Acute Kidney Injury Flashcards
What is the name given to the criteria for ranking kidney injury?
RIFLE criteria
Name some of the major extra-renal effects of AKI
Pulmonary function - fluid overload → oedema, ARDS
CNS - Electrolyte imbalance, altered conscious level, confusion, convulsions, coma
Cardiac - Heart failure, cardiac hypertrophy, arrythmias
What type of ARF are the following classed as:
Intravascular volume depletion
Decreased effective blood volume
Altered intrarenal haemodynamics
Pre-renal ARF
GFR reduced as a result of haemodynamic disturbances → decreased glomerular perfusion (basically not enough fluid)
How does systemic vasoconstriction affect the glomeruli pressure?
The inlet is under systemic control, therefore there will be vasoconstriction
The outlet is controlled locally, therefore it will not be affected by systemic effects
Therefore systemic vasoconstriction → decreased glomerular pressure
How it the outlet of the glomerulus controlled mainly?
It is controlled locally, by angiotensin II → constriction
If angiotensin II blocked, outlet opening increases, so pressure decreases
e.g. Ramipril - ACE inhibitor
Name some common types of intrinsic acute renal failure
Acute tubular necrosis
Acute interstitial nephritis
Acute glomerulonephritis
Acute vascular syndromes
Which type of AKI will have its renal function restored when the altered haemodynamic factors are reversed by giving fluids?
Pre-renal AKI - no cellular injury
What type of AKI is caused by third space sequestration?
Pre-renal AKI
How is pre-renal ARF diagnosed?
Hx and Examination
high BUN to Cr ratio (BUN:Cr > 20:1)
Abnormal urine chemistry
What are the clinical manifestations of third space sequestration?
Respiratory compromise
Cardiac - decreased CO
GI - intestinal ischaemia
Hepatic dysfunction
Oliguric renal failure - if intrabdominal pressure >15mmHg → oliguria; >30mmHg → anuria
What is the treatment for Third Space Sequestration?
Abdominal decompression
Paracentesis - drain abdomen
Surgical decompression
Renal failure usually recovers after relief of intra-abdominal pressure
What is the major aetiology of Post-renal AKI?
Obstruction - stone, fibrosis, clot, cancer, bladder pathology
- Hydroureter
- Hydronephrosis
What is the treatment for post-renal faliure?
Treatment of cause
After relief of obstruction: monitor for post-op diuresis (parenteral fluid)
Monitor electrolyte loss with polyuria
Treat metabolic acidosis
What is the most common form of intrinsic ARF?
Acute tubular necrosis
- Nephrotoxic
- Ischaemic
- Multifactorial
What happens to the cells in acute tubular necrosis recovery?
They dedifferentiate and remaining viable tubular epithelial cells proliferate
How does radio-contrast affect the kidney?
It induces vasodilation followed by prolonged vasoconstriction
This leads to renal ischaemia and ROS release: Direct tubular toxicity
How is Acute tubulo-interstitial nephritis diagnosed?
Exposing factor: drug, infection
Fever/Rash
Arthralgia
Oesinophilia/Oesinophiluria
Biopsy: Cellular infiltrate in tubulo-interstitium
What is the treatment for acute tubulo-interstitial nephritis?
Withdraw offending agent
Steroids
What are the life threatening complications of AKI?
Metabolic Acidosis
Hyperkalaemia
Acute pulmonary oedema
What are the clinical effects of acidosis?
Muscle weakness
Altered mental state
Kussmaul breathing - to reduce CO2 in blood
Hyperkalaemia - K moves out to balance
Hypotension (negative inotropic effect)
What is the treatment for metabolic acidosis?
Treat the cause
Volume expansion
IV Sodium Bicarbonate (pH <7.1)
Dialysis
What are the clinical effects of hyperkalaemia?
Muscle weakness:
Smooth muscle - constipation
Cardiac muscle effects
ECG signs: Tall slender peak T waves, broad QRS (→very broad QRS)
What is the treatment for hyperkalaemia?
Treat cause
IV Calcium gluconate - balance Ca and K for heart
IV dextrose insulin/IV salbutamol - shift K into intracellular compartment
Bicarbonate therapy - correct acidosis
Cation exchange resin: Ca polystyrene
