Dehydration

• Serum sodium:
  • Hypernatremia
  • Serum sodium levels can be used to determine the amount of free fluid needed to correct dehydration (see treatment of hypernatremia).
• ↑ Hematocrit
• ↓ Serum bicarbonate levels
• BUN to serum creatinine ratio > 20:1 → renal hypoperfusion due to hypovolemia
  • Children have a low serum creatinine value → spuriously high BUN to creatinine ratio
• Urine osmolality: See sodium imbalance for more information.
  • < 800 mOmol/L → renal free water loss
  • > 800 mOmol/L → extrarenal free water loss
• Blood glucose levels
  • Hypoglycemia → decreased fluid intake as a possible cause of dehydration
  • Hyperglycemia → osmotic diuresis as a possible cause of dehydration

References:^{[3][4][8][9][10][11][12]}

Patient who are hypovolemic as a result of severe dehydration require immediate fluid resuscitation with crystalloid solutions.

1. Fluid resuscitation
   • Severe hypovolemia
     • Children: rapid infusion of 20 mL/kg of isotonic saline → reassess → repeat as needed
     • Adults: rapid infusion of isotonic crystalloid → reassess → repeat as needed
   • Moderate hypovolemia
     • Children: consider oral hydration therapy or 10 mL/kg of isotonic saline → reassess → repeat as needed
2. Correction of electrolyte abnormalities
   • Sodium imbalance should only be addressed once the patient is adequately resuscitated.
     • Hypernatremia → Once volume resuscitated, free water deficit can be used to determine further management (see correct free water deficit).
     • Hyponatremia → Once volume resuscitated, monitor closely, and consider hypotonic fluids to avoid rapid overcorrection (see sodium disorders).

References:^{[3][13][14][15]}