What is the treatment for a patient with impaired renal function (low GFR)?

Treatment of Low GFR (Impaired Renal Function)

Initiate ACE inhibitor or ARB therapy immediately as first-line treatment for patients with low GFR, regardless of the severity of renal impairment, and expect an initial 10-20% decline in GFR as evidence of appropriate hemodynamic effect. 1, 2, 3

Immediate Nephrology Referral

• Refer to a nephrologist when GFR falls below 60 mL/min/1.73 m² (Stage 3A CKD or worse), as this threshold marks increased risk for multiple metabolic complications 2, 4
• Urgent referral is required for GFR <30 mL/min/1.73 m² (Stage 4 CKD), albuminuria ≥300 mg per 24 hours, or rapid GFR decline 4
• Approximately 20% of patients with GFR around 36 mL/min/1.73 m² have three or more metabolic abnormalities requiring specialist management 2

ACE Inhibitor/ARB Therapy: The Cornerstone

Start ACE inhibitor or ARB therapy and uptitrate to maximally tolerated doses, accepting an initial GFR decline of 10-20% as therapeutic confirmation rather than treatment failure. 1, 2, 3

• There is no serum creatinine level that contraindicates ACE inhibitor use—the drugs work by reducing intraglomerular pressure through efferent arteriolar dilation 1, 5
• The initial GFR decline represents reversal of maladaptive glomerular hyperfiltration and predicts long-term kidney protection 1, 3
• Do not discontinue ACE inhibitor/ARB unless creatinine rises >30% from baseline or severe hyperkalemia develops 1, 2, 6
• ACE inhibitors prevent end-stage renal disease most effectively when started early and continued long-term, with maximal benefit in patients with the lowest baseline GFR 5
• For type 1 diabetes with macroalbuminuria, ACE inhibitors are strongly recommended; for type 2 diabetes with macroalbuminuria, ARBs are strongly recommended 1

Critical Monitoring Protocol

• Check serum creatinine and potassium at baseline, then 1 week after initiation or dose adjustment 1, 2
• A creatinine rise ≤30% within the first 2-4 months is expected and acceptable 1, 3, 6
• Monitor GFR regularly, with changes >20% on subsequent tests requiring further evaluation 2, 3

High-Risk Situations Requiring Caution

ACE inhibitor/ARB therapy requires heightened vigilance but should not be withheld in patients with: 1, 6

• Volume depletion from aggressive diuresis, diarrhea, or hyperglycemia with osmotic diuresis
• Bilateral renal artery stenosis or stenosis of a solitary kidney
• Concurrent NSAID use (which impairs renal autoregulation)
• Heart failure with systolic blood pressure <100 mmHg
• Hyponatremia (indicating excessive renin-angiotensin system activation)

Blood Pressure Management

Target systolic blood pressure <120-130 mmHg using standardized office measurement, typically requiring 3-4 antihypertensive medications including an ACE inhibitor or ARB. 1, 2, 3

• Aggressive blood pressure control is essential for both renal and cardiovascular protection 2, 3
• The KDIGO guideline recommends <120 mmHg systolic, though this has not been specifically validated in glomerular disease 1
• ACE inhibitor or ARB should be the foundation, with additional agents added to achieve target 2, 3

Metabolic Acidosis Correction

• Treat metabolic acidosis with sodium bicarbonate or sodium citrate to reduce kidney endothelin production and slow GFR decline 1, 7
• Sodium citrate (or baking soda: 1/4 teaspoon = 1 g sodium bicarbonate) is an effective kidney-protective adjunct to ACE inhibition and blood pressure control 1, 7
• Correction of acidosis in patients with low GFR significantly reduces urine endothelin-1 excretion and markers of tubulointerstitial injury while slowing estimated GFR decline 7

Dietary Protein Restriction

• Restrict protein intake to 0.8 g/kg body weight/day (the adult RDA), with consideration of further restriction to 0.6 g/kg/day in selected patients 2
• This is a Grade A recommendation for slowing nephropathy progression 2

Cardiovascular Risk Management

Treat all patients with CKD as high cardiovascular risk and offer statin therapy, antiplatelet agents (unless bleeding risk outweighs benefit), and standard care for ischemic heart disease. 1

• CKD patients should receive the same level of care for ischemic heart disease and heart failure as those without CKD 1
• In patients with GFR <15 mL/min/1.73 m², the benefit of antiplatelet agents is uncertain due to increased bleeding risk 1
• Interpret troponin elevations cautiously but recognize they have excellent prognostic accuracy in CKD patients 1

Nephrotoxin Avoidance

Discontinue NSAIDs immediately and avoid radiocontrast media whenever possible. 2, 6, 4

• NSAIDs impair renal autoregulation and can precipitate acute kidney injury, especially when combined with ACE inhibitors and diuretics (the "triple whammy") 6, 4
• ACE inhibitors predispose to radiocontrast-induced acute renal failure 1
• Review all medications for drugs competing with creatinine for tubular secretion 2

Medication Dosing Adjustments

• Adjust doses of renally cleared medications including many antibiotics and oral hypoglycemic agents 4
• Monitor for drug interactions: ACE inhibitors may increase hypoglycemia risk with antidiabetic medications 6
• Avoid dual RAS blockade (ACE inhibitor + ARB + aliskiren) due to increased risks of hypotension, hyperkalemia, and acute renal failure without proven benefit 6

Monitoring for CKD Complications

Screen and treat the following complications: 4

• Hyperkalemia (monitor potassium frequently, especially with ACE inhibitor/ARB and potassium-sparing diuretics) 6
• Metabolic acidosis (treat as above)
• Hyperphosphatemia and vitamin D deficiency
• Secondary hyperparathyroidism
• Anemia

Common Pitfalls to Avoid

• Do not stop ACE inhibitor/ARB for modest, stable creatinine increases up to 30%—this represents therapeutic effect, not harm 1, 2, 3
• Do not delay nephrology referral in patients with GFR <60 mL/min/1.73 m² 2, 4
• Do not withhold ACE inhibitor/ARB based on absolute creatinine level—there is no contraindicated level per se 1
• Do not combine ACE inhibitor with ARB in routine practice—dual RAS blockade increases adverse events without benefit 6
• Do not prescribe NSAIDs to patients on ACE inhibitors, especially if also taking diuretics 6