AKI: MANAGEMENT

• Acute kidney injury (AKI) is an abrupt reduction in kidney function
• absolute increase in serum creatinine of either ≥26.4 µmol/L within 48 hr or
• ≥50% (1.5 x baseline) within 7 days or
• reduction in urine output documented as oliguria <0.5 mL/kg/hr for >6 hr
• E-Alert for AKI stages in Patient Management System

AKI stage 1

Clearance

• Increase in creatinine ≥26.4 µmol/L within 48 hr or
• 1.5–2 fold increase from baseline within 7 days

Urine output

• <0.5 mL/kg/hr for >6 hr

AKI stage 2

Clearance

• Increase in creatinine >2–3 fold from baseline

Urine output

• <0.5 mL/kg/hr for >12 hr

AKI stage 3

Clearance

• Increase in creatinine >3 fold or
• Serum creatinine >350 µmol/L with an acute rise of 1.5 fold within 7 days

Urine output

• <0.3 mL/kg/hr for 24 hr or anuria for 12 hr

Causes

• Pre-renal (perfusion)
• volume depletion
• hypotension, pump failure
• sepsis
• Renal (organ)
• established acute tubular necrosis – ischaemic or toxic
• glomerulonephritis/vasculitis
• tubulointerstitial nephritis
• Post-renal (obstructive)

Relevant clinical history

• Obtain previous U&E for evidence of pre-existing renal dysfunction
• Full medication history
• prescribed and non-prescribed drugs; iodinated contrast investigations
• History of urinary tract symptoms OR renal stone disease
• History suggestive of sepsis
• History of vascular disease

Fever, arthralgias, rashes

• Small vessel vasculitis
• granulomatosis with polyangiitis, microscopic polyangiitis
• SLE
• Anti-glomerular basement membrane antibody disease

Haemoptysis

• Small vessel vasculitis
• Anti-glomerular basement membrane antibody disease

Haemolysis, thrombocytopenia

• Haemolytic–uraemic syndrome

Hypercalcaemia, hyperuricaemia, bone pain, lytic lesions

• Multiple myeloma

Recent vascular intervention

• Cholesterol emboli syndrome
• ± livedo reticularis, hypocomplementaemia

Prolonged severe immobility, crush injuries

• Rhabdomyolysis
• raised serum creatinine, creatine kinase >10,000 U/L

Physiological observations and examination

• Haemodynamic (including volume) assessment
• signs of shock/hypoperfusion
• Palpation for enlarged bladder
• Evidence of vascular disease
• Signs suggestive of a less common cause (e.g. vasculitis)
• haematuria/proteinuria may indicate acute glomerulonephritis/vasculitis

Sepsis

• Suspected or confirmed infection
• qSOFA score >2
• RR >22 breaths/min
• Systolic BP <100 mmHg
• GCS ≤13

Complications of AKI

• Pulmonary oedema
• Hyperkalaemia – see Hyperkalaemia guideline
• Tachypnoea suggests fluid overload and/or acidosis
• Pericardial/pleural rub
• Neurological manifestations of uraemia
  • e.g. encephalopathy (exclude other causes of confusion/delirium)

Multiple organ failure

• Hypotension
  • mean arterial pressure (MAP) <65 mmHg] despite initial fluid resuscitation up to 30 mL/kg, or
  • inotrope or vasopressor dependency
• Impaired gas transfer: hypoxaemia (PaO₂ <10 kPa) despite 40% oxygen
• Metabolic acidosis – compensated as well as uncompensated
• Pulmonary shadowing/oedema on chest X-ray
• Patient looks severely ill/exhausted/obtunded

Ultrasound

• If cause not identified, renal ultrasound scan within 24 hr of AKI recognition
• assess renal size/exclude obstruction
• If pyonephrosis [infected and obstructed kidney(s)] suspected, immediate ultrasound of the urinary tract
• perform within 6 hr of assessment

Referral

Critical care

• Identify patients with developing or established multiple organ failure early
• Refer to critical care

Renal

• Discuss with renal team or AKI specialist nurse any patient with:
  • creatinine >350 µmol/L or >3 fold rise in creatinine from known baseline (AKI Stage 3)
  • CKD stage 5 or renal transplant
  • AKI without obvious cause (e.g. volume depletion, sepsis)
  • AKI with haematuria/proteinuria
  • AKI with complications (see above)
• Discuss patients with suspected tumour lysis syndrome (massively increased serum uric acid) urgently with renal team or oncology
• Refer patients whose renal function declines (even if creatinine <300 µmol/L) despite initial resuscitation to renal team within 48 hr of diagnosing AKI

Sepsis

• See Sepsis guideline

Fluid balance

• Careful assessment of volume status including calculation of any fluid deficit
• Accurately chart fluid input and urine output (urinary catheter may be required)
• Fluid resuscitation with crystalloids to achieve appropriate physiological targets
  • systolic blood pressure >100 mmHg or MAP >65 (higher if normally hypertensive) and/or
  • resolution of tachycardia and/or
  • restoration of adequate urine output as per Fluid resuscitation guideline
• Insert CVP line if necessary and maintain CVP pressure 10–14 cm H₂O
• In patients who remain oliguric, carry out careful reassessment to avoid fluid overload
• Once rehydrated, continue IV crystalloid to match urine output + 30 mL/hr plus continuing fluid losses
• If patient is fluid overloaded (i.e. pulmonary oedema with oliguria), give furosemide 250 mg in 25 mL by IV infusion over 2 hr using infusion pump or syringe driver
  • do not use furosemide unless evidence of fluid overload
• If no response, contact renal team urgently
• Recheck U&E daily to assess changes in renal function
• Do not use dopamine or mannitol

Urinary tract obstruction

• Undertake nephrostomy or stenting as soon as possible and within 12 hr of diagnosis

Drugs

• Discontinue/avoid nephrotoxins
  • e.g. NSAIDs/ACE inhibitors/angiotensin-II receptor antagonists
• Stop metformin/sulphonylurea drugs
  • may accumulate in acute kidney injury
• Adjust dose of any drugs given in renal failure. consult BNF or renal drug handbook
• Consider appropriateness of restarting drugs following resolution of AKI

Renal replacement therapy

• Refer to renal team for possible haemodialysis or continuous renal replacement therapy if evidence of:
  • fluid overload with oliguria
  • potassium >6.5 mmol/L – see Hyperkalaemia guideline
  • uraemia
  • severe acidosis

• Discuss with renal team

• Daily weight and fluid balance
• Daily U&E
• Monitoring of underlying cause

• If renal function remains abnormal despite treatment and eGFR <30 mL/min, arrange outpatient review by renal team
• U&E check in community within 6 weeks with GP team or, if eGFR <30, within 2 weeks
• Patient medication advice leaflet available for patients with CKD, hypertension and cardiac failure