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

Management of Decreased Glomerular Filtration Rate

Patients with GFR <30 mL/min/1.73 m² require immediate nephrology referral and comprehensive monitoring every 3 months, including blood pressure checks at every visit, complete metabolic panels with mineral-bone disorder assessment, anemia workup, lipid panels, and initiation of renal replacement therapy planning. 1, 2

Immediate Nephrology Referral

Refer immediately to nephrology services when GFR falls below 30 mL/min/1.73 m² 1, 2. This threshold represents Stage 4 chronic kidney disease where specialized management becomes mandatory to prevent progression to kidney failure and manage complications 1, 2.

• Referral may be deferred only if GFR is stable, diagnosis is clear, and the patient has very advanced age or comorbidities indicating short life expectancy 1
• Patients should be managed at centers with experience in advanced CKD care 1

Blood Pressure Management

Check blood pressure at every clinic visit, with visits scheduled at minimum every 3 months 1, 2. Target systolic blood pressure <130 mmHg and diastolic <80 mmHg 1, 2.

First-Line Antihypertensive Therapy

Use ACE inhibitors or ARBs as first-line agents, up-titrated to maximally tolerated doses 1. These medications provide both blood pressure control and proteinuria reduction 1.

• Counsel patients to hold ACE inhibitors/ARBs during intercurrent illness with risk of volume depletion 1
• Use potassium-wasting diuretics and/or potassium-binding agents if hyperkalemia develops, to allow continuation of RAS inhibition 1
• Avoid dual RAS blockade (combining ACE inhibitors with ARBs) as this increases risks of hyperkalemia, acute kidney injury, and hypotension without additional benefit 3
• In patients with diabetes and GFR <60 mL/min, avoid combining aliskiren with ACE inhibitors or ARBs 3

Medication Adjustments

Metformin Dosing

Metformin can be continued with dose reduction when GFR is 30-45 mL/min/1.73 m² 1. However, metformin is contraindicated when eGFR falls below 30 mL/min/1.73 m² due to increased risk of lactic acidosis 4.

• Obtain eGFR at least annually in all patients taking metformin 4
• In patients at risk for renal impairment (elderly), assess renal function more frequently 4
• When eGFR falls below 45 mL/min/1.73 m², assess benefit-risk of continuing therapy 4

ACE Inhibitor/ARB Monitoring

Monitor renal function and serum potassium closely when using these agents at GFR <30 mL/min/1.73 m² 3, 5. The elimination half-life of ACE inhibitors like lisinopril increases significantly when GFR falls below 30 mL/min 5.

Anemia Management

Check hemoglobin and complete iron studies if hemoglobin is <12 g/dL in women or <13 g/dL in men 1, 2. Anemia evaluation is critical at this GFR threshold as erythropoietin deficiency becomes prevalent 2.

• If iron deficiency is present despite appropriate evaluation and iron therapy, initiate erythropoietin or analogue 1
• Monitor hemoglobin every 3 months 2

Mineral-Bone Disorder Assessment

Measure serum calcium, phosphorus, and intact parathyroid hormone (iPTH) every 3 months 1, 2.

Vitamin D Management

• If iPTH >100 pg/mL (or >1.5 times upper limit of normal), measure 25(OH) vitamin D levels 1, 2
• If 25(OH) vitamin D is <30 ng/mL, administer vitamin D2 50,000 units orally monthly for 6 months 1

Calcium Supplementation

• If corrected serum calcium is <8.5 mg/dL after addressing phosphorus issues, provide elemental calcium 1 g/day between meals or at bedtime 1

Phosphorus Control

• Address elevated phosphorus levels before treating hypocalcemia 1

Cardiovascular Risk Management

Obtain complete lipid panel including triglycerides, LDL, HDL, and total cholesterol 1, 2. Monitor for dyslipidemias every 3 months 1.

Lipid Targets

• Target LDL <100 mg/dL 1
• Target non-HDL cholesterol <130 mg/dL 1
• Treat fasting triglycerides ≥500 mg/dL 1

Statin Therapy

• Consider statin therapy as first-line for persistent dyslipidemia, particularly in patients with other cardiovascular risk factors including hypertension and diabetes 1
• Evaluate for secondary causes of dyslipidemia including comorbid conditions and medications 1, 2

Nutritional Monitoring

Monitor nutritional status by measuring body weight and serum albumin every 3 months 1, 2.

Malnutrition Intervention

• If body weight decreases unintentionally by >5% or serum albumin decreases by >0.3 g/dL or is <4.0 g/dL (Bromo-Cresol-Green assay), evaluate for causes 1
• If CKD is determined to be the cause after ruling out other etiologies, provide diet assessment and counseling by qualified personnel 1
• If GFR <20 mL/min/1.73 m² with malnutrition unresponsive to nutritional intervention, initiate renal replacement therapy 1

Renal Replacement Therapy Planning

Begin discussions about RRT modalities (hemodialysis, peritoneal dialysis, transplantation) when GFR <30 mL/min/1.73 m² 1, 2.

Transplant Evaluation

• If patient is willing to have renal transplant, provide transplant evaluation unless unacceptable surgical risk or failure to satisfy UNOS Ethics Committee criteria 1
• Early referral for transplant evaluation improves outcomes 1

Vascular Access Preservation

• If hemodialysis is planned, preserve veins suitable for vascular access placement 1
• Avoid venipuncture and intravenous lines in potential access sites 1

Timing of RRT Initiation

• No specific GFR level alone mandates RRT initiation 1
• Consider RRT when GFR <20 mL/min/1.73 m² with refractory malnutrition, severe uremic symptoms, or fluid overload unresponsive to medical management 1

Metabolic Acidosis Management

Treat metabolic acidosis if serum bicarbonate is <22 mmol/L 1. Metabolic acidosis contributes to bone disease, muscle wasting, and CKD progression 1.

Common Pitfalls to Avoid

• Do not delay nephrology referral when GFR <30 mL/min/1.73 m² even if patient appears stable 1, 2
• Do not combine ACE inhibitors with ARBs as dual RAS blockade increases harm without benefit 3
• Do not continue metformin when eGFR falls below 30 mL/min/1.73 m² due to lactic acidosis risk 4
• Do not use NSAIDs chronically in patients with GFR <30 mL/min/1.73 m² as they worsen renal function and blunt antihypertensive effects 3
• Do not wait for symptoms to develop before initiating RRT planning, as early preparation improves outcomes 1