Red Book - Acute Kidney Injury Flashcards
Which system classifies AKI
KDIGO (Kidney Disease: Improving Global Outcomes)
Previously there was AKIN and RIFLE
Classify AKI
1: 1.5-2x Creatinine from base UO 0.5mg/kg/hr fo6 6-12 hrs
OR 26.5 umol/l rise
2: 2-3x Rise 0.5mg/kg/hr > 12 hours
3 >3x rise 0.3mg/kg/hr >25 hours
OR >354 umol/l ruse Anuria for 12
OR needs RRT
Definition of a Contrast Induced Nephropathy
Development of AKI within 48 hours of contrast load
Rise in serum Cr by 44umol/l
OR rise by 25% from baseline within 48 hours of procedure
Potential mechanisms of CIN
Direct nephrotoxicity of ROS
Impaired vasoconstriction/dilation
Increased O2 consumption
Contrast dieuresis
Increased urine viscosity
Risk facts for contrast AKI
Age>75
Underlying renal disease
Pre-renal - hypovolaemia/hypoaxemia, sepsis, cardiac failure
Renal - DM, vascular disease, renal art. stenosis
Post renal - calculi, obstruction
Nephrotoxics - NSAID, gentamicin, ACEi, ARBs
IV instead of oral contrast
Risk increasing with increasing load
Prevent contrast induced nephropathy
1) does it even exist
2) Avoid contrast if at risk - different imaging
3) If you must, low dose, avoid repeat doses, low osmolality
4) stop other nephrotoxics
5) Pre load with saline
6) NAC (no good evidence)
7) Bicarb
RRT
Managing AKI - principles
ABCDE treat as found
STOP-AKI
S - Sepsis - treat and ensure euvolaemia
T - Toxins - stop nephrotoxics
O - Obstruction - US and catheter
P - Primary renal - Urine dip, viral screen, immuno, antibodies etc
Indications for RRT
1) persistent metabolic acidosis
2) refractory pulmonary oedema
3) symptomatic uraemia
4) hyperkalaemia
5) Overdose 0 lithium, aspirin
Principle of CVVHF
Filtration, uses CONVECTION
Aims to mimic glomerular filter
Bulk flow of solute/water down hydrostatic pressure gradient
Across semi-permeable membrane
Principle of CVVHD
Uses diffusion
Aims to replicate counter current
Counter current of blood to dialystate
Diffusion down CONCENTRATION gradient
across semi-permeable membrane
Apply a pressure difference - FLUID REMOVAL
What affects rate of fluid removal in HF
Proportional to:
Blood flow rate
Hydrostatic pressure gradient
Membrane surface area
Other RRT modes
CVVHDF - combines convection and diffusion
SCUF - uses ultrafiltartion without changing biochemistry
Intermittant HD
How to prescribe RRT
1) Continuous or intermittant
2) HF or HD
Convection good for clearing middle molecules, Diffusion form smaller
3) Dose of effluent (how much filtrate made)
25-35mls/kg/hour Higher rates do not get better outcomes
4) Pre/post filter replacement
5) Fluid balance
6) Anticoagulation
What should you aim to reduce urea by to prevent disequilibrium
30% or less in first 24 horus
Advantages/Disadvantages of pre/post dilution
Pre - fluid before filter
Reduces viscosity of blood - less clotting
But reduces solute clearence
Post - after filter
But shortens life of the filter
Usually a 30:70 ratio
