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NITMED TUTORIALS INC

NITMED TUTORIALS INC. ACUTE RENAL FAILURE. Acute Renal Failure. Definition The loss of renal function (measured as GFR) over hours to days Expressed clinically as the retention of nitrogenous waste products in the blood. Acute Renal Failure. Definitions

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NITMED TUTORIALS INC

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  1. NITMED TUTORIALS INC

  2. ACUTE RENAL FAILURE

  3. Acute Renal Failure • Definition • The loss of renal function (measured as GFR) over hours to days • Expressed clinically as the retention of nitrogenous waste products in the blood

  4. Acute Renal Failure • Definitions • Azotemia - the accumulation of nitrogenous wastes • Uremia - symptomatic renal failure • Oliguria - urine output < 400-500 mL/24 hours • Anuria - urine output < 100 mL/24 hours

  5. Functions of the Renal System • Maintenance of fluid balance: • The kidneys maintain the fluid balance in the body by regulating the amount and makeup of fluid inside and outside (mainly) the cells. • The kidneys are continuously exchanging water, (plus sodium, potassium, chloride, and other ions across their cell membranes.) • Two hormones play a key role in the kidney’s ability to maintain fluid balance in the body

  6. Functions of the Renal System • 1. ADH: controls the collecting tubules permeability to water according to the osmoreceptor’s ability to sense high concentration of solute in the plasma. (In other words when the plasma is concentrated, ADH is secreted to hold on to more water. When the plasma is dilute, ADH is not secreted so the permeability to water changes in the collecting tubules, and water is released.) • 2. Aldosterone: regulates water reabsorption in the distal tubules by increasing sodium reabsorption and therefore water reabsorption when released from the adrenal cortex. (It is released as the final response in the renin angiotensin aldosterone system.) The presence of Aldosterone also helps increase the excretion of potassium. NB: when this fails fluid retention occurs

  7. Functions of the Renal System The regulation of acid-base balance: The kidneys regulate acid base balance by: • Excreting just enough hydrogen ions to keep the ph of the blood in the normal range. • Manufacturing bicarbonate (a base) as needed to maintain ph between 7.35-7.45. • When the kidneys fail: • Metabolic acidosis results. • Patients may develop Kussmaulrespirations

  8. Functions of the Renal System Maintenance of electrolyte balance: • The kidneys function to regulate electrolyte concentrations. • When the kidneys fail, electrolyte levels are not maintained: K+, Na, Phosphate, Ca+ • Potassium: • Hypokalemiamay occur… • with vomiting or excessive diarrhea in early renal failure when uremic toxins begin to circulate. in the diuretic phase of acute renal failure as the kidney is unable to conserve water and electrolytes. ………………. ARRYTHMIAS, NAUSEA, and LETHARGY occur. • Hyperkalemiaoccurs with….. decreased renal excretion of potassium both in the oliguric phase of acute renal failure and in end stage renal disease. Hyperkalemia could lead to life threatening ARRYTHMIAS!!

  9. Functions of the Renal System> Failure • Sodium: • Hyponatremiaalso occurs in the diuretic phase of acute renal failure when the kidneys cannot conserve sodium or water. MUSCLE WEAKNESS, CONFUSION, and ABDOMINAL CRAMPING occur. • Hypernatremiaoccurs with decreased renal excretion of sodium. This will occur in the end stages of renal disease and the person will be on a sodium-restricted diet. ……DRY MUCOUS MEMBRANES, and OLIGURIA occurs. Calcium: • Hypocalcemia occurs for two reasons: 1.A hyperphosphatemia occurs because of a decreased excretion of phosphate. There is an inverse relationship between phosphate and Calcium, so a hypocalcemia occurs. ( These electrolytes are regulated by the parathyroid gland, so when the phosphate level rises out of control due to the kidneys inability to excrete it, the parathyroid hormone (from the gland) is over secreted and starts to get Calcium from the bones, due to a depletion in the serum) OSTEOPOROSIS, OSTEODYSTROPHY (bone disease), AND TETANY occurs.

