Renal - AKI 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 rise2: 2-3x Rise 0.5mg/kg/hr > 12 hours3 >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 loadRise 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>75Underlying renal disease Pre-renal - hypovolaemia/hypoaxemia, sepsis, cardiac failure Renal - DM, vascular disease, renal art. stenosis Post renal - calculi, obstructionNephrotoxics - NSAID, gentamicin, ACEi, ARBsIV instead of oral contrastRisk increasing with increasing load
Prevent contrast induced nephropathy
1) does it even exist2) Avoid contrast if at risk - different imaging3) If you must, low dose, avoid repeat doses, low osmolality4) stop other nephrotoxics5) Pre load with saline6) NAC (no good evidence)7) BicarbRRT
Managing AKI - principles
ABCDE treat as foundSTOP-AKIS - Sepsis - treat and ensure euvolaemiaT - Toxins - stop nephrotoxicsO - Obstruction - US and catheterP - Primary renal - Urine dip, viral screen, immuno, antibodies etc
Indications for RRT
1) persistent metabolic acidosis2) refractory pulmonary oedema3) symptomatic uraemia4) hyperkalaemia5) Overdose 0 lithium, aspirin
Principle of CVVHF
Filtration, uses CONVECTIONAims to mimic glomerular filterBulk flow of solute/water down hydrostatic pressure gradientAcross semi-permeable membrane
Principle of CVVHD
Uses diffusionAims to replicate counter currentCounter current of blood to dialystateDiffusion down CONCENTRATION gradient across semi-permeable membraneApply 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 diffusionSCUF - uses ultrafiltartion without changing biochemistryIntermittant HD
How to prescribe RRT
1) Continuous or intermittant2) HF or HD Convection good for clearing middle molecules, Diffusion form smaller3) Dose of effluent (how much filtrate made) 25-35mls/kg/hour Higher rates do not get better outcomes4) Pre/post filter replacement5) Fluid balance6) 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 filterReduces viscosity of blood - less clottingBut reduces solute clearencePost - after filterBut shortens life of the filterUsually a 30:70 ratio
