Coronary Artery Bypass Grafting

Airway: ETT
Access: 14G IVC or MAC line, arterial line, CVC, +/- PAC
Pain: Substantial, especially in younger patients
Position: Supine/crucifix
Time: 3-4 hours
Blood loss: G+H required. Keep units available if re-do surgery, anaemic, small, sick, or emergency.
Special: CPB - higher risk for anaesthetic awareness

Use of an autologous artery or vein to bypass a stenosed section of coronary artery and restore downstream perfusion. CABGs:

Considerations

This covers factors unique to CABG. Factors relating to cardiac surgery in general are covered here.

  • B
    • Atelectasis
    • Bronchospasm
  • C
    • CAD
      High risk features:
      • History:
        • Unstable angina
        • AMI within last 3 months
        • Cardiogenic shock
        • Emergency revascularisation.
        • Decompensated CCF
        • LV aneurysm
          Indicates poor myocardial function.
      • Coronary anatomy:
        • Left main disease
          Avoid drop in perfusion pressure in the case of critical left main stenosis.
          • Significant >50%
          • Severe >80%
          • Critical ~>95%
          • Note also that high-grade stenosis of the LAD and LCx lead to an effective critical stenosis of the LMCA
          • Note that effective stenosis depends on degree of collateralisation
            Well-developed collaterals compensate for poor native disease.
        • Triple vessel disease
        • Proximal LAD stenosis
      • Ventricular function
        Dysfunction may be unable to wean from bypass.
        • LVEF < 30%
        • Concomitant RV dysfunction
    • Valvular disease
      Particularly AS or MR.
    • Severe LV or RV dysfunction
      • Pulmonary oedema
  • H
    • Massive haemorrhage

Induction

  • Aim for haemodynamic stability, especially in the setting of critical left main stenosis

Intraoperative

This covers factors unique to CABG. Factors relating to bypass are covered here.

On-pump CABG can be divided into pre-, intra-, and post-bypass phases:

  • Pre-bypass
    • If LIMA harvest is occurring:
      • ↓ VT to 5-6ml/kg
      • Reduce anaesthetic
        Period of minimal stimulation following the very stimulating sternotomy.
      • ↑ FiO2 as there is a frequent surgical requirement for apnoea
  • Bypass
  • Post-bypass

Surgical Stages

For standard approach:

  • Sternotomy
  • Establish CPB
  • Establish diastolic arrest
  • Grafting performed
    • Internal mammary grafting
      • A pedicled graft may be taken
        The origin is left attached to the SCA.
      • Bilateral IMA grafts may be used
        ↑ the risk of sternal wound infection due to poor perfusion.
    • Saphenous vein graft
      ~50% of SVG grafts will be occluded at 10 years (compared to ~10% of arterial grafts).
    • Radial artery
      Non-dominant or dominant vessels may be used, provided there is adequate collateral flow via the ulnar artery.
  • Cross-clamp is removed and coronary perfusion commences
  • Wean from CPB occurs once air is removed from circulation

Postoperative Care

Medication:

  • Aspirin
    • Within 6 hours
    • Consider clopidogrel if aspirin allergy
  • Statin
    • When PO intake resumes
  • β-blockers
    • When able
      Limited by pacing requirement, inotrope requirement, or hypotension.
  • ACE-I/ARB
    • Consider in all patients
    • Initiation limited by hypotension and AKI

References

  1. Chikwe J, Kim M, Goldstone AB, Fallahi A, Athanasiou T. Current diagnosis and management of left main coronary disease. Eur J Cardio-Thoracic Surg. 2010;38(4):420-428.