Acute Kidney Injury Flashcards
What is AKI?
The syndrome arising from a rapidly falling GFR (drop in urine output)
What is AKI characterised by?
Retention of nitrogenous (urea and creatinine) and non-nitrogenous waste products, as well as disordered electrolytes
What are the 3 ways that AKI can be diagnosed?
1) Serum creatinine has increased by ≥26.5µmol/l in ≤48h
2) Serum creatinine has risen to ≥1.5-fold from baseline in the preceding 7 days
3) Urine output has been <0.5 ml/kg/h for 6 hours
How many stages of AKI are there?
3
What are the 3 diagnostic features of Stage 1 AKI?
1) Serum creatinine has increased by ≥26.5µmol/l in ≤48h
2) Serum creatinine has risen to ≥1.5-fold from baseline in the preceding 7 days
3) Urine output has been <0.5 ml/kg/h for 6 hours
What are the 2 diagnostic features of Stage 2 AKI?
1) Serum creatinine rises 2-2.9 times from baseline
2) Urine output has been <0.5 ml/kg/h for 12 hours
What are the 5 diagnostic features of Stage 3 AKI?
1) Serum creatinine rises ≥ 3 times from the baseline
2) Serum creatinine rises to ≥353.6µmol/l
3) RRT irrespective of serum creatinine
4) Urine output has been <0.3 ml/kg/h for ≥24h hours
5) Anuria for ≥12h
What diagnostic features are used in CKD but not AKI
Estimated GFR and proteinuria
Describe normal creatinine levels
- Normal range is 50-80
- However with lots of muscle mass can be higher e.g. 110 or if v thin 35 may be normal
- If don’t know their normal or don’t know if they already have CKD, assume it is abnormal and have AKI if not in the normal range
What are the proximal tubules v susceptible to and why?
Hypotension and hypoxia → they are very vascular and receive 80% of the renal blood flow
What are the 3 classifications of AKI causes?
1) Pre-renal
2) Intrinsic (renal)
3) Post-renal
What are pre-renal causes of AKI related to?
Reduced BP or volume
What are 3 types of pre-renal causes of AKI?
1) Volume depletion
2) Decreased effective volume
3) Altered intrarenal haemodynamics → NSAIDs or ACEi-A2RB induced
What are intrinsic causes of AKI related to?
Diseases that affect blood vessels, glomerulus, tubules and cells
What are 5 types of intrinsic causes of AKI?
1) Acute tubular necrosis
2) Acute glomerulonephritis
3) Acute interstitial nephritis → inflammation e.g. drugs/sarcoidosis/autoimmune disease
4) Vasculitis
5) Drugs → damage tubular cells
What are 6 types of post-renal causes of AKI?
1) Ureteric obstruction e.g. stone in ureter, pelvis, bladder
2) Bladder outflow obstruction
3) Prostate hypertrophy
4) Pregnancy (v gravid e.g. twins)
5) Extrinsic e.g. retroperitoneal haematoma
6) Urethro valve obstruction
What is the most common cause of post-renal AKI in men and why does it lead to AKI?
Prostate hypertrophy → prostate can herniate and block off connection between the bladder and urethra
What is the most common cause of post-renal AKI in children?
Urethro valve obstruction
Describe what happens in a ureteric obstruction
Urine isn’t flowing leading to back pressure on the glomerulus so the kidneys don’t work
What are the 7 functions of kidneys?
1) Excretion of electrolytes
2) Clearance of waste products
3) Gluconeogenesis
4) Production of hormones
5) Control of water balance
6) Regulation of acid-base status (produce and reabsorb bicarbonate)
7) Receptor site for hormones
For what hormones does the kidney act as a receptor site for?
ADH, aldosterone, ANP, PTH, renin
What are the 5 consequences of AKI?
1) Fluid overload
2) Hyperkalaemia
3) Metabolic acidosis
4) Uraemia
5) Organ cross-talk
Why does fluid overload/accumulation occur in AKI?
