Understanding Common Lab Values

Common Lab Values and Nursing Considerations

• This worksheet aims to deepen the understanding of lab values encountered in clinical practice
• Connect your knowledge of fluids and electrolytes to clinical practice, understanding common causes for abnormal lab values and nursing responses for patient care.

Basic Metabolic Panel (BMP)

• Includes glucose, sodium, potassium, carbon dioxide, chloride, calcium, BUN, and creatinine

Comprehensive Metabolic Panel (CMP)

• Includes BMP components plus albumin, total protein, ALP, ALT, AST, and bilirubin
• May also include magnesium, phosphorus, and anion gap

Complete Blood Count (CBC)

• Includes white blood cell count (WBC), red blood cell count (RBC), hemoglobin, hematocrit, platelets, mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), and red cell distribution width (RDW)

CBC with Differential

• Involves CBC plus percentage and absolute differential counts of different types of blood cells

Blood Chemistries: Sodium (135-145 mEq/L)

• The most abundant cation in extracellular fluid
• Maintains osmotic pressure
• Regulates renal retention and excretion of water
• Stimulates neuromuscular reactions and maintains SBP

Hyponatremia (Lower than 135 mEq/L, Critical: <120 mEq/L)

• Causes include excessive GI fluid loss, excess diuresis, excess water intake/administration of non-electrolyte IV fluids, and conditions causing fluid retention (CHF, cirrhosis, liver failure).
• Treat with sodium containing fluids (0.9% NaCl or 3% NaCl) or oral NaCl tablets/high sodium foods
• Complications include nausea/vomiting, muscle cramps, confusion, lethargy, seizures, cerebral edema, and coma
• Nursing considerations: think VOLUME, monitor neuro status for worsening hyponatremia, monitor I&O, monitor for fluid overload when administering fluids

Hypernatremia (Greater than 145 mEq/L, Critical: >160 mEq/L)

• Causes include excessive salt intake without adequate fluid, decreased water intake, watery diarrhea, osmotic diuresis from glycosuria, high fever, and severe burns
• Treat with fluid replacement (D5W), hypotonic fluids (0.45% NaCl), or diuretics to facilitate sodium excretion
• Complications include lethargy, confusion, focal brain hemorrhage, seizures, and coma
• Nursing considerations: think VOLUME, monitor neuro status worsening hypernatremia, monitor serum electrolytes (lower serum sodium by 10 mEq/L in 24 hours to prevent cerebral edema), and monitor I&O

Blood Chemistries: Potassium (3.5 - 5.0 mEq/L)

• The most abundant intracellular cation
• Transmits electrical impulses in cardiac and skeletal muscle
• Maintains acid-base balance
• Has an inverse relationship to metabolic pH
• 80-90% is filtered through the kidney

Hypokalemia (Less than 3.5 mEq/L, Critical <2.4 mEq/L)

• Causes include inadequate intake of K+, ETOH abuse, GI losses, renal losses, and loop diuretics
• Treat with oral/parenteral potassium, diet high in potassium, balanced electrolyte solutions, Pedialyte, or sports drinks
• Complications include increased ectopy and cardiac arrhythmias
• Nursing considerations: think ELECTRICITY, monitor electrolyte levels, use oral potassium replacement if possible, do not crush extended-release K+ tablets, IV potassium can irritate veins, infuse slowly (10 mEq/hour)

Hyperkalemia (Higher than 5.0 mEq/L, Critical >6.0 mEq/L)

• Causes include excessive potassium intake, potassium-sparing diuretics, severe burns, and renal failure
• Treat with shifting K+ into cells with IV insulin (with D50), calcium gluconate, sodium bicarbonate, sodium polystyrene, or hemodialysis for severe cases
• Complications include cardiac arrest, muscle weakness, and paresthesias
• Nursing considerations: think ELECTRICITY, monitor electrolyte levels, monitor for hypoglycemia when shifting K+ using IV insulin, monitor for EKG changes (peaked T-waves, wide QRS complex), address underlying cause, sodium polystyrene causes diarrhea and K+ loss, be aware of foods containing potassium

Blood Chemistries: Magnesium (1.6 - 2.3 mg/dL)

• The second most abundant intracellular cation
• Required for transmission of nerve impulses and muscle relaxation
• Controls absorption of sodium, potassium, calcium, and phosphorus
• Magnesium, potassium, and calcium all go low or high together!

