ACUTE KIDNEY INJURY

Recognition

Definition (Acute Kidney Injury Working Group)

• Acute Kidney Injury (AKI) is defined as any of the following:
  • Increase in serum creatinine (SCr) by 26 µmol/L within 48 hours
  • Increase in SCr to X 1.5 times baseline, which is known or presumed to have occurred within the prior 7 days
  • Urine volume < 0.5 ml/kg/h for 6 hours

Risk Factors

• Age greater than 75 years
• Female gender
• Black race
• Chronic Kidney Disease (estimated glomerular filtration rate (eGFR ) < 30 mls/min/1.73 m2)
• Hypertension (one or more anti-hypertensive drugs)
• Cardiac failure
• Liver disease
• Diabetes Mellitus
• Nephrotoxins (e.g. Non-steroidal anti-inflammatory drugs (NSAIDs), gentamicin, iodinated contrast)
• Hypovolaemia
• Sepsis
• Burns
• Trauma
• Major surgery
• Intravenous (IV) Contrast
• Cancer
• Anaemia

Causes

• Pre-renal
  • Hypotension
    • Burns
    • Cardiac failure
    • Diarrhoea and Vomiting
    • Diuretics
    • Heamorrhage
    • Medication (e.g. Angiotensin-Converting Enzyme inhibitor (ACEi))
  • Hepatorenal Syndrome
  • Renal Artery Stenosis
  • Sepsis
  • Toxins (e.g. IV contrast)
• Intrinsic
  • Acute tubular injury
  • Glomerulonephritis
  • Heamolytic Uraemic Syndrome
  • Lupus
  • Myeloma
  • Tubulointerstitial injury
  • Thrombotic Thrombocytopenic Purpura
  • Vasculitis
• Post-renal
  • Obstruction
    • Bladder cancer
    • Kidney stones
    • Pelvic mass
    • Prostatic hypertrophy
    • Retro-peritoneal fibrosis

History

If possible, ascertain if patient has:

• Previous admissions with AKI
• Any previous operations related to the kidneys
• Any allergies

General symptoms

• Nausea
• Vomiting
• Diarrhoea
• Loin pain
• Prostatic symptoms
• Systemic symptoms of possible vasculitis
  • Fever
  • Weight loss
  • Rash
  • Joint pain or swelling
  • Haemoptysis
  • Uveitis

General Signs

• Shortness of breath (dyspnoea) from pulmonary oedema
• Cyanosis
• Delayed capillary refill time
• Reduced skin turgor
• Dry mucous membranes
• Hypotensive
• Tachycardic
• Decreased urine output
• Peripheral oedema

Stage (Acute Kidney Injury Working Group)

• The stage is taken to be the highest stage which is obtained through the SCr or Urine Output (UO)

Stage	Serum Creatinine (SCr)	Urine Output (UO)
1	Rise ≥26 µmol/L within 48 hours Or Rise ≥1.5 to 1.9 X baseline SCr	<0.5 mL/kg/hr for >6 consecutive hours
2	Rise ≥2 to 2.9 X baseline SCr	<0.5 mL/kg/h for >12hr
3	Rise ≥3 X baseline SCr Or Rise ≥354 µmol/L Or Initiation of Renal Replacement Therapy Or In patients <18 years, decrease in eGFR to <35 ml/min per 1.73 m2	<0.3 mL/kg/h for >24hr Or Anuria for ≥12hr

 

Initial Assessment and Investigations

• ABCDE assessment
• Sit patient up if able to tolerate
• Assess patient’s airway
• Monitor oxygen saturations and respiratory rate
  • If patient is hypoxic give Oxygen (O₂) to achieve target saturations. Initially give 15 L/min via a reservoir mask if the patient is acutely unwell
• Target saturations:
  • 94 - 98% for patients not at risk of hypercapnic respiratory failure
  • 88 - 92% for patients at risk of hypercapnic respiratory failure due to conditions such as Chronic Obstructive Pulmonary Disease (COPD)
• Examine patient’s chest
• Consider chest X-ray (pulmonary infiltrates could indicate fluid, infection or haemorrhage). If the patient is unwell request a portable X-ray
• Obtain intravenous access by placing 2 large bore cannulae in the antecubital fossa. Take blood to check Full Blood Count (FBC), Urea and Electrolytes (U&Es), Bicarbonate, Liver Function Tests (LFTs), Calcium, Phosphate, Glucose and Venous Blood Gas
• Check Capillary Refill Time (CRT) - hold for five seconds and refilling should occur in 3 seconds
• Assess pulse rate, rhythm and character
• Monitor heart rate and blood pressure
• Listen to patient’s heart sounds
• Check urine output and consider catheterisation
• IV fluids as required by clinical picture and balanced with patients’ risk of fluid overload
• 12 lead echocardiogram (ECG)
• Consider sepsis six if sepsis suspected including urine dipstick (presence of blood and protein suggests infection or vasculitis). For further information see “Sepsis” Section in “Medical Emergencies” Chapter
• Renal tract ultrasound to assess renal anatomy and exclude renal tract obstruction
• Check pupils are equal and reactive
• Assess Glasgow Coma Scale or ACVPU using the NEWS2 chart
• Check patient’s temperature and blood sugar
• Examine patient’s abdomen and legs
• Consider venous thromboembolism prophylaxis
• Call for senior help if not already done

Response

Management

Immediate management

STOP AKI

• Sepsis 
• complete Sepsis 6 if sepsis suspected
• Toxins
• stop/avoid nephrotoxins e.g. gentamicin, NSAIDs, iodinated contrast
• Optimise blood pressure and volume status assessment
• consider withholding antihypertensive medication
• Prevent harm
• Treat complications
• Acidosis
• Hyperkalaemia
• Pulmonary oedema
• Identify cause - if the cause is not sepsis, toxins, hypotension or hypovolaemia consider obstruction or a rarer cause of AKI
• Review all medications and doses
• Review fluid prescription

• Monitor
  • Daily volume assessment
  • Fluid Balance
  • U&Es
  • Bicarbonate

Referrals

• Discuss with senior member of the team
• Contact critical care outreach team
• Referral to the renal team for patients with:
  • AKI stage 3
  • Persistent oliguria and/or rising serum creatinine despite supportive therapy
  • Complications refractory to medical management
    • Intractable pulmonary oedema
    • Intractable hyperkalaemia
    • pH < 7.15
    • Uraemic pericarditis
    • Encephalopathy
  • AKI with
    • Absence of defined cause
    • Systemic features
    • Paraproteins
    • Heamolysis and low platelets
    • Suspected poisoning
• Consider referral to Intensive Care Unit (ICU) if:
  • Failure to respond to medical management
  • Patient requires ventilator support
  • Patient requires blood pressure support
  • Deterioration of blood gas following medical management