Why Na+ Remains 156 Despite IV Dextrose/Dex-Saline - and the Full Electrolyte Picture

1. Persistent Hypernatraemia (Na 156) - Reasons for Failure to Correct

A. Ongoing losses exceed replacement rate

• Insensible losses from fever/infection - he is on IV Tazocin for HAP/?UTI. Pyrexia dramatically increases insensible losses (roughly +10% per 1°C above 37°C). These are often not accounted for in fluid prescriptions.
• Respiratory losses - particularly relevant if he is tachypnoeic from pneumonia.
• Reduced oral intake - he has delirium, agitation, and difficult IV access. If oral fluids are not being reliably consumed, and IV fluids are running behind or being interrupted due to cannula issues, the deficit is not being replaced.

B. Free-water deficit calculation almost certainly underestimates the true deficit

• Deficit ≈ 0.6 × 67 × (156/140 - 1) = ~4.6 L just as the static deficit

C. Type and rate of IV fluids

• 5% Dextrose (D5W) delivers free water but raises blood glucose - and this patient has Type 2 Diabetes. Hyperglycaemia causes an osmotic diuresis, which drives further free-water loss and perpetuates hypernatraemia. The glucose in dextrose is metabolised, leaving free water, but if he is hyperglycaemic, glucose is acting as an osmotic diuretic.
• Dex-saline (0.18% NaCl / 4% Dextrose) is a hypotonic solution but still delivers some sodium. If large volumes are used, the sodium load can slow correction.
• If either is running too slowly (e.g. short IV access, infiltration, nursing holds for agitation), it will not correct.

D. Diabetes insipidus (nephrogenic or central) - less likely but worth considering

E. Post-zoledronate considerations

• Pyrexia and sweating - increased insensible losses
• Anorexia and reduced oral intake
• Contributes to his hypocalcaemia (zoledronate inhibits osteoclasts, reducing calcium release from bone; this is the expected mechanism - hence the repeated IV calcium gluconate)

F. CKD Stage 3

G. Delirium impairs voluntary fluid intake

2. Anaemia - Hb 79

3. Hypokalaemia - K 3.1

4. The Vicious Cycle This Patient Is In

Delirium + agitation
        ↓
Poor oral intake + difficult IV access
        ↓
Ongoing free-water deficit not replaced
        ↓
Persistent hypernatraemia → worsens delirium
        ↓
Infection (HAP/?UTI) → pyrexia → more insensible losses
        ↓
Hypokalaemia (Tazocin + poor intake + RAAS activation)
        ↓
Further muscle weakness, delirium, cardiac risk

5. Practical Actions to Address This

1. Recalculate free-water deficit properly and add ongoing losses (especially insensible if febrile). Target correction at 10-12 mmol/L per 24 hours (not faster). Use this PMC correction guide as a framework.
2. Monitor Na every 6-12 hours - daily bloods are insufficient when Na is 156 and not responding.
3. Secure IV access - PICC line or midline if peripheral cannulas keep failing. Without reliable access, fluids cannot be delivered.
4. Account for hyperglycaemia - if blood glucose is elevated, D5W will worsen osmotic diuresis. Consider 0.45% NaCl (half-normal saline) as an alternative, or tight glycaemic control alongside D5W.
5. Potassium replacement - add KCl 20-40 mmol/L to maintenance fluids. Recheck K 4-6 hourly. Target K >3.5.
6. Treat pyrexia actively (paracetamol regularly) to reduce insensible losses.
7. Consider NG tube if oral intake remains minimal - allows free-water delivery, medications, and nutrition without IV access dependency.
8. Anaemia - check iron studies, B12, folate. Consider transfusion if symptomatic (Hb 79 in context of angina and delirium is clinically significant) - discuss with haematology/cardiology. A threshold of 80 g/L is often used in surgical patients with cardiovascular disease.
9. Review all medications - ensure no agents contributing to K loss, and consider dose adjustment for CKD.
10. Delirium care - non-pharmacological bundle: orientation aids, adequate lighting, familiar faces, sleep-wake cycle preservation. Pharmacological management only as last resort.