Hypernatremia Correction with D5W in an Elderly Female
For this elderly female patient with hypernatremia (sodium 156 mEq/L) and weight 43.2 kg, administer D5W at approximately 50-75 mL/hour to achieve a safe correction rate of 8-10 mEq/L per 24 hours, assuming this represents chronic hypernatremia. 1, 2
Calculating the Water Deficit and Correction Rate
The free water deficit for this patient is approximately 2.6 liters, calculated using the formula: Water deficit = 0.5 × body weight (kg) × [(current Na / 140) - 1]. For this 43.2 kg patient: 0.5 × 43.2 × [(156/140) - 1] = 2.47 liters. 1
The correction should not exceed 8-10 mEq/L per 24 hours for chronic hypernatremia (>48 hours duration), as more rapid correction risks cerebral edema. 1, 2, 3 If this is acute hypernatremia (<48 hours), a faster rate of 1 mEq/L per hour for the first 6-8 hours is acceptable, but this scenario is less common in elderly patients. 2
D5W Infusion Rate Calculation
Start with D5W at 50-75 mL/hour as the initial rate, which provides approximately 1.2-1.8 liters over 24 hours. 4, 3 This rate should lower sodium by approximately 8-10 mEq/L in the first 24 hours based on the estimated water deficit. 2, 3
The specific calculation: To decrease sodium from 156 to 146-148 mEq/L over 24 hours requires replacing approximately 1.2-1.5 liters of the calculated 2.6 liter deficit in the first day. 1, 2
Monitor serum sodium every 4-6 hours initially, then adjust the D5W rate based on the actual rate of sodium decline. 1, 2 If sodium is correcting too rapidly (>10 mEq/L per 24 hours), reduce the infusion rate; if too slowly, increase cautiously. 2
Special Considerations for Elderly Patients
Elderly patients require particularly cautious correction due to increased risk of cerebral edema with rapid changes in osmolality. 5 This population often has chronic hypernatremia from inadequate fluid intake and impaired thirst sensation. 5
Check for signs of volume depletion including orthostatic hypotension, dry mucous membranes, decreased skin turgor, and sunken eyes. 5 If the patient shows moderate to severe volume depletion (at least 4 of 7 signs: confusion, non-fluent speech, extremity weakness, dry mucous membranes, dry tongue, furrowed tongue, sunken eyes), initial resuscitation with isotonic saline may be needed before switching to D5W. 5
Assess for underlying causes including diabetes insipidus, excessive diuretic use, diarrhea, vomiting, or limited access to water. 5, 2, 6 In elderly patients, impaired thirst sensation and reduced mobility limiting water access are common contributors. 5
Monitoring and Adjustment Protocol
Check serum sodium every 4-6 hours during active correction, along with serum glucose levels to monitor for hyperglycemia from D5W administration. 4, 2 The maximum rate of dextrose administration without producing glycosuria is 0.5 g/kg/hour, which for this 43.2 kg patient equals approximately 21.6 g/hour or 432 mL/hour of D5W. 4
Target sodium reduction of 8-10 mEq/L per day until reaching 145 mEq/L or below. 1, 2, 3 For this patient starting at 156 mEq/L, expect 2-3 days of treatment to normalize sodium levels safely. 2
If sodium corrects too rapidly (>10 mEq/L in 24 hours), immediately reduce the D5W infusion rate by 25-50%. 2 Conversely, if correction is inadequate (<6 mEq/L per 24 hours) and the patient remains symptomatic, the rate can be cautiously increased. 2
Critical Safety Considerations
Never correct chronic hypernatremia faster than 10 mEq/L per 24 hours, as overly rapid correction can cause cerebral edema, seizures, and permanent neurological damage. 1, 2, 7 One case report documented fatal ventricular arrhythmias with extreme hypernatremia and rapid correction. 7
Monitor for signs of cerebral edema including worsening mental status, headache, nausea, vomiting, or seizures during correction. 2, 7 If these develop, slow or temporarily halt D5W infusion and reassess. 2
Ensure adequate ongoing fluid intake once the patient is stable, as elderly patients with hypernatremia often have impaired thirst sensation and require scheduled fluid administration rather than relying on thirst alone. 5