Acute Kidney Injury Flashcards
Abdominal compartment syndrome
from increased intra-abdominal pressure
(e.g. from intra-abdominal bleeding, ascites, or severe gut edema etc).
Perfusion to the organs can be critically reduced - leading to pre-
renal AKI. Pressure on the ureters etc can result in post-renal AKI.
AKIN criteria
define and classify the severity of acute kidney injury. Uses urine output and serum
creatinine levels as criteria.
Glomerular filtration rate
Compares the amount of creatinine excreted in the urine with the amount in the blood over 24 hours
Intra-renal AKI cause
Intra-renal AKI refers to AKI that affects the nephron function.
Factors contributing to intra-renal AKI include those that result in ischemia, and those that arise from nephrotoxins.
Myoglobinuria
Presence of myoglobulin in the urine; occurs when myoglobulin is released into the blood subsequent to muscle breakdown e.g. during crush injury, extensive trauma etc.
It contributes to intra-renal AKI because it is nephrotoxic
Nephrotoxic
cause damage to the tubular cells in the nephron. They include drugs (aminoglycoside antibiotics), furosemide, contrast
Post-renal AKI cause
occurs from causes ‘beyond’ the kidney
Pre-renal AKI cause
Pre-renal AKI is renal dysfunction that arises from inadequate blood flow to the kidney
Primary Function of the Kidney:7
o Maintain fluid and electrolyte balance
o Remove metabolic waste products
o Maintain acid-base balance
o Maintain endocrine functions
oHelp regulate blood pressure
o Release of erythropoietin for RBC production
o Produces active form of Vitamin D
Juxtaglomerular Cells (Granular Cells)
Located in the smooth muscle cells of the afferent arteriole
They store, produce and secrete renin.
Play critical role in RAAS
Autoregulation of renal blood flow.
RAAS system is a….
RAAS is one of the body’s compensatory mechanisms.
Renal Assessment
Patient history Monitoring volume status -Intake and output , 24 hour balance -Hourly urine output -Daily weights -Color and consistency of urine
Monitoring hemodynamic parameters
- Hourly blood pressure and heart rate
- Frequent CVP (if available)
Monitoring oxygen supply/respiratory parameters (hourly)
Reviewing urine and serum lab values
Urine Volume
- One of the first indicators of decreased renal perfusion
- Subject to other conditions, so trends and full assessment required
- Monitor on hourly basis
Urinalysis
Aids in locating site of damage
Guides management of renal dysfunction
Urine Sodium
Reflects renal perfusion
Decreased perfusion, RAAS, sodium retained, therefore urinary sodium concentration falls.
Urine Osmolality
Measure of the concentration of solutes in the urine (the ratio of urine density compared with water density). Provides information on the kidney’s ability to concentrate urine. It’s included as part of urinalysis
Creatinine
By product of muscle breakdown and cell metabolism
Produced and cleared at a constant rate
Filtered out by glomerulus- NOT reabsorbed
In patients with low perfusion states, a small rise in creatinine might occur as a result of decreased filtering at the glomerular level
May be falsely elevated in hypercatabolism seen in CC patients not properly fed.
Urea
By product of protein metabolism
Not a reliable indicator of renal function on its own (affected by protein intake, digestion of blood from UGIB).
BUN:Cr Ratio
Can help identify etiology of AKI
Urea-filtered out of the blood at glomerulus, significant percentage of it is reabsorbed as the filtrate passes through the renal tubules
Creatinine-filtered out of the blood at the glomerulus but is NOT reabsorbed in the renal tubules (so it’s peed out!)
In low perfusion states: Filtrate flow rate through tubules slows
Tubules still working normally therefore MORE BUN is reabsorbed = increased serum BUN levels
Creatinine not affected by slower flow rate as not reabsorbed = no/minimal increase in creatinine
Creatinine Clearance Test
•Compares the amount of creatinine excreted in the urine in 24 hours against the amount that has been reabsorbed into the blood
.The number that we get then provides us with an accurate GLOMERULAR FILTRATION RATE!
decreased creatinine clearance indicates decreased renal function!