What is the best way to prevent contrast induced nephropathy and avoid acute kidney injury in patients at risk? An expert opines.
A 78-year-old woman with CKD stage G4A3 from diabetes presents to a Heart Hospital for a cardiac catheterization, planned for later in the day. She has unstable angina. The cardiologist wants to reduce her risk of acute kidney injury. She is euvolemic. Nephrology is consulted to help prevent contrast nephropathy.
CIN is a significant complication, being the third leading cause of iatric kidney injury and accounting for up to 10% of acute kidney failure cases in hospitalized patients.
Hydration is the most evidence-supported intervention to prevent contrast nephropathy.
Discussion:
Prevent contrast nephropathy
Definition and Overview
Contrast-induced nephrotoxicity (CIN) is a type of acute kidney injury that occurs after exposure to intravascular contrast media. It is a significant complication, being the third leading cause of iatric kidney injury, accounting for up to 10% of acute kidney failure cases in hospitalized patients. CIN is associated with increased morbidity and mortality both in the short and long term.
Incidence and Usage of Contrast Media
The purpose of radiographic contrast agents is primarily to enhance imaging in diagnostic and therapeutic procedures. The rising use of contrast media has led to a corresponding increase in the incidence of CIN. In 2003, approximately 8 million liters of contrast media were used in 80 million examinations, highlighting its status as one of the most frequently used medicinals.
Risk Factors and Mechanisms
CIN is more likely to develop in patients with pre-existing risk factors, including pre-existing chronic kidney disease. The condition is defined as acute kidney impairment following the administration of radiocontrast dye, with no other identifiable causes of renal failure.
Typically, CIN manifests within 24–48 hours post-exposure, peaking by day 5. The most common definition includes an increase of ≥25% in serum creatinine level (SCr) or an absolute increase of 0.5 mg/dL from baseline.
Prevent contrast nephropathy – Strategies
Hydration is the most evidence-supported intervention to prevent contrast nephropathy. Although no randomized controlled trials have directly compared hydration methods, intravenous hydration appears to be more effective than unrestricted oral hydration. There is a need for standardized prospective studies to determine the optimal hydration strategy.
Mechanisms of Volume Expansion
Several mechanisms may explain the beneficial effects of volume expansion in preventing CIN:
* Dilution of contrast media within the tubule lumen, increased diuresis, reduced activation of the renin-angiotensin system due to increased sodium delivery to the distal nephron, minimization of renal nitric oxide production
Hydration Protocols for At-Risk Patients to Prevent Contrast Nephropathy
Different hydration protocols are recommended for patients at risk of CIN during procedures:
* Outpatients: Administer 3 mL/kg over one hour pre-procedure, followed by 1 to 1.5 mL/kg/hour during the procedure and for four to six hours post-procedure, with at least 6 mL/kg given post-procedure. * Inpatients: Administer 1 mL/kg/hour for 6 to 12 hours pre-procedure, intra-procedure, and for 6 to 12 hours post-procedure.
It is important to note that practices may vary by site, and it is advisable to consult with the local nephrology team for best practices.
