Acute Kidney Injury

1
Acute Kidney Injury

• Dr Rob Lewis
• Consultant in Intensive Care
• Ipswich Hospital

2
Introduction

• Normal functions of the Kidney
• Classical description of renal failure
• Acute Kidney Injury/Failure
• RIFLE Classification
• Incidence within Intensive Care
• Sepsis and AKI
• Mortality
• Treatment and Prevention
• Myths

3
Normal Kidney Function

• Fluid Balance
• Electrolyte Control
• Acid-base balance
• Metabolism and Excretion
• Hormone production
• Erythropoietin production

4
Classical approach

• Three classic causes
• Pre-renal failure
• Hypovolaemia, hypotension
• Intrinsic renal failure
• Acute Tubular Necrosis,
• Toxic injury
• Post-renal failure
• Renal outflow tract obstruction

5
Acute Kidney Injury

• Spectrum of disorders from reduced function to
  established failure
• Multi-factorial causes
• Associated with reduced Glomerular filtration and
  Oliguria, which may initially be appropriate.
• Involves sub lethal damage causing depolarization
  and loss of normal function
• Cell death through necrosis and apoptosis

6
RIFLE classification
7
RIFLE classification

• Represents
• 3 Classes of increasing severity
• 2 Outcome groups
• Shift from supposed pathologies i.e. ATN
• Clinical spectrum with associated morbidity and
  mortality

8
Incidence In ICU

• 67 of Critical care patients have AKI
• 12 class R
• 27 class I
• 28 class F
• However more than half of patients with class R
  will progress to either class I or F
• Hoste et al Crit Care 2006

9
Incidence in ICU

• Approximately 5 of patients in general intensive
  cares will require RRT
• Equates to 200-300 per million population
• Similar numbers to severe sepsis or ARDS
• 10-20 of surviving patients require ongoing RRT
  beyond hospital discharge

10
Sepsis and AKI

• Sepsis accounts for nearly 50 of all causes of
  AKI
• Combination of Factors
• Immunological
• Toxic
• Inflammatory
• Effect renal microvasculature and Tubular cells

11
AKI and Mortality

• AKI is an independent risk factor for death
• Patients dont just die with AKI they die because
  of AKI
• RIFLE class F have a mortality of 57
• RIFLE class I 45
• RIFLE class R 21
• Compared to 8.4 of patients without AKI
• Ostermann M, Chang RW CCM 2007

12
AKI and Mortality

• As already mentioned rising RIFLE class
  associated with increasing mortality
• Despite advances in critical care medicine and
  technology, patients who are treated with RRT
  still have a mortality of 50-60

13
Treatment

• Prevent it in the First Place!!
• Treat / Remove the Cause
• Restore adequate circulating Volume
• Restore adequate blood pressure
• Restore adequate flow
• Control fluid intake
• Wait, Patience is a virtue!
• Renal replacement therapy

14
Prevention

• Early intervention and resuscitation
• Little evidence available
• Mainly in Contrast induced AKI
• Best evidence for volume loading with isotonic
  fluid
• Sodium Bicarbonate may be better than Normal
  Saline
• N-Acetylcysteine shown to reduce risk

15
Myths

• Frusemide
• Theoretically may reduce tubular injury
• Due to shutting down Na/K/Cl ATPase
• Reduces oxygen demand
• May help with fluid balance
• But
• No clinical evidence
• Accumulates in Oliguria
• Nephrotoxic and Ototoxic
• May actually increase mortality and or need for
  RRT

16
Myths

• Dopamine
• Low dose Dopamine (2-3mcg/kg/min), known as
  renal dose
• No effect on mortality or need for Renal
  replacement therapy

17
Myths

• Vasopressors and AKI
• Although Noradrenaline causes vasoconstriction
  with renal vasculature
• No evidence of worsening AKI
• But should be used after adequate volume
  resuscitation

18
Myths

• Mannitol
• Currently no evidence of protective effect
• Causes an osmotic diuresis with may benefit fluid
  balance

19
Questions?