 20:1

Anion Gap: 12 to 18 mmol/L (older equipment)
Anion Gap: -4 to 7 mmol/L (newer equipment)

McFarland M, Grant M. Nursing Implications of Laboratory Tests, 3rd ed. Delmar Publishers Inc

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