Lecture 11 - Acute Kidney Injury (AKI) Flashcards
What is Acute Kidney injury (AKI)?
A sudden deterioration of renal function over hours to days
What metabolic products rapidly rise in AKI?
Urea
Creatinine
What usually happens to urine output in an AKI?
Oliguria
Or
Anuria
What is oliguria?
Reduced urine output
100ml - 400ml
What is Anuria?
No urine output or <100ml
What is Uraemia?
Clinical symptoms which arise when nitrogenous metabolic waste products accumulate in the blood (urea and creatinine) as a result of decreased filtration of these products by the kidney
What is the likely cause of patients pathology:
High creatinine
Reduced eGFR
Hypotrophic kidneys
Chronic kidney disease
Since the deterioration/reduced function in the kidneys leads to kidney tissue shrinkage
What diuretic is most appropriate in a patient with pulmonary oedema?
What type of diuretic is it?
How does it work?
Loop Diuretic
Blocks the NKCC channel in the ascending limb of loop of Henle
Reduces reabsorption of Na+ so more Na+ stays in lumen
This impairs the corticopapillary gradient so less water gets reabsorbed in the CD
More water lost in urine
What are the stages of an AKI?
1
2
3
What 2 things can be measured to determine stage of an AKI?
Serum creatinine
Urine output
What are the serum creatinine levels in stage 1 AKI?
What are the urine output levels in a stage 1 AKI?
Serum creatinine = 1.5 - 1.9 times baseline
Urine output = <0.5ml/kg/h between hours 6 and 12
What are the serum creatinine levels in stage 2 AKI?
What are the urine output levels in a stage 2 AKI?
Serum creatinine = 2 - 2.9 times baseline
Urine output = <0.5ml/kg/h for more than 12hrs
What are the serum creatinine levels in stage 3 AKI?
What are the urine output levels in a stage 3 AKI?
Serum creatinine = 3 times baseline or serum creatinine > 353.6mmol/L
Urine output = <0.3ml/kg/h for 24hrs or more
Or
Anuria for 12hrs or more
Stage the AKI on Slide 8
70ml urine output
70ml / 6 = 11.67ml/h
11.67 / 69kg = 0.17ml/kg/h
0.17ml/kg/h between 6-12 so STAGE 1 AKI
What are the 3 types of cause of AKI?
Pre-renal AKIs
Intrinsic renal AKIs
Post renal AKIs
What are some causes of Pre-renal AKIs?
Sepsis
Hypovolaemia
Shock
Renal artery stenosis
Congestive Cardiac Failure (CCF)
NSAIDs
ACE inhibitors
Essentially anything that leads to reduced perfusion of kidneys
How does Sepsis cause Pre-renal AKIs?
Toxins lead to systemic vasodilation
Massive drop in BP
Leads to Renal hypoperfusion
How does Hypovoloaemia cause Pre-renal AKIs?
Reduced kidney perfusion
How does shock cause Pre-renal AKIs?
Catastrophic fall in BP
Hypovolaemic
Leads to renal hypoperfusion
How does Renal artery stenosis cause Pre-renal AKIs?
Occlusion of renal artery
Leads to reduced perfusion of kidney
How does Congestive Cardiac Failure cause Pre-renal AKIs?
Reduced cardiac output
Less blood to kidneys
How do NSAIDs cause Pre-renal AKIs?
Blocks prostaglandins so kidneys cant vasodilates afferent arteries or renal artery so reduced blood flow to it
How do ACE inhibitors cause Pre-renal AKIs?
Can’t restore BP if it drops
RAAS system cant be activated
Leads to renal hypoperfusion
What are some intrinsic renal causes of AKI?
Acute tubular necrosis
Acute interstitial nephritis
Glomerular disease
Vasculitis
How does Acute Tubular necrosis cause Intrinsic-renal AKIs?
What can cause Acute Tubular necrosis?
Toxins can cause cell necrosis leading to acute tubular necrosis
Rhabdomyolysis - myoglobin is toxin to the kidney
What is Acute Interstitial nephritis?
Inflammation in kidney
What happens in glomerular disease causing intrinsic Renal AKI?
Where the glomerular capilaries are destroyed
What is vasculitis?
How can it cause intrinsic renal AKI?
Inflammation of blood vessels in kidney
What are the general causes of post-renal AKI?
Anything that blocks the urine output
So anything after urine leaves kidney
What are some post-renal causes of AKI?
Bilateral calculus
Uteric/urethral stricture
BPH
Tumor
Retro-peritoneal fibrosis
What is Calculus?
Why does the calculus have to be bilateral to cause post renal AKI?
Urinary stones
If on one side the other kidney can filter the blood
How does a Uteric/urethral stricture cause post-renal AKI?
Blocks urine outflow
How does a BPH cause post-renal AKI?
Enlarged prostate squeezes the prostatic urethra
How does a retro-peritoneal fibrosis cause post-renal AKI?
Pushes ureters from outside compressing them
What are the 4 main complications of AKI?
Metabolic acidosis
Hyperkalaemia
Uraemia
Volume overload
How does metabolic acidosis occur with AKI?
Reduced GFR kidney not filtering as much
Less able to reabsorb and produce HCO3-
How does hyperkalaemia occur with AKI?
Low GFR means less able to remove K+
The hyperkalaemia also contributes to the metabolic acidosis
How does volume overload happen with AKI?
Less able to remove water due to reduced GFR
What bedside investigations can be done to check for AKI?
Bladder scan
Urinalysis, microscopy, culture and specimen
ECG (to see any effects of K+)
What blood investigations can be done for AKI?
VBG
Creatinine kinase (rhabdomyolysis)
Immunology screen (vasculitis)
What imaging investigations can be done for AKI?
Ultrasound of Kidneys, ureters and Bladder
CT scan
CXR
What is a nephrostomy?
Bag which drains the contents of the kidney
What is cytoscopy?
Camera into bladder
What are some treatments for a Pre-renal AKI?
Treat underlying cause
IV fluids (Hypovolaemia)
Stop potentially Nephrogenic medication (NSAIDs ACE inhibitors
Diuretics
What are some treatments for intrinsic renal AKIs?
Correct electrolytes
Renal replacement therapy
Call nephrology
What are some post-renal treatments of AKI?
Urinary or suprapubic Catheter
Ureteric stents
Nephrostomy
