Oliguria and acute renal failure

Question 1

Discuss acute renal failure

Answer 1

• reduction in glomerular filtration rate by 75%
• threefold increase in creatinine >350 or an acute ris of more then 45
• Anuria >12hours or urine uoutput <0.3ml/kg/hr for 24 hours

Question 2

Discuss pathophysiology of ARF

Answer 2

It should be noted that oxygen extraction of the outer medulla is almost maximum and as such is at high risk of hypoxic damage

Risk factors:

• preexisting renal failure
• long standing hypertension
• DM
• vasuclar disease, abdominal aortic surgery
• crush injury m
• large contrast load
• diuretic-dependent renal function

Question 3

Discuss causes of ARF

Answer 3

Pre-renal

• hypovolaemia
• low cardiac output
• renal vasuclar obtruction, eg constriction, emboli thormbosis, vasculitis, atherosclerosis, abdominal aortic dissection
• hepatorenal syndrome

Parenchymal

• Drugs ++
• – ABs (aminoglycosides)
• –contrast
• –ACE
• –NSAIDS
• pigment related
• –rhybdomyolysis
• –haemolysis
• glomerular cuases
• –immune complex

Post renal
-obstruction via stone or mass

Multifactorial

• • Sepsis
• -abdominal compartment syncrome

Question 4

Discuss management of ARF

Answer 4

1) haemodynamic resuscitation
2) prevention
3) aggresive treatment of sepsis
4) exclusion of obstruction
5) treatment of hyperkalaemia and acid-base disturbance
6) diuretics
7) renal replacement therapy

Question 5

Discuss haemodynamic resuscitation

Answer 5

This involves prompt and adequate resuscitation with rapid and carefully monitored restoration of intravascular filling, blood pressure and cardiac output
MAP of>70-75
Norad might be used to increase renal perfusion once adequate preload has been achieved

Question 6

Discuss prevention

Answer 6

Can be broken into primary and secondary

Primary prevention

• • early adequate resuscitation and avoidance of hypovolaemia
• -avoid nephortoxic ABs if possible
• • radiocontrast nephropathy (give saline hydration)

Secondary prevention
– Aim is to maintain renal perfusion, medullary oxygenation and glomerular filtration by a combination of volume resuscitation, vasopresspr amd avoid further injury

Question 7

Discuss renal replacement therapy in the ICU

Answer 7

The two main forms of renal replacement in ICU are continuous venovenous haemofiltration and inttermittent haemodialysis

Indications

• severe K
• severe metabolic acidosis
• severe pulmonary oedema due to fluid overload
• uraemic patients

Question 8

Discuss rhabdomyolysis

Answer 8

Involves pre-renal, renal and post renal factors

Outcome is good if aggresive fluid rehydration, alkalinization or urine and maintenance of polyuria are achieved

Specific therapy for condition causing rhabdo include

• compartment syndrome reperfusion of ishcaemic muscle and fasciotomy
• control of seizure
• cooling in heatstroke
• specific drugs – dantrolene for malignant hyperthermia