Acute Renal Failure Flashcards
What is the AKI?
A rapid deterioration in renal function occuring over hours and days.
Measured by serum urea and creatinine.
- failure to maintian electrolytes and acid base balance
What is the amount of urine that should normally be produced per hour?
0.5ml / Kg / hour
how common is AKI?
AKi occurs in 18% of hospital patients
What is the criteria for diagnosing AKI
1) Rise in creatinine >26umol/L in 48h
2) greater than 1.5X baseline.
3) Urine output <0.5ml/Kg/hour for more than 6 consecutive hours
What is the criteria for STAGE 1 AKI?
1) Serum creatinine rise by 1.5X baseline OR more than 26umol/L in 48hrs.
2) Urine output is less than 0.5mL/Kg/hour for 6 consecutive hours
What should the normal creatinine level be?
70 - 150 umol/L
What is the criteria for STAGE 2 AKI?
1) Serum creatine rise 2-2.9 X baseline.
2) Urine output of less than 0.5ml/kg/h for 12h
What is the criteria for STAGE 3 AKI?
1) Serum creatinine rise more than 3X baseline or >354umol/L
2) urine output of less 0.3mL/Kg/h for 24 h (or anuria for 12h)
What are the causes of raised creatinine other than altered renal function?
- high muscle mass
- red meat ingestion
- rhabdomyolysis (muscle damage)
What are the pre-renal causes of AKI?
Pre-renal = reduced perfusion leads to fall in GFR.
Hypovolaemia:
- dehydration,
- haemorrhage
- vomiting
(cirrhosis / Sepsis —-> hypotension)
(cardiac failure / cardiogenic shock —> low cardiac output)
Drugs:
- diuretics
- NSAIDs
- ACEi (renal stenosis —> AKI)
- amphotericin B
What are the intra renal causes of AKI?
Renal = (damage to tubule, vessel or glomerulus)
- acute tubular necrosis
- nephrotic syndrome
- scarring from pyelonephritis
Vascular
- vasculitis
- cholesterol embolus
- glomerulonephritis
-gentamicin
What are the post renal causes of AKI?
Post renal = obstruction —> can’t pass urine —-> back pressure affects function.
What are the symptoms of AKI?
Uraemia:
- loss of appetitie
- nausea + vomiting
- pruritis (itch)
Neuro:
- drowsiness
- fits
- coma
Bleeding:
- epistaxis (nose bleed)
- GI bleed
What are the metabolic complications of AKI?
- hyperK+
- metabolic acidosis
- HypoNa (in fluid overload)
- Pulmonary oedema due to salt and water retention
What are the invx done for AKI?
1) identify if pre-renal, renal, or post renal cause. Identify if acute or acute of CKD.
2) Urine dipstick (nitrites? Leuc? haem?)
3) MSU (look for red cells - glomerulonephritis, protein?)
4) Kidney injury molecule 1,neutrophil gelatinase associated lipocalin. (rises within few hours of AKI.
5) Bloods FBC U+E (serum urea, electolytes, creatinine,) calcium LFTS (albumin, alk phos) serum phosp Coagulation screen Blood cultures
How is AKI managed?
- monitor fluid balance and electrolytes
- daily weight
- lying standing BP
- withhold nephrotoxins
- treat hyper K+ with IV sodium bicarbonate.
- Treat pulmonary oedema with IV furosemide
- Sepsis treat with IV Abx
- renal replacement therapy ( haemodialysis and haemofiltration) if hyperK+ not controlled, Pulmonary oedema unresponsive to diuretics, removal of nephrotoxic drugs.
When would renal replacement therapy (haemodialysis and haemofiltration) be used to treat AKI
1) symptomatic Uraemia (pericarditis)
2) HyperK+ (that is uncontrollable)
3) Pulmonary oedema (unresponsive to diuretic)
4) sever acidosis
5) removal of nephrotoxic drugs e.g. gentamicin, lithium, severe aspirin overdose.
What are the complications of HyperK+?
life threatening as it can cause cardiac dysrhythmias, particularly ventricular fibrillation.
What are the risk factors for AKI?
Vascular:
- Cardiac failure
- Peripheral vascular disease
Infective:
- sepsis
- history of urinary symptoms
Metabolic:
- Diabetes
Iatrogenic:
- Nephrotoxic drugs (gentamicin, lithium, aspirin overdose)
- Poor fluid intake
Degenerative:
- CKD
- Chronic liver disease
Other
- Age 75+
How can you tell if its AKI or CKD?
- if kidneys are small on USS then suspect CKD
Signs of chronic disease:
- low Ca2+
- high phosphate
- anaemia
Previous blood results showing high creatinine / low GFR