Bc not making enough urine
What does fluid overload lead to?
Peripheral and pulmonary oedema
What is the life-threatening complication of AKI linked to fluid overload?
Pulmonary oedema → can’t breathe
What are the effects of sacral and ankle oedema?
Might be more susceptible to skin break down and ulcers
What does hyperkalaemia affect?
Conduction of the heart and therefore the ECG (arrhythmia)
What is the normal serum potassium level?
Up to 4.5 (4-5.5) mmol/L
What is the first sign of hyperkalaemia on an ECG?
Peaked T waves after the QRS complex
What would you see on an ECG with a serum potassium of 5.5-6.5?
- Peaked T waves
- Prolonged PR segment
What would you see on an ECG with a serum potassium of 6.5-8?
- Loss of P waves
- Prolonged QRS complex
- ST segment elevation
- Ectopic beats and escape rhythms
What would you see on an ECG with a serum potassium of > 8?
- Sine wave
- Progressive widening of QRS complex
- Ventricular fibrillation
- Asystole
- Axis deviations
- Bundle branch blocks
- Fascicular blocks
What width of the QRS complex is abnormal?
> 3 small squares
What is the immediate temporary solution to hyperkalaemia but why is it only temporary?
- Giving dextrose insulin
- Just shifts potassium in cells (right thing to do in emergency) but it will come out of the cells again
What can be given to briefly reduce the response to hyperkalaemia and what does it do?
Calcium chloride → stabilises cell membrane and makes it less irritable
What do you need to organise for someone with hyperkalaemia?
Dialysis
What can happen if someone goes untreated with hyperkalaemia?
Cardiac arrest → no CO → death
What does hyperkalaemia + ECG changes mean?
An emergency
What are the typical ABGs of someone with AKI?
- pH < 7.3
- pCO2 low
- pO2 normal or high
- HCO3 low
Why might pO2 be high in someone with AKI/metabolic acidosis?
If they are breathing a lot
What are the typical symptoms of metabolic acidosis?
1) Breathless/tachypneic
2) Nausea
3) Non-specifically unwell
Why might someone be breathless/tachypneic with AKI/metabolic acidosis?
1) Pulmonary oedema
2) Urge to breathe faster to compensate for metabolic acidosis
What is uraemia?
Retention of metabolic waste products e.g. urea, sulfate, creatinine, phosphate
What are the effects of uraemia?
1) Pericarditis
2) Pleurisy
3) Encephalopathy
Describe pericarditis
- Causes pleuritic chest pain, worse on a deep breath → but cardiac function at this point should be fine
- Both layers of the pericardium are inflamed and rubbing together, which can cause fluid to build up
- This can lead to haemorrhagic pericarditis
- Need to listen to check for murmur (crunchy, high pitched noise) to diagnose pericarditis
- Needs to go on dialysis
What is pleurisy and what can it lead to?
Inflammation of the pleura (pleural membrane) → pleural effusion
Describe encephalopathy
- Inflammation of the brain
- Patients can present with different neurological symptoms (if gets too far can be uraemic coma)
- Leakage and inflamed membranes
How can AKI lead to organ cross-talk?
AKI affects other organs mainly as a result of uraemic toxin and fluid build up (gut, liver, bone marrow)
What are the 4 domains of AKI management?
1) Exclude a life-threatening complication
2) Identify the aetiology of AKI
3) Supportive treatment
4) Avoidance of progression
How do you exclude a life-threatening complication of AKI?
Check potassium, ECG, listen to chest and check breathlessness and keep checking up on these throughout treatment
What do you do if a life-threatening complication is present in AKI?
Correct/treat immediately
How do you treat if the is AKI due to hypovolaemia?
Give fluids
How do you treat if the AKI is due to low BP?
Give fluids/medication
How do you treat if the AKI is drug induced?
Stop drugs
What is an example of a drug that can cause AKI?
