Chronic renal failure secondary prevention

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Aarti Narayan, M.B.B.S [2]Sargun Singh Walia M.B.B.S.[3]

Overview

Effective measures for the secondary prevention of chronic renal failure include reducing progression, treating complication, and renal replacement therapy(RRT).

Secondary Prevention

Reduce Progression

• Protective therapy most effective if initiated early, before Creatinine > 1.5-2.0 mg/dL
  • Treat Hypertension
    • Systemic hypertension--elevated intraglomerular pressure +/or glom hypertrophy.
    • Blood Pressure (BP) control shown in multiple trials to slow progression of renal disease.
    • Goal Blood pressure < 130/80-85; < 125/75 in patients with proteinuria > 1-2 g/d.
    • ACE inhibitors (ACEI) and Angiotensin II receptor blockers (ARB) preferred 1st line agents due to reno-protective effects.
    • Additional agents as needed, including diuretics if volume overload.
  • Restrict Dietary Protein
    • Controversial – may decrease intraglomerular pressure.
    • Conflicting studies – some show benefit, others do not.
    • No significant adverse effects shown in large trial.
    • Recommendations
      • No restriction (> 0.8 g/kg/d) if GFR 25-55 mL/min.
      • Limit protein to 0.8 g/kg/d if progression or uremic symptoms.
      • Limit to 0.6 g/kg/d if severe renal insufficiency (GFR 13-25 mL/min).
    • Close follow-up by dietician given risk of malnutrition in this population.
  • Control Blood sugar:
    • Tight control (HbA1c < 7.0, [[Fasting blood sugar 70-120) reduces progression in DM I.
    • Unclear if as beneficial in DM II, but potentially helpful.

Treat complications

• Volume Overload
  • Impaired excretion of sodium and water due to decreased GFR +/- AII/aldo activation.
  • Restrict dietary sodium to 1-2 g/d if hypertension or edema.
  • Diuretics
    • Thiazides ineffective if GFR < 25 mL/min (~Creatinine > 2-3).
    • Switch to Loop diuretic as Creatinine rises; may need bid dosing.
    • Addition of thiazide to Loop diuretic can--additional Diuresis.
    • Watch for excessive volume depletion
• Hyperkalemia
  • Potassium usually maintained until GFR < 15-20 mL/min.
  • Increased risk of hyperkalemia with Oliguria, high potassium diet, (ACE inhibitors therapy).
  • Increased risk with many meds: ACEI, NSAIDs, Potassium-sparing diuretics, digoxin, TMP.
  • Increased risk in diabetics with type IV RTA
• Management
  • Low potassium diet (< 60 mEq/d) once GFR < 15 mL/min.
  • Avoidance of salt substitutes (may contain potassium salts).
  • +/- loop diuretic
  • Low dose Kayexelate (5 g with meals) if needed.
• Calcium/phosphate Abnormalities
  • Reduced renal synthesis Calcitriol/Vitamin D--low serum Calcium-- Secondary hyperparathyroidism.
  • (Occurs when GFR < 40 mL/min)
  • Reduced GFR--phosphate retention
  • Elevated parathyroid hormone (PTH)--mobilization of Calcium from bone; increased excretion phosphate.
  • Allows maintenance of normal Calcium/phosphate while GFR > 30 mL/min.
  • Causes renal osteodystrophy
  • Once GFR < 25-30 mL/min, hyperphosphatemia occurs
  • Therapy goals = normalize Calcium/Phosphate and maintain parathyroid hormone (PTH)< 200 (2-3x uln).
    • Calcium/Phosphate management should be initiated when Creatinine ~ 2.
    • Calcium x phosphate product should be < 60 to prevent met calcification.
    • Low phosphate diet: < 800 mg/d (challenging)
    • Calcium-based oral phosphate binders: Calcium acetate or Calcium carbonate with meals.
    • Avoid Aluminium-based phosphate binders except for acute therapy of high Calcium x Phosphate products.
      • (Aluminium toxicity = osteomalacia, anemia, encephalopathy)
    • Avoid Calcium citrate (increases gastrointestinal absorption of aluminum)
      • RenaGel = new non-Calcium/Aluminium-containing phosphate binder (cationic polymer).
        • (For patients who cannot tolerate Calcium carbonate or need additional agent)
      • Calcitriol 0.125-0.25 mg/d improves Calcium & Parathyroid hormone levels, decreases bone disease.
        • (Monitor Calcium--reduce dose if hypercalcemic)
• Metabolic Acidosis
  • Occurs when GFR < 25 mL/min due to inability to excrete H+ ions.
  • Underlying cause = impaired renal ammonia production and bicarbonate reabsorption.
  • Risk = bone buffering of acidosis--worsened Osteodystrophy via Calcium/phosphate loss.
  • Increased skeletal muscle breakdown--loss of lean body mass.
  • Therapy goal = bicarbonate > 22 mEq/L via alkali therapy (NaHCO3 0.5-1 mEq/kg/d)
• Anemia
  • Normocytic normochromic anemia due to reduced Erythropoietin production.
  • May be exacerbated by reduced RBC survival, coexistent iron/folate deficiency, etc.
  • Generally occurs when Creatinine > 2-3 mg/dL.
  • If untreated, hematocrit (Hct) usually stabilizes at ~ 25.
  • Therapy recommendations = Erythropoietin if symptomatic anemia or Hemoglobin < 10 g/dL (in pre-dialysis patients).
  • Goal Hematocrit 33-36
  • Must replete iron stores first (oral ferrous sulfate)
  • Initial dose ~ 150 U/kg sc weekly to increase Hematocrit.
  • Maintenance dose ~ 75 U/kg weekly once Hematocrit goal reached.
  • Improves symtoms and may reduce left ventricle (LV) mass (via improvemt of hyperdynamic state).
  • Side effects = increased blood pressure (BP); may need to augment Antihypertensive regimen.

Plan for Renal Replacement Therapy (RRT)

• Indications for Dialysis
  • Malnutrition
  • Creatinine clearance 10-15 mL/min
  • acidosis not responsive to medical therapy
  • Volume overload / CHF
  • Uremic pericarditis
  • Uremic encephalopathy
  • Intractable muscle cramps
  • Anorexia and nausea not attributable to reversible causes such as peptic ulcer disease
  • Protein energy malnutrition
  • Hyperkalemia
  • Extracellular fluid volume overload

Recent studies have shown no benefits of initiating early dialysis with improved patient survival. However, advanced preparation for dialysis can help avoid complications like poorly functioning fistula for hemodialysis or malfunctioning peritoneal dialysis catheter, sepsis, bleeding and thrombosis.

• RRT modalities
  • Hemodialysis
  • Peritoneal dialysis
  • Renal transplant
• Access for hemodialysis should be established when GFR < 25 mL/min (estimated Chronic renal failure within 1 year).
• Diabetics tend to require dialysis sooner than non-diabetics because more symptomatic at given GFR.
• Indications for referral to nephrologist
  • Unclear etiology of new or chronic renal insufficiency
• For diagnostic evaluation, e.g. biopsy
• GFR < 50 mL/min: i.e. before vascular access/RRT required

References

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