Overview
This lecture covers essential lab values for nursing exams, with a focus on understanding critical ranges, related pathophysiology, and priority interventions for patient safety.
Basic Metabolic Panel (BMP) & Electrolytes
- BMP includes sodium (Na), potassium (K), chloride (Cl), CO2 (bicarb), BUN, creatinine, and glucose.
- Sodium (135-145): swells the body; low causes mental changes, seizures; high causes edema, flushed skin.
- Potassium (3.5-5.0): pumps muscles; low causes flat T waves, muscle weakness; high causes peak T waves, muscle cramps, dysrhythmias.
- Potassium rules: never IV push, cardiac monitor, IV infusion max 10-20 mEq/hr, use IV pump.
- Hyperkalemia priority: IV calcium gluconate (if dysrhythmias), then insulin/dextrose, sodium polystyrene, dialysis.
- Calcium (9.0-10.5): contracts muscles; low causes diarrhea, positive Trousseau/Chvostek; high causes stones, constipation.
- Magnesium (1.3-2.1): mellows muscles; low causes hyperreflexia/arrhythmias; high causes hypo-reflexia.
Complete Blood Count (CBC)
- Hemoglobin (12-18): carries oxygen; <7 critical, report to HCP, signs are pallor, fatigue, cool skin.
- Hematocrit (36-54): ratio of RBCs/blood volume; high = dehydration, low = overload/bleeding.
- RBCs (4-6 million): low in anemia or kidney failure.
- WBCs (5,000-10,000): low increases infection risk; <5,000 needs neutropenic precautions.
- Platelets (150,000-400,000): low increases bleed risk; <50,000 is very risky.
Coagulation Studies
- Platelets: <150,000 = notify HCP; <50,000 = high bleed risk.
- PTT (46-70): monitors heparin; >70, stop heparin, give protamine sulfate.
- INR (2-3 for warfarin): >3, stop warfarin, give vitamin K; <2 at risk for clots.
- Antiplatelets (aspirin, clopidogrel): hold if platelets <150,000 or bleeding.
Cardiac, Renal, and Liver Labs
- Troponin (>0.5): indicates MI/heart damage.
- BNP (<100): indicates heart failure.
- Creatinine (>1.3): bad kidney, risk for toxicity.
- BUN (>20): dehydration or kidney injury.
- Urine output (<30 mL/hr): kidney distress.
- Urinalysis: high specific gravity = dehydration; RBCs = trauma/stones; WBCs/nitrites = infection.
Acid-Base Balance & ABGs
- pH (7.35-7.45): <7.35 = acidosis; >7.45 = alkalosis.
- PaCO2 (35-45): high = acidosis; low = alkalosis.
- HCO3 (22-26): regulates metabolic acid/base.
- Hypoxia: PaO2 <80; mental status change is earliest sign.
Diabetes & Cholesterol Labs
- Glucose (70-115): <70 is hypoglycemia, treat with fast sugar.
- A1C (<6.5): long-term glucose control.
- Total cholesterol (<200), LDL (<100), HDL (>40), triglycerides (<150): elevated increases cardiac risk.
- Statins: lower cholesterol, avoid with liver disease or grapefruit juice.
Liver Function & Related Interventions
- Ammonia: high = confusion (hepatic encephalopathy).
- Albumin: low in liver failure.
- Bilirubin: high causes jaundice.
- ALT/AST: elevated in liver disease.
- Key interventions: low protein, low sodium, no alcohol, oral care, soft toothbrush, monitor for bleeding/bruising.
Key Terms & Definitions
- BMP — Basic Metabolic Panel, measures core electrolytes and kidney function.
- CBC — Complete Blood Count, measures blood cells and clotting.
- PTT/INR — Coagulation times, used to monitor anticoagulant therapy.
- Troponin — Cardiac enzyme indicating heart muscle injury.
- BNP — Peptide indicating heart failure.
- Hepatic Encephalopathy — Brain dysfunction from high ammonia in liver failure.
- Neutropenic Precautions — Infection prevention steps for low WBCs.
- Hypoglycemia — Low blood sugar, dangerous for brain function.
Action Items / Next Steps
- Memorize key lab value ranges and critical highs/lows for exams.
- Review study guides and practice questions as recommended.
- Complete assigned readings on lab value interpretation and nursing interventions.
- Write out ABG normal values multiple times before your exam.