Critical Care E3 - Chapter 15

Acute Kidney Injury Has a role in water reabsorption

ADH

Acute Kidney Injury Has a role in water and sodium reabsorption

Aldosterone

Acute Kidney Injury Most common intrarenal condition (reason):

acute tubular necrosis (ATN) Due to ischemia; causes of prerenal; hypotension; hypovolemia; contrast media; transfusion reaction

Acute Kidney Injury - cardinal signs are:

azotemia (increased in BUN/Creatinine) oliguria (urine output <0.5 mL/kg/hr)

Acute Kidney Injury Postrenal Causes of AKI:

decrease GFR Obstruction to the flow of urine, HOW = increase in intratubular pressure decreases GFR and abnormal nephron function

Acute Kidney Injury Maintenance Phase:

last 8 to 14 days 1. Intrinsic renal damage is established; GFR stabilizes at 5 to 10 mL/min; oliguric; BUN/creatinine increase daily 2. Urine outputs <400 mL in 24 hours; complications are hyperkalemia and infection due to uremia 3. Fluid overload, electrolyte imbalance, acidosis; renal replacement therapy needed

Acute Kidney Injury Normal GFR: Normal filtrate produced:

80 to 125 mL/min 180 L/day

Acute Kidney Injury Acute kidney injury from post renal etiology is caused by: a. obstruction of the flow of urine. b. conditions that interfere with renal perfusion. c. hypovolemia or decreased cardiac output. d. conditions that act directly on functioning kidney tissue.

ANS: A Acute kidney injury resulting from obstruction of the flow of urine is classified as postrenal or obstructive renal injury. Conditions that result in AKI by interfering with renal perfusion are classified as prerenal and include hypovolemia and decreased cardiac output. Conditions that produce AKI by directly acting on functioning kidney tissue are classified as intrarenal.

The patient is in the critical care unit and will receive dialysis this morning. The nurse will: (Select all that apply.) a. evaluate morning laboratory results and report abnormal results. b. administer the patient's antihypertensive medications. c. assess the dialysis access site and report abnormalities. d. weigh the patient to monitor fluid status. e. give all medications except for antihypertensive medications.

ANS: A, C, D The patient receiving hemodialysis requires specialized monitoring and interventions by the critical care nurse. Laboratory values are monitored and abnormal results reported to the nephrologist and dialysis staff. The patient is weighed daily to monitor fluid status. On the day of dialysis, dialyzable (water-soluble) medications are not given until after treatment.

Acute Kidney Injury A normal glomerular filtration rate is: a. less than 80 mL/min. b. 80 to 125 mL/min c. 125 to 180 mL/min d. more than 189 mL/min

ANS: B At a normal glomerular filtration rate (GFR) of 80 to 125 mL/min, the kidneys produce 180 L/day of filtrate. As the filtrate passes through the various components of the nephron's tubules, 99% is reabsorbed into the peritubular capillaries or vasa recta.

Acute Kidney Injury The term used to describe an increase in blood urea nitrogen (BUN) and serum creatinine is: a. oliguria. b. azotemia. c. acute kidney injury. d. prerenal disease.

ANS: B Azotemia refers to increases in blood urea nitrogen and serum creatinine. Oliguria is defined as urine output less than 0.5 mL/kg/hr. Elevation of BUN and creatinine can be the result of acute kidney injury or chronic kidney diseases. Conditions that result in AKI by interfering with renal perfusion are classified as prerenal.

Acute Kidney Injury Peritoneal dialysis is different from hemodialysis in that peritoneal dialysis: a. is more frequently used for acute kidney injury. b. uses the patient's own semipermeable membrane (peritoneal membrane). c. is not useful in cases of drug overdose or electrolyte imbalance. d. is not indicated in cases of water intoxication.

ANS: B Peritoneal dialysis is the removal of solutes and fluid by diffusion through a patient's own semipermeable membrane (the peritoneal membrane) with a dialysate solution that has been instilled into the peritoneal cavity. This renal replacement therapy is not commonly used for the treatment of acute kidney injury because of its comparatively slow ability to alter biochemical imbalances. Clinical indications for peritoneal dialysis include acute and chronic kidney injury, severe water intoxication, electrolyte disorders, and drug overdose.

