AKI Flashcards
What is AKI?
Acute (usually reversible) decreased renal function occurring over hours to days.
How is AKI defined using creatinine and urine output?
1) Rise in creatinine of 26micromol/l or greater within 48 hours
2) Rise in creatinine 1.5x baseline or greater within 7 days
3) Urine output <0.5ml/kg/h for >6 consecutive hours
What is a stage 1 AKI?
Rise of creatinine of 26 micromol/l or more OR 1.5-1.99x baseline OR Urine <0.5ml/kg/h for 6 hours
What is a stage 2 AKI?
2.0-2.99x baseline
OR
Urine <0.5ml/kg/h for 12 hours
What is a stage 3 AKI?
Rise of creatinine to 353.6 micromol/l or more
OR
3.0x baseline
OR
Urine <0.3ml/kg/h for >24 hours or anuria for 12 hours
Pre-renal causes of AKI (4 classes)
most common
Decreased vascular volume e.g. haemorrhage, D+V, burns, pancreatitis
Decreased cardiac output e.g. cardiogenic shock, MI
Systemic vasodilation e.g. sepsis, drugs
Renal vasoconstriction e.g. NSAIDs, ACE-i, ARB, hepatorenal syndrome
Renal causes of AKI
Intrinsic damage to the glomeruli, renal tubules or interstitium e.g. glomuleronephritis, acute tubular necrcosis, acute interstitial nephritis, rhabdomyolysis, tumour lysis syndrome, vasculitis, thrombosis, toxins and drugs
Post-renal causes of AKI
Ureteric stone, malignancy, stricture, clot, or compression from outside e.g. pelvic malignancy, BPH, retro-peritoneal fibrosis
Symptoms + signs
May have none
Reduced urine output
Pulmonary and peripheral oedema
Arrhythmias (due to changes in potassium and acid-base balance)
Features of uraemia e.g. pericarditis or encephalopathy (confusion, fatigue, drowsiness)
Dehydration
Nausea and vomiting, diarrhoea
Pathological consequences of AKI
Rise in molecules that they kidneys normally excrete
–> hyperkalaemia, uraemia, high creatinine
Oliguria –> fluid overload
ECG changes in hyperkalaemia
Tall-tented T waves, small P waves, widened QRS leading to a sinusoidal pattern and asystole
How to manage hyperkalaemia? (6)
10-20ml calcium gluconate 10% by slow IV injection
IV soluble insulin (5-10 units) with 50ml glucose 50% given over 5-15 minutes
Salbutamol nebs
Consider sodium bicarbonate infusion
Stop exacerbating drugs
May need haemodialysis
How to diagnose AKI?
U+E
Urinalysis
Renal USS if no identifiable cause or at risk of obstruction
Renal biopsy if possibility of vasculitis/AIN/GN
How to manage uraemia?
Dialysis
How to manage met. acidosis?
Sodium bicarb
How to manage AKI
Supportive
Stop meds e.g. NSAIDs, ACE-I, ARB, diuretics
Involve nephrology if severe or cause unknown
Involve urology if obstruction
RRT used if not responding to medical treatment
How to do fluid balance assessment
Consider fluid requirements e.g. if trauma, sepsis, burns, D+V, diuretics
Ask about these in the history + symptoms of dehydration/overload
Inspect - age, recent surgery, oedema, colour, drains, catheter, stoma etc.
Obs + fluid balance charts + daily weights + stool chart + drug chart +op note
Hands + arms - inspect, temperature, pulse, cap refill, BP, skin turgor
Face + neck - mucous membranes, sunken eyes, conjunctival pallor, JVP
Chest + abdomen - resp rate, central cap refill, heart sounds, lungs, sacral oedema, ascites
Legs - oedema
Outputs - urine volume + colour, drain quantity, wound losses
What are the two main causes of ATN?
Ischaemia and nephrotoxins
What are the features of ATN?
raised urea, creatinine, potassium, muddy brown casts in the urine
How can pre-renal uraemia be distinguished from ATN?
In pre-renal, the kidneys hold on to sodium to preserve volume so…
Urine sodium low sodium excretion low, urine osmolality high
There are brown granular casts in urine
Good response to fluid challenge in pre-renal
When is RTT indicated?
Signs of uraemia e.g. encephalopathy, pericarditis
Not responding to med treatment
