Acute Renal Failure Flashcards
What is acute renal failure?
Decreased GFR leading to the retention of nitrogenous wastes
How can acute kidney injury be classified? On what basis are they classified?
Risk Injury Failure Loss End-stage kidney disease
Classified based on proportion of serum creatinine increased and urine output decrease
What are etiologies for pre-renal acute kidney injury?
Insuffient blood flow to kidney
- dehydration
- hypoxia
- ischemia
- hypotension
- decreased circulatory volume
- anesthesia
- hypoadrenocorticism
- trauma
- surgery
- heatstroke
- hypoalbuminemia
- hypoperfusion
What are renal etiologies of acute kidney injury?
Renal hypoperfusion -> tubular hypoxia Obstruction Vasoconstriction Thrombosis and DIC Transfusion rxn Infectious (Leptospirosis) Immune mediated Neoplasia Secondary to systemic dz Nephrotoxic s
What are some nephrotoxic agents?
Ethylene glycol
NSAIDS
Aminoglycosides
Radiocontrast agents Trimethoprim sulphonamides Methotrexate Cyclosporine Cimetidine Dextran 4 Heavy metal Raisins
Myoglobin (endogenous)
What are post-renal etiologies of acute renal injury?
Urine leakage -> lead to uroabdomen/septic peritonitis
Obstruction -> pressure on collecting tubule disrupt aquaporins and distrust normal hydrostatic and oncotic pressure
What are the 4phases of acute renal failure?
Initial -> extension -> maintenance -> recovery
What is the initial phase of acute renal failure?
No clinical signs
Triggered by ischemic event
Definable by a decrease in urine output or increase in creatinine
What is the extension phase of acute renal failure?
Continued hypoxia and inflammation
Proximal tubule most susceptible to toxic ischemic damage
Compromised Na:K pumps -> cells swelling and damage
Increased cytosolic Ca
Loss of brush border or apical and basal cell surfaces
What is the maintenance phase of acute renal failure?
1-3weeks duration
Urine output is increased or decreased
Urine=ultrafiltate
What is the recovery phase of acute renal failure?
Polyuria
Extreme Na loss
Weeks to months to recover
What causes of acute tubular necrosis (intrinsic renal failure)?
Intra-renal vasoconstriction
Tubular dysfunction
What are causes of intra-renal vasoconstriction ?
Imbalance between the vasoconstrictors (endothelium) and vasodilator (NO)
Endothelial injury
Decreased O2
ATP-> AMP (energy deficit)
Mitochondrial damage
Oxidant injury
Na/K pump stops working- cellular swelling
Intracellular acidosis
Intracellular hypercalcemia
What are causes of tubular dysfunction?
Tubular obstruction from crystals or detached RTE cells
Cytoskeletal injury with loss of polarity
Loss of tight junctions between cells
Cell necrosis
What are risk factors for acute renal failure?
Dehydration, hypovolemia
Anesthesia
Hypoxia
Systemic inflammatory response syndrome
What are renoprotective drugs?
Ca channel blockers
Selective DA-2 receptor agonists (vasodilation)- dopamine
Selective DA-1 receptor agonists- fenoldopam
Erythropoietin analogs
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How can you prevent acute renal failure ?
BP > 80mmHg
CVP < 10mmHg
Correct hypoxia
- PCV > 30%
- SpO2>96%
- PaO2>80mmHg
ECG - avoid hyperkalemia induced bradyarrhythmia
Fluid bolus - 10-15ml/kg crystalloids or 2-5ml/kg colloid
Pressures if low BP or no response from fluids
How would you diagnose AKI/ARF?
Predisposing cause
Reduced urine output < 0.5ml/kg/hr
UA- casts, Azotemia FexNa> 1% Renal tubular biomarkers -GGT:CREA -NAG:CREA -
What is the treatment of acute renal failure?
FLUIDS
Correct shock- 60-90ml/kg (canine); 45ml/kg (feline) over a hour given in 15min interval boluses
Correct dehydration: %dehydration xBW = liters
What are the components of maintence fluids?
