Acute kidney injury Flashcards
What is classified as acute kidney injury
<48 hours reduction in kidney function = increase in serum creatinine by >26.4 µm/l or by >50% or reduction in urine output
What are the types of causes of AKI
Prerenal
Intrinsic (renal)
Post-renal
What is the pre renal cause of AKI
Impaired blood flow to the kidney = reduction in perfusion
What conditions can cause pre renal AKI
Hypovolaemia - haemorrhage / burns / vomiting / diarrhoea
Hypotension
Drugs - ACEi, ARB, NSAID, COX-2
Renal artery stenosis
What conditions can cause hypotension
Sepsis
Anaphylaxis
Cardiogenic shock
What are the drugs that can cause pre renal AKI
NSAID
COX-2
ACEi
ARB
How does ACEi cause pre-renal AKI
Because ACEi causes vasodilation of the efferent arteriole hence prevents vasoconstriction as a compensatory mechanism for low perfusion pressure (which leads to low perfusion)
How does NSAID cause pre-renal AKI
It causes vasoconstriction of the afferent arteriole = reduction in perfusion
What is the renal cause of AKI
Diseases that causes inflammation or damage to cells of the kidney structures - glomeruli, tubules, interstitium of kidneys
What causes intrinsic (renal) AKI
Glomerulonephritis
Acute tubular necrosis
Acute interstitial nephritis
Drugs (damage tubules and interstitium)
Contrast exposure (from imaging)
Rhabdomyolysis (damage tubules)
What can be damaged through contrast exposure
Tubules
What causes acute tubular necrosis
Sepsis
Severe dehydration -> shock
Rhabdomyolysis
Drug toxicity
Contrast exposure
Which drug can cause acute tubular necrosis
Gentamicin
What conditions can cause interstitial nephritis
TB infection
Sarcoidosis
What is the post renal cause of AKI
due to obstruction of urine flow leading to back pressure and thus loss of concentrating ability
What conditions causes post renal AKI
Ureteric stone
Urinary retention caused by benign prostatic hyperplasia / malignancy
External compression of the ureter
Which type of causes of AKI is the most common
Pre-renal
Which condition is the most common cause of AKI
Acute tubular necrosis
Risk factors of AKI
Other organ failure - HF, liver disease
History of AKI
Chronic kidney disease
>65 years old
Use of nephrotoxic drugs
Contrast exposure within the past week
What are the nephrotoxic drugs
NSAID
ACEi / ARB
Aminoglycosides (gentamicin, streptomycin)
Diuretics
Symptoms of AKI
May experience no symptoms
Reduced urine output
Pulmonary and peripheral oedema
Arrhythmias
Uraemia symptoms (itch, pericarditis, encephalopathy)
What are the uraemia symptoms
Itch
Pericarditis
Encephalopathy
What is the diagnostic criteria of AKI
Rise in creatinine of 26 µmol/L or more in 48 hours
OR
> 50 % rise in creatinine over 7 days
OR
Fall in urine output to <0.5 ml/kg/hour for more than 6 hours in adults (8 hours in children)
OR
> 25% fall in eGFR in children or young adults in 7 days
What is the staging criteria used for AKI
KDIGO (Kidney Disease: Improving Global Outcomes)
Describe stage 1 AKI
Increase in creatinine to 1.5-1.9 times baseline
OR
Increase in creatinine by ≥26.5 µmol/L
OR
Reduction in urine output to <0.5 mL/kg/hour for ≥ 6 hours
Describe stage 2 AKI
Increase in creatinine to 2.0 to 2.9 times baseline
OR
Reduction in urine output to <0.5 mL/kg/hour for ≥12 hours
Describe stage 3 AKI
Increase in creatinine to ≥ 3.0 times baseline
OR
Increase in creatinine to ≥353.6 µmol/L
OR
Reduction in urine output to <0.3 mL/kg/hour for ≥24 hours
OR
The initiation of kidney replacement therapy
OR
In patients <18 years, decrease in eGFR to <35 mL/min/1.73 m2
Investigations for AKI
Bloods - U+E, serum creatinine
Arterial blood gas
Urinalysis
Renal ultrasound if suspect urinary tract obstruction / no other identifiable cause
Autoantibodies
ECG
CXR
What may arterial blood gas show in AKI
Hypoxia if there is pulmonary oedema
What may ECG show in AKI
Hyperkalaemia
- tall T waves
- wide QRS
- Flattening of P waves
What electrolyte imbalance does AKI cause
Hyperkalaemia
Hyperphosphataemia
Acidosis
Management of AKI
ABCDE
- correct hypoxia / hyperkalaemia / hypovolaemia / sepsis
Identify which type of AKI it is and treat
Management of pre-renal AKI
give fluids if the patient is hypovolaemic
- 0.9% NaCl
give IV antibiotics if the patient is septic
Correct hyperkalaemia
Stop nephrotoxic drugs.
