Volume depletion - causes
1. GI losses: vomiting, NGT suction, diarrhea
2. Urinary losses: diuretics, osmotic diureses (hyperglycemia, mannitol, hypertonic IV contrast media), post-obstructive diuresis, DI, recovery phase of ATN, AI
3. Surface losses: skin (increased sweating due to fever, burns), respiratory (hyperventilation, nonhumidified inhalation therapy)
4. Fluid sequestration: pancreatitis, ileus, burns
5. Blood losses: GI tract, surgical, trauma, iatrogenic (lab. sampling)
6. Inadequate oral or parenteral intake.