Acute Renal Failure (injury) Flashcards
1
Q
What are the 3 types of arf?
A
- prerenal
- intrarenal
- postrenal
2
Q
What kidney functions are decreased in arf?
A
- inability to maintain acid-base balance
- inability to maintain electrolyte balance
- Accumulation of nitrogenous wastes (Azotemia), urine creatinine
3
Q
Epidemiology of ARF
A
- 5% of hospital pts
- 30% of ICU admissions
- 25% of hospitalized pts
Pts with arf have higher mortality risk
4
Q
ARF definition
A
Abrupt or rapid decline in renal filtration, thus ↓renal function
5
Q
sxs of arf
A
1. Generally secondary to uremia Nausea/Vomiting Malaise Altered mental status (delirium) Hypertension or Hypotension Pericardial friction rub: rubbing sound with beat due to backup of fluid around the heart. Only when hypervolemic Arrhythmias Rales: crackling sound when fluid is around the alveoli. Only when hypervolemic Abdominal pain
6
Q
How prevalent is prerenal failure?
A
Most common type of arf, 60-80% of cases
7
Q
Pathophys of prerenal arf
A
Kidneys do not recieve enough blood to be filtered
8
Q
Results of prerenal arf
A
Impaired blood flow results in: Hypoxemia Decreased GFR Decreased renal perfusion Increased tubular re-absorption of Na+ & H2O
Results in electrolyte imbalances and metabolic acidosis
9
Q
Which type of arf is metabolic acidosis a result of ?
A
prerenal
10
Q
Causes of prerenal arf
A
Disruption of blood flow to kidneys:
Significant hypotension
Dehydration / hypovolemia
Renal artery stenosis (RAS)
Impaired cardiac output: low ejection fraction
Heart failure, MI, cardiac tamponade(hear friction rub and decreased heart sounds), shock
Liver failure
Severe Burns: loss of fluids into third spaces
Diuretic therapy
Hemorrhage
11
Q
Is prerenal arf reversible or irreversible?
A
- reversible with early detection and treatment
- No damage to kidneys early in process
- Prolonged decrease in the blood flow to the kidneys can cause permanent damage to the kidney tissues (ischemia)
12
Q
Another name for postrenal failure
A
Obstructive failure
13
Q
How common is postrenal failure?
A
5-10% of all arf cases
14
Q
What causes postrenal failure?
A
- Obstruction of urethra:
Urethral stricture
BPH: Most common cause in males
Prostate CA - Obstruction of one or both ureters: Kidney stone(s)
Cancer of urinary tract/reproductive tract organs or structures - Obstruction at bladder level
Bladder stone
Blood clot
Neurologic disorders of bladder/anticholinergics
15
Q
Pathophysiology of postrenal failure
A
- Obstruction leads to increased intraluminal pressure (hydronephrosis) kidney arteriole parenchymal damage (local ischemia) affects renal blood flow and tubular filtration decreased GFR
- UTI often associated
16
Q
Is postrenal arf reversible or irreversible?
A
- Reversible, Unless obstruction is present long enough to cause damage to kidney tissue
- Once the blockage is removed, the kidneys usually recover in 1-2 weeks if there is no infection or other problem
17
Q
What is the most complicated type of arf?
A
Intrarenal arf
18
Q
How common is intrarenal arf?
A
25-40%
19
Q
What is primary parenchymal damage & what arf is it related to?
A
- Primary renal parenchymal damage
Problems with filtering function of the kidney
Problems with blood supply within the kidney
Problems affecting the kidney tissue that handles salt and water processing - Intrarenal
20
Q
What is the pathophys of intrarenal failure?
A
Results from damage to filtering structures of kidney
Nephrotoxicity or inflammation damages delicate epithelial layers of nephrons
Nephrotoxins damage renal cortex
21
Q
What are 3 causes of intrarenal failure and which is most prevalent?
