Pharmacotherapy 7
Fluids, Electrolytes, and Nutrition
Card 1 of 16Fluids
📖 Chapter Opening
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Water follows salt
Fluids and Osmolality
Osmolality governs water movement between the intracellular and extracellular compartments.
Serum osmolality = 2 x Na + glucose/18 + BUN/2.8 (normal ~285-295). Sodium is the main determinant of tonicity, so sodium problems are really water problems.
Fluid tonicity
Isotonic (0.9% NaCl, LR) stays vascular; hypotonic (0.45% NaCl) enters cells; hypertonic (3% NaCl) pulls water out.