SU2M - Renal Failure

Question 0

RIFLE Criteria for AKI

Answer 0

1. RISK: 1.5 fold increase in serum creatinine or GFR decreased by 25% or urine output <0.5 mL/kg/hr for 6 hrs
2. INJURY: Twofold increase in the serum creatinine or GFR decrease by 50% or urine output <0.5 mL/kg/hr for 12 hrs
3. FAILURE: Three fold increase in serum creatinine or GFR decreased by 75% or urine output <0.5 mL/kg/hr for 24 hours, or anuria for 12 hrs
4. LOSS: Complete loss of kidney function (requiring dialysis) for more than 4 wks
5. ESRD: Complete loss of kidney function for more than 3 mnths

Question 1

Acute Renal Failure: definition?

Answer 1

• AKA Acute Kindey Injury (AKI)
• rapid decline in renal function
• with an increase in serum creatinine
• at first the creatinine can be normal, despite the low GFR, bc it takes time for the creatinine to accumulate in the body

Question 2

Most common clinical findings in AKI?

Answer 2

1. Weight gain
2. Edema
   * *due to water and sodium retention

Question 3

Azotemia: definition?

Answer 3

-elevated BUN and Creatinine

Question 4

What are 3 non-kidney causes of an elevated BUN?

Answer 4

1. Catabolic drugs (ex. Steroids)
2. GI/soft tissue bleeding
3. Dietary protein intake

Question 5

2 non-kidney causes of elevated creatinine?

Answer 5

1. Increased muscle breakdown –> baseline creatinine varies proportionately with muscle mass
2. Some drugs

Question 6

3 Categories of AKI?

Answer 6

1. Prerenal
2. Intrinsic renal failure
3. Postrenal failure

Question 7

2 Ssx of prerenal failure?

Answer 7

1. Signs of volume depletion

2. Signs of CHF

Question 8

Signs of acute interstitial nephritis?

Answer 8

• aka intrinsic renal failure

- signs of an allergic rxn, ex. Rash

Question 9

3 ssx that suggest post renal failure etiology?

Answer 9

1. Suprapubic mass
2. BPH
3. Bladder dysfunction

Question 10

Pathophysiology of prerenal AKI?

Answer 10

• renal blood flow decreases enough (by whatever cause, CHF, hypovolemia, etc.) to lower GFR –> decreased clearance of metabolites (ex. BUN, creatinine)
• kidney conserves as much sodium and water as possible –> renal parenchyma is undamaged, tubular function & concentrating ability is preserved!
• *reversible if blood flow is restored before extensive damage from ischemia occurs

Question 11

8 Things to monitor in AKI?

Answer 11

1. Daily weights
2. Intake
3. Output
4. BP
5. Serum electrolytes
6. Hb –> watch for anemia
7. Hct –> watch for anemia
8. Watch for infection

Question 12

Urine osmolarity: prerenal failure v. ATN?

Answer 12

• prerenal: > 500 –> kidney is still able to resorb water!

- ATN: 250-300mOsm –>water reabsorption is impaired

Question 13

Urine Na+: prerenal failure v. ATN?

Answer 13

• prerenal failure = < 20 –> because kidney can still resorb Na!
• ATN = > 40 –> Na is poorly absorbed

Question 14

Fractional excretion of Na: prerenal failure v. ATN?

Answer 14

• prerenal = <1%

- ATN = > 2-3%

Question 15

Urine sediment: prerenal failure v. ATN?

Answer 15

• prerenal = scant

- ATN = full brownish pigment, granular casts w/ epithelial casts

Question 16

BUN/Cr ratio: prerenal v. ATN?

Answer 16

• prerenal = > 20:1 –> kidney can still resorb urea!

- ATN = < 20:1 –> less urea can be absorbed

Question 17

Intrinsic renal failure: definition?

Answer 17

• kidney tissue is damaged
• glomerular filtration and tubular function are significantly impaired
• kidneys are unable to concentrate urine effectively

Question 18

4 causes of intrinsic renal failure?

Answer 18

1. Tubular disease = ATN, can be caused by ischemia or nephrotoxins
2. Glomerular disease = acute glomerular nephritis, ex. Goodpastures, Wegener’s, poststreptococcal GN, lupus
3. Vascular disease –> ex. Renal artery stenosis, etc
4. Interstitial disease –> ex. Allergic interstitial nephritis (often due to hypersensitivity rxn to a medication)

Question 19

Rhabdomyolysis: 5 causes

Answer 19

• skeletal muscle breakdown, caused by:
  1. Trauma
  2. Crush injuries
  3. Prolonged immobility
  4. Seizures
  5. Snake bites

Question 20

Rhabdomyolysis: pathophysiology?

Answer 20

• release of muscle fiber contents (myoglobin) into the blood stream
• myoglobin is toxic to the kidneys
• can lead to AKI

Question 21

Rhabdomyolysis: lab findings?