Insensible fluid loss (sweat and respiration)
Sensible fluid loss (urine, feces, vomit)
What is the average maintenance level of fluid ?
60ml/kg/day
*can vary in ARF
What would you use to rehydrate a patient with ARF?
Crystallioids (RLS, normosol R)
0.9% NaCl if hyperkalemia then reduce to 0.45% Na with 2.5% dextrose
What is oliguria?
<0.5ml/kg/hour urine production
Not producing sufficient amount of urine
Treatment for oliguria???
FLUID
Mannitol
Furosemide
Dopamine
Ca channel blockers
What is the best way to determine if your patient is overhydrated??
Central venous pressure
-if over 10cmH20 then overhydrated
MOA of mannitol
Osmotic diuretic
Increase circulatory volume-flashes through tubules
Decreases cell swelling
Reduced cellular aggregation
Free radical scavenger
Blunts the influx of Ca intracellularly
When is mannitol contraindicated?
Anuria
Dehydration
What is the MOA of furosemide?
Loop diuretic
Inhibit NA-K-2Cl symporter in ascending loop of Henle
Increased urine production without increasing GFR
Renoprotective
When is furosemide contraindicated?
Dehydration
Lethargy
Tachycardia
Ototoxicity
What is the MOA of dopamine with renal failure?
May convert to non-oligura
Not effective in cats
Only benefit as a pressor when ARF is secondary to CO failure or severe hypotensive
How do calcium channel blockers treat acute renal failure ?
Pre-glomerular vasodilation
Prevent Ca moving intracellularly
Use in post-transplant as renoprotective agent
Standard of care in leptospirosis
What is the definitive treatment for acute renal failure?
Dialysis AKA extracoproeal renal replacement therapy (ERRT)
When in dialysis indicated?
Fluid overload with pulmonary edema
Hyperkalemia
Progressive azotemia
Acute toxicity
What are complications for periotneal dialysis?
Dialysis disequilibrium syndrome (cerebral oedema)
Blockage of the peritoneal drain by omentum
What is the therapy for ethylene glycol toxicity?
4-methylpyrazole/ fomepizole
What is the therapy for renal failure due to NSAIDS?
Misoprostal (PGE analogue)
Treatment for leptospirosis?
Penicillin and doxycycline
Specific therapy for pyelonephritis?
Culture
Fluoroquinolones or TMS
Therapy for aminoglycoside toxicity?
Ticarcillin IV- binds getamycin
Treatment for TMS toxicity?
Urinary alkalinization (citrate or bicarb)
Why do you see acidosis with hyperkalemia ?
H+ is exchanged for K+
T/F: all the following are complications due to hyperkalemia.. bradycardia, sinus arrest, muscle weakness, and ileus
True
How can you correct hyperkalemia ?
Insulin
Dextrose
Ca gluconate (cardioprotective)
Correct acidosis with bicarb
When is bicarb as a treatment for acidosis contraindicated?
When CO2 elevated (will lead to excess H+ ions)
Could lead to paradoxical CNS acidosis
Hypocalcemia associated with renal fialure is caused by? How is it treated?
Deficiency of calcitriol
Treat with calcium gluconate 10%
How is hypercalcemia associated with renal failure treated?
Diuretics or ERRT
Furosemide/glucocorticoids
Calcitonin
Biphosphonates
How can you treat a hyperphosphatemia associated with renal fialure?
Reduce PO4 intake by protein restriction diet and oral phosphate binders that are dosed with food
Aluminum hydroxide/carbonate
How would you treat a hypertension associated with acute renal fialure?
Avoid ACE -> inhibit arterial vasoconstriction (hypoxia)
Amlodipine and hydralaizne
How does hypertension arise from acute renal failure ?
Secondary to RAAS activation and fluid overload
What treatments can be used in uremic gastropathy?
Omeprazole
Pantoprazole
Famotidine
Ranitidine
What is the prognosis for kidney disease caused by leptospirosis or obstruction?
Good outcome
What is the prognosis for kidney disease with decreased urine production, hypothermia, and hyperkalemia ?
Poor outcome