Gentamicin → overdose or on it for too long
How do you treat if the AKI is sepsis induced (most common cause of AKI in hospital setting)?
Treat sepsis
What is supportive treatment given in AKI?
- Nutrition
- Ulcer prophylaxis
How do you avoid progression of AKI?
Avoid nephrotoxic drugs, hypovolaemia and hypotension
What treatment is a life threatening complication of AKI an indication for?
Renal replacement therapy (RRT)
What are 5 examples of life threatening complications of AKI that are an indication for RRT?
1) Life threatening pulmonary oedema
2) Severe metabolic acidosis
3) Severe hyperkalaemia, esp. if ECG changes
4) Uraemic pericarditis
5) Uraemic encephalopathy
Why is severe metabolic acidosis life threatening?
pH < 7.1 → cardiac function affected, risk of arrhythmia
Why is uraemic pericarditis life threatening?
Risk of fluid accumulation and bleeding into cardiac space → cardiac arrest
Describe RRT
- Uses filter that acts as an artificial kidney
- Hair sized tiny columns that blood goes through
- Can correct AKI emergencies
- Effluent is like urine
- Dual lumen catheters → one lumen removes blood and in the other one it comes back
Where are the insertion sites for RRT?
To be effective needs to be a big vein → internal jugular, femoral, subclavian
Describe RRT as part of multi-organ support
- Routine life support
- Can combine with ECMO → artificial oxygenation + cleaning of blood
Describe how cancer/chemotherapy can lead to AKI
- Chemotherapy can lead to tumour lysis syndrome
- This is when tumour cells are killed, releasing intracellular electrolytes (potassium) and substances (toxicity from chemo)
- This can lead to diarrhoea and vomiting → hypovolaemia
- This patient population is v high risk for this, look out for it, can’t prevent, just give RRT
What do you need to do if someone has high potassium?
An ECG
What treatment do you give if you have excluded a life-threatening cause but creatinine is high, potassium is a bit high but ECG is normal?
IV fluids
What treatment do you give to someone with high potassium and ECG changes?
Calcium, dextrose insulin and call ICU/renal team to start RRT
What are the sub-classifications of AKI causes?
1) Pre-renal AKI
2) Renal artery
3) Small vessel disease
4) Glomerular disease
5) Acute tubular necrosis
6) Acute interstitial nephritis
7) Intra-tubular obstruction
8) Post-renal obstruction
What are 3 causes of pre-renal AKI?
1) Hypovolaemia e.g. ruptured aneurysm or trauma bleeding
2) Cardiac failure
3) Hepatorenal syndrome
What are 2 causes of renal artery related AKI?
1) Renal artery occlusion
2) Large/medium vessel vasculitis
What are 3 causes of small vessel disease?
1) Thrombotic microangiopathy
2) Renal atheroembolism
3) Small vessel vasculitis
What are 7 causes of glomerular disease?
1) Anti-GBM disease
2) Lupus nephritis
3) Post-infectious glomerulonephritis
4) Infective endocarditis
5) Membrano-proliferative glomerulonephritis
6) Cryoglobulinemia
7) IgA nephropathy/HSP
What are the 8 causes of acute tubular necrosis (mainly drugs)?
1) Amphotericin
2) Aminoglycosides
3) Antiretrovirals
4) Cisplatin
5) Paracetamol (acetaminophen)
6) Radiocontrast
7) Organic solvents
8) IV immunoglobulin
What are 3 causes of acute interstitial nephritis?
1) Drugs
2) Infection
3) Systemic disease
What are 3 causes of intra-tubular obstruction?
1) Cast nephropathy (kidney injury in myeloma)
2) Drugs
3) Crystalluria (benign, side effect of sulfonamides and penicillins)
What are 5 causes of post-renal obstruction?
1) Papillary necrosis
2) Tumours
3) Retroperitoneal fibrosis
4) Renal calculi
5) Urinary retention