A
Acute Tubular Necrosis (ATN)
Accounts for 85% of cases of primary acute kidney failure
Acute Glomerulonephritis
Acute Interstitial Nephritis (AIN)
22
Q
How is ATN diagnosed?
A
FENa (fractional excretion of Na+) >3%
23
Q
What color will urine be in ATN? Describe the casts found in ATN
A
“Tea colored” due to Tubule lumen is often filled with cellular debris or heme-pigment precipitate
Granular muddy brown casts
24
Q
Pathophys of ATN
A
Characterized by necrosis of the epithelial cells within the renal tubules
Due to toxicity or ischemia
25
What part of the tubule is affected in ATN?
PCT and TALH
26
What antimicrobial exogenous toxins can cause ATN?
1. Aminoglycosides (Gentamicin, Tobramycin, Vanco): antimicrobial
2. Amphotericin B: anti fungal
3. Cephalosporins: used very frequently
4. IV Acyclovir: anti-viral, Herpes
27
How does hypovolemic shock cause ATN?
Decreased blood supply to the kidneys
| Hypovolemic shock caused by trauma, septicemia, and pancreatitis
28
What immunosuppressive exogenous toxins can cause ATN?
Cyclosporine: used for organ transplant as an anti-rejection drug
29
When can radiographic contrast dyes cause ATN?
1. Pre-existing factors:
DM, renal insufficiency, age, dehydration, CHF,
NSAIDs, ACE inhibitors, Metformin
30
What can be given to reduce ATN risk with radiographic contrast dyes?
N-acyteylcystine/ Mucomyst given pre and post contrast dye
31
How should you manage a pt who is on metformin and needs contrast dye?
Stop metformin before the test, cannot be put back on metformin until the BUN/Cr levels are rechecked and back to normal
32
What endogenous toxins can cause ATN?
1. Myoglobinuria
- Released by necrotic muscle
- Clogs the distal tubule causing injury
2. Hyperuricemia: high uric acid in blood
-Asst with chemo (Leukemia/Lymphoma)
-Prevent by giving Allopurinol prophylactically
3. Hemoglobin:
Transfusion reaction (hemolysis)
4. Bence Jone protein: Multiple myeloma
33
What causes Myoglobinuria?
Rhabdomyolysis, crush injury, seizures, ETOH abuse, cocaine abuse
34
Definition of acute glomerulonephritis
Glomeruli damaged by infection, autoimmune, or vascular disorders
35
What 2 primary infectious agents can cause glomerulonephritis?
Group A beta hemolytic strep, S. aureus bacteremia
36
What autoimmune disorders can cause acute glomerulonephritis?
SLE, HUS, TTP
37
What vascular disorders can cause Acute glomerulonephritis?
Small vessel vasculitis (Wegener’s Granulomatosis, “Goodpasture Syndrome”)
38
What is the most prevalent cause of Acute interstitial nephritis?
Medications (>70% of cases)
| PCN, Cephalosporins, Sulfonomides (diuretics), NSAIDs, Rifampin (TB), Phenytoin (antiseizure), Allopurinol (gout)
39
What infectious agents can cause AIN?
Streptococcal, CMV, Histoplasmosis, Leptospirosis, Rocky Mt. Spotted Fever
40
What autoimmune disorders can cause AIN?
SLE, Sjogren syndrome, Sarcoidosis, cryoglobinemia
41
General ARF sxs
```
Azotemia symptoms
Malaise
Nausea, vomiting, diarrhea
Confusion, seizures, coma
Hypotension
Edema
Decreased urine output
Pericardial friction rub
Asterixis (tremor)
Hypertension
```
42
Define oliguria
Oliguria - <500 mL/d
| 50% are non-oliguric
43
Define anuria
<100 mL/d
| Suggests obstruction
44
ARF diagnostic studies: BUN/CR results
Increased
45
ARF diagnostic studies: K+
INcreased
46
ARF diagnostic studies: HCO3-
Decreased
47
ARF diagnostic studies: Hgb/Hct
Decreased
48
ARF diagnostic studies: pH
Decreased (metabolic acidosis)
49
ARF diagnostic studies: Urinalysis
Decreased sg
| proteinuria
50
ARF diagnostic studies: Urine sediment
casts
| cellular debris: renal tubule epithelium
51
ARF diagnostic studies: CrCl
Decreased, reflects # of functional nephrons
52
What are RBC casts indicative of?
