Acute renal failure Flashcards
Definition
Deterioration in kidney function over days/hours, demonstrated by + in urea and creatinine.
- Increase in serum creatinine by ≥26.5 micromol/L (≥0.3 mg/dL) within 48 hours; or
- Increase in serum creatinine to ≥1.5 times baseline, which is known or presumed to have occurred within the prior 7 days; or 3. Urine volume <30ml/hour
Life threatening consequences
- Fluid overload
- Hyperkalemia
- Metabolic acidosis
Etiology
- Pre-renal Hypovolemia Hemorrhage Sepsis Third spacing Overdiuresis Heart failure Hepatorenal Renal artery stenosis NSAIDs, ACEi
- Intrinsic Glomerular->GN Tubules->Toxins, ATN Interstitium->infection Vascular->vasculitis, TE, malignant HTN, HUS, TTP
- Post-renal Urinary tract obstruction
Nephrotoxins
- Aminoglycosides
- Amphotericin
- Radiological contrast
- Uric acids
- Haemoglobinuria/Myoglobinuria
Most common cause of acute kidney injury
Acute tubular necrosis due to ischemia
Pathophysiology
- Prerenal->reduced perfusion->+RAAS, vasoconstriction, salt and water reabsortion
- ATN->ischemia, free radicals, complement, inflammation, necrosis
- Obstruction->Pressure, ischemia, atrophy
Three important questions to ask
Is this chronic or acute? Is this due to obstruction? Is there a rare cause of ARF?
Features suggestive of CRF
- Comorbidities->DM, HTN, long duration of symptoms
- Previously abnormal blood results
- Small kidneys on USS
- Anaemia and phosphate+->not distinguishing as can occur within days, absence does suggest AKI
History
- In pre-renal
Hemorrhage,
GIT loss,
sweating,
fluid replacement
Sepsis,
pancreatitis
Thirst, dizziness, tachyC, oliguria, anuria
Orthopnea/PND
- Intrinsic
Rash
Hematuria, Edema w/ HTN
Myeloproliferative
Medicine/contrast NSAIDs
Rhabdomyolysis->muscle tender, seizure,
drug abuse, alcohol abuse, ++exercise, limb ischemia
- Post
Urgency, frequency, hesitancy
Hx of malignancy, nephrolithiasis, previous surgery
Flank pain, hematuria
Physical examination
- HypoT, HTN
- pulmonary edema, peripheral edema
- Asterixis, mental state
- Hydrations
- Sepsis
- Pancreatitis
- HTN, edema, proteinuria, hematuria
- Rash, petechiae, eccymoses
- Abdominal bruit, Abdominal distension,
- +bladder
Prostate enlargement
Investigations
- Bloods/urine
UEC->+urea/creatinine, +potassium, metabolic acidosis Ratio
Urinalysis->RBC, WBC, casts, nitrite, bacteria Urine MCS
FBC->anaemia, leukocytosis, thrombocytopenia (HUS, TTP)
VBG->metabolic acidosis
CK->rhabdoM
Clotting, LFTs
Urine osmolarity
- Unclear cause:
ANA, ANCA, anti-dsDNA, antiGBM, ASOT, hepatitis, bence jones
- Imaging
Renal USS->dilation, reduced size
CXR->pulmonary edema, cardiomegaly
ECG->peaked T waves, +PR, wide QRS if hyperkalemia
Management
- Specialist help
- Catheterise, start fluid chart
- Assess IV volume->BP, JVP, skin turgor, fluid balance
- Attach ECG.
- Examine for palpable bladder
- 2 large bore IV cannulae->Investigations: UEC, CMP, FBC, ESR/CRP, INR. LFT, CK, LDH, protein electroP, hepatitis serology, ANA/ANCA/complement, anti-GBM, ASOT, blood cultures Urgent urine MCS USS ECG, CXR
- Assess and treat hyperkalemia: calcium gluconate IV, insulin + glucose, salbutamol, calcium resonium
- Treat the treatable
- If dehydrated/hemorrhage->fluid 250-500ml NS bolus/transfusion
- Stop nephrotoxic medications
- Treat pulmonary edema: sit up, high flow, morphine + metoC, frusemide.
- May need hemodialysis, IV nitrates
- Manage hemorrhage: PPI, FFP/PLTs, blood transfusion
- Reassess
- Continue IVF to maintain urine output
- If fluid overloaded->consider urgent dialysis. Nitrate, frusemide, dopamine in short term.
- Treat sepsis
- Admit
- Regular monitoring->BP, urine, pulse
- Daily weights, fluid balance, input/output
- Nutrition
Indications for dialysis
Refractory pulmonary edema Persistent hyperkalemia Severe metabolic acidosis Uremic encephalopathy Uremic pericarditis
