How should a patient be hydrated in preparation for coronary (cor) angiography?

Hydration Protocol for Coronary Angiography

Administer intravenous isotonic saline at 1 mL/kg/hour starting 12 hours before the procedure and continuing for 24 hours afterward to prevent contrast-induced acute kidney injury. 1

Risk Assessment Before Hydration

Assess all patients for contrast-induced AKI risk before proceeding, particularly focusing on: 1

• Glomerular filtration rate (GFR) - especially if <60 mL/min/1.73 m² 1
• Chronic kidney disease stage - higher stages carry incrementally higher risk 1
• Diabetes mellitus - independent risk factor 1, 2
• Heart failure or left ventricular dysfunction - increases risk 1, 2
• Advanced age - associated with higher risk 1, 3

Standard Hydration Protocol

For Patients with Moderate CKD (GFR 30-60 mL/min/1.73 m²):

Administer isotonic saline (0.9% normal saline) at 1 mL/kg/hour for 12 hours before and 24 hours after contrast exposure. 1, 2

• This represents a Class I, Level A recommendation from the European Society of Cardiology 1, 4
• The American College of Cardiology recommends 1.0-1.5 mL/kg/hour for 3-12 hours before and 6-24 hours after 3, 2
• Reduce the rate to 0.5 mL/kg/hour if ejection fraction <35% or NYHA heart failure class >2 to avoid volume overload 2

For Patients with Severe CKD (GFR <30 mL/min/1.73 m²):

Administer isotonic saline at 1000 mL/hour without negative fluid loss, continuing for 24 hours after the procedure. 1, 4

• This is a Class IIb, Level B recommendation 1
• These patients require more aggressive monitoring for fluid overload 1, 4

Alternative Hydration Regimen (Sodium Bicarbonate)

Sodium bicarbonate (154 mEq/L in dextrose and water) may be used as an alternative: 1, 3

• 3 mL/kg bolus over 1 hour before contrast 1
• Followed by 1 mL/kg/hour for 6 hours after the procedure 1
• However, the European Society of Cardiology states that sodium bicarbonate infusion instead of standard saline hydration is not indicated (Class III, Level A) 1
• The evidence remains mixed, with no clear superiority over isotonic saline 1, 3

Emergency/Urgent Cases (STEMI)

For patients requiring urgent primary PCI where 12-hour pre-hydration is not feasible: 4, 2

• Administer a rapid 250 mL bolus of isotonic saline over 30 minutes (reduce to 150 mL if left ventricular dysfunction present) 1, 4
• Continue at 1 mL/kg/hour during and for 24 hours after the procedure 4, 2
• The mortality benefit of revascularization in STEMI outweighs AKI risk when adequate periprocedural hydration measures are taken 1

What NOT to Do

Do not use oral hydration alone in patients at increased risk of contrast-induced AKI - this is a Class I, Level C recommendation. 1, 2

• While one study showed oral hydration was equivalent to IV hydration in patients with normal renal function or stage 1-2 CKD 5, guidelines explicitly recommend against relying on oral fluids alone for at-risk patients 1, 2
• IV hydration is superior to oral hydration for high-risk patients 2

Do not administer N-acetylcysteine (NAC) for contrast-induced AKI prevention - this is a Class III, Level A recommendation. 1, 3

• The ACT trial showed identical CIN incidence (12.7%) in both NAC and control groups 3
• The American College of Cardiology explicitly states NAC is not useful 3

Do not give prophylactic renal replacement therapy - this is a Class III, Level B recommendation. 1, 2

Additional Protective Measures During Hydration

While hydrating the patient, implement these concurrent strategies: 1

• Minimize contrast volume - keep total volume <350 mL or <4 mL/kg, or ensure total contrast volume/GFR ratio <3.4 1
• Use iso-osmolar or low-osmolar contrast media (Class I, Level A) 1
• Pretreat with high-intensity statins - rosuvastatin 40 mg, atorvastatin 80 mg, or simvastatin 80 mg before the procedure (Class IIa, Level A) 1
• Use radial artery access when feasible - significantly reduces AKI risk compared to femoral access 1
• Discontinue nephrotoxic medications - hold NSAIDs, metformin, and aminoglycosides before the procedure 4, 3

Post-Procedure Monitoring

Continue isotonic saline hydration for at least 24 hours after contrast exposure, especially in patients with severe CKD. 1, 4, 2

• Monitor serum creatinine at 48-72 hours post-procedure 4, 3
• Contrast-induced AKI is defined as an increase in serum creatinine ≥0.5 mg/dL or ≥25% from baseline within 2-5 days 4, 3
• Target urine output >150 mL/hour during the first 6 hours post-procedure, which typically requires approximately 1.5 mL/kg/hour of isotonic fluid 1

Common Pitfall to Avoid

The most critical error is inadequate pre-procedural hydration time. 1, 2

• Starting hydration only at the time of the procedure or giving a bolus immediately before contrast is inferior to the 12-hour pre-hydration protocol 2
• For elective cases, always plan for the full 12-hour pre-hydration period 1
• Patients should not be fluid restricted before the procedure - this historical practice increases AKI risk 1