What are the nephrotoxic drugs that should be stopped in AKI
NSAID (except aspirin at cardiac protective dose 75mg)
Aminoglycosides
ACEi
ARB
Diuretics
What are the drugs that may be required to be stopped in AKI because it increases risk of toxicity (it is not nephrotoxic)
Metformin
Lithium
Digoxin
How do you correct hyperkalaemia
- IV calcium gluconate
- IV insulin + dextrose / Nebulised salbutamol
- Calcium resonium / loop diuretics / dialysis
How is calcium resonium adminsitered in treating hyperkalaemia
Enema / orally
Enema is more effective
What is the function of IV calcium gluconate in correcting hyperkalaemia
Stabilisation of cardiac membrane
It DOES NOT lower potassium level
What are the agents used to remove potassium from the body to treat hyperkalaemia
Calcium resonium
Loop diuretics
Dialysis - for AKI with persistent hyperkalaemia
What is the effect of IV insulin and nebulised salbutamol in treating hyperkalaemia
Short term shift in potassium to intracellular fluid compartment
It lowers K+ for a short time. K+ will still come out of the ICF eventually so removal of K+ is needed by other agents
Management of renal AKI
give fluids if the patient is hypovolaemic
- 0.9% NaCl
give IV antibiotics if the patient is septic
Correct hyperkalaemia
Stop nephrotoxic drugs.
Nephrology review to identify uncommon causes of renal AKI
Management of post-renal AKI
catheterisation and urologist review
What are the indications for haemodialysis (AEIOU)
Acidosis (severe metabolic acidosis with pH < 7.20)
Electrolyte imbalance (persistent hyperkalaemia > 7 mmol)
Intoxication (poisoning)
Oedema (refractory pulmonary oedema)
Uraemia (encephalopathy or pericarditis)
What is classified as chronic kidney disease
Reduction in kidney function or structural damage or both, present for more than 3 months
Causes of chronic kidney disease
diabetic nephropathy
hypertension
chronic glomerulonephritis
chronic pyelonephritis
polycystic kidney disease
Alport syndrome
SLE
Vasculitis - GPA, EGPA, MPA
What is pyelonephritis
infection of one or both kidneys
What are the most common causes of CKD
Hypertension
Diabetic nephropathy
Symptoms of CKD
Usually asymptomatic
May be symptomatic with pruritus, nausea, oedema, muscle cramps at severe late stage (stage 4 or 5)
What is used to stage CKD
eGFR
What are the variables in eGFR calculation
Serum creatinine
Age
Gender
Ethnicity
Why is serum creatinine used in AKI rather than eGFR
Because eGFR calculations assume that the level of creatinine in blood is stable over days hence eGFR is not used in a unsteady state such as AKI
What factors may affect the eGFR calculation
Severely malnourished
Severely overweight
Bodybuilder
Past organ transplant / amputees
Eating red meat 12 hours prior to sample being taken
Describe Stage 1 CKD
> / 90 eGFR with some sign of kidney damage
No sign of damage = not CKD
Describe Stage 2 CKD
eGFR 60-90 ml/min with some sign of kidney damage
No sign of damage = not CKD
What tests are used to indicate kidney damage for CKD classification
Urinary ACR
Renal ultrasound
Urinalysis - Haematuria/proteinuria
Describe stage 3a and 3b CKD
3a: eGFR 45-59 ml/min with moderate reduction in kidney function
3b: eGFR 30-44 ml/min with moderate reduction in kidney function
Describe stage 4 CKD
eGFR 15-29 ml/min with severe reduction in kidney function
Describe stage 5 CKD
eGFR < 15ml/min = kidney failure
Investigations for CKD
U+E
Urinalysis
Renal ultrasound
What are the complications of CKD (CRF HEALS)
Cardiovascular disease
Renal osteodystrophy
Fluid (oedema)
Hypertension
Electrolyte disturbance
Anaemia
Leg restlessness
Sensory neuropathy (parasthesia)