Acute Kidney Injury The patient's serum creatinine level is 0.7 mg/dL. The expected BUN level should be: a. 1-2 mg/dL. b. 7-14 mg/dL. c. 10-20 mg/dL. d. 20-30 mg/dL.

ANS: B The normal BUN/creatinine ratio is 10:1 to 20:1. Therefore, the expected range for this creatinine level would be 7 to 14 mg/dL.

Acute Kidney Injury Conditions that produce acute kidney injury by directly acting on functioning kidney tissue are classified as intrarenal. The most common intrarenal condition is: a. prolonged ischemia. b. exposure to nephrotoxic substances. c. acute tubular necrosis (ATN). d. hypotension for several hours.

ANS: C The most common intrarenal condition is ATN. This condition may occur after prolonged ischemia (prerenal), exposure to nephrotoxic substances, or a combination of these. Some patients have ATN after only several minutes of hypotension or hypovolemia, whereas others can tolerate hours of renal ischemia without having any apparent tubular damage.

Acute Kidney Injury T/F Use Diuretics

F Not recommended; increase renal blood flow and GFR

Acute Kidney Injury Treatment of Postrenal Injury:

Treated by bladder catheterization; ureteral stenting; placement of nephrostomy tubes

Acute Kidney Injury Normal BUN/Creatinine ratio:

10:1 to 20:1; if more, suspect nonrenal causes

Acute Kidney Injury The nurse is caring for a patient who has undergone major abdominal surgery. The nurse notices that the patient's urine output has been less than 20 mL/hour for the past 2 hours. It is 0200 in the morning. The patient's blood pressure is 100/60 mm Hg, and the pulse is 110 beats per minute. Previously, the pulse was 90 beats per minute with a blood pressure of 120/80 mm Hg. The nurse should: a. contact the provider and expect an order for a normal saline bolus. b. wait until 0900 when the provider makes rounds to report the assessment findings. c. continue to evaluate urine output for 2 more hours. d. ignore the urine output, as this is most likely postrenal in origin.

ANS: A Most prerenal causes of AKI are related to intravascular volume depletion, decreased cardiac output, renal vasoconstriction, or pharmacological agents that impair autoregulation and GFR. These conditions reduce the glomerular perfusion and the GFR, and the kidneys are hypoperfused. For example, major abdominal surgery can cause hypoperfusion of the kidney as a result of blood loss during surgery or as a result of excess vomiting or nasogastric suction during the postoperative period. The body attempts to normalize renal perfusion by reabsorbing sodium and water. If adequate blood flow is restored to the kidney, normal renal function resumes. Most forms of prerenal AKI can be reversed by treating the cause.

The patient's potassium level is 7.0 mEq/L. Besides dialysis, which of the following actually reduces plasma potassium levels and total body potassium content safely in a patient with renal dysfunction? a. Kayexalate b. Kayexalate with sorbitol c. Regular insulin d. Calcium gluconate

ANS: A Only dialysis and administration of cation exchange resins (sodium polystyrene sulfonate [Kayexalate]) actually reduce plasma potassium levels and total body potassium content in a patient with renal dysfunction. In the past, sorbitol has been combined with sodium polystyrene sulfonate powder (Kayexalate) for administration. The concomitant use of sorbitol with Kayexalate has been implicated in cases of colonic intestinal necrosis; therefore, this combination is not recommended. Other treatments, such as administration of regular insulin and calcium gluconate only "protect" the patient for a short time until dialysis or cation exchange resins can be instituted.

Acute Kidney Injury Renin plays a role in blood pressure regulation by: a. activating the renin-angiotensin-aldosterone cascade. b. suppressing angiotensin production. c. decreasing sodium reabsorption. d. inhibiting aldosterone release.

ANS: A Specialized cells in the afferent and efferent arterioles and the distal tubule are collectively known as the juxtaglomerular apparatus. These cells are responsible for the production of a hormone called renin, which plays a role in blood pressure regulation. Renin is released whenever blood flow through the afferent and efferent arterioles decreases. A decrease in the sodium ion concentration of the blood flowing past the specialized cells (e.g., in hypovolemia) also stimulates the release of renin. Renin activates the renin-angiotensin-aldosterone cascade, which ultimately results in angiotensin II production. Angiotensin II causes vasoconstriction and release of aldosterone from the adrenal glands, thereby raising blood pressure and flow and increasing sodium and water reabsorption in the distal tubule and collecting ducts.

