Case 13 - Acute Kidney Injury Flashcards
How is an AKI staged?
Via KIDIGO guidelines (how raised creatinine is)
Stage 1 - creatinine 1.5-2 x baseline
Stage 2 - creatinine 2-3 x baseline
Stage 3 - >3 x baseline
Which class of drugs should be suspended in an AKI and why?
ACE inhibitors / Angiotensin receptor blockers
NSAIDS
Aminoglycosides e.g, Gentamicin
They cause nephrotoxicity
Also consider stopping metformin
What are the pre-renal causes of an AKI?
Anything that causes reduced renal perfusion:
- Dehydration
- Sepsis
- Hypotension
- Shock
- Hepatorenal syndrome
- Renal artery stenosis
- Severe heart failure
- Intra abdominal hypertension /compartment syndrome
What are the Intra-renal causes of an AKI?
Drugs: NSAIDS, ACEi / ARBs, Gentamicin Glomerulonephrisis/vasculitis Contrast Acute tubular nephrosis (ATN) Interstitial nephritis (inflammation of kidney) Myeloma (Plasma cell cancer) Rhabdomyolysis
What are the post-renal causes of an AKI?
Prostate enlargement
Renal stones
Pelvic cancer
What are recommend criteria for diagnosing an AKI?
Rise in creatinine >26umol/L in 48 hours
Rise in creatinine >1.5 x baseline (best figure in last 3/12)
Urine output <0.5mL/kg/hr for 6 consecutive hours
What are the risk factors for developing an AKI?
Age > 75 years Chronic kidney disease Cardiac failure Peripheral vascular disease Chronic liver disease Diabetes Drugs Sepsis Poor fluid intake History of urinary symptoms
What are the signs and symptoms for an AKI?
Note: there may be no signs
Main signs: fatigue, malaise, rash, joint pains, nausea, vomiting, chest pain, palpitations, SOB, fluid overload, abdominal pain, oliguria (urine output less than 0.5mL/kg/hr), hypo or hypertension
What is the most urgent management in an AKI?
Assess potassium status
U&Es
Urgent ABG/VBG to check K+
ECG to look for signs of hyperkalamia
What are the main goals of treatment in an AKI?
Treat any life threatening hyperkalaemia
Treat hypotension by giving fluids
What would be raised on blood tests if a patient was dehydrated?
Urea (significantly raised)
Creatinine
Albumin
Heamtocrit
What are the ECG changes in severe hyperkalamia
Small or indiscernible p waves - low and flat
Wide QRS complex (similar to LBBB)
Slurring of S-T segment
Peaked T waves (think lots of Pot, lots of Tea)
How do you treat acute hyperkalaemia in adults?
Stabilise cardiac membrane - 10mL 10% calcium gluconate IV via a big vein over 2 mins, repeat until ECG improves
Give intravenous insulin + dextrose (glucose) - insulin stimulates intracellular uptake of K+, lowering the serum K+ by 1-2mmol/L over 60 mins
Alternately nebulised salbutamol
What is the definition of an acute kidney injury?
A clinical syndrome characterised by a rapid reduction in renal excretory function due to several different causes
What specific things would you look for on an examination of someone with an AKI?
Do full systemic examination Look specifically for: - Palpable bladder - Palpable kidneys - Abdominal/pelvic masses - Renal bruits (sign of renovascular disease) - Rashes
What tests and investigations would you do in a suspected AKI?
Bloods: U&E, LBC, LFT, clotting, CK, ESR, CRP
ABG
Urine dipstick - look for blood and protein
Urine culture - look for urine infection
Renal tract USS - look for obstructed kidneys (hydronephrosis)
Chest X-Ray (if signs of fluid overload) - look for pulmonary oedema or pneumonia
Stool culture - look for pathogens causing diarrhoea
Why do you have to check kidney function before offering contrast investigations?
Contrast can be nephrotoxic
Why is a urine dipstick in investigating a possible AKI?
+ proteinuria indicates intrinsic renal disease
If urine dipstick negative then this can exclude intrinsic renal disease - can look for pre and post renal causes
What should you consider if both blood and protein are positive on a urine dipstick?
Glomerulonephtitis
When is dialysis indicated in an AKI?
Persistent Hyperkalemia (K+ >7mmol/L) Severe Metabolic acidosis (pH <7.2 or base excess <10) Refractory pulmonary oedema Uraemia encephalopathy (confusion, myoclonic jerks, seizures, coma) Uraemia pericarditis (pericardial rub)
Why is creatinine used as a marker of glomerular filtration?
It is normally completely filtered by the kidneys and therefore will only rise in the blood when the kidney is damaged
Why are the renal tubules particularly susceptible to ischaemic damage during dehydration?
There is very little blood flow to the renal tubules (particularly in the medulla) - this is in order for the countercurrent multiplication mechanism to work
When you are dehydrated, blood flow to the kidney is reduced, resulting in ischaemia
How does the RAAS system help to maintain renal blood flow?
When little blood flow reaches the juxtaglomerular apparatus
Kidneys release renin
Renin converts angiotensiongen to angiotensin I
ACE converts angiotensiongen I to angiotensin II
Angiotensin II causes aldosterone secretion
Aldosterone causes more sodium is reabsorbed
This increases blood pressure to allow more perfusion to the kidney
What is acute tubular necrosis?
A condition usually due to the combination of factors which cause renal ischaemia and toxicity
e.g, hypotension, dehydration, sepsis with associated nephrotoxic drugs