Hypomagnesemia (Lower than 1.8 mg/dL, Critical < 1.2 mg/dL)

• Causes include chronic alcoholism, diabetic ketoacidosis, GI losses, impaired absorption, renal disease, pancreatitis, and pregnancy-induced hypertension
• Treat with oral/parenteral magnesium replacement
• Complications include cardiac arrhythmias, neuromuscular irritability, muscle cramping, altered mental status, and seizures
• Nursing considerations: think CARDIAC/NEUROMUSCULAR, monitor vital signs, cardiac rhythm, and neuromuscular status

Hypermagnesemia (Greater than 2.6 mg/dL, Critical > 4.0 mg/dL)

• Causes include severe metabolic acidosis, renal failure, and tissue trauma
• Treat by discontinuing magnesium-containing medications, hemodialysis, or calcium gluconate for adverse reactions
• Complications include cardiac arrhythmias, respiratory depression, muscle weakness, and coma
• Nursing considerations: think CARDIAC/NEUROMUSCULAR, monitor vital signs, cardiac rhythm, respiratory status, and avoid medications containing magnesium

Blood Chemistries: Calcium (9-11 mg/dL)

• The most abundant cation in the body
• Necessary for almost all vital processes
• Half of total body calcium circulates as free ions to participate in coagulation, neuromuscular conduction, intracellular regulation, control of skeletal and cardiac muscle contractility
• 98-99% of calcium reserves are stored in teeth and skeleton

Hypocalcemia (Less than 9 mg/dL, Critical < 7 mg/dL)

• Causes include ETOH abuse, pancreatitis, chronic renal failure, inadequate intake, decreased vitamin D (sunshine), lack of weight bearing, loop diuretics, and hypomagnesemia
• Treat with oral calcium carbonate or parenteral calcium gluconate/chloride
• Complications include extravasation of parenteral medications, decreased cardiac output, hypotension, dysrhythmias, risk for bleeding, mental changes, and seizures
• Nursing considerations: think MUSCLE RESPONSE, monitor electrolytes/vital signs, monitor neuromuscular responses like seizures, tetany, paresthesias, muscle spasms, and monitor for bleeding

Hypercalcemia (Greater than 11 mg/dL, Critical > 12 mg/dL)

• Causes include prolonged immobilization, dehydration, cancer, excessive antacid intake, parathyroid gland tumors, and excessive vitamin D intake
• Treat by correcting underlying cause (IV fluids loop diuretic to eliminated Ca via the kidneys)
• Complications include hypertension and dysrhythmias
• Nursing considerations: think MUSCLE RESPONSE, monitor electrolytes/vital signs, monitor for hypertension, GI: N&V and anorexia

Blood Chemistries: Blood Urea Nitrogen (BUN) (10 - 20 mg/dL)

• Urea represents the end product of protein metabolism performed in the liver
• Urea diffuses freely in intra/extracellular fluid and is then excreted by the kidneys
• BUN reflects the balance between production and excretion of urea
• Ratio is 15-24:1 if creatine 1.0, expected BUN should be 15-24
• An indirect measurement of renal function, but does not reflect glomerular filtration

BUN Less than 10 mg/dL

• Causes include poor protein intake/malnutrition, liver disease, and malabsorption syndromes
• Treat by improving nutritional status and high-protein diet
• Not typically life-threatening, but nursing considerations include assess I&O closely, assess for signs of fluid retention/edema, assess for agitation, confusion, fatigue, N&V, and assess liver profile labs for correlating liver damage

BUN Greater than 20 mg/dL

• Causes include acute renal failure, CHF, hypovolemia-dehydration, pyelonephritis, and hyperalimentation/TPN
• Treat with fluid resuscitation and low protein diet
• Complications include renal failure and liver failure
• Nursing considerations include assess I&O closely, assess for signs of fluid retention/edema, assess for agitation, confusion, fatigue, N&V, and assess liver profile labs for correlating liver damage

Blood Chemistries: Creatinine (0.5 - 1.3 mg/dL)

• The end product of creatine metabolism, which is performed in skeletal muscle
• Small amount of creatine is converted to creatinine, which is then secreted by the kidneys
• Amount of creatinine generated is proportional to skeletal muscle mass
• The gold standard for kidney function because creatinine is produced in consistent quantity, and the rate of clearance reflects glomerular filtration

Creatinine less than 0.5 mg/dL

• Causes include decreased skeletal muscle and inadequate protein intake
• Treat with increased protein intake and monitor electrolyte levels
• Not typically life-threatening, but nursing considerations include assess I&O closely, assess for signs of fluid retention/edema, and assess for worsening hypokalemia

Creatinine Greater than 1.3 mg/dL

• Causes include CHF, dehydration, acute & chronic renal failure, and shock
• Treat by correcting the underlying problem, fluid resuscitation to keep SBP>90, fluid restriction, diarrhea, and kidney failure
• Nursing considerations include assess I&O closely, assess for signs of fluid retention/edema, and assess for declining renal function

