Acute renal failure Flashcards
Acute Renal Failure aka Acute Kidney Injury
● Defined as rapid decrease in kidney function, resulting in…
○ Inability to maintain acid-base balance
○ Inability to maintain electrolyte concentrations/water homeostasis
○ Inability to excrete nitrogenous waste products (urea and
creatinine)
Several causes of Acute renal failure
hypovolemia, glomerulonephritis, BPH, etc.
○ Pre-renal, intrinsic, post-renal
Approximately ____% of all ICU patients have AKI
65
What is the 2012 Kidney Disease Improving Global Outcomes (KDIGO) AKI Diagnostic Criteria?
Diagnose acute kidney injury in
patients with any one of the following criteria:
GU-ACUREN-1
○ Increase in serum creatinine by ≥ 0.3
mg/dL within 48 hours
○ Increase in serum creatinine to ≥ 1.5 times
baseline, within prior 7 days
○ Urine volume less than 400-500 ml/day
(oliguria) or output < 0.5 mL/kg/hour for six
hours
Staging the severity of Acute Kidney Injury
○ Stage 1-
■ Serum creatinine criteria - Increase by ≥ 0.3 mg/dL in 48 hours or
a 150-199% (1.5 to 1.9 times) increase from baseline OR
■ Urine output criteria - decline to < 0.5 mL/kg/hour for > 6-12
hours.
○ Stage 2-
■ Serum creatinine criteria - Increase to 200%-299% from baseline
OR
■ Urine output criteria - < 0.5 mL/kg/hour for > 12 hours.
○ Stage 3-
■ Serum creatinine criteria - Increase to > 300% from baseline, or
to ≥ 4 mg/dL OR
■ Urine output criteria - < 0.3 mL/kg/hour for 24 hours +, or
anuria for 12 hours + OR
■ Initiation of renal replacement therapy OR if <18 y/o and a
eGFR of 35
When the kidney is injured, _____ decreases, which results in accumulation of _____
glomerular filtration; nitrogenous waste (BUN and Creatinine)
______- The laboratory increase in
BUN and Creatinine (may be
asymptomatic)
Azotemia
______- Pathologic manifestation of
Azotemia (these patients are ill)
Uremia-
To sort out the causes of acute kidney injury, we break them into 3 main categories:
○ Pre-Renal Azotemia i.e. hypovolemia
○ Intra-renal (Intrinsic) Azotemia i.e. glomerulonephritis
○ Post-Renal Azotemia i.e. BPH
Look at slide ____
13
Pre-Renal AKI
● Most common of the 3 categories, causing 40-80% of AKI cases.
● When you think of Pre-Renal causes, think of Renal Hypoperfusion.
● Whatever the cause may be, the body is not able to maintain adequate blood flow to the kidneys, resulting in decreased GFR, azotemia, and possible oliguria. Hydrostatic pressure
Pre-Renal Causes of AKI
○ Hypovolemia (hemorrhage, dehydration, burns, third spacing, GI fluid loss).
○ Hypotension (due to low volume or due to decrease vascular resistance, such as from some medications)
○ Ineffective circulation or Low Cardiac Output (CHF, sepsis)
○ Abdominal Aortic Aneurysm/Dissection (AAA)
○ Renal Artery Stenosis with acute thrombosis
○ Nearby neoplasm (causing renal artery blood flow obstruction)
Pre-Renal Tx of AKI
dependent upon the cause.
● However, mainstay of therapy is based on…
○ Maintenance of intravascular volume level
(IVFs)
■ Need to restore renal perfusion
○ Attention to serum electrolyte imbalances
○ Avoidance of nephrotoxic drugs in order to
not add insult to injury
Intrinsic (Intra) AKI
● Intrinsic causes account for a range of 25-40% of AKI cases
● The sites of damage with Intrinsic
Kidney Injury include the glomeruli, the
interstitium, and/or the tubules
● When you think of Intrinsic (Intrarenal)
kidney injury, think of Direct Organ Insult
● First, r/o pre- and post-renal issues
Intrinsic (Intra) Renal Causes
○ Acute Tubular Necrosis (most common intrinsic cause)
■ Disease secondary to ischemia or nephrotoxins
■ Prolonged pre-renal AKI can become intrinsic AKI
○ Acute Interstitial Nephritis
○ Acute Glomerulonephritis (various types)
○ Others (infections like TB or pyelonephritis, vasculitis)
Post-Renal AKI
● The least common category of Acute Renal Failure (5-10%).
● These are important to detect because of their reversibility
● Azotemia only occurs if outflow obstruction affects BOTH kidneys
● If only one is obstructed, renal
function is usually maintained by the
other kidney
● With post-renal AKI, think of Urinary Outflow Obstruction that causes pressure to back up through the kidneys
Post-Renal Causes
○ Benign Prostatic Hyperplasia (BPH) (most common cause in men)
○ Urolithiasis - stones anywhere in the urinary tract
○ Bladder Outlet Obstruction (mass, pregnancy- rare)
○ Anticholinergic medications - inhibits smooth muscle contractions
○ Obstructive bladder, prostate, or cervical cancers