Answer 21

• markedly elevated creatinine phosphokinase (CPK)
• hyperkalemia
• hypocalcemia
• hyperuricemia

Question 22

Rhabdomyolysis: tx?

Answer 22

1. IV fluids
2. Mannitol = osmotic diuretic
3. Bicarbonate = drives K back into the cells

Question 23

Ischemic AKI

Answer 23

• cause of ATN
• secondary to severe decline in renal blood flow –> shock, hemorrhage, sepsis, DIC, heart failure
• ischemia ==> death of tubular cells

Question 24

Nephrotoxic AKI

Answer 24

- cause of ATN - kidney injury secondary to substances that directly injure renal parenchyma ==> death of cells - causes: antibiotics, radiocontrast, NSAIDs (esp w/ CHF), poisons, myoglobinuria (ex from rhabdo), hemoglobinuria, chemotx, and kappa and gamma light chains produced in multiple myeloma

Question 25

Post renal failure: definition

Answer 25

- obstruction of any segment of the urinary tract (with intact kidneys) --> increased tubular pressure bc the urine produced cant be excreted --> decreased GFR - blood supply and renal parencyma are intact * *both kidneys must be obstructed for creatinine to rise - renal fctn can be restored if obstruction is relieved before the kidneys are damaged - can lead to ATN if untreated

Question 26

6 common causes of postrenal failure?

Answer 26

1. Obstruction due to enlarged prostate --> most common cause 2. Obstruction of one kidney 3. Nephrolithiasis 4. Obstructing neoplasm 5. Retroperitoneal fibrosis 6. Urethral obstruction --> uncommon, bc must be bilateral to cause renal failure

Question 27

3 basic tests for postrenal failure?

Answer 27

1. Palpate the bladder 2. Ultrasound --> look for obstruction or hydronephrosis 3. Catheter --> look for large volume of urine

Question 28

3 phases of ATN?

Answer 28

1. Oliguric phase: - azotemia and uremia - usually lasts 10-14 days - urine output <400-500 mL/day 2. Diuretic phase: - begins when urine outflow is >500 mL/day - high urine output due to: fluid overload (excess retained during oliguric phase) osmotic diuresis (due to retained solutes during oliguric phase), tubular cell damage (delayed recovery of epithelial cell function relative to GFR) 3. Recovery phase: - recovery of tubular function

Question 29

What are hyaline casts seen in?

Answer 29

-prerenal failure

Question 30

RBC casts seen in?

Answer 30

-glomerular disease

Question 31

WBC casts indicate?

Answer 31

-indicate renal parenchymal inflammation

Question 32

What do fatty casts indicate?

Answer 32

-nephrotic syndrome

Question 33

In early phase of AKI, what are the 2 most deadly complications?

Answer 33

1. Hyperkalemic cardiac arrest | 2. Pulmonary edema

Question 34

4 possible complications of Acute Kidney Injuries?

Answer 34

1. ECF volume expansion --> pulmonary edema 2. Metabolic disturbances --> hyperkalemia (decreased excretion, and K is moving from ICF --> ECF) metabolic acidosis (decreased excretion of H+), hypoCa, hypoNa, hyperphos, hyperuricemia 3. Uremia --> toxic end products from metabolism accumulate 4. Infection --> occurs in 50-60% of cases (possibly bc uremia impairs immune fctn)

Question 35

3 tx for prerenal failure?

Answer 35

1. Tx underlying disorder 2. Give normal saline to maintain euvolemia and restore BP --> do not give with edema or ascites though! 3. Eliminate any offending agents (ex. ACEi or NSAIDs)

Question 36

3 Tx for intrinsic renal failure?

Answer 36

1. Supportive 2. Eliminate causal/offending agent 3. If oliguric --> furosemide to increase urine flow

Question 37

Postrenal tx?

Answer 37

1. Bladder catheter

Question 38

Chronic kidney disease: definition?

Answer 38

-decreased kidney function (GFR <60mL/min) or kidney damage (structural or functional) for at least 3 months, regardless of cause

Question 39

5 Causes of Chronic kidney disease?

Answer 39

1. Diabetes --> MOST common! (30%) 2. HTN --> second most common! (25%) 3. Chronic glomerular nephritis (15%) 4. Interstitial nephritis, polycystic kidney disease, obstructive uropathy 5. Any cause of AKI can lead to CKD

Question 40

At what BUN does uremia typically occur?

Answer 40

- >60

Question 41

Chronic renal insufficiency?

Answer 41

- when a pts renal function os irreversibly compromised, but NOT failed - chronic elevation of serum creatinine to 1.5-3.0mg/dL

Question 42

What is the major cause of mortality in pts with CKD?

Answer 42

- infection | - have increased susceptibility --> uremia inhibits cellular and humoral immunity

Question 43

Why can CKD lead to fragile bones and fractures?

