Renal 2- acute kidney injury and nephritic/ nephrotic syndrome

Question 1

Definition of AKI

Answer 1

A rapid (within hours to days) fall in glomerular filtration rate which impedes the kidney’s normal functions

Question 2

AKI stage 1

Answer 2

Increase in serum cratinine of 26 micromol/ litre or more within 48 hours

OR

1.5-2x increase from baseline

Less than 0.5ml/kg/hour for more than 6 hours

Question 3

AKI stage 2

Answer 3

Increase in serum creatinine to more than 2-3x from baseline

Less than 0.5ml/kg/hour for more than 12 hours

Question 4

AKI stage 3

Answer 4

Increase in serum creatinine to more than 3x from baseline

OR

Serum creatinine more than 354 micromol/litre with an acute increase of at least 44 micromol/litre

Less than 0.3ml/kg/hour for 24 hours or anuria for 12 hours

Question 5

What is creatinine?

Answer 5

A normal product of muscle turnover

Non-toxic

Transported by the blood and excreted by the kidneys

Used as a surrogate marker for glomerular filtration

Less filtration -> less creatinine removed -> a creatinine rise

GFR is estimated from creatinine results

Question 6

Normal range of creatinie

Answer 6

In Brighton 60-100 micromols/litre

What is normal for one patient may not be for another

Question 7

Oliguria

Answer 7

<0.5ml/kg/hour urine output

Usually <500ml/ 24 hours in adults

Question 8

Anuria

Answer 8

Officially would mean no urine output

Softly defined as <100ml/ 24 hours

Question 9

Four phases of AKI

Answer 9

Onset phase

Oliguric/ anuric phase

Polyuric/ diuretic phase

Recovery phase

Question 10

Onset phase- hours to days

Answer 10

Common triggering events

• significant blood loss
• burns
• fluid loss
• diabetes insipidus

Renal blood flow 25% of normal

Tissue oxygenation 35% pf normal

Urine output below 0.5ml/kg/hour

Question 11

Oliguric/ anuric phase- 8-14 days or longer depending on nature of AKI

Answer 11

Urine output below 400ml/day, possibly as low as 100ml/day

Increase in BUN and creatinine levels

Electrolyte disturbances, acidosis and fluid overload (from kidney’s inability to excrete water)

Question 12

Diuretic phase- 7-14 days

Answer 12

Occurs when AKI is corrected

Renal tubule scarring and oedema

Increased GFR

Daily urine output above 400ml

Possible electrolyte depletion from excretion of more water and osmotic effects of high BUN

Question 13

Recovery phase- several months to 1 year

Answer 13

Decreased oedema

Normalisation of fluid and electrolyte balance

Return of GFR to 70% or 80% of normal

Question 14

Kidney functions

Answer 14

Excretion of toxins

Electrolyte balance

Acid base balance

Fluid balance

NP control

Control of bone metabolism, vit D activation, phosphate excretion

Production of erythropoietin

Question 15

Hyperkalaemia

Answer 15

K+ >6.0 = bad

K+ >6.5 = medical emergency

ECG

• reduced P wave with widened QRS
• tented T waves
• sine wave pattern

Question 16

Fluid overload

Answer 16

Symptoms

• breathlessness
• orthopnoea
• limb swelling

The danger- pulmonary oedema- severe tissue hypoxia

If patient is oliguric/ anuric they won’t be able to get rid of excess water

Question 17

When to think about dialysis

Answer 17

1. Refractory hyperkalaemia
2. Pulmonary oedema
3. Refractory acid/ base disturbance
4. Uraemic complications (coma, pericarditis)

Question 18

What causes AKI?

Answer 18

1. Pre-renal causes
2. Renal causes
3. Post-renal causes

Question 19

Pre-renal causes

Answer 19

Decrease in perfusion pressure resulting in ischaemia or infarction

• bleeding
• septic shock
• dehydration
• myocardial infarction
• iatrogenic
• renal artery stenosis

VERY LIKELY

Question 20

Renal causes

Answer 20

Direct toxic effects

• drugs
• calcium and other metals

Overproduction leading to blockage of the tubules

• rhabdomyolysis
• myeloma

Inflammation in the kidney

• GN
• interstitial nephritis
• ATN

UNLIKELY

Question 21

Post renal causes

Answer 21

Plumbing problem/ outflow obstruction

• stones
• ureteric/ urethral strictures
• BPH
• prostate cancer
• urinary retention e.g. neurogenic, constipation

Relatively LIKELY

Question 22

Who is at risk of AKI?

Answer 22

Chronic background risk:

• elderly
• CKD
• cardiac failure
• liver disease
• diabetes
• vascular disease
• background nephrotoxic medications

Acute risk:

• S: sepsis and hypoperfusion
• T: toxins
• O: obstruction
• P: parenchyma

Question 23

Predict/ prevent AKI- the 4 Ms

Answer 23

Monitor
- obs/NEWS, regular blood tests, fluid balance charts, pathology alerts

Maintain circulation
- hydration, resuscitation, oxygenation

Minimise kidney insults
- nephrotoxic meds, surgery, contrast, hospital acquired infection

Mange the acute illness
- sepsis, heart failure, liver failure

Question 24

Treatment of AKI

Answer 24

Make the patient safe

• ABCDE
• what is K+
• what is volume status

If hypovolaemic give 250/500ml bolus of saline

Monitoring

• check catheter
• strict fluid inputs/ outputs
• check VBG

Investigate the cause once stable

Question 25

Red flags in history

Answer 25

Haemoptysis

Rashes

Joint pain/ swelling

ENT- crusting of nose/ acute hearing impairment

Significant acute limb swelling

Noticeable urine frothiness

Jaundice

Question 26

Drugs to hold in AKI

Answer 26

ACE inhibitors

Angiotensin receptor blockers

NSAIDS: ibuprofen, diclofenac, naproxen

Any diuretics

Metformin

Question 27

Causes of polyuria

Answer 27

Known and common phase of AKI of any cause

Post relief of obstruction

Diabetes mellitus

Psychogenic

Beer potomania

Rare endocrine causes (e.g. diabetes insipidus)

Question 28

Managing polyuria

Answer 28

Encourage the patient to drink

Depending on your assessment of fluid balance

• provide IV fluids to match the output +/- additional input if dry
• once renal function begins to improve reduce to 75% of urine output

Question 29

Managing oliguria

Answer 29

Depending on your assessment of fluid balance

If you have given 2-3 litres and can’t see blood on the floor ask for help