Acute Renal Failure Flashcards
What is the definition of Acute Renal Failure?
Decreased GFR leading to the retention of nitrogenous wastes.
What is the definition of Acute Kidney Injury?
Encompasses mild damage, that does not cause azotemia to severe damage associated with complete anurira.
T/F AKI is reversible.
True!
T/F AKI can be pre renal, renal or post renal.
True!
What does the RIFLE acronym stand for?
R: Risk I: Injury F: Failure L: Loss E: End- stage kidney dz
What are some of the main pre renal etiologies of AKI?
Dehydration, hypoxia, ischemia, anesthesia (one of most common causes because it causes hypotension so decrease GFR so decreases O2 to kidney), Addison’s, trauma, shock, hypoALB ( oncotic pressure super low so decrease GFR).
What are some of the main aspects/causes of renal etiologies of AKI?
- prolonged renal hypoperfusion will lead to tubular hypoxia
- prolonged obstruction (> 1 week)
- excessive vasoconstriction
- thrombosis and DIC
- infectious causes (lepto, bacterial pyelonephritis)
- Immune mediated causes
- neoplasia
- secondary to systemic dz (sepsis, DIC, pancreatitis, snake envenomation)
What are some major nephrotoxins associated with renal AKI?
ethylene glycol, Nsaids, aminoglycosides, heavy metals, raisins
What are the post renal etiologies of AKI?
urine leakage or obstruction
What exactly goes wrong in post renal AKI?
Pressure on the collecting tubule will damage aquaporin 2 channels, disrupt normal hydrostatic and oncotic balance
What are the four phases of ARF?
- initial
- extension
- maintenance
- recovery
What is the first phase of ARF and how is it defined?
Initial ! Definable by a decrease in urine output or increase in creatinine.
T/F The initial phase of ARF present with major clinical signs.
False! Usually no clinical signs!
What triggers the initial phase of ARF?
usually an ischemic event triggers it
Is intervention necessary in the initial phase of ARF?
Absolutely !
What is the second phase of ARF and what is happening?
Extension phase ! The proximal tubule and loop of Henle receive 90% of the blood flow going to the kidney and are susceptible to toxic and ischemic damage.
Compromised Na:K pumps- leads to swelling and death :(
Increased cytosolic calcium
Loss of brush border or apical and basal cell surfaces
Continued hypoxia and inflammation
Tell me bout the third phase of ARF.
Maintenance phase
1-3 weeks duration
Urine output is increased OR decreased
Urine = ultrafiltrate
What is the fourth and final stage of ARF?
Recovery!
Polyuria!!!!
Extreme Na loss (ascending limb of Henle and AQP-2 loss)
Takes weeks to months to recover
T/F Intra -renal vasoconstriction deals with the imbalance between vasoconstrictors (endothelin) and vasodilators (NO).
True!
What are some of the major things that happen when intra renal vasoconstriction happens?
- decreased O2
- ATP cannot the formed to leads to energy deficit
- Mitochondrial damage
- Oxidant injury
- Intracellular acidosis
- Intracellular hypercalcemia
What happens with tubular dysfunction?
- cytoskeletal injury with loss of polarity- cells don’t know where they are anymore
- loss of tight jxns btwn cells
- cell necrosis
What are some of the preventative measures with regards to ARF?
- address BP: keep >80 mmHg (avg= 120 in cats and dogs)
- address circulatory volume: ensure CVP >0 and 30% SpO2 > 96% PaO2> 80mmHg
- ECG: avoid hyperkalemia induced bradyarrhythmias
What fluids do we give to patients with ARF?
Fluid Bolus: 10-15ml/kg crystalloids (oliguric patients) OR 2-5 ml/kg colloid
How do we diagnose AKI/ARF?
- Identify predisposing cause (shock, nephrotoxin)
- Reduce urine output: normal= 1-2 ml/kg/hr; abnormal (OLIGURIA): 1%
- Renal tubular biomarkers (relative to creatinine as a ratio): GGT = creatinine; NAG= creatinine . . . helps localize the region of the tubular structure, multiple enzymes will provide a great diagnostic accuracy
How do we treat ARF?
FLUIDS FLUIDS FLUIDS. Hydrate these mofos
How do we correct shock?
60-90 ml/kg = canine
45 ml/kg= feline
over 60 mins, 15 min interval boluses
What is the formula to correct dehydration ?
% dehydration x 10 x BW in kg = ___ ml (over 6-12 hrs)
What is the definition of oliguria?
How do we know if the oliguria is pre renal?
Give fluid and if the dog starts urinating then we know there wasn’t enough volume in the dog so this is a physiological aka a pre renal cause.
What is the prognosis for pre renal oliguria?
Not good. Animal is pretty fucked.
We already know the main treatment for ARF is to give fluids but what kinda drugz do we give?
Mannitol, Furosemide, Dopamine, Calcium channel blockers
How does Mannitol work?
Osmotic diuretic
Increase circulatory volume: flushes through tubules
Decreases cell swelling
Blunts the influx of calcium intracellularly
Contraindications:
-anuria, dehydration
How does Furosemide work?
Loop diuretic
Inhibits the Na-K-Cl symporter in thick ascending loop of Henle
increased urine production WITHOUT increasing GFR
Renoprotective!
Output should increase within 2-60 mins
Contraindications:
-dehydration, lethargy, tachycardia, ototoxity
What’s up with Calcium Channel Blockers?
MOA: preglomerular vasodilation
Prevents Ca moving intracellularly
used in post transplant as renoprotective agent
Standard of care in Lepto!
What is the definitive treatment of ARF?
Extracorporal renal replacement therapy ak dialysis!
What are the indications for dialysis?
- fluid overload with pulmonary edema
- hyperkalemia
- progressive azotemia
- acute toxicity
What’s the specific tx for ethylene glycol toxicity?
4-methylpyrazole within 8 hours of ingestion
What’s the specific tx for Nsaids?
Misoprostal
What’s the specific tx for Lepto?
Penicillins and doxy- immediately use!
What’s the specific tx for pyelonephritis?
Culture, fluoroquinilones or TMS
What is the specific tx for amino glycoside toxicity?
Ticarcillin IV: binds to gentamycin
What is the specific tx for TMS toxicity?
Urinary alkalinization
Why does hyperkalemia develop in ARF?
inability to excrete k so acidosis bc H+ exchanged for K+
complications include bradycardia/sinus arrest, muscle weakness and ileus
How do we correct the hyperkalemia that develops in ARF?
Insulin followed by dextrose then calcium gluconate and correct metabolic acidosis by giving HCO3
Why does acidosis develop in ARF?
the failing kidney is unable to absorb HCO3- or excrete H+
How do we tx the acidosis that develops?
HCO3- administration IV
Contraindications:
-when CO2 elevated
How do we tx the hypercalcemia that develops?
Diuresis or ERRT Furosemide/ GC's Calcitonin Biphosphonates Bad prognosis :(
Why does hypertension develop in ARF?
secondary to RAAS activation and fluid overload
Avoid ACE inhibitors in ARF b of arterial vasoconstriction!
What circumstances have a good prognosis?
Dialysis, Lepto, obstructive and infective