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CIN - Risk Assessment and Prevention Strategies

Risk Assessment

Chronic renal disease (CRD) is the single biggest predictor of contrast induced nephropathy CIN and CRD is highly unlikely in the absence of risk factors listed below.

Risk factors for acute or chronic renal impairment and/or development of CIN.

  • Diabetes mellitus
  • Renal disease or Solitary kidney
  • Sepsis or acute hypotension
  • Dehydration or volume contraction
  • Age >70 years
  • Previous chemotherapy
  • Organ transplant
  • Cardio-Vascular disease (hypertension, congestive heart disease, cardiac or peripheral vascular disease)
  • Nephrotoxic Drugs - loop diuretics, amphotericin B, aminoglycosides, vancomycin, non steroidal anti inflammatory drugs, cancer and immune suppressant chemotherapy.
  • Human immunodeficiency syndrome or acquired immunodeficiency syndrome

Further stratification can be based on glomerular filtration rate (GFR):

GFRRisk
30-60mL/minModerate risk
<30mL/minHigh risk

Although absolute values of creatinine are less accurate they are nevertheless commonly used in practice when making decisions on risk of CIN. A serum creatinine < 130 mmol/L is considered low risk when in isolation.

In patients with no risk factors and GFR >60mL/min then risk for CIN is negligible.

Prevention Strategies

Hydration strategies

If patients with no risk factors are poorly hydrated then rehydration is indicated with normal saline, but no specific preventative strategies are required.

In patients with 1 risk factor and/or GFR 30-60 then there is moderate risk (1-10%) for CIN. Hydration strategies should be used if the contrast cannot be avoided or deferred. In the Emergency Department (ED) setting this means giving a minimum of 300-500mLs over a period of 30 minutes - 4 hours, depending on the urgency of the test required, and continuing this for 12 hours at 1mL/kg/hr for 12 hours. Where fluid overload is a risk this should be assessed on a case by case basis, with the use of N acetyl cysteine (NAC) a possibility where fluid is contraindicated but the majority of patients will tolerate fluid and the evidence for using NAC is weak.

In patients with 2 or more risk factors and/or GFR <30 then there is high risk (10-80%) for CIN. Check again - can this test be avoided? If not, hydrate with normal saline as below.

Hydration strategies for moderate and high risk patients:

Hydration with Saline Guidelines

1 mL/kg/hr (MAX100mL/hr) 12 hours pre and 12 hours post contrast.

If CHF or left ventricular ejection fraction (LVEF) <40% then 0.5mL/kg/hr (MAX 50mL/hr) 12 hours pre and post contrast (24 hour total infusion duration).

Emergent procedure

Fluid bolus of minimum 300-500mLs up to 1L as tolerated prior (30 minutes - 2 hours) to procedure. Hydration during procedure and/or 12 hours after if possible as above (dependent on clinical status).

N acetyl cysteine (NAC)

NAC is still used in some institutions but it is advised for use in high risk patients only. The guideline below is a commonly used regimen. Evidence for benefit is lacking while accepted limited risk exists.

Acetylcysteine Dosing Guidelines

Non acute: 600-1200mg PO Q12h X 4 doses

2 doses pre-contrast and 2 doses post-contrast is optimal

Emergent Procedure

1 dose before and 3 doses post cath or procedure is acceptable (Q12h x 4 doses total)

IV Acetylcysteine

600-1200mg IV x 1 over 15 minutes, then 600-1200mg PO/PT Q12h x 4 doses post-procedure.

Sodium bicarbonate

This is no longer considered useful in CIN preventative strategies.

Metformin

Metformin is excreted unchanged by the kidneys and is not metabolised by the liver. It is recommended that the dose of metformin should be reduced when the GFR is between 30-60mL/min and its use is not recommended when the GFR is <30mL/min.

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