What is the main cause of death in patients with CKD
Cardiovascular disease
Management of CVD risk in CKD
Smoking cessation, weight loss
Control hypertension
Correct hyperlipidaemia
What are the electrolyte disturbances in CKD
Hyperkalaemia
Hyperphosphataemia
Low vitamin D
Hypocalcaemia
What causes low vitamin D in CKD
because the conversion of vitamin D to its active form occurs in the kidneys
What is renal osteodystrophy
Skeletal complications of CKD
- osteomalacia
- Osteoporosis
- secondary / tertiary hyperparathyroidism
- spinal osteosclerosis (due to hyperparathyroidism)
What is the other name for spinal osteosclerosis
Rugger jersey spine - due to hyperparathyroidism
What causes osteomalacia in CKD
low vitamin D
high phosphate level
Why is there hyperphosphataemia in CKD
Because the kidneys normally excrete phosphate
How does hyperphosphataemia cause osteomalacia
high phosphate level drags calcium from bones
Management of electrolyte imbalance and parathyroid hormone levels for CKD
Reduce diet intake of phosphate
Phosphate binders
Vitamin D tablets
Example of phosphate binders
sevelamer
Function of sevelamer (phosphate binder)
Binds to dietary phosphate and prevent its absorption
has benefits in reducing uric acid and lipids
What are the vitamin D tablets used for CKD
Alfacalcidol
Calcitriol
What is the most common cause of anaemia in CKD
Reduced erythropoietin levels
Management of anaemia in CKD
Check iron status before administration
1. Oral iron
2. IV iron if oral iron is insufficient
3. ESA (erythropoiesis-stimulating agents) + IV iron
Management of hypertension in CKD
ACEi / ARB
Aim for 140/90
Management of dyslipidaemia in CKD
Atorvastatin
Increase dose if 40% reduction in non-HDL cholesterol is not achieved and eGFR is 30 ml/min/1.73 m2 or more
Why is it important to control hypertension and hyperlipidaemia
Because it can contribute to accelerated CKD progression
And it can increase risk of CVD
CKD increases the risk of which type of malignancies
Renal tract cancer
Thyroid gland cancer
Causes of hyperkalaemia
AKI
CKD
Addison’s
Rhabdomyolysis
Drugs
What drugs can cause hyperkalaemia
Aldosterone antagonists (spironolactone / eplerenone)
ACEi / ARB
Heparin
Ciclosporin
Beta blockers in renal failure patients
Symptoms of hyperkalaemia
fatigue
Muscle weakness
Palpitations
Chest pain
(very non-specific)
Investigations for hyperkalaemia
Bloods- U+E, eGFR, serum creatinine
ECG
What is the ECG pattern in hyperkalaemia
Tall T waves
Widened QRS
Flattening / absence of P waves
What is rhabdomyolysis
A condition where skeletal muscle tissue breaks down and releases breakdown products into the blood
Causes of rhabdomyolysis
Seizures
Prolonged immobility
Extremely rigorous exercise beyond the person’s fitness level
Crush injury
Drugs - statin
What drug interactions can cause rhabdomyolysis
Statins can interact with
- clarithromycin
- colchicine
What is released by the muscle cells in rhabdomyolysis
Myoglobin
Potassium
Phosphate
Creatine kinase
Symptoms of rhabdomyolysis
Muscle aches and pain
Red-brown urine
Oedema
Fatigue
Confusion
How is rhabdomyolysis usually presented
A patient who has had a fall / prolonged seizure and is found to have AKI on admission
Investigations for rhabdomyolysis
CK level
Urine - red-brown
ECG - to assess for hyperkalaemia
U+E - for AKI and hyperkalaemia
What level of CK suggests rhabdomyolysis
CK significantly elevated - at least 5 times the upper normal limit
2-4 times is not rhabdomyolysis
What are the results suggesting rhabdomyolysis
CK level at least 5 times higher
Myoglobinuria - red-brown urine
Hypocalcaemia
Hyperphosphate
Hyperkalaemia
metabolic acidosis
Management of rhabdomyolysis
rapid IV fluids
