AKI (Londono) Flashcards
Objectives
- understand the basic pathophysiological causes of renal injury
- become familiar with the staging systems of AKI and their application
- recognize the differences in clinical presentation and lab findings between AKI and CKD
- learn management strategies for animals with AKI
AKI definition
- inc in serum Cr by >/= 0.3 mg/dL OR
- inc in serum Cr by >/= 1.5 times baseline OR
- Urine production < 0.5 ml/kg/hr (6 hours)
pathophys AKI
- Initiation =>
- Extension =>
- Maintenance =>
- Recovery
Recognition AKI
Cr measurement
- principal biomarker of AKI
- will inc once > 75% of renal function is lost
- delayed recognition of novel biomarkers
Recognition AKI
Urine output
- normal: 20-50 ml/kg/day or 1-2 ml/kg/hr
- oliguria < 1.0 ml/kg/hr
- anuria < 0.1 ml/kg/hr
Other indications for recognizing AKI
- Urea Nitrogen (BUN)
- Complete history
-
thorough physical examination
- pre/post renal
- clearance studies
Staging AKI
Rifle (Humans)
- Risk
- inc Cr 1.5-2 times baseline or
- urine output of < 0.5 ml/kg/hr for > 6 hours
- Injury
- inc Cr 2-3 times baseline (loss of 50% GFR) or
- urine otput < 0.5 ml/kg/hr for more than 12 hours
- Failure
- inc Cr > 3 times baseline (loss of 75% of GFR) or
- inc in Cr greater than 4 mg/dL
- urine output < 0.3 ml/kg/hr for > 24 hours or anuria for > 12 hrs
- Loss of function
- persistent renal failure (need dialysis) for > 4 weeks
- End-stage renal dz
- persistent renal failure (need dialysis) for more than 3 months
IRIS staging
(veterinary)
- Grade I: < 1.6 mg/dl
- Grade II: 1.7-2.5 mg/dl
- Grade III: 2.6-5.0 mg/dl
- Grade IV: 5.1-10.0 mg/dl
- Grade V: 10.0 mg/dl
*subgrades of each category into non oliguric (NO) or oliguric (O) or requiring renal replacement therapy (RRT)
AKI
Common presenting complaints
- non-specific clinical signs
- gastrointestinal signs common
- PU/PD may be reported by owners
- secondary to critical illness (burns)
- can develop AKI in the hospital
AKI Clinical presentation
PE
- Dehydration
- dry MM, skin tent, sunken eyes
- hypovolemia
- weakness, tachycardia, faint pulses
- arrhythmias
- bradyardia with severe K+ elevation
- abdominal pain
- large +/- painful kidneys
- normal body condition or overweight
Clinical presentation AKI
HX
- Acute onset of clinical signs (hours to days)
- previously healthy
- exposure to toxins
- travel history/environment
- frequent visits to the litter box
Etiology
causes of renal AKI
- Glomerular disease
- GN, thrombosis
- Tubular injury
- ischemia, toxins
- interstitial nephritis
- vascular disease
- vasculitis, thrombosis
Etiology: Pre-renal AKI
- Renal autoregulation
- pre-glomerular vasodilation
- prostaglandins: affected by NSAIDS
- post-glomerular vasoconstriction
- angiotensin II: affected by ace inhibitors
- pre-glomerular vasodilation
*questions on clinics!!!!
