Metabolic Panels & Electrolytes – ICU Advantage Study Notes

1. Overview

• Labs in ICU: Essential for diagnosing, guiding treatment, and monitoring critically ill patients.

• Caution: Test results must always be interpreted in context of the overall clinical picture.

• Role of ICU Nurse:

  • Collect labs

  • Interpret early results

  • Notify providers

  • Initiate treatment changes

2. Types of Metabolic Panels

• BMP (Basic Metabolic Panel / Chem 8): Focuses on electrolytes + kidney function.

• CMP (Comprehensive Metabolic Panel): Includes BMP + liver function tests.

• Collection tube: Green top.

3. Lab Result "Skeleton"

• Column 1: Cations (Na⁺, K⁺, Ca²⁺).

• Column 2: Anions (Cl⁻, HCO₃⁻).

• Column 3: Kidney function (BUN, Creatinine).

• Side: Glucose.

4. BMP / Chem 8 Components

Sodium (Na⁺)

• Normal: 135–145 mEq/L

• Hypernatremia (>145–150):

  • Causes: dehydration, meds (NaHCO₃, Na citrate), DKA, DI, Cushing’s

  • S/Sx: AMS, weakness, irritability, coma, seizures

  • Tx: Correct water balance (↓ Na⁺ by 0.5–1 mEq/hr)

• Hyponatremia (<130):

  • Causes: fluid overload, renal failure, SIADH, CHF, cirrhosis, diuretics

  • S/Sx: N/V, headache, lethargy, seizures, cerebral edema, coma

  • Tx: Gradual ↑ Na⁺ (0.5 mEq/hr; if seizures → 2–4 mEq/hr)

Potassium (K⁺)

• Normal: 3.5–5 mEq/L

• Hyperkalemia (>6 mild, >7 severe):

  • Causes: renal failure, metabolic acidosis (DKA), rhabdo, Addison’s

  • S/Sx: weakness, paresthesias, peaked T waves (ECG), risk of asystole

  • Tx: Dialysis, Ca gluconate/chloride (stabilize), insulin + glucose, β₂-agonists, alkalinization

• Hypokalemia (<3.5):

  • Causes: GI losses, diuretics, alkalosis, malnutrition

  • S/Sx: weakness, leg cramps, constipation, U waves/flattened T waves → arrhythmias

  • Tx: K⁺ replacement

Calcium (Ca²⁺)

• Normal (total): 8.5–10.5 mg/dL

• Hypercalcemia (>10.5):

  • Causes: hyperparathyroidism

  • S/Sx: depression, weakness, confusion → hallucinations, seizures, AV block, cardiac arrest (>15)

  • Tx: Saline diuresis, loop diuretics

• Hypocalcemia (<8.5):

  • Causes: post-thyroid surgery, tumor lysis, altered Mg²⁺, toxic shock

  • S/Sx: paresthesia, tetany, stridor, seizures

  • Tx: Ca replacement (gluconate/chloride)

Chloride (Cl⁻)

• Normal: 95–105 mEq/L

• Hyperchloremia:

  • Causes: NS overload, HCO₃⁻ loss → metabolic acidosis

• Hypochloremia:

  • Causes: GI/renal loss, dilution → metabolic alkalosis

Bicarbonate / CO₂

• Normal: 23–29 mEq/L

• Represents HCO₃⁻ (95% of CO₂ measured).

• Major buffer in acid–base balance.

BUN (Blood Urea Nitrogen)

• Normal: 6–20 mg/dL

Creatinine

• Normal: 0.8–1.3 mg/dL

Glucose

• Normal: 65–110 mg/dL

5. CMP (BMP + Liver Function Tests)

• Alkaline phosphatase (ALP): 20–30 U/L

• AST / ALT: 5–30 U/L

• Bilirubin: 0.2–1.9 mg/dL

• Total protein: 6.3–7.9 g/L

• Albumin: 3.4–5.4 g/dL

6. Additional Important Electrolytes

Ionized Calcium

• Normal: 4.5–5.6 mg/dL (1.1–1.3 mmol/L)

• 50% bound to albumin; ionized = physiologically active fraction.

Phosphorus

• Normal: 3–4.5 mg/dL

• Inverse with calcium.

• ↑: renal/liver disease, ↓ PTH, hypocalcemia

• ↓: EtOH abuse, poor nutrition, ↑ PTH, hypercalcemia

Magnesium

• Normal: 1.5–2 mEq/L

• Hypermagnesemia (>2.2):

  • Causes: renal failure

  • S/Sx: weakness, confusion, vasodilation → hypotension, bradycardia, arrhythmias

  • Tx: Ca binding, dialysis

• Hypomagnesemia (<1.2):

  • Causes: GI/kidney losses, thyroid effects

  • S/Sx: tremors, tetany, seizures, torsades

  • Tx: Mg replacement

7. Key Takeaways

• BMP = Electrolytes + Kidney + Glucose

• CMP = BMP + Liver panel

• Always interpret labs in clinical context

• Know normal ranges, common causes, signs, and treatments of abnormal values