What are the management strategies for a patient with impaired renal function, elevated creatinine (Creatinine) and Blood Urea Nitrogen (BUN) levels, and decreased Glomerular Filtration Rate (GFR)?

Management of Impaired Renal Function with Elevated Creatinine, BUN, and Decreased GFR

In patients with impaired renal function (elevated creatinine and BUN with decreased GFR), immediately assess for reversible causes including volume depletion, hypotension, excessive diuresis, and nephrotoxic medications, while continuing ACE inhibitors or ARBs unless creatinine rises >30% or continues to worsen progressively. 1, 2, 3

Initial Assessment and Cause Identification

The first priority is determining whether renal dysfunction is acute, chronic, or acute-on-chronic:

• Establish chronicity by reviewing past measurements of GFR, creatinine, and urinalysis; imaging findings showing reduced kidney size or cortical thinning; or repeat measurements over 3 months 1
• A BUN/creatinine ratio >35 indicates pre-renal azotemia, suggesting volume depletion, heart failure, or decreased renal perfusion 2
• Evaluate for reversible causes including hypotension, dehydration, excessive diuretic use, NSAIDs, renal artery stenosis, and other nephrotoxic medications 1, 2

Medication Management: ACE Inhibitors and ARBs

Do not automatically discontinue ACE inhibitors or ARBs when creatinine rises, as modest increases are expected and protective:

• Continue ACE inhibitors/ARBs if creatinine increases up to 30% and stabilizes within 2 months, as this acute rise is strongly associated with long-term renal protection 2, 3, 4
• Discontinue only if: creatinine rises >30% above baseline, continues to worsen progressively beyond 2 months, reaches >500 μmol/L (5 mg/dL), or refractory hyperkalemia (>5.6 mmol/L) develops 1, 2, 3, 4
• For serum creatinine >250 μmol/L (2.5 mg/dL), specialist nephrology supervision is recommended 1, 2
• Patients with the greatest degree of baseline renal insufficiency derive the greatest benefit from ACE inhibitors, with 55-75% risk reduction in disease progression 4

Diuretic Management

Adjust diuretic therapy based on volume status and renal function:

• Use loop diuretics preferentially when creatinine clearance <30 mL/min, as thiazides become ineffective at this level 1
• Avoid excessive ultrafiltration and volume depletion, as episodes of intravascular volume depletion accelerate loss of residual kidney function 1
• Consider twice-daily dosing of loop diuretics over once-daily for better efficacy 1
• Paradoxically, loop diuretics may benefit patients by reducing fluid removal requirements, despite concerns about worsening renal function with overuse 1

Blood Pressure Management

Target systolic blood pressure <120 mmHg using standardized office measurement:

• This target applies to most patients with CKD, though formally not validated specifically in all glomerular diseases 1
• Uptitrate ACE inhibitors or ARBs to maximally tolerated doses as first-line therapy for both hypertension and proteinuria 1
• Control of severe hypertension can sometimes improve residual kidney function enough to allow discontinuation of dialysis 1

Monitoring Strategy

Implement systematic monitoring to detect progression and medication toxicity:

• Monitor renal function and electrolytes within the first few weeks after starting or adjusting ACE inhibitors/ARBs 1, 3
• Use both creatinine-based eGFR (eGFRcr) and cystatin C-based eGFR (eGFRcr-cys) when eGFRcr is less accurate and clinical decisions depend on precise GFR 1
• Serial measurements of creatinine and BUN together provide more useful information than either alone 5
• Monitor for hyperkalemia, especially with concurrent use of ACE inhibitors/ARBs, aldosterone antagonists, potassium-sparing diuretics, or potassium supplements 1, 3

Nephrology Referral Criteria

Refer to nephrology for:

• Progressive decline in renal function despite appropriate management 2
• Serum creatinine >250 μmol/L (2.5 mg/dL) 1, 2
• Significant proteinuria or abnormal urinalysis suggesting intrinsic renal disease 2
• Uncertainty about cause of renal dysfunction requiring kidney biopsy consideration 1

Additional Protective Measures

Implement strategies to preserve residual kidney function:

• Avoid nephrotoxic agents including NSAIDs, aminoglycosides, and radiocontrast when possible 1
• Maintain hemodynamic stability during any dialysis procedures by avoiding hypotension through reduced dialysate temperature, increased dialysate sodium, or midodrine administration 1
• Restrict dietary sodium to <2.0 g/day (<90 mmol/day) to reduce volume overload and blood pressure 1
• Adjust doses of renally-cleared medications (e.g., digoxin) to avoid toxicity 1

Common Pitfalls to Avoid

• Do not stop ACE inhibitors/ARBs prematurely for modest creatinine rises <30%, as this eliminates their long-term renoprotective benefit 2, 3, 4
• Do not rely solely on creatinine or eGFR in patients receiving nephrotoxic chemotherapy, as these may remain normal despite significant GFR decline 6
• Do not use thiazide diuretics alone when GFR <30 mL/min, as they are ineffective at this level 1
• Do not assume irreversible kidney disease without excluding reversible causes like volume depletion, hypotension, or medication effects 1, 2