Question 1

The patient has elevated blood urea nitrogen (BUN)and serum creatinine levels with a normal BUN/creatinine ratio.These levels most likely indicate

Accepted Answer

A normal BUN/creatinine ratio is present in ATN.In ATN,there is actual injury to the renal tubules and a rapid decline in the GFR; hence,BUN and creatinine levels both rise proportionally as a result of increased reabsorption and decreased clearance.Hypovolemia would result in prerenal condition,which usually increases the BUN/creatinine ratio.

Question 2

The nurse is caring for a patient with acute kidney injury who is being treated with hemodialysis.The patient asks if he will need dialysis for the rest of his life.Which of the following would be the best response?

Accepted Answer

Renal dysfunction is potentially reversible during the initiation phase.This phase spans several hours to 2 days,during which time the normal renal processes begin to deteriorate,but actual intrinsic renal damage has not yet occurred.During the maintenance phase,intrinsic renal damage is established,and the GFR stabilizes at approximately 5 to 10 mL/min.This phase usually lasts 8 to 14 days,but it may last up to 11 months.The longer a patient remains in this stage,the slower the recovery and the greater the chance of permanent renal damage will be.The recovery phase is the period during which the renal tissue recovers and repairs itself.A gradual increase in urine output and an improvement in laboratory values occur.Recovery may take as long as 4 to 6 months.

Question 3

A normal urine output is considered to be

Accepted Answer

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 nephrons' tubules,99% is reabsorbed into the peritubular capillaries or vasa recta.Eventually,the remaining filtrate (1% of the original 180 L/day)is excreted as urine,for an average urine output of 1 to 2 L/day.

Question 4

The critical care nurse knows that in critically ill patients,renal dysfunction

Accepted Answer

The kidney is the primary regulator of the body's internal environment.With sudden cessation of renal function,all body systems are affected by the inability to maintain fluid and electrolyte balance and eliminate metabolic waste.Renal dysfunction is a common problem in critically ill patients,with nearly two thirds of patients experiencing some degree of renal dysfunction.The most severe cases,requiring renal replacement therapy,have a reported mortality rate of 50% to 60%.Acute kidney injury that progresses to chronic renal failure is associated with increased morbidity,mortality,and reduced quality of life.

Question 5

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.The patient's blood pressure is 100/60 mm Hg,and the pulse is 110 beats/min.Previously,the pulse was 90 beats/min with a blood pressure of 120/80 mm Hg.The nurse should

Accepted Answer

Most prerenal causes of AKI are related to intravascular volume depletion,decreased cardiac output,renal vasoconstriction,or pharmacological agents that impair autoregulation and GFR (Box 16-2).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.

Question 6

Renin plays a role in blood pressure regulation by

Accepted Answer

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.

Question 7

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:

Accepted Answer

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.

Question 8

Acute kidney injury from postrenal etiology is caused by

Accepted Answer

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.

Question 9

The term used to describe an increase in blood urea nitrogen (BUN)and serum creatinine is

Accepted Answer

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.

Question 10

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

Accepted Answer

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.

Question 11

The patient's serum creatinine level is 0.7 mg/dL.The expected BUN level should be

Accepted Answer

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.

Question 12

In calculating the glomerular filtration rate (GFR)results for women,the creatinine clearance is usually:

Accepted Answer

For women,the calculated result is multiplied by 0.85 to account for the smaller muscle mass as compared to men.

Question 13

A normal glomerular filtration rate is

Accepted Answer

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 nephrons' tubules,99% is reabsorbed into the peritubular capillaries or vasa recta.

Question 14

Conditions that produce acute kidney injury by directly acting on functioning kidney tissue are classified as intrarenal.The most common intrarenal condition is

Accepted Answer

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.

Question 15

In determining the glomerular filtration rate (GFR)or creatinine clearance,a 24-hour urine is obtained.If a reliable 24-hour urine collection is not possible,

Accepted Answer

Historically,timed 24-hour urine collections have been used to evaluate GFR or creatinine clearance.If a reliable 24-hour urine collection is not possible,the Cockcroft and Gault formula may be used to determine the creatinine clearance from a serum creatinine value.The BUN level is not a reliable indicator of kidney function because the rate of protein metabolism is not constant.An increased BUN/creatinine ratio is typically noted with prerenal conditions,but does not provide an estimate of GFR.

Question 16

Which of the following patients is at the greatest risk of developing acute kidney injury? A patient who

Accepted Answer

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.

Question 17

The nurse is caring for an elderly patient who was admitted with renal insufficiency.An expected laboratory finding for this patient may be

Accepted Answer

The most important renal physiological change that occurs with aging is a decrease in the GFR.After age 40,renal blood flow gradually diminishes at a rate of 10% per decade.With advancing age,there is also a decrease in renal mass,the number of glomeruli and peritubular density.Serum creatinine levels may remain the same in the elderly patient,even with a declining GFR,because of decreased muscle mass and hence decreased creatinine production.Tubular changes include a diminished ability to excrete drugs,including radiocontrast dyes used in diagnostic testing,which necessitates a decrease in drug dosing to avoid nephrotoxicity.Many medications,including antibiotics,require dose adjustments as kidney function declines.Age-related changes in renin and aldosterone levels also occur,which can lead to fluid and electrolyte abnormalities.Renin levels are decreased by 30% to 50% in the elderly,resulting in less angiotensin II production and lower aldosterone levels.Together these can cause an increased risk of hyperkalemia.The aging kidney is also slower to correct an increase in acids,causing a prolonged metabolic acidosis and the subsequent shifting of potassium out of cells and worsening hyperkalemia.

Question 18

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

Accepted Answer

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.

Question 19

The patient undergoes a cardiac catheterization that requires the use of contrast dyes during the procedure.To detect signs of contrast-induced kidney injury,the nurse should

Accepted Answer

Contrast- induced kidney injury is diagnosed by an increase in serum creatinine of 25%,or 0.5 mg/dL,within 48 to 72 hours following the administration of contrast.Urine output usually remains normal.The renal ultrasound and postvoid residual assessment are not warranted.

Question 20

The most common cause of acute kidney injury in critically ill patients is

Accepted Answer

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.

Quiz 16: Acute Kidney Injury

The patient has elevated blood urea nitrogen (BUN) and serum creatinine levels with a normal BUN/creatinine ratio.These levels most likely indicate