Uremia

Background

• Uremia = clinical syndrome a/w end-stage renal disease (contamination of blood w/ urine)
  • Correlation exists between uremia symptoms and low GFR (15-20% of nl)
  • BUN/Cr are inaccurate markers of clinical syndrome of uremia
• Contributing Factors:
  • Excretory failure
    • Leads to toxin accumulation
  • Biosynthetic failure
    • Loss of Vitamin D and erythropoietin
  • Regulatory failure
    • Uremic state produces excess free radicals -> atherosclerosis, amyloidosis

Clinical Features and Management

Neurologic

• Uremic encephalopathy
  • Diagnosis of exclusion
  • Cognitive defects, memory loss, decreased attentiveness, slurred speech
  • Asterixis, seizure, coma
  • Improves w/ dialysis
• Dialysis dementia
  • Similar to uremic encephalopathy except progressive, no improvement w/ dialysis
  • EEG findings can differentiate uremic encephalopathy from dialysis dementia
• CVA
  • Cerebrovascular disease, trauma, bleeding dyscrasias, anticoagulant, HTN
• Subdural hematoma
  • 10x more likely than in general population
  • Headache, focal neurologic deficits, seizure, coma
• Peripheral neuropathy
  • Occurs in 60-100% of dialysis pts
  • Paresthesias, impaired proprioception, weakness
  • Autonomic neuropathy (postural dizziness, gastroparesis, bowel dysfunction)

Cardiovascular

• CK-MB and troponin are specific markers of MI even in pts undergoing regular dialysis
• Mortality from CV disease is 10-30x higher in dialysis pts than general population
• HTN is common
• Uremic cardiomyopathy
  • Diagnosis of exclusion
  • Circulating digitalis-like substances have been implicated
  • Dialysis rarely improves LV function
• Pericarditis
  • Uremic pericarditis (75% of cases)
    • Most common when the other symptoms of uremia are most severe
    • BUN is nearly always >60
    • Loud friction rub that is often palpable
    • Typical pericarditis ECG changes are absent (inflammation does not involve myocardium)
      • If ECG does have typical changes consider infection
  • Dialysis-related (25% of cases)
    • Most common during increased catabolism (trauma, sepsis) or missed dialysis sessions
    • Constitutional symptoms, such as fever, are more common than in uremic pericarditis
  • Treatment
    • Dialysis
• Tamponade
  • Presents w/ AMS, hypotension, dyspnea
    • Rarely present w/ classic signs of Beck's triad
  • Pericardiocentesis should only be attempted if hemodynamically unstable
• Pulmonary Edema
  • Commonly ascribed to fluid overload; also consider MI
    • Treat similar to non-ESRD pt
      • Lasix 80mg IV may be effective even if minimal Urine output (pulmonary vasodilation)
    • Preload reduction can be accomplished via:
      • Induced diarrhea (sorbitol)
      • Phlebotomy - withdrawal of as little as 150 mL is safe and effective
• CHF
  • May be preexisting
  • May be caused by uremic cardiomyopathy, fluid overload, AV-related high-output failure

Hematologic

• Anemia
  • Without tx the hematocrit in ESRD pts should stabilize at 15-20%
  • Treatment = erythropoietin
• Bleeding diathesis
  • Increased risk for of bleeding (GI, ICH, liver hematoma) due to impaired plt function
  • Treatment = desmopressin, cryoprecipitate, conjugated estrogen
• Immunodeficiency

GI

• Anorexia, N/V
• Increased incidence of GI bleeding, diverticular disease, ascites

Renal bone disease

• Metastatic calcification (calciphylaxis)
  • When calcium-phosphate product (Ca x PO4) > 70-80, metastatic calcification can ensue
  • Symptoms of pseudogout, skin/finger necrosis (small vessel involvement)
  • Life-threatening calcifications can occur in the cardiac and pulmonary systems
  • Tx = use of low-calcium dialysate and phosphate-binding gels
• Hyperparathyroidism (osteitis fibrosa cystica)
  • Calciphylaxis + vitamin D3 deficiency results in depressed Ca, stimulation of PTH
  • Leads to high bone turnover > weakened bones > increased fracture susceptibility
  • Tx = phosphate binding gels, vitamin D3 replacement
• Vitamin D3 deficiency and aluminum intoxication (osteomalacia)
  • Leads to osteomalacia (defect in bone calcification)
  • Symptoms similar to hyperparathyroidism (muscle weakness, bone pain)
  • Tx = desferrioxamine
• Amyloidosis
  • Common in pts >50yr who have received dialysis for >10yr
  • Complications: GI perforation, bone cysts w/ pathologic fx, arthropathies