Fluid and Electrolytes

Hyperkalemia  Hyperkalemia is defined as:Serum potassium > 5.0 mEq/L(this value is different in different guidelines i.e >5.2mEq/L,>5.5mEq/L) Severity Classification(even this is not universal) Severity Potassium Level Mild 5.1 – 5.5 mEq/L Moderate 5.6 – 6.4 mEq/L Severe ≥ 6.5 mEq/L or ECG changes Clinical severity correlates more with rate of rise rather than absolute level. […]

HYPOMAGNESEMIA  Serum magnesium < 1.7 mg/dL/< 0.7 mmol/L/< 1.4 mEq/L Serum magnesium represents <1% of total body magnesium → normal serum levels do not exclude intracellular depletion. Severity Classification Severity Serum Mg Level Mild 1.6–1.8 mg/dL (0.66–0.74 mmol/L) Moderate 1.2–1.5 mg/dL (0.49–0.62 mmol/L) Severe <1.2 mg/dL (<0.49 mmol/L) Normal serum magnesium: 1.8–2.4 mg/dL (0.74–1.0 mmol/L)

Hypokalemia Hypokalemia = Serum potassium (K⁺) <3.5 mEq/L,it is is less dangerous than hyperkalemia. Severity Serum K⁺ Mild 3.0–3.5 mEq/L Moderate 2.5–2.9 mEq/L Severe <2.5 mEq/L 98% intracellular and Only 2% extracellular,Therefore serum potassium may not accurately reflect total body stores. Potassium Homeostasis Mechanism Site/Stimulus Action on Potassium Na⁺/K⁺-ATPase Pump Stimulated by insulin, β₂-agonists, thyroid

HYPONATREMIA   DEFINITION Hyponatremia = Serum Na⁺ < 135 mEq/L Most common electrolyte abnormality in ICU Severity classification Severity Serum Na⁺ Mild 130–134 Moderate 125–129 Severe <125  PATHOPHYSIOLOGY   Hyponatremia is fundamentally a disorder of water balance, NOT sodium deficit Excess ADH (vasopressin) → water retention → dilution of Na⁺ ADH PHYSIOLOGY Released from posterior pituitary Stimuli: