Laboratory Values: Metabolic Panel (BMP)

The Basic Metabolic Panel (BMP) provides essential information about electrolyte balance, kidney function, and glucose metabolism. These values directly impact cardiac function, neurological status, and fluid balance. Understanding the BMP is crucial for safe nursing practice and NCLEX success.

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Overview of the BMP

The BMP typically includes:

• Electrolytes: Sodium, Potassium, Chloride, CO2 (bicarbonate)
• Kidney Function: BUN, Creatinine
• Glucose: Fasting blood sugar

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Sodium (Na+)

Normal Range: 135-145 mEq/L

Sodium is the primary extracellular cation and regulates fluid balance and neurological function.

Hyponatremia (Na < 135 mEq/L)

Common Causes:

• SIADH (syndrome of inappropriate ADH)
• Heart failure (dilutional)
• Excessive hypotonic IV fluids
• Diuretics
• Vomiting/diarrhea

Nursing Interventions:

• Fluid restriction (for dilutional causes)
• Monitor neurological status closely
• Administer hypertonic saline SLOWLY if ordered (risk of osmotic demyelination)
• Seizure precautions

Memory Aid: "Low sodium = Low neuro function" (confusion, seizures)

Hypernatremia (Na > 145 mEq/L)

Common Causes:

• Dehydration (most common)
• Diabetes insipidus
• Excessive sodium intake
• Fever, burns (insensible fluid loss)

Signs/Symptoms:

• Extreme thirst
• Dry mucous membranes
• Altered mental status
• Fever
• Restlessness progressing to lethargy

Nursing Interventions:

• Fluid replacement (hypotonic solutions)
• Monitor I&O strictly
• Assess mental status frequently

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Potassium (K+)

Normal Range: 3.5-5.0 mEq/L

Potassium is the primary intracellular cation and is critical for cardiac conduction and muscle function. Potassium abnormalities are life-threatening.

Hypokalemia (K < 3.5 mEq/L)

ECG Changes:

• Flattened T waves
• U waves (pathognomonic)
• Prolonged QT interval
• Dysrhythmias

Common Causes:

• Diuretics (loop, thiazide)
• Vomiting/diarrhea
• NG suction
• Alkalosis

Signs/Symptoms:

• Muscle weakness, cramps
• Fatigue
• Cardiac dysrhythmias
• Diminished bowel sounds (ileus)
• Shallow respirations

Nursing Interventions:

• Potassium replacement (oral preferred, IV if severe)
• NEVER give IV potassium push (causes cardiac arrest)
• Maximum IV rate: 10-20 mEq/hour via infusion pump
• Dilute IV potassium properly
• Monitor ECG during replacement
• Increase dietary potassium (bananas, oranges, potatoes)

Hyperkalemia (K > 5.0 mEq/L)

ECG Changes:

• Peaked T waves (early sign)
• Widened QRS complex
• Flattened P waves
• Sine wave pattern (imminent arrest)

Common Causes:

• Renal failure (cannot excrete K)
• ACE inhibitors, potassium-sparing diuretics
• Tissue destruction (burns, crush injuries)
• Acidosis (K shifts out of cells)

Signs/Symptoms:

• Muscle weakness (similar to hypokalemia)
• Cardiac dysrhythmias
• Nausea, diarrhea
• Paresthesias

Nursing Interventions:

• Stop all potassium intake immediately
• Administer calcium gluconate (cardioprotective, does not lower K)
• Give insulin + glucose (drives K into cells)
• Kayexalate (removes K through GI tract)
• Dialysis for severe cases
• Continuous cardiac monitoring

Critical Value: K > 6.5 mEq/L - notify provider immediately

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Creatinine

Normal Range: 0.6-1.2 mg/dL

Creatinine is the most specific indicator of kidney function. It is a waste product of muscle metabolism filtered by the kidneys.

Elevated Creatinine (> 1.2 mg/dL)

Indicates:

• Acute Kidney Injury (AKI)
• Chronic Kidney Disease (CKD)
• Dehydration
• Nephrotoxic medication effects

Nursing Considerations:

• Monitor urine output (< 30 mL/hr may indicate AKI)
• Review medications for nephrotoxic drugs (NSAIDs, aminoglycosides, contrast dye)
• Hold metformin if receiving IV contrast
• Notify provider of rising creatinine trends

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Blood Urea Nitrogen (BUN)

Normal Range: 10-20 mg/dL

BUN is a waste product of protein metabolism. Less specific than creatinine for kidney function.

Elevated BUN

Causes:

• Dehydration (prerenal - BUN rises more than creatinine)
• Kidney disease
• GI bleeding (blood is digested protein)
• High protein diet
• Catabolic states

BUN:Creatinine Ratio

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Glucose

Normal Fasting: 70-100 mg/dL

Hypoglycemia (< 70 mg/dL)

Signs/Symptoms (Cold, Clammy):

• Diaphoresis, tremors
• Confusion, irritability
• Tachycardia
• Hunger
• Seizures (severe)

Memory Aid: "Cold and clammy, give some candy"

Nursing Interventions:

• If conscious: Give 15-20g fast-acting carbohydrate (juice, glucose tablets)
• If unconscious: Glucagon IM or D50W IV
• Recheck glucose in 15 minutes
• Follow up with complex carbohydrate/protein

Hyperglycemia (> 100 mg/dL fasting)

Signs/Symptoms (Hot, Dry):

• Polyuria, polydipsia, polyphagia (3 Ps)
• Warm, dry skin
• Fruity breath (DKA)
• Kussmaul respirations (DKA)
• Altered mental status

Memory Aid: "Hot and dry, sugar is high"

Nursing Interventions:

• Administer insulin as ordered
• IV fluids for dehydration
• Monitor potassium (insulin drives K into cells)
• Frequent glucose monitoring

Critical Values:

• Hypoglycemia: < 50 mg/dL
• Hyperglycemia: > 400 mg/dL

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Quick Reference Table

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On the Exam

The NCLEX frequently tests:

• Potassium abnormalities (life-threatening, know ECG changes)
• Safe IV potassium administration (never IV push)
• Sodium and neurological symptoms
• Creatinine trends indicating kidney function
• Hypoglycemia vs. hyperglycemia recognition

Priority Tip: Potassium and glucose abnormalities can be immediately life-threatening. These often take priority over other electrolyte imbalances.