Labs Bmp

Understanding the Basic Metabolic Profile (BMP) Jennifer Lyon, M.S., M.L.I.S. [email_address]

BMP 138 102 16 4.1 0.9 115 27 What do these numbers represent?

What is a BMP?

The Basic Metabolic Profile (BMP) can vary somewhat from institution to institution and may also be called the Complete Metabolic Profile (CMP) or a Chem-7.

It usually involves the following sets of measurements:

Four serum electrolytes: potassium, sodium, chloride, and bicarbonate

Two measures of renal function: blood urea nitrogen (BUN) and creatinine

A measurement of blood sugar (glucose)

Why is it important?

These values provide the physician with a lot of important information about the patient’s metabolic state.

Sodium and potassium levels are important to the body’s healthy function and abnormalities can have serious clinical consequences including death.

Renal (Kidney) function is important for a number of reasons including the ability of the body to metabolize drugs

Abnormal blood glucose levels can cause serious problems including coma and death

These values can also be used to get an overall sense of the body’s metabolic status and can provide useful clues to narrow down the differential diagnosis.

Examples of Clinical Questions

Is hyperkalemia (serum potassium > 5 mEq/l) diagnostic for acute digoxin overdose?

How should hyponatremia (low sodium) in a marathon runner be treated?

How should insulin be administered to treat adult patients in diabetic ketoacidosis (DKA); particularly should an initial bolus be given?

How long does it take to get metabolic acidosis from hemorrhage and how quickly does your bicarbonate fall from blood loss?

What is the significance of low BUN values in alcoholics?

What are the indications for the use of sodium bicarbonate to treat tricyclic antidepressant overdose?

Basic Metabolic Panel Sodium (Na) 135-145 Chloride (Cl) 100-108 Blood Urea Nitrogen (BUN) 8-25 Potassium (K) 3.5-5.0 Bicarbonate (HCO 3 ) 24-30 Creatinine 0.6-1.5 Serum Glucose 70-120 BMP = 4 Serum Electroytes (Na,K, Cl, HCO 3 ) + BUN & Creatinine + Glucose

Serum Sodium (Na)

Reported as milliequivalents (mEq) per liter of fluid (serum).

Conversion from milligrams (mg) to mEq

Divide # mg by 23 to get # mEq

Normal adult levels are 135-145 mEqs/L

For Na, the same normal level is used for all age groups; a 2-3mEq drop may occur with pregnancy

Abnormal Na Levels

High Na > 145 mEq/L = Hyp er natremia

Most common cause is dehydration

Other causes include impaired renal function, exchange transfusion with stored blood, overuse of IV saline

Low Na < 135 mEq/L = Hyp o natremia

Causes include excess water intake, Na loss due to sweating, vomiting, diarrhea, use of diuretics, sodium loss in urine

Fluid volume changes are usually the cause of changes in serum sodium levels

Potassium - K

Reported as milliequivalents (mEq) per liter of fluid (serum).

Adult dietary intake of K should be 40-80 mEqs

Normal adult levels are 3.5-5.0 mEqs/L

In pregnancy values may drop 0.2-0.3 mEq and for newborns, standard values are 4.0-6.0mEq/L

Abnormal K Levels

Hyperkalemia (Serum K>5.0mEq/L)

Causes include renal failure, too rapid infusion or K+ replacement, tissue damage,

Is associated with metabolic acidosis

Can cause cardiac arrhythmias, paralysis, muscle weakness

Is a medical emergency! Check the EKG!

Hypokalemia (Serum K<3.5mEq/L)

Causes include thiazide diuretics, vomiting/diarrhea, corticosteroids in large doses, tissue damage,

Is associated with metabolic alkalosis

Can cause paralysis, muscle weakness, cardiac arrhythmias

Dangerous in patients taking digitalis

Again, check the EKG!

Serum Chloride (Cl)

Also measured in mEqs

Normal adult values are 100-108 mEq/L

Remains same for all age groups and doesn’t fall in pregnancy

High Cl (Hyperchloremia; Cl > 108 mEq/L) is rarely considered alone clinically; it is usually secondary to increased sodium or decreased bicarbonate

Hypochloremia

Hypochloremia = Cl <100 mEq/L

Commonly caused by Cl loss in vomiting, gastric suction, diarrhea, and diuretic use

Usually, hypochloremia is part of a larger problem involving the other electrolytes as well

Bicarbonate

Changes in bicarbonate (HCO 3 - ) signify a change in acid-base balance

Value is 95% of total carbon dioxide (CO 2 )

Can be used with Na and Cl levels to determine the anion gap.

Normal Values

Adult 24-30 mEq/L

Children slightly lower than adults

Pregnancy 19-20mEq/L

Infant 20-26 mEq/L

Abnormal Bicarb

Usually involved in acid/base problems

The bicarbonate:carbonate ratio is important for buffering serum; should be 20:1.

