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BIOC33H3 (127)

Acute Renal Failure and Chronic Kidney Disease

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Biological Sciences
Stephen Reid

Chapter 47: Acute Renal Failure and Chronic Kidney Disease  Renal failure is the partial or complete impairment of kidney function resulting in an inability to excrete metabolic waste products and water.  Renal failure causes functional disturbances of all body systems.  Renal failure is classified as acute or chronic. ACUTE RENAL FAILURE (ARF)  Acute renal failure (ARF) usually develops over hours or days with progressive elevations of blood urea nitrogen (BUN), creatinine, and potassium with or without oliguria. It is a clinical syndrome characterized by a rapid loss of renal function with progressive azotemia.  ARF is often associated with oliguria (a decrease in urinary output to <400 ml/day).  The causes of ARF are multiple and complex. They are categorized according to similar pathogenesis into prerenal (most common), intrarenal (or intrinsic), and postrenal causes. o Prerenal causes are factors external to the kidneys (e.g., hypovolemia) that reduce renal blood flow and lead to decreased glomerular perfusion and filtration. o Intrarenal causes include conditions that cause direct damage to the renal tissue, resulting in impaired nephron function. Causes include prolonged ischemia, nephrotoxins, hemoglobin released from hemolyzed RBCs, or myoglobin released from necrotic muscle cells. Acute tubular necrosis (ATN) is an intrarenal condition caused by ischemia, nephrotoxins, or pigments. ATN is potentially reversible if the basement membrane is not destroyed and the tubular epithelium regenerates. o Postrenal causes involve mechanical obstruction of urinary outflow. Common causes are benign prostatic hyperplasia, prostate cancer, calculi, trauma, and extrarenal tumors.  Clinically, ARF may progress through four phases: initiating, oliguric, diuretic, and recovery. In some situations, the patient does not recover from ARF and chronic kidney disease (CKD) results, eventually requiring dialysis or a kidney transplant. Oliguric Phase  Fluid and electrolyte abnormalities and uremia occur during the oliguric phase. The kidneys cannot synthesize ammonia or excrete acid products of metabolism, resulting in acidosis.  Damaged tubules cannot conserve sodium resulting in normal or below-normal levels of serum sodium. Uncontrolled hyponatremia or water excess can lead to cerebral edema. Fluid intake must be closely monitored.  Hyperkalemia is a serious complication of ARF. The serum potassium levels increase because the ability of the kidneys to excrete potassium is impaired. Acidosis worsens hyperkalemia as hydrogen ions enter the cells and potassium is driven out of the cells.  When potassium levels exceed 6 mEq/L (6 mmol/L) or dysrhythmias are identified, treatment must be initiated immediately.  Hematologic disorders associated with ARF include anemia due to impaired erythropoietin production and platelet abnormalities leading to bleeding from multiple sources.  A low serum calcium level results from the inability of the kidneys to activate vitamin D. When hypocalcemia occurs, the parathyroid gland secretes parathyroid hormone, which stimulates bone demineralization, thereby releasing calcium from the bones. Phosphate is also released, leading to elevated serum phosphate levels.  The two most common causes of death in patients with ARF are infection and cardiorespiratory complications.  The best serum indicator of renal failure is creatinine because it is not significantly altered by other factors.  Neurologic changes can occur as the nitrogenous waste products increase. Symptoms can include fatigue and difficulty concentrating, later escalating to seizures, stupor, and coma. Diuretic Phase  The diuretic phase begins with a gradual increase in daily urine output of 1 to 3 L/day, but may reach 3 to 5 L or more. The nephrons are still not fully functional. The uremia may still be severe, as reflected by low creatinine clearances, elevated serum creatinine and BUN levels, and persistent signs and symptoms. Recovery Phase  The recovery phase begins when the GFR increases, allowing the BUN and serum creatinine levels to plateau and then decrease. Renal function may take up to 12 months to stabilize. Collaborative Management  Because ARF is potentially reversible, the primary goals of treatment are to eliminate the cause, manage the signs and symptoms, and prevent complications while the kidneys recover.  Common indications for dialysis in ARF are (1) volume overload; (2) elevated potassium level with ECG changes; (3) metabolic acidosis; (4) significant change in mental status; and (5) pericarditis, pericardial effusion, or cardiac tamponade.  Hemodialysis (HD) is used when rapid changes are required in a short period of time. Peritoneal dialysis (PD) is simpler than HD, but it carries the risk of peritonitis, is less efficient in the catabolic patient, and requires longer treatment times. Continuous renal replacement therapy (CRRT) may also be used in the treatment of ARF, particularly in those who are hemodynamically unstable.  Prevention of ARF is primarily directed toward identifying and monitoring high-risk populations, controlling exposure to nephrotoxic drugs and industrial chemicals, and preventing prolonged episodes of hypotension and hypovolemia.  The patient with ARF is critically ill and suffers not only from the effects of renal disease but also from the effects of comorbid diseases or conditions (e.g., diabetes, cardiovascular disease).  