Clinical Topic 1: Acute Kidney Injury Flashcards
What are pre-renal causes of an AKI?
- Hypovolaemia secondary to diarrhoea & vomiting, burns, major haemorrhage, shock, heart failure
- Renal artery stenosis
- Renal vein thrombosis
What drugs should definitively be stopped during an AKI, as it may worse it? 5 examples
What drugs should also be stopped during an AKI, which will increase in toxicity but not necessarily worsen the AKI?
- NSAIDs
- Aminoglycosides
- ACE Inhibitors
- ARBS
- Diuretics
- Digoxin
- Metformin
- Lithium
How can you prevent an AKI in patients about to have an investigation with contrast agent?
Give IV fluids before and after the investigation
What is the acute management of patients with Hyperkalaemia?
- Calcium gluconate (first-line, to protect cardiac membrane)
- Insulin/dextrose infusion and salbutamol (short term movement of K intracellularly)
- Loop diuretics / Dialysis (to remove K+)
Is Aspirin safe to use during an AKI?
ONLY if low dose at 75mg OD
What are the two main causes of Renal Artery Stenosis? What do they characteristically appear like on renal arteriography?
- Atherosclerosis: Narrowing of renal artery proximal to aorta
- Renal fibromuscular dysplasia: “String of beads” appearance of renal artery distal to aorta
What abdominal examination finding is characteristic of renal artery stenosis?
Renal artery bruit
What is the pathophysiology of Renal Artery Stenosis? What are the symptoms / signs of this condition?
Reduced perfusion to kidneys causes activation of RAAS, leading to a persistent HTN. There is also atrophy and fibrosis of the kidney
Symptoms: Persistent HTN, headaches, blurry vision, possible stroke / MI
Oligouria is defined as what?
< 0.5 ml / kg / hr
What is Stage 1, 2 and 3 Acute Kidney Injury defined as?
Stage 1:
1.5-2x increase in Creatinine
<0.5ml/kg/hr for 6-12 hours
Stage 2:
2-2.9x increase in Creatinine
<0.5ml/kg/hr for >12 hours
Stage 3:
3x increase in Creatinine
<0.3ml/kg.hr for >24 hours OR
Anuria for >12 hours
What is the most common intra-renal AKI?
Acute Tubular Necrosis
Acute Tubular Necrosis commonly affects which aspects of the kidneys?
Proximal Convoluted Tubule
Thick Ascending Limb
What are the causes of Acute Tubular Necrosis? Toxic vs. Ischaemic
- Ischaemic i.e. due to hypotension (shock, sepsis)
- Toxins i.e. aminoglycosides, myoglobin (rhabdomyolysis), anti-freeze, radio-contrast dye, uric acid
What are the clinical features of Acute Tubular Necrosis?
Muddy brown casts
In someone with Pre-renal failure, what is the sodium concentration of the urine likely to be? Why?
< 20 mmol / L
Renal tubular function is preserved so reabsorption of sodium is preserved and in fact increased
In someone with acute tubular necrosis, what is the sodium concentration of the urine likely to be? Why?
> 30 mmol / L
Renal tubular function is damaged hence reabsorption of sodium does not occur
In someone with Pre-renal failure, what is the osmolality of the urine likely to be? Why?
High
Renal tubular function is preserved so reabsorption of water occurs
In someone with acute tubular necrosis failure, what is the osmolality of the urine likely to be? Why?
Low
Renal tubular function is lost so rebabsorption of water does not occur hence is excreted in urine
What is the affect of ACEI on the afferent / efferent arterioles?
Vasodilation of efferent arteriole
What is the effect of NSAIDs on the afferent / efferent arterioles?
Vasoconstriction of afferent arteriole
How does angiotensin II act to increase the filtration fraction in the kidney?
Vasoconstriction of efferent arteriole