What are the basic principles of managing impaired renal function?

Managing Impaired Renal Function: Core Principles

The fundamental approach to managing impaired renal function centers on accurate assessment of kidney function using GFR-based staging, aggressive blood pressure and proteinuria control with ACE inhibitors or ARBs, monitoring for progression and complications, and timely referral for multidisciplinary care and renal replacement therapy planning. 1

Assessment and Staging

• Measure GFR using standardized equations (not serum creatinine alone) and stage chronic kidney disease according to KDIGO criteria, which divides CKD into categories G1-G5 based on GFR levels normalized to 1.73 m² body surface area 1
• Assess albuminuria using albumin-creatinine ratio, as this provides independent prognostic information beyond GFR and guides treatment intensity 1
• Monitor renal function periodically with frequency determined by GFR and albuminuria category—higher risk patients (lower GFR, higher albuminuria) require more frequent monitoring, ranging from 1-4 times per year 1
• Recognize that serum creatinine alone is inadequate, particularly in elderly patients where age-related muscle mass loss can mask significant renal dysfunction 1

Blood Pressure and Proteinuria Management

Use ACE inhibitors or ARBs as first-line therapy for patients with both hypertension and proteinuria, uptitrating to maximally tolerated doses 1

Blood Pressure Targets

• Target systolic BP <120 mmHg using standardized office measurement in most adult patients 1
• For patients with albuminuria ≥30 mg/24 hours, target BP ≤130/80 mmHg 1
• For patients with albuminuria <30 mg/24 hours, target BP ≤140/90 mmHg 1

ACE Inhibitor/ARB Management

• Do not discontinue ACE inhibitors or ARBs for modest, stable increases in serum creatinine up to 30% 1
• Stop ACE inhibitors or ARBs if kidney function continues to worsen beyond 30% increase or if refractory hyperkalemia develops 1
• Avoid initiating ACE inhibitors or ARBs in patients presenting with abrupt onset nephrotic syndrome, as these can precipitate acute kidney injury, especially in minimal change disease 1
• Monitor labs frequently when on these medications, checking potassium and creatinine 1

Dose Adjustments for Renal Impairment

• For creatinine clearance 50-79 mL/min: reduce fludarabine dose to 20 mg/m² if using chemotherapy 1
• For creatinine clearance 40-49 mL/min: reduce fludarabine dose to 15 mg/m² 1
• Do not use nephrotoxic therapies in patients with creatinine clearance <40 mL/min unless benefits clearly outweigh risks 1

Lifestyle Modifications

Implement dietary sodium restriction to <2.0 g/day (<90 mmol/day) as this synergistically improves blood pressure and proteinuria control 1

Additional lifestyle interventions include:

• Achieve and maintain healthy body weight (BMI 20-25 kg/m²) 1
• Complete smoking cessation 1
• Regular exercise for 30 minutes, 5 times per week 1
• Counsel patients to hold ACE inhibitors/ARBs and diuretics during sick days when at risk for volume depletion 1

Monitoring for Progression

Define progression as both a change in GFR category AND ≥25% decline in eGFR to avoid misinterpreting small fluctuations as true progression 1

• Small fluctuations in GFR are common and do not necessarily indicate progression 1
• This dual criterion approach (category change plus percentage decline) identifies patients at genuinely increased risk for adverse outcomes 1
• Serial measurements every 2-4 hours are needed during acute complications like uremia with hyperammonemia 2

Managing Complications

Hyperkalemia

• Use potassium-wasting diuretics and/or potassium-binding agents to normalize serum potassium, enabling continued use of ACE inhibitors/ARBs 1
• Monitor potassium periodically in all patients on renin-angiotensin system blockers 3

Metabolic Acidosis

• Treat when serum bicarbonate <22 mmol/L 1

Volume Overload

• Monitor for respiratory crackles, peripheral edema, jugular venous distension, and worsening oxygenation every 2-4 hours in acute settings 4
• Consider urgent hemodialysis if severe volume overload develops with respiratory compromise 4

Uremic Symptoms

• Initiate dialysis when BUN >100 mg/dL with uremic symptoms (altered mental status, encephalopathy, pericarditis) or rapidly deteriorating neurological status 2
• Urgent hemodialysis is first-line treatment for symptomatic uremia in CKD stage 4 2

Specialist Referral and Multidisciplinary Care

Refer to nephrology when GFR falls below 30 mL/min/1.73 m² or earlier if rapid progression, difficult-to-control hypertension, or persistent proteinuria despite treatment 1

Multidisciplinary care should include:

• Dietary counseling for sodium, protein, and potassium restriction 2
• Evaluation for permanent dialysis access when appropriate 2
• Patient education about treatment options including different dialysis modalities and transplantation 2
• Advance care planning and discussion of conservative management options for those who choose not to pursue renal replacement therapy 1

Medication Safety

Adjust all renally-cleared medications based on creatinine clearance, as impaired renal function reduces drug elimination and increases toxicity risk 1

• Hydration status should be assessed and optimized before initiating potentially nephrotoxic drugs 1
• Avoid nephrotoxic agents including certain antibiotics, NSAIDs, and contrast media when possible 4, 3
• NSAIDs should be avoided or limited in patients with any baseline renal compromise to prevent further deterioration 1, 3

Critical Pitfalls to Avoid

• Excessive fluid resuscitation in patients with advanced CKD can precipitate pulmonary edema more rapidly than in patients with normal kidney function 4
• Delaying nephrology consultation when considering dialysis initiation leads to poor outcomes 4
• Relying solely on serum creatinine rather than calculated GFR, particularly in elderly patients where creatinine may appear falsely reassuring 1
• Stopping ACE inhibitors/ARBs prematurely for small creatinine increases <30%, as these medications provide long-term renal protection despite initial modest GFR decline 1