Hematology: White Blood Count (WBC) (4,500 - 11,000 cells/mm³)

• WBC represents the primary defense against invading infections
• Total count of all five leukocytes: neutrophils, lymphocytes, eosinophils, basophils, and monocytes
• Indicates the overall degree of the body's response to pathology (must be evaluated and correlated through differential count)
• Elevated WBC due to significant increase in one differential usually the neutrophil
• Physiologic stress or steroids will increase WBC

WBC Less than 4,500 (Critical < 2,500)

• Causes include ETOH abuse, anemia, bone marrow depression, viral infections, and immunosuppression
• Treat with leukocyte growth factors (filgrastim) and neutropenic precautions
• Complications include increased risk for infection, sepsis, and multi-system organ failure.
• Low or elevated WBC can represent sepsis, assess closely for hypotension with known infection (septic shock), assess closely for any change in temperature trend (hypothermia or febrile can both represent sepsis, especially in elderly)

WBC Greater than 11,000 (Critical > 15,000)

• Causes include infection, anemia, inflammatory disorders, and steroid use
• Treat the underlying cause of infection or inflammation
• Complications include increased risk for infection, sepsis, and multi-system organ failure.
• Nursing considerations include assess closely for hypotension with known infection (septic shock), assess closely for any change in temperature trend (hypothermia or febrile can both represent sepsis, especially in elderly)

Hematology: Hemoglobin (Hgb) (13 - 18 mg/dL)

• Primary protein of erythrocytes that is composed of heme (iron) and globin (protein)
• Carries O2 to cells and CO2 back to the lungs
• Parallels hematocrit which is the the % of RBC in proportion to total plasma volume
• The gold Standard for evaluating blood/RBC adequacy (anemia, blood loss)

Hgb Critical < 7 mg/dL

• Other anemia levels includes Mild anemia: Hgb 10-12 mg/dL, Moderate anemia: Hgb 7-10 mg/dL, and Severe anemia: Hgb < 7 mg/dL
• Causes of hemoglobin including blood loss, hemorrhage, cancer, fluid volume overload, and renal failure
• Correct underlying problem, stop the source of blood loss, blood transfusion, iron supplementation, erythropoietin if caused by renal failure
• Complications include tissue hypoxia, shock, hypotension, cardiac insufficiency, pulmonary insufficiency, and renal insufficiency

Labs: Cardiac Troponin (<0.05 ng/mL)

• Is a contractile protein found in cardiac muscle that will be released into the systemic circulation with cardiac ischemia or acute MI
• Levels will rise 2-6 hours after injury and peak at 16-24 hours and then remain elevated for days
• If acute onset, CP to r/o MI done every 6 hours ×3 to determine pattern
• Treat with standards of cardiac care include continuous telemetry, and beta-blockers to decrease cardiac workload, and heparin or nitroglycerin drips
• Complications: irreversible cardiac muscle damage and arrhythmias

Troponin Values Greater than 0.05 ng/mL

• Causes: acute MI, unstable angina, minor myocardial damage after CABG or PTCA/stent placement, and ongoing cardiac stress (troponin leak)
• Treatment of MI angiogram with or without PCI or CABG for multi-vessel disease
• Nursing Considerations include assessing closely for recurrent or new onset of chest pain, assess cardiac rhythm and for any changes, PVC's, V-tach, or atrial fibrillation, assess HR and SBP to promote decreased cardiac workload, heart rate <80 SBP <140
• Nursing considerations: assess tolerence tol activity and anticipate rechecking trop levels until they peak

Labs: Brain Natriuretic Peptide (BNP) (<100 pg/mL)

• A hormone that is stored in the ventricle of the heart
• When the left ventricle is distended and stretched due to CHF exacerbation, BNP is released into circulation
• Treat with aggressive diuresis for fluid overload and nitroglycerin drip or PO to decrease preload, which reduces the workload of the heart
• Complication: pulmonary edema, respiratory failure, cardiogenic shock
• Nursing considerations: think CARDIAC - CHF, inhibiting the release of renin by kidneys promotes water and sodium loss and increases glomerular filtration rate, assess respiratory status for tachypnea and breath sounds, assess HR and SBP to promote decreased cardiac workload and <80 and <140, assess tolerance to activity, assess I&O, assess K+ with loop diuretics

High BNP

• 100-500 = abnormal, but not critical

• 500 correlates with acute CHF exacerbation

• Causes: CHF exacerbation, ventricular hypertrophy (cardiomyopathy), and severe hypertension