Acute Kidney Injury The most common cause of acute kidney injury in critically ill patients is: a. sepsis. b. fluid overload. c. medications. d. hemodynamic instability.

ANS: A The etiology of AKI in critically ill patients is often multifactorial and develops from a combination of hypovolemia, sepsis, medications, and hemodynamic instability. Sepsis is the most common cause of AKI.

Acute Kidney Injury Noninvasive diagnostic procedures used to determine kidney function include which of the following? (Select all that apply.) a. Kidney, ureter, bladder (KUB) x-ray b. Renal ultrasound c. Magnetic resonance imaging (MRI) d. Intravenous pyelography (IVP) e. Renal angiography

ANS: A, B, C Noninvasive diagnostic procedures are usually performed before any invasive diagnostic procedures are conducted. Noninvasive diagnostic procedures that assess the renal system are radiography of the kidneys, ureters, and bladder (KUB); renal ultrasonography; and magnetic resonance imaging. Invasive diagnostic procedures for assessing the renal system include intravenous pyelography, computed tomography, renal angiography, renal scanning, and renal biopsy.

Acute Kidney Injury The patient is admitted with acute kidney injury from a postrenal cause. Acceptable treatments for that diagnosis include: (Select all that apply.) a. bladder catheterization. b. increasing fluid volume intake. c. ureteral stenting. d. placement of nephrostomy tubes. e. increasing cardiac output.

ANS: A, C, D The location of the obstruction in the urinary tract determines the method by which the obstruction is treated and may include bladder catheterization, ureteral stenting, or the placement of nephrostomy tubes. Fluid volume intake may be recommended to treat prerenal causes of AKI. Increasing cardiac output would be indicated in certain prerenal causes of AKI

Acute Kidney Injury The most common reasons for initiating dialysis in acute kidney injury include which of the following? (Select all that apply.) a. Acidosis b. Hypokalemia c. Volume overload d. Hyperkalemia e. Uremia

ANS: A, C, D, E The most common reasons for initiating dialysis in acute kidney injury include acidosis, hyperkalemia, volume overload, and uremia. Dialysis is usually started early in the course of the renal dysfunction before uremic complications occur. In addition, dialysis may be started for fluid management when total parenteral nutrition is administered.

Acute Kidney Injury Identify which substances would indicate a problem with renal function. (Select all that apply). a. protein. b. sodium. c. creatinine. d. red blood cells. e. uric acid.

ANS: A, D, E The glomerular capillary membrane is approximately 100 times more permeable than other capillaries. It acts as a high-efficiency sieve and normally allows only substances with a certain molecular weight to cross. Normal glomerular filtrate is basically protein free and contains electrolytes, including sodium, chloride, and phosphate, and nitrogenous waste products, such as creatinine, urea, and uric acid, in amounts similar to those in plasma. Red blood cells, albumin, and globulin are too large to pass through the healthy glomerular membrane.

Acute Kidney Injury The patient is complaining of severe flank pain when he tries to urinate. His urinalysis shows sediment and crystals along with a few bacteria. Using this information along with the clinical picture, the nurse realizes that the patient's condition is: a. prerenal. b. postrenal. c. intrarenal. d. not renal related.

ANS: B Analysis of urinary sediment and electrolyte levels is helpful in distinguishing among the various causes of acute kidney injury. Postrenal conditions may present with stones, crystals, sediment, bacteria, and clots from the obstruction. Coarse, muddy brown granular casts are classic findings in ATN (intrarenal), along with microscopic hematuria and a small amount of protein. In prerenal conditions, the urine typically has no cells but may contain hyaline casts. The flank pain and urinalysis definitely indicate a renal condition.

The patient is admitted to the unit with the diagnosis of rhabdomyolysis. The patient is started on intravenous (IV) fluids and IV mannitol. Because mannitol is an osmotic diuretic, the nurse should: a. assess the patient's hearing. b. assess the patient's lungs. c. decrease IV fluids once the diuretic has been administered. d. give extra doses prior to giving radiological contrast agents.

