Section 4.5: Patient Assessment & Physical Examination Interpretation

Patient Assessment & Physical Examination Interpretation

Interpretation of Vital Signs

Vital signs are baseline physiological measurements used to evaluate overall bodily function and acute clinical status.

• Blood Pressure (BP): Classified based on the 2017 ACC/AHA Hypertension guidelines:
  • Normal: $< 120 / < 80 \text{ mmHg}$.
  • Elevated: $120\text{–}129 / < 80 \text{ mmHg}$.
  • Stage 1 Hypertension: $130\text{–}139$ systolic OR $80\text{–}89 \text{ mmHg}$ diastolic.
  • Stage 2 Hypertension: $\ge 140$ systolic OR $\ge 90 \text{ mmHg}$ diastolic.
• Heart Rate (HR): Normal adult range is 60–100 beats per minute (bpm).
  • Tachycardia ($> 100 \text{ bpm}$) can be secondary to fever, dehydration, anemia, hyperthyroidism, or medications (e.g., albuterol, pseudoephedrine).
  • Bradycardia ($< 60 \text{ bpm}$) can occur in trained athletes, hypothyroidism, or secondary to beta-blockers, non-dihydropyridine CCBs, or digoxin.
• Respiratory Rate (RR): Normal adult range is 12–20 breaths per minute. Tachypnea ($> 20$) is an early sign of respiratory distress, pulmonary embolism, metabolic acidosis, or sepsis.
• Temperature: Normal core body temperature is 36.5°C to 37.5°C (97.7°F to 99.5°F). Fever is typically defined as a temperature $\ge 38.0^\circ\text{C}$ ($100.4^\circ\text{F}$).
• Oxygen Saturation ($\text{SpO}_2$): Normal range is 95% to 100% on room air. Levels $< 90%$ indicate hypoxemia requiring oxygen therapy.

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Complete Blood Count (CBC) Interpretation

The CBC measures cellular components of blood and is essential for diagnosing anemia, infection, and clotting disorders.

• Red Blood Cells (RBC), Hemoglobin (Hb), and Hematocrit (Hct):
  • Normal Hb: Men: $13.5\text{–}17.5 \text{ g/dL}$; Women: $12.0\text{–}15.5 \text{ g/dL}$. Low levels indicate anemia.
  • Mean Corpuscular Volume (MCV): Reflects RBC size (Normal: $80\text{–}100 \text{ fL}$).
    • Microcytic Anemia ($MCV < 80 \text{ fL}$): Typically caused by iron deficiency, thalassemia, or chronic disease.
    • Macrocytic Anemia ($MCV > 100 \text{ fL}$): Typically caused by Vitamin B12 or folate deficiency, alcohol abuse, or drugs (e.g., methotrexate, hydroxyurea).
• Platelets (Plt): Normal range is 150,000 to 450,000/mcL. Thrombocytopenia ($< 150,000$) increases bleeding risk. Severe risk occurs when Plt $< 20,000$ (spontaneous hemorrhage risk). Can be drug-induced (e.g., heparin-induced thrombocytopenia, linezolid).
• White Blood Cells (WBC): Normal range is 4,500 to 11,000/mcL. Leukocytosis ($> 11,000$) indicates infection, inflammation, leukemia, or systemic corticosteroid therapy.
• Differential & Left Shift: An increase in the percentage of band (immature) neutrophils ($> 10%$) is termed a "left shift" and strongly suggests an acute bacterial infection.
• Absolute Neutrophil Count (ANC): Calculated to assess infection risk in neutropenic patients (e.g., post-chemotherapy): $ANC = WBC \text{ (cells/mcL)} \times \frac{\% \text{Neutrophils} + \% \text{Bands}}{100}$
  • Neutropenia: $ANC < 1,500 \text{ cells/mcL}$.
  • Severe Neutropenia: $ANC < 500 \text{ cells/mcL}$ (mandates protective precautions and empiric broad-spectrum antibiotics if fever is present).

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Serum Electrolyte Interpretation

• Sodium ($\text{Na}^+$): Normal range: 135–145 mEq/L.
  • Hyponatremia ($< 135$): Can be hypervolemic (heart failure, cirrhosis), euvolemic (SIADH), or hypovolemic (diuretic use, vomiting). Severe acute hyponatremia causes cerebral edema. Clinical Safety: Correcting sodium too rapidly ($> 8\text{–}12 \text{ mEq/L}$ in 24 hours) risks Osmotic Demyelination Syndrome (ODS) (formerly central pontine myelinolysis), causing irreversible neurological damage.
  • Hypernatremia ($> 145$): Caused by water deficit or diabetes insipidus.
• Potassium ($\text{K}^+$): Normal range: 3.5–5.0 mEq/L.
  • Hyperkalemia ($> 5.0$): Caused by renal failure, potassium-sparing diuretics, ACEIs/ARBs, and NSAIDs. ECG changes: peaked T waves, prolonged PR interval, QRS widening, and flat P waves. Treatment: IV Calcium Gluconate (stabilizes cardiac membrane), Insulin + Dextrose (shifts potassium intracellularly), and Sodium Bicarbonate or Albuterol.
  • Hypokalemia ($< 3.5$): Caused by loop/thiazide diuretics or vomiting. ECG changes: flat T waves, ST depression, and U waves. Exacerbates digoxin toxicity.
• Calcium ($\text{Ca}^{2+}$): Normal range: 8.5–10.5 mg/dL.
  • Corrected Calcium: Calcium is 50% bound to albumin. In patients with hypoalbuminemia, measured calcium is falsely low. Corrected calcium must be calculated: $\text{Corrected Calcium} = \text{Measured Calcium (mg/dL)} + 0.8 \times (4.0 - \text{Albumin [g/dL]})$
• Magnesium ($\text{Mg}^{2+}$): Normal range: 1.5–2.5 mEq/L. Hypomagnesemia predisposes to hypokalemia and hypocalcemia, and causes Torsades de Pointes.

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Renal and Hepatic Function Assessment

• Renal Function Tests:
  • Blood Urea Nitrogen (BUN): Normal: $7\text{–}20 \text{ mg/dL}$.
  • Serum Creatinine (SCr): Normal: $0.6\text{–}1.2 \text{ mg/dL}$.
  • BUN:Cr Ratio: A ratio $> 20:1$ indicates prerenal acute kidney injury (renal hypoperfusion/dehydration) because urea is reabsorbed with water while creatinine clearance remains relatively stable. In intrinsic renal injury, the ratio is typically $10\text{–}15:1$.
• Hepatic Function Tests (LFTs):
  • Hepatocellular Injury: Elevated Alanine Aminotransferase (ALT) and Aspartate Aminotransferase (AST). ALT is more liver-specific. An AST:ALT ratio $> 2:1$ suggests alcoholic liver disease.
  • Cholestatic Pattern: Elevated Alkaline Phosphatase (ALP) and Gamma-Glutamyl Transferase (GGT) indicate biliary tract obstruction or drug-induced cholestasis.
  • Synthetic Function: Albumin (decreased in chronic liver disease) and Prothrombin Time/INR (prolonged in liver dysfunction because the liver synthesizes clotting factors II, VII, IX, and X).