  10. Functions of the Renal System> Failure Hypocalcemia • 2. The kidneys normally secrete an active form of vitamin D (2-3 DPG), which help the intestines absorb calcium. When there’s decreased absorption, there’s hypocalcemia.

  11. Functions of the Renal System Maintenance of blood pressure: The kidneys help regulate blood pressure by producing and secreting the enzyme renin in response to an actual or perceived decline in extra cellular fluid volume. (Angiotensinogen) turns Renin into angiotensin I which is converted into angiotensin II (by an enzyme), the most potent vasoconstrictor in the body. Angiotensin II raises arterial blood pressure by…

  12. RENIN… 1. Increasing peripheral vasoconstriction 2. Stimulating Aldosterone secretion Aldosterone promotes the reabsorption of sodium and water to correct the fluid deficit and/or inadequate blood flow (renal ischemia)

  13. Functions of the Renal System> Failure • When the kidneys fail: Patients are often HYPERTENSIVE.

  14. Functions of the Renal System The collection and elimination of metabolic waste such as urea and creatinine: The kidney’s job is to excrete the waste products of metabolism. Urea is a byproduct of protein metabolism. It is not as adequate an indicator of renal disease as elevated creatinine levels are because urea (BUN) levels elevate with an increased protein intake, trauma, dehydration etc.. Serum creatinine levels are an accurate indicator of renal function/dysfunction. The urinary excretion should equal the amount produced by the body (by skeletal muscle catabolism).

  15. Functions of the Renal System> Failure • When the kidneys fail: • The patient suffers from an overload of these circulating uremic toxins. All body systems may be affected. • the CNS is affected by the uremic toxins. Drowsiness, poor memory, inability to concentrate, seizures, and even come may result. • GI distressmay result such as nausea, vomiting, abdominal distension, diarrhea, and constipation.

  16. Functions of the Renal System • The secretion of erythropoietin: • The kidneys secrete erythropoietin when the oxygen supply in the tissue blood drops. This hormone prompts the bone marrow to produce more RBCs. • When the kidneys fail: The patient becomes anemic. (Remember also they are anemic due to the increased destruction of RBCs & PLTS by the uremic toxins, and even due to their bleeding tendency secondary to their low PLTS.)

  17. Functions of the Renal System> Failure • Pericarditis may result as pericardium is inflamed due to the buildup of these uremic wastes. A pericardial friction rub and pain may result. • Pruritis may result as the excretory function of the skin attempts to excrete the waste products. A uremic frost may be notable on skin and collect on eyebrows. Skin may become a pale yellowish color, as urochrome pigments are present. • Anemia and thrombocytopenia occur because the uremic toxins destroy RBCs and PLTS.

  18. Assessment of Renal Function • Glomerular Filtration Rate (GFR) • = the volume of water filtered from the plasma per unit of time. • Gives a rough measure of the number of functioning nephrons • Normal GFR: • Men: 130 mL/min./1.73m2 • Women: 120 mL/min./1.73m2 • Cannot be measured directly, so we use creatinine and creatinine clearance to estimate.

  19. Assessment of Renal Function (cont.) • Creatinine • A naturally occurring amino acid, predominately found in skeletal muscle • Freely filtered in the glomerulus, excreted by the kidney and readily measured in the plasma • As plasma creatinine increases, the GFR exponentially decreases. • Limitations to estimate GFR: • Patients with decrease in muscle mass, liver disease, malnutrition, advanced age, may have low/normal creatinine despite underlying kidney disease • 15-20% of creatinine in the bloodstream is not filtered in glomerulus, but secreted by renal tubules (giving overestimation of GFR) • Medications may artificially elevate creatinine: • Trimethroprim (Bactrim) • Cimetidine

