AKI Flashcards
What are some common definitions of AKI?
Solute clearance (urea, creatinine) Urine output (oliguria) Distinguish patients with pre-existing renal impairment Some defined by requirement for dialysis (AKI3)
What is the definitive definition of AKI?
An abrupt (<48hours) reduction in kidney function:
Absolute increase in serum creatinine by >26.4
OR
Increase in baseline creatinine by >50% (1.5 times baseline)
OR
Reduction in UO (harder to measure)
What is stage 1 AKI?
Increase >26 in creatinine or increase in 1.5-1.9x the reference Cr
<0.5ml/kg/hr urine for more than 6 hours
What is stage 2 AKI?
Increase in more than 2-2.9x reference SCr
More than <0.5ml/kg/hr of urine for more than 12 hours
What is stage 3 AKI?
More than 3x reference SCr OR increase to >354 OR need for RRT
Less than 0.3 ml/kg/hr for more than 24 hours or 12 hours of anuria
What are risk factors for AKI?
Older age CKD Diabetes Cardiac failure Liver disease PVD Previous AKI
What exposure risk factors can cause an AKI?
Hypotension Hypovolemia Sepsis Deteriorating NEWS Recent contrast Exposure to certain medications: gentamicin for example
What are the 3 different causes of AKI?
Pre-renal (functional) Renal (structural) Post renal (obstruction)
What causes hypovolemia related pre-renal AKI?
Hemorrhage
Volume depletion - diarrhoea, vomiting, burns
What causes hypotensive related pre-renal AKI?
Cardiogenic shock
Distributive shock - sepsis, anaphylaxis
What can cause renal hypoperfusion?
NSAIDs/ COX-2
ACEi/ ARBs
Hepatorenal syndrome
What is the definition of pre-renal AKI?
Reversible volume depletion leading to oliguria and increase in creatinine
What is normal urine output and therefore what is oliguria?
Normal: 0.5 ml/kg/hr, e.g. 30mls/hr in a 60 kg patient
Oliguria: <0.5 mls/kg/hr
Describe normal renal perfusion?
Decreased renal perfusion causes the release of renin which in turn causes vasoconstriction of the efferent arteriole via angiotensin 2, maintaining GFR
Why does ACEI increase the risk of AKI?
Reduce angiotensin 2, therefore in decreased renal perfusion the kidneys cannot respond normally and the efferent arterioles will stay vasodilated resulting in a decreased GFR
What will untreated pre-renal AKI lead to?
Acute tubular necrosis
What will cause acute tubular necrosis?
Combo of factors leading to decreased renal perfusion
Common causes are sepsis and severe dehydration
How is hydration assessed?
Clinical observations (BP, HR, UO)
JVP, CRT, oedema
Pulmonary oedema
How is pre-renal AKI treated?
Fluid challegnge for hypovolaemia:
Crystalloid (0.9% NaCl) or colloid (gelofusin)
Do NOT use 5% dextrose
Give 250 ml bolus at a time and repeat
Get senior help when 1000ml is used with no affect - needs vasopression
Why is hartmann’s not used in treatment of pre-renal AKI?
Contains potassium
Why is 5% dextrose not used for treatment of pre-renal AKI?
It will not stay in the capillaries so wont increase the circulating volume
What is renal AKI?
Disease causing inflammation or damage to cells causing AKI
Split by structure: blood vessels, glomerular disease, interstitial disease, tubular injury
What are the vascular causes of renal AKI?
Vasculitis - GPA, MPA, goodpasture’s
Renovascular disease
What is the glomerular cause of renal AKI?
Glomerulonephritis
What are the interstitial nephritis causes of renal AKI?
Drugs - penicillins, trimethoprim, NSAIDs, PPI
Infection - TB
Systemic - sarcoidosis
What are the tubular injury causes of renal AKI?
Ischaemia - prolonged renal hypoperfusion
Drugs - gentamicin
Contrast
Rhabdomyolysis
What are the symptoms of AKI?
Constitutional: anorexia, wt loss, fatigue, lethargy
Nausea and vomiting
Itch
Fluid overload - SOb, oedema
What are the signs of AKI?
