A 55-year-old patient on chronic lithium therapy for bipolar disorder is scheduled for elective total knee replacement. Preoperative serum sodium is 140 mEq/L and creatinine is 1.1 mg/dL. Which perioperative fluid management strategy is most appropriate regarding the risk of nephrogenic diabetes insipidus?
- A Use isotonic crystalloid (0.9% saline or Ringer's lactate) as maintenance and monitor urine output closely ✓
- B Use 0.45% half-normal saline as the primary maintenance fluid to account for free water loss
- C Restrict all IV fluids to less than 500 ml intraoperatively to avoid volume overload
- D Administer a 25% mannitol infusion perioperatively to promote free water excretion
Correct answer: A. Use isotonic crystalloid (0.9% saline or Ringer's lactate) as maintenance and monitor urine output closely
Explanation
Lithium causes nephrogenic diabetes insipidus by impairing the kidney's concentrating ability, so these patients depend on adequate hydration to excrete lithium and avoid toxicity. Isotonic crystalloid is the appropriate maintenance fluid. Restricting fluids worsens lithium retention and risks acute kidney injury. Hypotonic fluids can cause hyponatraemia. Mannitol is not indicated and can worsen renal injury in a volume-depleted patient.
Reference: Stoelting's Pharmacology and Physiology in Anesthetic Practice, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.