  20. Assessment of Renal Function (cont.) • Creatinine Clearance • Best way to estimate GFR • GFR = (creatinine clearance) x (body surface area in m2/1.73) • Ways to measure: • 24-hour urine creatinine: • Creatinine clearance = (Ucr x Uvol)/ plasma Cr • Cockcroft-Gault Equation: • (140 - age)  x  lean body weight [kg] CrCl (mL/min)    =    ——————————————— x 0.85 if                                         Cr [mg/dL]  x  72 female • Limitations: Based on white men with non-diabetes kidney disease • Modification of Diet in Renal Disease (MDRD) Equation: • GFR (mL/min./1.73m2) = 186 X (SCr)-1.154 X (Age)-0.203 X (0.742 if female) X (1.210 if African-American )

  21. AKI Definition-Criteria

  22. RIFLE criteria for diagnosis of AKI based on The “Acute Dialysis Quality Initiative” Am J Kidney Dis. 2005 Dec;46(6):1038-48

  23. Definition of Acute Kidney Injury (AKI) based on “Acute Kidney Injury Network”

  24. Acute Renal Failure- Phases Phases: • The course of acute renal failure is characterized by three phases. • The oliguric phaseoccurs at the onset of symptoms and could last as long as eight weeks. It is characterized by a decreased urine output …(less than 400ml in 24 hours). The kidney is trying to conserve sodium and water, and therefore hypervolemia, edema, weight gain, pulmonary edema, and elevated blood pressure occur. The BUN and creatinine rise thereby causing uremic signs and symptoms. (nausea, changes in mental acuity, fatigue, pericarditis)

  25. Acute Renal Failure- Phases • The diuretic phase is marked by urine output that can range from 1-5 L/day. The kidney has lost its ability to conserve water. Hypovolemia, (fluid) weight loss, hypokalemia, hyponatremia all can result. The BUN and creatinine begin to level out. May last 7-14 days.

  26. Acute Renal Failure- Phases • The recovery phase is reached when the BUN and creatinine have returned to normal. This phase can last from 3-12 months.

  27. Acute Renal Failure- Diagnostic Findings: Laboratory data and other assessments reveal the following: .....(In the oliguric phase) • Decreased or absent urinary output • Increased BUN, creatinine, sodium, potassium, chloride • Decreased calcium (high phos), bicarbonate (acidosis), H/H (anemic) • Metabolic acidosis

  28. Causes of ARF • Pre-renal = • vomiting, diarrhea, poor fluid intake, fever, use of diuretics, and heart failure • cardiac failure, liver dysfunction, or septic shock • Intrinsic • Interstitial nephritis, acute glomerulonephritis, tubular necrosis, ischemia, toxins • Post-renal = • prostatic hypertrophy, cancer of the prostate or cervix, or retroperitoneal disorders • neurogenic bladder • bilateral renal calculi, papillary necrosis, coagulated blood, bladder carcinoma, and fungus

  29. Symptoms of ARF • Decrease urine output (70%) • Edema, esp. lower extremity • Mental changes • Heart failure • Nausea, vomiting • Pruritus • Anemia • Tachypenic • Cool, pale, moist skin

  30. Hyperkalemia Symptoms • Weakness • Lethargy • Muscle cramps • Paresthesias • Dysrhythmias

  31. Hyperkalemia Treatment • Calcium gluconate (carbonate) • Sodium Bicarbonate • Insulin/glucose • Diuretics (Furosemid) • Albuterol • Hemodialysis

  32. Prerenal Acute Renal Failure • Volume Depletion • Decreased effective blood volume • congestive heart failure • cirrhosis • nephrotic syndrome • sepsis • Renal vasoconstriction • hepatorenal syndrome • hypercalcemia • nonsteroidal anti-inflammatory drugs

  33. Prerenal Acute Renal Failure:Clinical Presentation • History • volume loss (e.g., diarrhea, acute blood loss) • heart disease • liver disease • evidence of infection • diuretic use • thirst • orthostatic symptoms

