What is the management approach for an elderly patient with impaired renal function (GFR 45)?

Management of an Elderly Patient with GFR 45

An elderly patient with GFR 45 mL/min/1.73 m² (CKD Stage 3a) requires nephrology referral consideration, medication dose adjustments, dietary protein modification, and regular monitoring of renal function and nutritional status. 1, 2

Initial Assessment and Monitoring

• Obtain comprehensive metabolic panel, complete blood count, and urinalysis to assess for proteinuria and other metabolic derangements 1
• Calculate urinary albumin-to-creatinine ratio to evaluate for kidney damage beyond reduced GFR 2
• Assess for comorbidities including hypertension, diabetes, cardiovascular disease, and current medication list, as these are strongly associated with reduced GFR in elderly patients 3
• Monitor renal function at least annually, or more frequently given the patient's age and GFR level 2, 4

Nephrology Referral

Consider nephrology referral when GFR falls below 45 mL/min/1.73 m², particularly in patients with confirmed proteinuria, diabetes with preexisting CKD, or when GFR is expected to decline below 30 after any intervention 1, 2

Medication Management

Dose Adjustments

• Review all medications for necessary dose adjustments based on current GFR rather than age alone, as elderly patients have altered pharmacokinetics for renally excreted drugs 1, 2
• Avoid or use with extreme caution potentially nephrotoxic medications including NSAIDs 2, 5, 6

Specific Medication Considerations

Metformin:

• Initiation is NOT recommended in patients with eGFR between 30-45 mL/min/1.73 m² 4
• If already taking metformin, assess benefit versus risk of continuing therapy and monitor more frequently 4
• Contraindicated if eGFR falls below 30 mL/min/1.73 m² 4

ACE Inhibitors/ARBs:

• Monitor renal function closely when using these agents; an initial small decline in GFR (10-20%) is acceptable 2
• Avoid dual RAS blockade (combining ACE inhibitors with ARBs or aliskiren) as this increases risks of hyperkalemia and acute kidney injury, particularly in patients with GFR <60 mL/min 5, 6
• Monitor serum potassium frequently when using these agents, especially if combined with potassium-sparing diuretics 5, 6

NSAIDs:

• Avoid NSAIDs in elderly patients with compromised renal function, as coadministration with ACE inhibitors or ARBs may result in acute renal failure 5, 6

Nutritional Management

Energy Intake

• Prescribe 30-35 kcal/kg/day for patients ≥60 years of age, as elderly individuals tend to be more sedentary 1
• Monitor for adequate energy intake as this is a principal reversible factor contributing to malnutrition 1

Protein Intake

• Recommend 0.6-0.8 g/kg/day protein intake with more than 50% from plant sources for patients with CKD Stage 3 7
• Monitor nutritional status closely when prescribing low-protein diets to prevent protein-energy wasting, particularly in patients >75 years, those with lower baseline nutritional status, or higher comorbidity burden 8
• Use subjective global assessment (SGA) every 3-6 months to monitor for nutritional deterioration 8
• Recent evidence from the EQUAL study (2024) demonstrates that low-protein diets are safe in older adults with advanced CKD when prescribed and monitored according to routine clinical practice 8

Electrolyte Management

• Encourage potassium-rich diet from food sources (fruits, vegetables, dairy) unless contraindicated 1
• Avoid potassium-rich diets in patients with chronic renal failure or those taking potassium-sparing diuretics 1
• Recommend sodium restriction to <5 g/day (approximately 2000 mg sodium) 1

Common Pitfalls and Caveats

• Do not rely on serum creatinine alone to assess renal function in elderly patients, as decreased muscle mass leads to underestimation of renal insufficiency 1, 2
• Recognize that GFR decline is nonlinear in older adults, decelerating with increasing age (approximately 1% per year after age 30-40) 2, 9
• Understand that isolated reduced GFR without comorbidities or kidney damage is rare (only 3.5% of elderly patients with GFR <60 have neither renal damage nor associated comorbidities) 3
• Optimize hydration status before initiating potentially nephrotoxic therapies 1, 2
• Temporarily discontinue metformin before iodinated contrast procedures if eGFR is 30-60 mL/min/1.73 m², and re-evaluate eGFR 48 hours after the procedure 4
• Monitor vitamin B12 levels in patients on metformin, as approximately 7% develop subnormal levels 4