Purpose of D5 Water (5% Dextrose in Water)
D5W serves primarily as a hypotonic fluid for free water replacement in hypernatremia and as a vehicle for medication administration, but it is contraindicated in hypotension and severe hypoxemia where isotonic crystalloids like normal saline are required for volume resuscitation. 1, 2
Primary Clinical Indications
Free Water Replacement in Hypernatremia
- D5W is the preferred solution for treating hypernatremia because it contains no sodium (0 mEq/L) and provides free water to dilute elevated serum sodium concentrations 3
- The solution allows controlled decrease in plasma osmolality when managing hypernatremic dehydration 2
- Parenteral D5W demonstrates effectiveness at lowering serum sodium by approximately -2.25 mEq/L per liter of treatment fluid 4
Correction of Overcorrected Hyponatremia
- When hyponatremia has been corrected too rapidly (>8 mmol/L in 24 hours), immediately switching to D5W can relower sodium levels to prevent osmotic demyelination syndrome 3
- This requires frequent sodium monitoring every 2-4 hours during active correction 3
Medication Vehicle
- D5W commonly serves as a diluent for intermittent drug administration and continuous medication infusions 5
- Drug diluents can account for approximately 21% of total infusion volume in critically ill patients 5
Critical Contraindications in Your Clinical Scenario
Hypotension
- D5W is absolutely contraindicated for resuscitation of hypotensive patients 6
- For hypotension management, rapid infusion of 1-2 liters of normal saline at 5-10 mL/kg in the first 5 minutes is recommended 1
- Crystalloids or colloids should be given in boluses of 20 mL/kg for fluid resuscitation 1
- D5W cannot effectively expand intravascular volume because dextrose is rapidly extravasated from intravascular to interstitial space 7
Severe Hypoxemia and Brain Injury
- Hypotonic dextrose-containing solutions like D5W are absolutely contraindicated in patients with CNS disorders, including those with severe hypoxemia 2
- In acute ischemic stroke, hypotonic solutions such as D5W (after glucose is metabolized) distribute into intracellular spaces and may exacerbate ischemic brain edema 1
- Animal studies demonstrate that D5W significantly worsens brain edema after closed head trauma compared to isotonic solutions 8
- Glucose-containing solutions should be avoided entirely in stroke patients as glucose can have detrimental effects in acute brain injury 7
Appropriate Fluid Choice for Hypotension and Hypoxemia
Isotonic Crystalloids Are Required
- For patients with hypotension and severe hypoxemia, use 0.9% normal saline or other isotonic crystalloids 1, 7
- Isotonic solutions like 0.9% saline are more evenly distributed into extracellular spaces (interstitial and intravascular) and are appropriate for acute resuscitation 1
- Normal saline contains 154 mEq/L sodium with osmolarity of 308 mOsm/L, making it isotonic and suitable for volume expansion 2
If Dextrose Is Needed
- Use D5 0.9% saline (D5NS) rather than D5W if glucose supplementation is required 7, 2
- D5NS contains 50 grams dextrose plus 154 mEq/L sodium and 154 mEq/L chloride with osmolarity of 308 mOsm/L, making it isotonic 2
- This provides both glucose and effective volume expansion without the risks of hypotonic solutions 7
Common Pitfalls to Avoid
- Do not assume D5W is appropriate for "maintenance fluids" in critically ill patients with hemodynamic instability - it lacks resuscitative capacity 6
- Do not use D5W in any patient with CNS disorders, respiratory distress, or conditions causing cerebral hypoxia - the hypotonic nature after glucose metabolism worsens cerebral edema 1, 2, 8
- Do not confuse the osmolarity of D5W before and after glucose metabolism - while initially isotonic (252 mOsm/L), it becomes hypotonic after dextrose is metabolized, leaving only free water 3
- Avoid hypotonic solutions in patients with syndrome of inappropriate antidiuresis (SIAD), which is common in acutely ill patients with pain, nausea, stress, hypoxemia, or CNS disorders 7