How to manage a patient with impaired renal function (low Glomerular Filtration Rate (GFR))?

Management of Patients with Low GFR

Patients with low glomerular filtration rate (GFR) should be managed with a structured approach that includes medication adjustments, monitoring for complications, and appropriate referral to nephrology when GFR falls below 30 mL/min/1.73 m².1

When to Refer to Nephrology

• Refer patients to nephrology services when GFR <30 mL/min/1.73 m² (CKD stages 4-5) 1, 2
• Additional referral criteria include:
  • Abrupt sustained fall in GFR or acute kidney injury 1
  • Significant albuminuria (ACR ≥300 mg/g or ≥30 mg/mmol) 1
  • Urinary abnormalities (red cell casts, RBC >20 per high power field) 1
  • Refractory hypertension (requiring 4+ antihypertensive agents) 1
  • Persistent electrolyte abnormalities 1
  • Recurrent nephrolithiasis 1
  • Hereditary kidney disease 1

Medication Management

Metformin Adjustments

• Metformin is contraindicated in patients with GFR <30 mL/min/1.73 m² 3
• Initiation of metformin is not recommended in patients with GFR between 30-45 mL/min/1.73 m² 3
• For patients already on metformin whose GFR falls below 45 mL/min/1.73 m², assess the benefit-risk of continuing therapy 3
• Temporarily discontinue metformin before iodinated contrast imaging procedures in patients with GFR between 30-60 mL/min/1.73 m² 3

Other Medication Considerations

• Adjust medication dosages based on GFR levels, particularly for drugs with renal clearance 4, 2
• Avoid nephrotoxic medications (e.g., NSAIDs) in patients with decreased GFR 4, 2
• For diabetes management in low GFR:
  • SGLT2 inhibitors are recommended for patients with type 2 diabetes and CKD regardless of HbA1c level 2
  • GLP-1 receptor agonists are preferred for patients with GFR <20 mL/min/1.73 m² 2
  • ACE inhibitors or ARBs are preferred for patients with diabetes, hypertension, and albuminuria 2

Blood Pressure Management

• Target blood pressure <130/80 mmHg in patients with GFR <30 mL/min/1.73 m² 4
• Use ACE inhibitors or ARBs as first-line agents for hypertension management 4
• Monitor serum potassium in patients with GFR <60 mL/min/1.73 m² receiving ACE inhibitors, ARBs, or mineralocorticoid receptor antagonists 2

Metabolic Management

• Consider bicarbonate supplementation to maintain serum bicarbonate within normal range for patients with metabolic acidosis 4
• Target LDL cholesterol to <100 mg/dL and non-HDL cholesterol to <130 mg/dL 4
• Monitor for vitamin D deficiency and consider supplementation if 25(OH) vitamin D levels are <30 ng/mL 4
• Address hypocalcemia (serum calcium <8.5 mg/dL) with elemental calcium supplementation after addressing phosphorus issues 4

Nutritional Management

• Restrict dietary protein to 0.8 g/kg/day for patients with GFR <60 mL/min/1.73 m² 4, 2
• Avoid protein restriction below 0.6 g/kg/day due to risk of malnutrition 4
• Restrict dietary sodium to <2.0 g/day to reduce edema, control blood pressure, and reduce proteinuria 4, 2
• Target caloric intake of 30-35 kcal/kg/day for patients with GFR <60 mL/min/1.73 m² 4

Monitoring and Assessment

• Monitor blood pressure at every clinic visit (at least every three months) for patients with GFR <30 mL/min/1.73 m² 4
• Check serum albumin and body weight every three months to monitor nutritional status 4
• Screen for dyslipidemias by measuring triglycerides, LDL, HDL, and total cholesterol 4
• Obtain eGFR at least annually in all patients taking metformin 3
• In patients at risk for renal impairment (e.g., the elderly), assess renal function more frequently 3

Planning for Renal Replacement Therapy (RRT)

• Discuss RRT modality options with patients who have GFR <30 mL/min/1.73 m² 4
• No specific GFR threshold alone should determine when to initiate RRT 4
• Consider initiating RRT in patients with GFR <20 mL/min/1.73 m² who have evidence of malnutrition that does not respond to nutritional intervention 4
• Refer patients willing to have renal transplantation for transplant evaluation 4
• Preserve veins suitable for vascular access placement if hemodialysis is planned 4
• Refer for surgery to construct primary AV fistula if hemodialysis is the chosen modality 4

Special Considerations and Pitfalls

• Patients with low GFRs are generally at increased bleeding risk, and antiplatelet medications further increase this risk 4
• Elevated troponin in CKD patients has good prognostic accuracy despite reduced diagnostic accuracy for acute coronary syndrome 4
• Recognize that GFR equations (MDRD vs. Cockcroft-Gault) may provide discordant estimations in over 60% of elderly patients, which can affect medication dosing 5
• Be aware that a decline in GFR in the context of a stable or improving clinical condition should not necessarily lead to discontinuation of life-saving therapies 6