What lab tests should be ordered for a patient with a history of recurrent Acute Kidney Injury (AKI) and hyperkalemia, currently with impaired renal function and a stage 4 sacral ulcer, who is taking an Angiotensin-Converting Enzyme (ACE) inhibitor or Angiotensin Receptor Blocker (ARB), Lokelma (sodium zirconium cyclosilicate), and has recently experienced vaginal bleeding treated with megestrol acetate?

Laboratory Monitoring for Recurrent AKI with Hyperkalemia

Order a comprehensive metabolic panel (CMP) within 1 week to assess potassium, creatinine, and electrolytes after medication adjustments, then recheck at 2-4 weeks, given this patient's recent hyperkalemia (K+ 5.7 mmol/L) and improving but still impaired renal function (creatinine 2.8 mg/dL). 1

Immediate Laboratory Panel (Within 1 Week)

Comprehensive Metabolic Panel including:

• Serum potassium - Critical given recent K+ 5.7 mmol/L requiring consideration for emergent dialysis 1
• Serum creatinine and eGFR - Monitor renal function trajectory after improvement from 3.0 to 2.8 mg/dL 1
• Blood urea nitrogen (BUN) - Assess degree of azotemia and volume status 1
• Serum sodium - Rule out hyponatremia from Lokelma (each 5g dose contains ~400mg sodium) 1
• Serum bicarbonate - Assess for metabolic acidosis which worsens hyperkalemia 1
• Serum magnesium - Hypomagnesemia makes hyperkalemia resistant to treatment and must be corrected 2
• Serum calcium - Monitor for hypocalcemia from Lokelma 1
• Blood glucose - Assess diabetes control and adjust insulin doses given AKI 1

Follow-Up Monitoring Schedule

Week 1 Post-Medication Adjustment

• Recheck CMP within 5-7 days after any ACE inhibitor/ARB dose reduction or discontinuation 1
• Recheck within 5-7 days after initiating or adjusting Lokelma dosing 1
• This timing is critical because potassium can rebound quickly after medication changes in patients with impaired renal function 1

Weeks 2-4 Post-Adjustment

• Repeat CMP at 2-4 weeks after medication stabilization 1
• This confirms sustained improvement and guides decisions about restarting ACE inhibitor/ARB at reduced dose 1

Long-Term Monitoring (After Stabilization)

• Monthly monitoring for first 3 months, then every 3 months thereafter 1
• More frequent monitoring needed if patient has multiple risk factors: stage 4 CKD (creatinine 2.8), diabetes, recurrent AKI, and concurrent use of Lokelma 1

Additional Essential Labs

Urinalysis with Microscopy

• Order immediately to assess for active sediment, proteinuria, or infection contributing to AKI 1
• Helps differentiate prerenal azotemia from intrinsic kidney disease 1

Hemoglobin A1c

• Order now to assess long-term diabetes control given need to adjust insulin doses with changing renal function 1
• Insulin requirements typically decrease with worsening kidney function due to reduced renal insulin clearance 1

Complete Blood Count (CBC)

• Order now to assess for anemia of chronic kidney disease and rule out infection (given stage 4 sacral ulcer) 1
• Infection can worsen hyperkalemia through tissue breakdown 1

Critical Monitoring Thresholds

Hold or reduce ACE inhibitor/ARB if: 1

• Potassium rises >5.5 mmol/L (halve dose and recheck in 1-2 weeks)
• Potassium >6.0 mmol/L (stop immediately and seek specialist advice)
• Creatinine increases >50% from baseline or >266 μmol/L (3 mg/dL)
• eGFR falls <20 mL/min/1.73 m²

Adjust Lokelma dosing if: 1

• Pre-dialysis potassium >6.5 mEq/L (increase to 10g daily on non-dialysis days if on chronic dialysis)
• Potassium normalizes <5.0 mmol/L consistently (consider reducing to 5g daily)
• Patient develops severe constipation or bowel obstruction (discontinue immediately given stage 4 sacral ulcer)

Common Pitfalls to Avoid

• Don't wait 4-6 weeks for first recheck - patients with creatinine 2.8 and recent severe hyperkalemia need monitoring within 1 week 1
• Don't forget magnesium - this is the most common reason for refractory hyperkalemia and must be checked and corrected 2
• Don't monitor potassium alone - always check creatinine simultaneously as worsening renal function dramatically increases hyperkalemia risk 1
• Don't assume stability - patients with multiple risk factors (CKD, diabetes, recurrent AKI, ACE inhibitor use) require more intensive monitoring than standard guidelines suggest 1, 3, 4