ANS: B Mannitol, an osmotic diuretic often used in acute kidney injury caused by rhabdomyolysis, increases plasma volume. Patients may be at risk for the development of pulmonary edema due to the rapid expansion of intravascular volume triggered by mannitol. Hearing is assessed with administration of loop diuretics, such as furosemide, which have been associated with deafness. Aggressive fluid administration is required in rhabdomyolysis. Diuretics may increase the risk of acute kidney injury from volume depletion when they are given before procedures requiring radiological contrast agents or if the patient is hypovolemic. Adequate hydration prior to administration of diuretics is essential.

Acute Kidney Injury The patient is a new postoperative patient. She weighs 75 kg. The nurse expects the minimal acceptable urine output to be: a. less than 30 mL/hour. b. 37 mL/hour. c. 80 mL/hour. d. 150 mL/hour.

ANS: B Normal urine output is 0.5 to 1 mL/kg of body weight each hour.

Acute Kidney Injury The patient has been admitted to the hospital with nausea and vomiting that started 5 days earlier. His blood pressure is 80/44 mm Hg and heart rate is 122 beats/min; he has not voided in 8 hours and his bladder is not distended. The nurse anticipates an order for "stat" administration of: a. a blood transfusion. b. fluid replacement with 0.45% saline. c. infusion of an inotropic agent. d. an antiemetic.

ANS: B This scenario indicates hypovolemia from the nausea and vomiting, requiring volume replacement. Hypovolemia resulting from large urine or gastrointestinal losses often requires the administration of a hypotonic solution, such as 0.45% saline. Blood products would be indicated only in the presence of bleeding following assessment of hemoglobin and hematocrit levels. The inotrope is contraindicated in the presence of volume depletion. An antiemetic may be needed; however, the priority to prevent shock and acute kidney injury is fluid administration ***why not isotonic solution?***

Acute Kidney Injury Which of the following patients is at the greatest risk of developing acute kidney injury? A patient who: a. has been on aminoglycosides for the past 6 days. b. has a history of controlled hypertension with a blood pressure of 138/88 mm Hg. c. was discharged 2 weeks earlier after aminoglycoside therapy of 2 weeks. d. has a history of fluid overload as a result of heart failure.

ANS: C Acute kidney injury can be caused by aminoglycoside nephrotoxicity, especially prolonged use of the drug (more than 10 days). Symptoms of acute kidney injury are usually seen about 1 to 2 weeks after exposure. Because of this delay, the patient must be questioned about any recent medical therapy for which an aminoglycoside may have been prescribed. The blood pressure of 138/88 mm Hg controlled by medication would not cause acute kidney injury, nor would fluid overload from exacerbation of heart failure.

Acute Kidney Injury The patient is admitted with complaints of general malaise and fatigue, along with a decreased urinary output. The patient's urinalysis shows coarse, muddy brown granular casts and hematuria. The nurse determines that the patient has: a. acute kidney injury from a prerenal condition. b. acute kidney injury from postrenal obstruction. c. intrarenal disease, probably acute tubular necrosis. d. a urinary tract infection.

ANS: C Analysis of urinary sediment and electrolyte levels is helpful in distinguishing among the various causes of acute kidney injury. Coarse, muddy brown granular casts are classic findings in ATN. Microscopic hematuria and a small amount of protein also may be seen. In prerenal conditions, the urine typically has no cells but may contain hyaline casts. Postrenal conditions may present with stones, crystals, sediment, bacteria, and clots from the obstruction. Bacteria would be present in a urinary tract infection.

Acute Kidney Injury The nurse is assessing a patient with a new arteriovenous fistula, but does not hear a bruit or feel a thrill. Pulses distal to the fistula are not palpable. The nurse should: a. reassess the patient in an hour. b. raise the arm above the level of the patient's heart. c. notify the provider immediately. d. apply warm packs to the fistula site and reassess.

ANS: C Inadequate collateral circulation past the fistula or graft may result in loss of this pulse. The physician is notified immediately if no bruit is auscultated, no thrill is palpated, or the distal pulse is absent. Loss of bruit and thrill indicate a loss of blood flow most likely due to clotting. The patient will need to return to surgery as soon as possible for declotting. Raising the arm above the level of the heart will not help. Warm packs may or may not help.

Acute Kidney Injury The nurse is caring for a patient who has sustained blunt trauma to the left flank area, and is evaluating the patient's urinalysis results. The nurse should become concerned when a. creatinine levels in the urine are similar to blood levels of creatinine. b. sodium and chloride are found in the urine. c. urine uric acid levels have the same values as serum levels. d. red blood cells and albumin are found in the urine.

