Fluid and Electrolytes

HYPOPHOSPHATEMIA  1. Definition Hypophosphatemia = serum phosphate < 2.5 mg/dL (0.81 mmol/L) Severity Serum Phosphate Mild 2.0–2.5 mg/dL (<0.65-0.81 mmol/L) Moderate 1.0–1.9 mg/dL (<0.32-0.65 mmol/L) Severe (life-threatening) < 1.0 mg/dL (<0.32 mmol/L) Symptoms usually appear when <1 mg/dL 2. Functions of phosphate  ATP synthesis → cellular energy 2,3-DPG in RBCs → oxygen delivery Cell membrane […]

Hypercalcemia Normal total serum calcium: Approximately 8.5–10.5 mg/dL (2.1–2.6 mmol/L) Ionized calcium >1.32 mmol/L This severity Classification values are different in Different sources(ionized calcium does not have a universally accepted equivalent 3-tier classification.) Severity Total serum calcium Ionized calcium Normal 8.5–10.5 mg/dL 1.12–1.32 mmol/L Mild 10.5–11.9 mg/dL ~1.33–1.50 mmol/L Moderate 12.0–13.9 mg/dL ~1.51–1.75 mmol/L Severe

HYPERPHOSPHATEMIA  Hyperphosphatemia = Serum phosphate > 4.5 mg/dL (1.45 mmol/L) in adults Severity Serum Phosphate Mild 4.6–6 mg/dL Moderate 6–9 mg/dL Severe >9–10 mg/dL  Life-threatening when associated with: Hypocalcemia Arrhythmias Acute kidney injury Tumor lysis syndrome Normal Phosphate Physiology  Distribution 85% – bone (hydroxyapatite) 14% – intracellular <1% – extracellular (measured serum phosphate) Normal Serum

Hypocalcemia Hypocalcemia is a reduction in serum ionized calcium, the biologically active form of calcium.calcium should not be checked daily as an “ICU routine.”Total calcium is useful for screening but is an unreliable indicator of ionized calcium, as ionized calcium is affected by factors such as pH, albumin, sodium, and phosphate concentrations.   Calcium exists

Ringer Lactate (RL) vs Plasma-Lyte Feature Ringer Lactate (RL / Hartmann’s) Plasma-Lyte (Plasma-Lyte A / Plasma-Lyte 148) Type Balanced crystalloid Balanced crystalloid Osmolality ~273–278 mOsm/L (slightly hypotonic) ~294–295 mOsm/L (isotonic) pH ~6.5 ~7.4 Sodium 130 mmol/L 140 mmol/L Chloride 109 mmol/L 98 mmol/L Potassium 4 mmol/L 5 mmol/L Calcium 2.7–3 mmol/L None Magnesium None 1.5

Dextrose containing fluids Feature D25 (25% Dextrose) ½ DNS (D5 + 0.45% NaCl) DNS (D5 + 0.9% NaCl) Composition 25 g dextrose/100 mL 5% dextrose + 0.45% saline 5% dextrose + 0.9% saline Dextrose 250 g/L 50 g/L 50 g/L Sodium 0 77 mEq/L 154 mEq/L Chloride 0 77 mEq/L 154 mEq/L Osmolarity ~1260–1400 mOsm/L

Maintenance Fluid in Critical Care (Adult ICU)  In modern critical care, maintenance fluid is prescribed far less frequently than in the past because: Early enteral nutrition provides water. Many IV medications already deliver substantial fluid. Excess maintenance fluid contributes significantly to fluid overload, prolonged ventilation, AKI, and mortality. Definition Maintenance fluid replaces Insensible water loss

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