Renal blood flow to the kidneys is limited when systolic blood flow
- drops below 70
- at this point auto-regulatory mechanisms are not as effective
Causes of low blood pressure
- blood loss/hypovolemia
- anesthetic protocols
Etiology: post-renal
- Obstructive dz
- urolithiasis (i.e. ureteroliths in cats)
- Neoplasia
- Prostatic disease
- FLUTD
- Uroabdomen
Etiology: Renal
4 intrinsic causes
-
Glomerular dz
- inflammation of glomerular membrane => can cause obstruction
- will lose protein, have low albumin
-
Renal tubular injury
- Toxins: ethylene glycol, lilies, grapes/raisins
- Nephrotoxic drugs: antibiotics (aminoglycosides), NSAIDS, radiocontrast agents
- Metabolic dz: hypercalcemia
- Endogenous substances: myoglobin, hemoglobin
-
Interstitial nephritis (usually do to infectious dz)
- Pyelonephritis
- leptospirosis
- granulomatous dz
- neoplasia (lymphoma)
-
Vascular dz
- vasculitis: systemic inflammation (sepsis, trauma, pancreatitis)
- thromboembolism: cushings, IMHA
AKI biochem
-
azotemia (BUN and Creatinine)
- may be disporportionate in GI hemorrhage or severe dehydration
- Electrolyte derangements
- hyperphosphatemia and hyperkalemia
- due to decreased renal excretion
- hyperphosphatemia and hyperkalemia
- Elevations in liver enzymes
- leptospirosis
- Elevated CK values
- rhabdomyolysis
- Low Albumin
- GN, SIRS (systemic inflammatory response syndrome), or sepsis
AKI: blood gas
- mild to severe metabolic acidosis
- dec renal reabsorption bicarb
- dec excretion of organic/inorganic acids
- Elevated Anion gap ( > 25 dogs; > 30 cats)
- consistent with EG intox
- anion gap: (Na+ + K+) - (HCO3 + Cl-)
- ionized hypocalcemia may be observed
AKI: Hematology
-
hematocrit can be normal or elevated
- non-regenerative anemai in CKD
- severe GI hemorrhage may also cause anemia (low TS)
- Leukocytosis
- mild in cases of sterile inflamatin or stress leukogram
- severe, left-shifted (infectious etiologies)
- leukopenia should raise concern for sepsis
- Thrombocytopenia
- leptospirosis
- thromboembolic dz
AKI: Urinalysis
- Hallmark signs is azotemia with inappropriately concentrated urine
- Dogs < 1.035
- Cats < 1.040
- Isosthenuria common in AKI (1.008-1.012)
- Glucosuria with tubular damage
- not specific, consider ddx for tubular damage
- proteinuria/pigmenturia
- markers for inflammation
- could be from a GI dz
- evaluate other parts of Urinary system
- pyuria and bacteruria
- suspect pyelonephritis
- granular casts with tubular damage
- non-specific
- Calcium oxalate monohydrate crystals
- ethylene glycol poisoning
AKI: Microbio
- always perform urine aerobic culture
- positive culture
- may indicate pyelonephritis
- negative culture
- doesn’t rule out pyelonephritis
- blood cultures in sepsis before antibiotics
- abdominal effusion culture in cases of uroabdomen
AKI: Serology
- Leptospirosis
- common in dogs, not cats
- titers: detect antibodies against infection OR recent vaccination
- may be negative during acute phase
- always perform convalescent titers (2-4 weeks post)
- Lepto PCR in urine or blood or both
- looks for DNA of LIVE organisms
- before antibiotics
- Other infectious organisms
- RMSF (rockky mountain spotted fever)
- Ehrlichia
- babesia
- leishmania (Europe)
AKI: Imaging
- Abdominal rads
- assess renal shape and size
- radiopaque uroliths (size limitation)
- Heavy metal intoxication
- Ultrasonography
- most sensitive modality for parenchymal/structural changes
- detection of small ureteroliths
- neoplastic disease (kidney, bladder, ureter)
AKI: Blood Pressure
- Several limitations in veterinary patients
- Diagnostic work up:
- hypotension (pre-renal causes of AKI)
- hypertension (end-organ damage)
- Monitoring
- should be performed at least twice daily
- endogenous epi and norepi in sick patients inc BP
- Hypertension and blood pressure control common in AKI
- should be performed at least twice daily
Persistent hypertension
- Affect GFR and cause AKI
AKI: Urine output
- measure output when possible
- urinary catheterization
- most accurate
- inc risk of infection