Glomerulonephritis
| AIN
53
What are Hyaline casts indicative of?
Nonspecific
| Concentrated urine or w/ diuretics
54
What are granular casts indicative of?
"Muddy brown"
| ATN
55
What are epithelial casts in urine indicative of?
ATN
AIN
Glomerulonephritis
56
What are WBC casts indicative of?
Pyelonephritis
AIN
Glomerulonephritis
57
What are broad casts indicative of?
Advanced chronic kidney disease
58
What are waxy casts indicative of?
Nonspecific
| Acute and chronic kidney diseases
59
What might an EKG show in arf?
Tall peaked T waves (↑ K+)
| Wide QRS
60
When are imaging studies beneficial in arf?
Postrenal
Renal ultrasound
Hydroureter and hydronephrosis
61
When are CT/MRI indicated in arf?
Indicated if renal U/S normal and suspect ARF
| Indicated if complex cyst or mass seen on U/S
62
Kidney biopsy indications
```
Unexplained acute renal injury
Acute nephritic syndrome
Unexplained proteinuria & hematuria
Systemic Dz assoc. w/ kidney dysfunction
Suspected transplant rejection
Guide Treatment
```
63
Kidney biopsy contraindications
```
Bleeding disorder
Thrombocytopenia
Uncontrolled HTN
Solitary kidney
Ectopic kidney
Horseshoe kidney
ESRD
Multiple cysts
Renal infection
Neoplasm: known cancer
Hydronephrosis
```
64
What are some complications of arf?
```
Arrhythmias
CHF
Cardiac Tamponade
Increased risk for infection
Electrolyte abnormalities
GI bleeding
Multiple organ failure
Anemia / thrombocytopenia
Acid-Base imbalance
Encephalopathy / seizures
```
65
What are the goals of treating arf?
Pinpoint the exact cause of the kidney failure
1. Determine degree to which accumulating wastes and water are affecting the body
- Impacts treatment decisions about medications and the need for dialysis
66
When is dialysis recommended?
Dialysis recommended when serum Creatinine reaches 8mg/dl
67
What are supportive treatment for arf?
1. Adequate hydration
Isotonic IV fluid replacement (D5W, NS or LR until Na+ reaches 125-130 mEq/L, then ∆ to ½ NS)
Attention to improving renal perfusion and oxygenation
Prevent fluid overload
2. Attention to serum K+ & Na+
3. Avoid nephrotoxic drugs if possible
68
What medications can be given for arf?
1. Loop diuretics: Inhibit co-transport of Na+/K+/Cl – in ascending Loop of Henle
2. Dopamine: Dilates renal & splanchnic arterioles by activating dopaminergic receptors
69
What diet are ppl with arf put on?
High calorie diet
| Low protein, low Na+, low K+
70
How can fluid and electrolyte balance be maintained in arf?
IV fluids with electrolytes
| Hemodialysis or peritoneal dialysis
71
How can edema be prevented in arf?
Fluid restriction
72
How is oliguria treated in arf?
Loop diuretics
73
How is severe hyperkalemia treated in arf?
Avoid ACE inhibitors, K+ sparing diuretics
| D50 IV, insulin, IV bicarbonate
74
What is the mortality rate in arf ppts with additional comorbidities?
70%
75
What factors increased mortality rates?
Advanced age
Severe underlying disease
Multisystem organ failure
76
What is the prognosis for atn?
Because the tubular cells continually replace themselves, the overall prognosis for ATN is good if the cause is corrected, and recovery is likely within 7 to 21 days
