What is the treatment approach for a patient with Chronic Kidney Disease (CKD) Stage 3b, characterized by impaired renal function with a creatinine level of 1.5 mg/dL and an estimated Glomerular Filtration Rate (eGFR) of 35-43 mL/min/1.73m²?

Treatment Approach for CKD Stage 3b (eGFR 35-43 mL/min/1.73m²)

For CKD Stage 3b with creatinine 1.5 mg/dL and eGFR 35-43 mL/min/1.73m², initiate or continue ACE inhibitor or ARB therapy if albuminuria is present, target blood pressure <130/80 mmHg if albuminuria ≥30 mg/24h, add an SGLT2 inhibitor if eGFR ≥20 mL/min/1.73m² with diabetes or significant albuminuria, and refer to nephrology for ongoing management. 1, 2

Blood Pressure Management

• Target blood pressure <130/80 mmHg if albuminuria ≥30 mg/24 hours (ACR ≥30 mg/mmol), or <140/90 mmHg if albuminuria <30 mg/24 hours. 1
• Start ACE inhibitor (lisinopril 2.5 mg daily) or ARB at half the usual recommended dose in patients with eGFR 30-44 mL/min/1.73m², which defines Stage 3b CKD. 3, 4
• Titrate upward as tolerated to maximum approved dose (lisinopril 40 mg daily) to achieve proven renoprotective and cardiovascular benefits demonstrated in clinical trials. 1, 3
• Check blood pressure, serum creatinine, and potassium within 2-4 weeks of initiation or dose increase. 1, 2
• Continue ACE inhibitor/ARB even as eGFR declines below 30 mL/min/1.73m², as discontinuation removes cardiovascular and renal protection. 2
• Accept creatinine rises up to 30% within 4 weeks of starting or increasing dose, as this reflects desired hemodynamic reduction in intraglomerular pressure, not acute kidney injury. 2

RAS Inhibitor Therapy Based on Albuminuria Status

• If albuminuria is severely increased (ACR ≥60 mg/mmol or PCR ≥100 mg/mmol, equivalent to >1 g/day proteinuria), strongly recommend ACE inhibitor or ARB regardless of diabetes status. 1
• If albuminuria is moderately increased (ACR 30-60 mg/mmol) without diabetes, consider ACE inhibitor or ARB therapy. 1
• Never combine ACE inhibitors with ARBs or direct renin inhibitors, as dual RAS blockade increases risks of hyperkalemia and acute kidney injury without additional benefits. 1, 2

Hyperkalemia Management

• Manage elevated potassium with potassium-lowering measures (dietary restriction, diuretics, sodium bicarbonate, gastrointestinal cation exchangers) rather than stopping the ACE inhibitor or ARB. 2
• Avoid all potassium supplements and potassium-based salt substitutes, and counsel on limiting high-potassium foods. 5
• Only discontinue RAS inhibitor if hyperkalemia remains uncontrolled despite medical management. 2, 5

SGLT2 Inhibitor Therapy

• Add an SGLT2 inhibitor if eGFR ≥20 mL/min/1.73m² and the patient has type 2 diabetes or albuminuria ≥200 mg/g, as this provides additional renoprotective benefits beyond ACE inhibition. 1
• SGLT2 inhibitors are generally not initiated at eGFR <20 mL/min/1.73m², but if already prescribed, can be continued until dialysis initiation. 5

Additional Pharmacologic Considerations

• Consider a nonsteroidal mineralocorticoid receptor antagonist (finerenone) if albuminuria persists despite maximum tolerated RAS inhibitor dose and eGFR remains >25 mL/min/1.73m². 1
• Nonsteroidal MRAs are contraindicated at eGFR <25 mL/min/1.73m². 5
• Continue or initiate statin therapy for cardiovascular protection in patients ≥50 years with eGFR <60 mL/min/1.73m². 5

Nephrology Referral

• Refer to nephrology for ongoing management of CKD Stage 3b (eGFR 30-44 mL/min/1.73m²), as this threshold indicates moderate-severe decrease in GFR requiring specialist input. 4
• Refer if persistent proteinuria with protein excretion >1 g/day (ACR ≥60 mg/mmol or PCR ≥100 mg/mmol), as renal biopsy may be indicated and immunosuppressive medications may need consideration. 4
• Refer if blood pressure remains refractory to treatment with 4 or more antihypertensive agents. 4
• Refer if abrupt sustained decrease in eGFR >20% after excluding reversible causes. 4

Metabolic Complications Monitoring

• Monitor for and treat metabolic complications that predict progression: anemia (hemoglobin), metabolic acidosis (bicarbonate), mineral abnormalities (calcium, phosphorus), and hypoalbuminemia. 6
• Patients with Stage 3b CKD who manifest greater metabolic complications at entry are more likely to progress to Stage 4 or 5, even when eGFR values are equivalent. 6
• Stage 3b patients have significantly higher risks of adverse renal and cardiovascular outcomes compared to Stage 3a patients (eGFR 45-59 mL/min/1.73m²). 7, 4

Cardiovascular Risk Reduction

• Recognize that Stage 3b CKD patients have elevated cardiovascular risk, with higher incidence rates of cardiovascular events compared to those without CKD. 8
• Primary care intervention for cardiovascular risk reduction should be strongly emphasized, as the majority of Stage 3 CKD patients die from cardiovascular causes rather than progressing to end-stage renal disease. 4

Common Pitfalls to Avoid

• Do not discontinue ACE inhibitors or ARBs prematurely when creatinine rises by less than 30%, as modest increases reflect hemodynamic changes from reduced intraglomerular pressure. 2
• Do not immediately stop RAS inhibitors for hyperkalemia without first attempting medical management with potassium-lowering measures. 2
• Do not use dual RAS blockade (ACE inhibitor plus ARB, or either with direct renin inhibitor), as this is contraindicated. 1, 5
• Do not delay nephrology referral until eGFR <15 mL/min/1.73m², as Stage 3b already warrants specialist involvement. 4