ANS: D Normal glomerular filtrate is basically protein free and contains electrolytes, including sodium, chloride, and phosphate, and nitrogenous waste products, such as creatinine, urea, and uric acid, in amounts similar to those in plasma. Red blood cells, albumin, and globulin are too large to pass through the healthy glomerular membrane. Their presence in urine may indicate glomerular damage.

Acute Kidney Injury The removal of plasma water and some low-molecular weight particles by using a pressure or osmotic gradient is known as: a. dialysis. b. diffusion. c. clearance. d. ultrafiltration.

ANS: D Ultrafiltration is the removal of plasma water and some low-molecular weight particles by using a pressure or osmotic gradient. Ultrafiltration is primarily aimed at controlling fluid volume, whereas dialysis is aimed at decreasing waste products and treating fluid and electrolyte imbalances. Diffusion (or clearance) is the movement of solutes such as urea from the patient's blood to the dialysate cleansing fluid, across a semipermeable membrane (the hemofilter).

Acute Kidney Injury used in AKI caused by rhabdomyolysis:

Mannitol **increase risk of pulmonary edema rapid expansion of IV volume

Acute Kidney Injury Antioxidant; reduce the incidence of contrast-induced AKI; prophylactic administration along with 0.45% saline is said to reduce amount of acute renal damage in high-risk patients undergoing procedures requiring contrast

N-Acetylcysteine: Mucomyst (600mg x2/daily)

Acute Kidney Injury Removal of solutes and fluids by diffusion through patient's own semipermeable membrane with dialysate solution

Peritoneal Dialysis

Acute Kidney Injury Nursing care of arteriovenous fistula or graft: Should be __auscultated/palpated__ for a __bruit/thrill__ and __auscultated/palpated__ for the presence of a __bruit/thrill__ or buzz every 8 hours

Should be auscultated for a bruit and palpated for the presence of a thrill or buzz every 8 hours Notify MD ASAP if no bruit is auscultated, no thrill is palpated, or the distal pulse is absent

Medical Management of Acute Kidney Injury Prerenal:

a. Prompt replacement of extracellular fluids and aggressive treatment of shock b. Patient with pancreatitis and peritonitis are treated with isotonic solution (ie. NS) c. If hypovolemia large urine or GI losses, give hypotonic solution (0.45%), antibiotics if sepsis d. If cardiac instability, give positive inotropic agents or intraaortic balloon pump; hemodynamic monitoring or PAC may be needed

Acute Kidney Injury 1. Said to protect against contrast-induced AKI; acts as vasodilator of peripheral arteries; also acts as potent renal vasodilator 2. More potent that dopamine in increasing renal blood flow; given via IV infusion several hours before contrast agent is given 3. Continued for 4 hours after procedure

d. Fenoldopam: Corlopam

Acute Kidney Injury Assessment findings of Prerenal will include:

oliguric patient with weight loss, tachycardia, hypotension, dry mucous membranes, flat neck veins, and poor skin turgor (why?)

Acute Kidney Injury Prerenal Causes of AKI:

renal perfusion GFR decreased hypovolemia, decrease C/O vasodilation, and meds

Acute Kidney Injury Initiation Phase:

several hours to 2 days Renal processes begin to deteriorate; intrinsic renal damage has not occurred; unable to compensate; reversible

Medical Management of Acute Kidney Injury Postrenal:

a. Insert indwelling bladder catheter (transurethral or suprapubic); ureteral stent if obstruction is caused by calculi or carcinoma

Acute Kidney Injury average urine output:

1 to 2 L/day

Acute Kidney Injury In ATN, urine sodium is:

>40 mEq/L

Acute Kidney Injury Intrarenal Causes of AKI:

Directly acting on functioning kidney tissue (glomerulus or renal tubules)

Acute Kidney Injury Recovery Phase:

last 4 to 6 months 1. Renal tissue recovers and repair itself; increase in urine output; improvement in lab values (BUN/Creatinine) 2. Diuresis may be experienced

Acute Kidney Injury signs of uremia:

malaise, fatigue, disorientation, and drowsiness

Acute Kidney Injury Assessment findings of Intrarenal will include

weight gain, edema, distended neck veins, and hypertension in the presence of oliguria (why?)