Calculating the Anion Gap

Defined as the difference between the number of cations (+ ions = NA + K) and the number of anions (-ions = Cl + Bicarb)

(Na + K) – (Cl + HCO 3 ) = anion gap

Note that the K level usually doesn’t change the results much and is often not included

A normal anion gap is 8-16

or 8-12 if K not included

A high value for the anion gap is called a “wide gap”.

Doctors will say that the patient has a wide gap acidosis.

What is the anion gap? 139 102 16 4.1 0.9 187 27 With K: (139 + 4.1)/(102 + 27) = 143.1 - 129 = 14 Without K: 139 – (102 + 27) = 139 – 129 = 10 Both are within normal limits.

Blood Urea Nitrogen (BUN)

Measures the amount of urea nitrogen in the blood

Is primarily a test of renal function because the kidney is responsible for clearing BUN from the body

Dehydration, overhydration and liver failure may cause BUN to lose its significance as a sign of renal function

Normal Values

Adult 8-15mg/dL

Aged May be slightly increased

Pregnancy May be decreased up to 25%

Newborn May be slightly decreased

Abnormal BUN

Elevated BUN (>25 mg/dL)

Diseased or damaged kidney

Reduced blood flow to kidneys

Dehydration

Bleeding into the GI tract

Patient is eating a high protein diet

Decreased BUN (<8 mg/dL)

Overhydration

Increased antidiuretic hormone

Decreased liver function

Usually not very clinically significant alone (look at creatinine and ammonia levels if BUN is low)

Creatinine

Is the waste product of creatinine phosphate (a high energy substance found in skeletal muscle)

Varies during the day, but is not sensitive to hydration or protein metabolism

Normal Values

Adult men 0.6-1.5 mg/dL

Adult women 0.6-1.1 mg/dL

Children 0.2-1.0 mg/dL

Pregnancy Reduced

Newborn Reduced

Abnormal Creatinine

Elevated Creatinine

Due to damage to nephrons in the kidney

Cr >1.5 = >50% nephron function loss

Cr >4.8 = Up to 75% nephron function loss

Cr ~10 = End-stage kidney disease (90% loss)

Decreased Creatinine

Usually means atrophy of muscle tissue

BUN-to-Creatinine Ratio

The ratio of BUN: creatinine is normally ~10:1 but ranges from 6:1 to 20:1 depending on diet (protein intake) and amount of muscle

An increased BUN: creatinine ratio

Dehydration, certain types of kidney disease, breakdown of blood in the intestinal tract, increased dietary protein, or insufficient blood flow to the kidneys.

Decreased BUN: creatinine ratio

Certain types of kidney disease, liver disease, malnutrition, and Sickle Cell Anemia.

Glucose

Normal values for serum glucose

fasting for 8 hrs or more

Adults 70-120mg/dL

Newborn Worry if <40mg/dL

Pregnancy Slightly lower

Aged Slightly higher

Casual (non-fasting) – up to 200mg/dL

Dependant on multiple factors

May be called “accu-check” because that is the name of a common bedside test (i.e. finger stick method)

Abnormal Glucose

Hyperglycemia

Usually caused by diabetes mellitus, but may be related to hormone, glucocorticoid, and epinephrine levels

Can lead to acidosis (diabetic ketoacidosis) and coma

Treat with insulin

Hypoglycemia

In diabetics

Too much insulin, too little food, increased exercise without enough food intake

In nondiabetics

Not well understood

Fasting hypoglycemia may be caused by pancreatic tumor, pituitary loss of function, Addison’s disease (lack of cortisone), Alcohol

Functional or reactive type is usually postprandial, following a meal high in carbohydrates but low in sugar; may be related to stress or anxiety

Looking at the BMP

Check the numbers! Check them twice. Do they make sense? (Labs can make mistakes)

Calculate the anion gap (Na + K) – (bicarb + chloride) = anion gap

Check the BUN/creatinine ratio if needed

Practice Example 1 125 89 30 7.4 <5 2.5 975 54 yo male found unconscious Diagnosis: Diabetic Ketoacidosis Patient didn’t use insulin for 3 days after running out of his supply.

Practice Example 2 14 yo male cc: muscle weakness 142 1.3 28 1.1 98 107 16 Diagnosis: Hypokalemic Periodic Paralysis

Practice Example 3 5.4 4.1 108 27 137 102 68yo female cc: trouble breathing w/ history of congestive heart failure Diagnosis: Renal failure complicating CHF 68

Review: Basic Metabolic Panel Sodium (Na) 135-145 Chloride (Cl) 100-108 Blood Urea Nitrogen (BUN) 8-25 Potassium (K) 3.5-5.0 Bicarbonate (HCO 3 ) 24-30 Creatinine 0.6-1.5 Serum Glucose 70-120 BMP = 4 Serum Electroytes (Na,K, Cl, HCO 3 ) + BUN & Creatinine + Glucose

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