How to manage a patient with decreased Glomerular Filtration Rate (GFR)?

Management of Patients with Decreased Glomerular Filtration Rate (GFR)

For patients with decreased GFR, implement a comprehensive management strategy that includes accurate GFR assessment, blood pressure control with ACEi/ARBs, dietary modifications, cardiovascular risk reduction, and regular monitoring to slow CKD progression and reduce complications. 1, 2

Assessment and Diagnosis of Decreased GFR

GFR Measurement

• Test patients at risk for and with CKD using both urine albumin measurement and GFR assessment 1
• Use creatinine-based estimated GFR (eGFRcr) for initial assessment 1
• If cystatin C is available, use the combination of creatinine and cystatin C (eGFRcr-cys) for more accurate GFR estimation, especially when eGFRcr is less reliable and GFR affects clinical decisions 1
• Consider measured GFR using exogenous filtration markers (iothalamate, iohexol) when more accurate GFR assessment will impact treatment decisions 1

Confirming CKD Diagnosis

• Repeat abnormal tests to confirm presence of CKD 1
• Establish chronicity (duration ≥3 months) through:
  • Review of past GFR measurements
  • Review of past albuminuria/proteinuria measurements
  • Imaging findings (reduced kidney size, cortical thinning)
  • Kidney pathology findings (fibrosis, atrophy)
  • Medical history of conditions known to cause CKD 1

Management Strategy

Blood Pressure Control

• Target systolic blood pressure <120 mmHg using standardized office BP measurement 2
• Use ACE inhibitors or ARBs as first-line therapy for both hypertension and proteinuria 1, 2
• Uptitrate ACEi/ARBs to maximally tolerated dose 2
• Do not stop ACEi/ARB with modest and stable increase in serum creatinine (up to 30%) 1
• Consider using potassium-wasting diuretics and/or potassium-binding agents if hyperkalemia develops to allow continued use of RAS blockers 2

Medication Considerations

• Adjust medication dosages based on GFR level 2
• For metformin:
  • Contraindicated if eGFR <30 mL/min/1.73 m² 3
  • Not recommended for initiation if eGFR between 30-45 mL/min/1.73 m² 3
  • Reassess benefit-risk if eGFR falls below 45 mL/min/1.73 m² 3
• Avoid nephrotoxic medications (NSAIDs) that may further reduce GFR 2
• Avoid dual RAS blockade (combining ACEi with ARB) as it increases risk of hyperkalemia and acute kidney injury without additional benefits 4

Dietary and Lifestyle Modifications

• Restrict dietary sodium to <2.0 g/day (<90 mmol/day) 1, 2
• For patients with GFR <60 mL/min/1.73 m² and proteinuria:
  • Limit protein intake to 0.8 g/kg/day
  • Target caloric intake of 30-35 kcal/kg/day
  • Emphasize plant-based protein sources 2
• Normalize weight, stop smoking, and exercise regularly 2

Cardiovascular Risk Management

• Assess cardiovascular risk factors and consider statin therapy 2
• Treat metabolic acidosis if serum bicarbonate <22 mmol/L 2

Management of Complications

• For edema management:
  • Use loop diuretics as first-line treatment
  • Consider twice daily dosing for better efficacy
  • Add thiazide-like diuretics for resistant edema 1
• Monitor for and treat anemia, especially when GFR falls below 60 mL/min/1.73 m² 2
• Evaluate for mineral bone disease (calcium, phosphate, vitamin D) 2

Monitoring and Follow-up

• Monitor GFR and albuminuria every 6-12 months 2
• Obtain eGFR at least annually in all patients taking medications that affect kidney function 1
• In patients at risk for development of renal impairment (e.g., the elderly), assess renal function more frequently 3
• Monitor for development of complications including anemia, metabolic acidosis, and mineral bone disorders 2

Common Pitfalls to Avoid

• Relying solely on serum creatinine can underestimate renal insufficiency, especially in elderly or those with low muscle mass 2
• Failing to recognize that GFR must decrease by at least 40% before serum creatinine significantly increases 2
• Overlooking cardiovascular risk in patients with decreased GFR, who have significantly increased cardiovascular risk compared to those with normal kidney function 2
• Assuming chronicity based on a single abnormal GFR or ACR value, as it could be due to acute kidney injury 1
• Continuing nephrotoxic medications in patients with decreased GFR 2
• Discontinuing ACEi/ARB prematurely with small increases in creatinine, which may be expected and not harmful 1