GGC Medicines


Adult Therapeutics Handbook

Management of Acute Kidney Injury (AKI)

Management of Acute Kidney Injury (AKI)

Introduction

The definition of AKI is abrupt and sustained decline in glomerular filtration rate leading to accumulation of urea and other chemicals. It is classed into 3 stages (see table 1). Risk factors of developing AKI are listed in boxes 1 and 2 below.

Table 1 – Stages of AKI

AKI stage Definition
I

Cr >150–200% from baseline or

Acute increase of Cr >25micromol/L/48 hours or

urine output <0.5ml/kg/hour for >6 hours

II

Cr >200–300% from baseline or

urine output <0.5ml/kg/hour >12 hours

III

Cr >300% from baseline or

Cr >350micromol/L or

urine output <0.3ml/kg/hour for 24 hours or anuric for 12 hours or

requires renal replacement therapy, irrespective of Cr

Box 1 – AKI risk factors

Clinical history
  • Kidney disease
  • Heart failure
  • Ischaemic heart disease
  • Malignancy
  • Liver disease
  • Urological intervention
During hospital admission
  • Surgery
  • IV contrast
  • >20mmHg decrease in BP
  • Urinary obstruction
  • Hypovolaemia
  • Malnourished

Box 2 – AKI avoidable risk factors

Nephrotoxins
  • Angiotensin-converting enzyme inhibitors / angiotensin-II receptor antagonists
  • Non-steroidal anti-inflammatory drugs
  • Antivirals / antifungals
  • Vancomycin / gentamicin
  • Chemotherapy / contrast
Contrast Administration

If patient is at risk:

  • Use low ionic low-osmolar contrast
  • Fluids - 1ml/kg/hour fluid 6–12 hours pre- and post study

Assessment / Monitoring

AKI stage I

  • Obtain clinical history. Check for risk factors (see box 1 above), any pointers towards aetiology and review medication (see examples in box 2 above).
  • Clinical examination:
    • Check patient's obs
    • Fluid status (assess peripheral perfusion, JVP (central venous pressure, CVP)), oedema (3rd spacing) and urine output.
  • Investigations:
    • U&Es, urinalysis, MSSU, CXR, ECG.
    • Consider renal ultrasound (US), sepsis screen

AKI stage II

As for Stage I but renal US within 24 hours and sepsis screen.


AKI stage III

  • As for stage II. Look for multi-organ failure and chase renal US report.
  • Mandatory blood tests are: U&Es and HCO3-, CRP, creatine kinase, LFTs, Ca2+, FBC, coagulation screen.
  • Consider: amylase level, urine PCR if proteinuria, autoantibody screen if haematuria or proteinuria, microscopy if haematuria, myeloma screen, abdominal US.

AKI complications include: sepsis, acidosis, hyperkalaemia, multi-organ failure, oedema, respiratory failure, encephalopathy, serositis, haemorrhage.

Management

AKI stage I

  • Stop nephrotoxins (see box 2 above)
  • Optimise fluid status.
    • Correct hypovolaemia, hydrate, optimise haemodynamics, keep accurate fluid balance chart.
    • Fluid challenge unless there is evidence of fluid overload. Aim for a mean arterial pressure >65 or SBP >100mmHg.
    • Consider: vasoactive agents if hypotensive and not volume depleted.
    • Assess response and repeat U&Es. Aim for urine output of 0.5ml/kg/hour.
  • Treat infection if present (see Infection Management Guideline)
  • Manage any contributing risk factors.
  • Consider: inserting urinary catheter, seeking senior review, assessing CVP, reviewing medication and adjusting doses.
  • Relieve obstruction if present with mandatory decompression, also request urgent urology review and/or discussion with interventional radiologist.
  • If evidence of rhabdomyolysis then:
    • Aim for urine output >100ml/hour
    • Alternate sodium chloride 0.9% IV with sodium bicarbonate 1.26% IV
    • Keep urine pH >6.5
    • Request surgical review if indicated

AKI stage II

  • Manage as per Stage I and also:
    • Seek senior review
    • Insert urine catheter and check urine volumes hourly.
  • Consider:
    • CVP / cardiac monitoring, 12 hourly bloods and level 2 care.
    • Refer to the Renal team if likely to need renal replacement therapy or if no clinical improvement in 24-48 hours.

AKI stage III

  • As per Stage II and also:
    • Refer to the Renal team and transfer to level 2 care.
    • Do cardiac monitoring
  • Consider:
    • CVP line insertion and 12 hourly bloods
    • Refer to ITU if patient is in respiratory failure or there is multi-organ involvement.

Referral Criteria to Renal Unit

  • Urgent inpatient referral if:
    • High suspicion of rapidly progressive glomerulonephritis
    • Indication for dialysis (refractory increase K+ >6.5mmol/L, or urea >30mmol/L and/or Cr >500micromol/L, tumour lysis syndrome, refractory volume overload, refractory acidosis pH <7.1, complications of uraemia, severe poisoning, severe hypothermia)
    • Stage III AKI
    • Stage II AKI and unresponsive to treatment after 24-48 hours
    • Renal transplant patient
    • Dialysis patient prior to admission

Call renal on call (0141 452 2417 or extension 82417 [Queen Elizabeth University Hospital]).

  • Non-urgent inpatient referral if:
    • Stage II AKI
    • Nephrotic syndrome
    • Positive ANCA or ANA and proteinuria with or without haematuria
    • Malignant hypertension

Telephone renal secretary during working hours on 0141 452 6198, response within 1 working day.