Definition
- Oliguria < 400ml / day
- ↓ in glomerular fxn, ↑ing urea/creat
- More on classification
| Stage | Serum creatinine | Urine output |
|---|---|---|
| 1 | 1.5 to 1.9 times baseline OR ↑ ≥26 µmol/L in 48hrs |
<0.5ml/Kg/h for 6-12 hrs |
| 2 | 2 to 2.9 times baseline | <0.5 ml/Kg/h for ≥12 hrs |
| 3 | 3 times baseline OR ↑ ≥354 µmol/L OR Initiation of renal replacement therapy OR in <18yrs old, ↓ eGFR to <35 ml/min per 1.73m2 |
<0.3 ml/Kg/h for ≥24 hrs OR Anuria for ≥12 hrs |
History
- Systemic disease (DM, vascular)
- Hx renal disease
- Systemic upset (GI Bleed, surgery, ACS)
- Medications (ACEI, NSAIDs, x-ray contrast, diuretics, Gentamicin, neomycin and other aminoglycosides)
Signs
- Dehydration (dry eyes/mucous membs, postural ↓BP)
- Volume overload (JVP, BP, Creps, peripheral oedema)
- Infection
- Arthralgia or rash
- Organ failure (hypoxia, hypotension, metabolic acidosis)
Causes ARF
Pre-renal
- Cardiogenic shock (AMI, septic etc.)
- Hypovolaemia/ dehydration
- Sepsis
- Contrast nephropathy (? check evidence)
- Rhabdomyolysis
- HUS, TTP, Hepatorenal syndrome
Renal
- ATN (often due to local ischaemia or drugs)
- Acute nephritis
- Inflammatory (vasculitis)
- Vascular (embolism or thrombus)
- Myeloid
Post-renal (NB - 30% of ARF)
- Obstruction (stones, malignancy)
Investigations
- Usual bloods, CXR, ECG
- Please remember calcium, ESR, CRP, CK
- Full septic screen (blood cultures, urine etc)
- NB EXCLUDE post-renal obstruction with imaging
- Urine and serum creat, osmolality, Na+ and K+:
- Pre-renal if urine Na+ low, Cl- low, osm > 500
- Urea:creat ratio>0.1 usually pre-renal
- Creat clearance =(140-age) x weight/Creat (µmol) (x1.2 for men) [CrCl normal = 100ml/min]
- Auto-antibody screen
- Dipstick urine and microscopy for casts etc:
- UOB/protein negative dipstick = glomerular disease unlikely
- Casts usually glomerular disease
- Lymphocytes or eosinophils usually = interstitial nephritis
Management
Initial
- Resuscitate with O2 and fluids
- Relieve any obstruction
- Stop any triggering meds
- Call renal team
- Consider:
- Diuretics, Mannitol (100ml of 20%), inotropes (noradrenaline) once fluid resuscitated
- Antibiotics if septic
- Record accurate input/output
- Lactate / pH / bicarb in VBG
Indications for urgent dialysis
- Metabolic acidosis - when correction with bicarb would cause fluid overload ph < 7.2
- Electrolytes – ↑K+ (>7.0 mmol/l)
- Intoxication – poisoning : SLIME
- Overload – pulmonary oedema not responding to diuretics
- Uraemia complications eg pericarditis, encephalopathy, GI bleeding BUN 70-100 mg/dL
Dialysable drugs
S L I M E
- Salicylate
- Lithium
- Ispropranolol, iron, isoniazid
- Magnesium, methanol
- Ethylene glycol
Renal referrals CUH
- All haemodialysis/peritoneal dialysis patients – please inform renal team irrespective of pathology
- Transplant patients – on-call team (med or surg etc.) should contact renal team
- AKI other – common sense should prevail!