Answer 43

- kidney cant clear phosphate as well --> hyperphosphetemia --> decreased production of 1,25-dihydroxy vitamin D --> hypocalcemia --> hyperparathyroidism --> removes Ca from bones --> bones become weak - this is called renal osteodystrophy!

Question 44

Calciphylaxis and CKD

Answer 44

- CKD causes hyperphosphetemia bc the kidney can get rid of phosphate as well - hyperphosphetemia can cause phosphate and calcium to precipitate --> vascular calcifications -->necrotic skin leasions

Question 45

In CKD what are the 2 most common complications that require urgent intervention?

Answer 45

1. Symptomatic volume overload | 2. Severe hyperkalemia

Question 46

3 life-threatening complications in CKD?

Answer 46

1. Hyperkalemia --> get EKG (but can have hyperK without EKG changes) 2. Pulmonary edema --> secondary to volume overload, monitor weight 3. Infection --> ex pneumonia, UTI, sepsis

Question 47

What are the preferred meds in CKD? What should you be cautious about when using them?

Answer 47

- ACEi | - can cause hyperK

Question 48

What can be used to correct hyperphosphetemia? MOA?

Answer 48

- calcium citrate | - MOA: binds phosphate

Question 49

Dialysate

Answer 49

- artificial solution that resembles human plasma used in all forms of dialysis - diffusion of fluid and solutes occurs through a semipermieable membrane between the blood and the solution

Question 50

3 Situation in which dialysis can be used?

Answer 50

1. CKD --> to bridge until renal transplant, or as a permanent tx when transplant is not an option 2. AKI --> until the kidneys heal & renal fctn improves 3. Overdose if medications or the ingestion of some substances cleared by the kidneys --> some, but not all can be dialyzed

Question 51

5 Absolute indications for dialysis?

Answer 51

1. Acidosis --> significant metabolic acidosis 2. Electrolytes --> severe, persistent hyperkalemia 3. Intoxication --> of methanol, ethylene glycol, lithium, aspirin 4. Overload --> hypervolemia that is not managed by other means 5. Uremia --> severe, based on CLINICAL presentation, not by labs (**uremic pericarditis is an absolute indication for dialysis!!) * *Think "A-E-I-O-U"

Question 52

4 Dialyzable substance?

Answer 52

1. Salicyclic acid 2. Lithium 3. Ethylene glycol 4. Magnesium-containing laxatives

Question 53

What is the usual frequency of hemodyalisis?

Answer 53

-3-5 hrs of dialysis for 3 days a week

Question 54

Which arteries are used to make an AV fistula for dialysis? What clinical sign indicates that it is patent?

Answer 54

- radial or brachial arteries are connected to veins in the forearm - an audible bruit indicates that the fistula is patent

Question 55

What are 2 advantages to hemodialysis?

Answer 55

1. More efficient than peritoneal dialysis --> high flow rates and efficient dialyzers = shorter time required for dialysis 2. Can be initiated more quickly in the emergency setting

Question 56

2 Disadvantages to hemodialysis?

Answer 56

1. Less similar to the physiology of the natural kidney than peritoneal dialysis, so the pt is predisposed to: a) hypotension - bc of rapid removal of intravascular volume --> rapid fluid shifts from extravascular space into cells b) hypo-osmolality - due to solute removal 2. Requires vascular access

Question 57

Frequency of peritoneal dialysis?

Answer 57

- dialysis fluid is drained and replaced every hour in acute peritoneal dialysis - but only needs to be drained and replaced every hour in CAPD ( = continuous ambulatory peritoneal dialysis)

Question 58

2 Advantages of peritoneal dialysis?

Answer 58

1. Patient can learn to perform dialysis on their own | 2. Mimics the physiology of the normal kidney more closely than hemodialysis

Question 59

4 Disadvantages to peritoneal dialysis?

Answer 59

1. High glucose load in the solution can lead to hyperglycemia and hypertriglyceridemia 2. Peritonitis is a significant potential complication 3. Patient must be highly motivated to self-administer 4. Cosmetic = the dialysate fluid will increase their abdominal girth

Question 60

Limitations to both forms of dialysis?

Answer 60

-dialysis cannot replace the kidneys synthetic functions --> pts are often epo and vit D deficiency

Question 61

6 Complications of hemodialysis?

Answer 61

1. Hypotension - can cause myocardial ischemia, fatigue, etc 2. Hypo-osmolality - relative to the brain, can cause nausea, vomiting, headache, seizures, or coma 3. "First-use syndrome" = chest pain, back pain, & anaphylaxis (rare) - can occur immediately after the use of a new machine 4. Anticoagulation complications - bleeding 5. Infection of vascular site - can lead to sepsis 6. Amyloidosis of beta2 microglobulin in bones and joints

Question 62

4 Complications associated with peritoneal dialysis?

Answer 62

1. Peritonitis - ssx: fever and abdominal pain 2. Abdominal/inguinal hernia - risk is increased bc of increased abdominal P 3. Hyperglycemia - esp in diabetics 4. Protein malnutrition