The nurse has an important role in managing fluid and electrolyte balance during the oliguric and diuretic phases. Observing and recording accurate intake and output and body weight are essential.  Because infection is the leading cause of death in ARF, meticulous aseptic technique is critical. The nurse should be alert for local manifestations of infection (e.g., swelling, redness, pain) as well as systemic manifestations (e.g., malaise, leukocytosis) because an elevated temperature may not be present.  Respiratory complications, especially pneumonitis, can be prevented. Humidified oxygen; incentive spirometry; coughing, turning, and deep breathing; and ambulation are measures to help maintain adequate respiratory ventilation.  Skin care and measures to prevent pressure ulcers should be performed because of edema and decreased muscle tone. Mouth care is important to prevent stomatitis.  Recovery from ARF is highly variable and depends on the underlying illness, the general condition and age of the patient, the length of the oliguric phase, and the severity of nephron damage. Good nutrition, rest, and activity are necessary. Protein and potassium intake should be regulated in accordance with renal function.  The long-term convalescence of 3 to 12 months may cause psychosocial and financial hardships for the family, and appropriate counseling, social work, and psychiatrist/ psychologist referrals are made as needed. If the kidneys do not recover, the patient will eventually need dialysis or transplantation. Gerontologic Considerations  The older adult is more susceptible than the younger adult to ARF as the number of functioning nephrons decreases with age.  Causes of ARF include dehydration, hypotension, diuretic therapy, aminoglycoside therapy, prostatic hyperplasia, surgery, infection, and radiocontrast agents. CHRONIC KIDNEY DISEASE  Chronic kidney disease (CKD) involves progressive, irreversible loss of kidney function.  CKD usually develops slowly over months to years and necessitates the initiation of dialysis or transplantation for long-term survival. The prognosis of CKD is variable depending on the etiology, patient’s condition and age, and adequacy of follow-up.  Uremia is a syndrome that incorporates all the signs and symptoms seen in the various systems throughout the body in CKD.  In the early stage of renal insufficiency, polyuria results from the inability to concentrate urine. As the GFR decreases, the BUN and serum creatinine levels increase.  Clinical manifestations of uremia develop. Fatigue, lethargy, and pruritus are often the early symptoms. Hypertension and proteinuria are often the first signs. Hyperglycemia, hyperinsulinemia, and abnormal glucose tolerance tests may be seen.  Many patients with uremia develop hyperlipidemia, with elevated very-low-density lipoproteins (VLDLs), normal or decreased low-density lipoproteins (LDLs), and decreased high-density lipoproteins (HDLs).  Hyperkalemia results from the decreased excretion by the kidneys, the breakdown of cellular protein, bleeding, and metabolic acidosis. Potassium may also come from the food consumed, dietary supplements, drugs, and IV infusions.  Because of impaired sodium excretion, sodium along with water is retained resulting in dilutional hyponatremia. Sodium retention can contribute to edema, hypertension, and heart failure.  Metabolic acidosis results from the impaired ability to excrete the acid load (primarily ammonia) and from defective reabsorption and regeneration of bicarbonate.  Normocytic or normochromic anemia is due to decreased production of erythropoietin. The most common cause of bleeding is a qualitative defect in platelet function.  Infectious complications are common in CKD. Clinical findings include lymphopenia, lymphoid tissue atrophy, decreased antibody production, and suppression of the delayed hypersensitivity response.  The most common cardiovascular abnormality is hypertension, which is usually present pre-ESRD and is aggravated by sodium retention and increased extracellular fluid volume. Diabetes mellitus is an additional risk factor.  Cardiac dysrhythmias may result from hyperkalemia, hypocalcemia, and decreased coronary artery perfusion.  Respiratory changes include Kussmaul respiration, dyspnea from fluid overload, pulmonary edema, uremic pleuritis (pleurisy), pleural effusion, and a predisposition to respiratory infections.  Neurologic changes are due to increased nitrogenous waste products, electrolyte imbalances, metabolic acidosis, axonal atrophy, and demyelination. Depression of the CNS results in lethargy, apathy, decreased ability to concentrate, fatigue, irritability, and altered mental ability.  Peripheral neuropathy may result in restless legs syndrome, paresthesias, bilateral footdrop, muscular weakness and atrophy, and loss of deep tendon reflexes.  The treatment for neurologic problems is dialysis or transplantation. Altered mental status is often the signal that dialysis must be initiated.  Renal osteodystrophy is a syndrome of skeletal changes that is a result of alterations in calcium and phosphate metabolism. Osteomalacia is demineralization resulting from slow bone turnover and defective mineralization of newly formed bone. Osteitis fibrosa cystica results from decalcification of the bone and replacement of bone tissue with fibrous tissue.  Pruritus results from a combination of the dry skin, calcium-phosphate deposition in the skin, and sensory neuropathy.  Both sexes experience infertility and a decreased libido. Sexual dysfunction may also be caused by anemia, peripheral neuropathy, and psychologic problems, physical stress, and side effects of drugs.  Personality and beh
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