  34. Prerenal Acute Renal Failure:Clinical Presentation • Physical Examination • Blood pressure and pulse • Orthostatic changes in blood pressure • Skin turgor • Dryness of mucous membranes and axillae • Neck veins • Cardiopulmonary exam • Peripheral edema

  35. Prerenal Acute Renal Failure: Clinical Presentation • BUN:Creatinine ratio • > 20:1 • Urine indices • Oliguria • usually < 500 mL/24 hours; but may be non-oliguric • Elevated urine concentration • UOsm > 700 mmol/L • specific gravity > 1.020 • Evidence of high renal sodium avidity • UNa < 20 mmol/L • FENa < 0.01 • Inactive urine sediment

  36. Fractional Excretion of Sodium • Etiologies of a fractional excretion of sodium <0.01 • normal renal function • prerenalazotemia • hepatorenal syndrome • early obstructive uropathy • contrast nephropathy • rhabdomyolysis • acute glomerulonephritis

  37. Treatment of Prerenal Acute Renal Failure • Correction of volume deficits • Discontinuation of antagonizing medications • NSAIDs/COX-2 inhibitors • Diuretics • Optimization of cardiac function

  38. Postrenal Acute Renal Failure • Urinary tract obstruction • level of obstruction • upper tract (ureters) • lower tract (bladder outlet or urethra) • degree of obstruction • partial • complete

  39. Pathophysiology of Renal Failure in Obstructive Uropathy • Early • Increased intratubular pressure • Initial increase followed by decrease in renal plasma flow • Late • Normal intratubular pressure • Marked decrease in renal plasma flow

  40. Etiologies of Postrenal Acute Renal Failure • Upper tract obstruction • Intrinsic • nephrolithiasis • papillary necrosis • blood clot • transitional cell cancer • Extrinsic • retroperitoneal or pelvic malignancy • retroperitoneal fibrosis • endometriosis • abdominal aortic aneurysm • Lower tract obstruction • benign prostatic hypertrophy • prostate cancer • transitional cell cancer • urethral stricture • bladder stones • blood clot • neurogenic bladder

  41. Postrenal Acute Renal Failure:Clinical Presentation • History • Symptoms of bladder outlet obstruction • urinary frequency • urgency • intermittency • hesitancy • nocturia • incomplete voiding

  42. Postrenal Acute Renal Failure:Clinical Presentation • History • Changes in urine volume • anuria • polyuria • fluctuating urine volume • Flank pain • Hematuria • History of pelvic malignancy

  43. Postrenal Acute Renal Failure:Clinical Presentation • Physical Examination • Suprapubic mass • Prostatic enlargement • Pelvic masses • Adenopathy

  44. Postrenal Acute Renal Failure:Clinical Evaluation • Diagnostic studies • BUN: Creatinine ratio > 20:1 • Unremarkable urine sediment • Variable urine chemistries

  45. Postrenal Acute Renal Failure:Clinical Evaluation • Diagnostic studies • Post-void residual bladder volume • > 100 mL consistent with voiding dysfunction • Radiologic studies • Ultrasound • CT scan • Nuclear medicine • Retrograde pyelography • Antegrade nephrostograms

  46. Treatment of Postrenal Acute Renal Failure • Relief of obstruction • Lower tract obstruction • bladder catheter • Upper tract obstruction • ureteral stents • percutaneous nephrostomies • Recovery of renal function dependent upon duration of obstruction • Risk of post-obstructive diuresis

  47. Intrinsic Acute Renal Failure • Acute tubular necrosis (ATN) • Acute interstitial nephritis (AIN) • Acute glomerulonephritis (AGN) • Acute vascular syndromes • Intratubular obstruction

  48. Acute Tubular Necrosis • Ischemic • prolonged prerenal azotemia • hypotension • hypovolemic shock • cardiopulmonary arrest • cardiopulmonary bypass • Sepsis • Nephrotoxic • drug-induced • radiocontrast agents • aminoglycosides • amphotericin B • cisplatinum • acetaminophen • pigment nephropathy • hemoglobin • myoglobin

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