- inc patient discomfort
- collect voided urine
- at ever walk or measure pee pads
-
monitor body weight
- cheap, non-invasive and reliable
- before and after walk
- urinary catheterization
AKI VS CKD
- AKI
- acute onset CS
- normal BC or overweight
- large/painful kidneys
- normal HCT/hemoconcentration
- hyperkalemia
- CKD
- hx of PU/PD, weight loss or absent CS
- poor body cond
- small/irregular kidneys
- non-regenerative anemia
- normal K or hypokalemia
Management principles
- Identify and correct pre-renal and post-renal factors
- Antibiotics
- Identify and treat acute compliations
- hyperkalemia
- metabolic acidosis
- Review other drugs
- Accurately monitor fluid balance and daily body weight
- Optimize nutritional support
- Management of GI signs
- Renal replacement therapies
Indentifying pre-renal factors
- fluid therapy should rapidly correct hydration deficits and ongoing losses
- use fluids with low Cl concentrations
- hypovolemic and hypotensive animals should receive shock doses of IV fluids
- something about risk of fluid overload and heart disease
- Goal directed therapy and improved markers of perfusion
- lactate is a marker of perfusion
Fluids:
Cl rich
Hetestarch
- Chloride rich soluntions
- may elevate mean serum creatinine level
- inc incidence of AKI
- inc need for renal replacement therapy
- Hetestarch
- assoc with in-hospital mortality
- inc need for renal replacement therapy
- Identify post-renal factors
- Cats commonly suffer from calcium oxalate uroliths
- study showing sx outcomes better than Med manag outcomes
- urethral stints…
- Urinary obstruction
- rapidly establish urinary tract patency
- Post obstructive diuresis
- keep up with urine output, post-renal may become pre-renal
- watch K+ levels
- Antibiotics
- Collect urine and blood samples first
- start antibiotic therapy and continue until infectious causes of AKI have been ruled out
- unasyn: broad spectrum
- lepto: doxy
- adjust antibiotic therapy based on sensitivity results
*culture may take 48 hours
- Identify and treat acute complications
- Medical management
- Aimed to provide window for kidney to recover
- not used when severe CS present
- narrow window for kidney recovery (hours to days)
- patients can die from uremia despite potential for recovery
- Hyperkalemia
- mech: dec renal excretion and metabolic acidosis
- conseq: cardiac arrhythmias, tremors
- prevalence: highly variable
- tx: shift intracell bicarb, glucose, insulin
- Acidosis
- corrected with med manag
- rarely is main indication for dialysis
- bicarb: be careful, something about crossing blood brain barrier
- Review other drugs
- Discontinue all potential nephrotoxic agents
- aminoglycoside antibiotics
- NSAIDS
- Sedation protocols
- Radiocontrast agent concerns
-
FLUIDS are therapeutic agents
- review, adjust frequently
- Accurately monitor fluid balance and daily body weight
- goal: convert oliguric animals to non-oliguric
- avoid volume overload at all costs
- clinically, anuric animals may be more likely to be fluid overloaded
- kidney capsule can also get edematous
- common reason for therapeutic failure
- weigh frequently
- fluid over load
- more than a 10% inc in body weight from baseline
- Optimize nutritional support
- improved survival
- Goal
- preserve lean body mass
- avoid further metabolic complications
- support immune system
- improve GI tract function
- Feeding tubes should be part of a therapeutic plan
- Do not force feed renal diets
- creates aversion
- Phosphate binder therapy with each meal
- Initialize dialysis before uremic complications emerge
- Severe hyperkalemia
- severe fluid overload
- with concurrent low urine production
- severe acid base disturbance
- severe or progressive azotemia
- oliguria/anuria
- uncontrolled CS
- re-surgical conditioning
- Management of GI signs
- Uremic Gastritis
- secondary to decreased Gastrin elimination
- anti-emetics
- cerenia
- ondansetron (non-dyalized)
- metaclopramide (prokinetic)
- decreased acid reduction
- H2-blockers
- proton pump inhibitors
- sulcralfate