Fluid overload including HTN, oedema, pulmonary oedema, effusions
Uraemia - itch, pericarditis
Oliguria
What clues in the history can point to a renal cause?
Sore throat (step pyogenes; rheumatic fever) Rash (vasculitis or lupus) Joint pains (lupus and vasculitis) Diarrhoea and vomiting Haemoptysis (TB, GPA, goodpastures)
What can be seen on urinalysis of renal AKI?
Protein and blood - this will NOT be seen in pre-renal
What drugs are important to look out for in renal AKI?
ACEi PPI NSAIDs Gent and vanc Recent contrast
What blood tests can aid in the diagnosis of renal AKI?
Eosinophilia (eGPA, intestitial nephritis; reaction to a drug) Cholesterol microemboli (renal failure and trash foot) CK for rhabdomyolysis
What are you looking for in U&Es?
Marker of renal function (Na, K, Ur, Cr)
Is potassium high - MEDICAL EMERGENCY
Why is an FBC and coagulation screen done in AKI?
Abnormal clotting - DIC in sepsis
Anaemia - lack of erythropoietin
What can urinalysis show in AKI?
Haematoproteinuria in renal AKI
Why is an USS doone in suspected AKI?
Obstruction (postrenal)
Size - hydronephrosis
What immunological markers are done in suspected AKI?
ANA - lupus ANCA - GPA, eGPA, MPA GMB - goodpastures Immunoglobulins C3/4 - lupus
What is protein electrophoresis and BJP done for?
Myeloma
Patient over 50 with hypercalcaemia and anaemia = DO THESE TESTS AND SUSPECT MYELOMA
What will RAS show on ultrasound?
One large kidney
How is a good perfusion pressure established in AKI?
Fluid resuscitate
If still not achieving adequate BP - inotropes/vasopressors
What is the further treatment of AKI?
Treat underlying cause e.g. antibiotics in sepsis
Stop nephrotoxins
Dialysis if remains anuria and uraemia
What are the life-threatening complications of AKI?
Hyperkalemia Fluid overload - pulmonary oedema Severe acidosis (pH <7.15) Uraemic pericardial effusion Severe uraemia (Ur >40)
What is post-renal AKI?
AKI due to obstruction of urine flow leading to back pressure (hydronephrosis) and thus loss of concentrating ability
What can cause post-renal AKI?
Stones
Cancers
Strictures
Extrinsic pressure
What will obstruction look like on USS?
Dilated renal pelvis
How is post-renal AKI treated?
Catheterisation
Nephrostomy
Refer to urology for ureteric stenting
How is hyperkalemia assessed?
ECG - predisposes to VT, VF and bradycardia
Muscle weakness
What level of potassium is considered life-threatening?
More than 6.5
What are the ECG changes of hyperkalemia?
Peaked T waves Prolonged PR interval Depressed ST segment Prolonged QRS Sine-wave pattern (this is peri arrest)
What is the 1st line treatment in hyperkalemia?
Stabilise myocardium
10 ml 10% calcium gluconate over 2/3 mins
What is performed after treatment with calcium gluconate in hyperkalemia?
Need to move K+ back into cells:
10 units actrapid with 50mls 50% dextrose over 30 mins
Salbutamol nebs over 90mins
What is the treatment for chronic hyperkalemia but NOT used in the acute setting?
Calcium resonium
What should you do if someone is severely acidotic with a very low bicarb?
Give sodium bicarbonate
What are the urgent indications of haemodialysis?
Hyperkalemia over 7
Severe acidosis - pH <7.15
Fluid overload - diuretics will NOT work
Urea >40, pericardial rub/effusion
What medicines should you stop on sick days (D+V OR fevers, shakes and sweats)?
ACEi ARB NSAIDs Diuretics Metformin Empagliflozin
Does furosemide cause hyper or hypokalemia?
Hypokalemia
What drugs commonly cause hyperkalemia?
Spironolactone ACEi Amiloride Beta-blockers CCB
What drugs should be avoided in those with AKI?
NSAIDs ACEi/ARB Diuretics Gentamicin IV Contrast for CT Trimethoprim/co-trimoxazole as will cause hyperkalemia and cause increased creatinine Potassium sparing diuretics
