Why is dexamethasone (Corticosteroid) administered before Coronary Artery Bypass Grafting (CABG)?

Dexamethasone Administration Before CABG: Rationale and Benefits

Dexamethasone is primarily administered before coronary artery bypass grafting (CABG) to reduce the incidence of postoperative atrial fibrillation by attenuating the inflammatory response to cardiopulmonary bypass, although it does not significantly improve major clinical outcomes such as mortality or major morbidity.

Mechanism and Rationale

• Cardiopulmonary bypass (CPB) during CABG triggers an exaggerated inflammatory response, which is a possible etiological factor for postoperative complications, particularly atrial fibrillation 1
• Dexamethasone, as a corticosteroid, helps attenuate this inflammatory response by:
  • Decreasing pro-inflammatory cytokines (TNF-alpha, IL-6, IL-8) 2
  • Increasing anti-inflammatory cytokines (IL-10) 2
  • Modifying the inflammatory mediator balance in a protective direction 3

Evidence for Atrial Fibrillation Prevention

• Atrial fibrillation occurs in 27-40% of cases after cardiac surgery and is associated with infection, renal failure, neurological complications, prolonged hospital stay, and increased costs 1
• Corticosteroid administration has been shown to significantly reduce the incidence of new-onset atrial fibrillation in randomized controlled trials 1
• A systematic review and meta-analysis demonstrated that perioperative corticosteroids are associated with a lower risk of new-onset atrial fibrillation, although they may increase the risk of myocardial injury 1

Dosing and Administration

• Common regimens include:
  • Single intraoperative dose of dexamethasone 1 mg/kg given before CPB 1, 4
  • Methylprednisolone (1 g) before surgery and dexamethasone (4 mg every 6 hours) for 24 hours 1

Clinical Outcomes and Benefits

• Intensive care unit stay reduction: Dexamethasone has been shown to decrease ICU length of stay (29 hours vs. 43 hours) 5
• Respiratory benefits:
  • Lower alveolar-arterial oxygen gradients during the first 24 hours 3
  • Reduced duration of mechanical ventilation 3
• Temperature control: Lower mean rectal temperature in the first 24 hours postoperatively 3
• Fluid management: Decreased requirement for supplemental fluid during the first 48 hours 3

Limitations and Caveats

• Major clinical outcomes are not significantly improved:

  • The Dexamethasone for Cardiac Surgery (DECS) trial with 4,494 patients showed no statistically significant reduction in the composite outcome of death, cardiac, renal, respiratory, or cerebral adverse events (7% vs. 8.5%, p=0.07) 1, 4
  • The Steroids in Cardiac Surgery (SIRS) trial with 7,507 patients showed no reduction in 30-day mortality or major morbidity 1
  • A recent trial showed dexamethasone did not increase the number of days alive and at home up to 30 days after surgery compared to control 5

• Potential adverse effects:

  • Increased postoperative glucose levels requiring monitoring 4
  • Possible increased risk of postoperative complications 1

Special Considerations

• The hypothesis that patients younger than 75 years might benefit more from corticosteroids in cardiac surgery has been investigated 1
• Pediatric patients may show more pronounced benefits from dexamethasone administration before CPB, with studies showing reduced inflammatory response and improved clinical outcomes 3

Conclusion

While dexamethasone administration before CABG does not significantly improve major clinical outcomes like mortality, it is primarily used to reduce postoperative atrial fibrillation and attenuate the inflammatory response to cardiopulmonary bypass, potentially improving secondary outcomes such as ICU length of stay and respiratory function.