Cardiopulmonary bypass
Cardiopulmonary Bypass
- 1. Expose great vessels
- 2. Purse string inserted into ascending aorta (adventitia) + aortic perfusion cannula + connect to bypass circuit
- Impracticalities: Aortic root surgery, dissection, severe adhesions - fem-fem bypass can be employed
- Purse string inserted into Rt atrium by appendage Cardiopulmonary bypass machine takes over circulation + ventilation
- Pumped from venous reservoir
- Oxygenated in membrane oxygenator (gas exchange across silicone membrane)
- Heat exchanger
- Filtered: remove particulate emboli
- Infused via roller pump (achieves even arterial pressure)
Post cardiopulmonary bypass
Air excluded from cardiac chambers
Restore beat is VF present
Epicardial wires for post-op bradycardia/heart block
Warm
Correct acidosis
Correct K
When BP acceptable, CPB discontinued
+ Protamine to reverse effects of heparinisation
+/- inotropic support
+/- intra-aortic balloon pump
Myocardial protection
- 1. Cardioplegic arrest
- Topical cooling + cardioplegic (intentional + temporary cessation of cardiac activity) solution
- K+ - containing (arrests heart in diastole by membrane depolarisation)
- Cold isotonic crystalloid - reduce metabolic rate
- Safe cardiac arrest can be maintained for 2hours
- Intermittent cross-clamp fibrillation
- Induce VF (by electrical voltage)
- Cross clamp aorta to render heart ischaemic
- Allow perfusion (10-20minutes) by intermittently releasing cross-clamped aorta + electrical cardioversion
- 3. Total circulatory arrest
Complications
- Access
- Infection, pulmonary injury, vascular injury
- Bypass
- Embolism
- Bleeding disorder (from heparin)
- Stress/consequences
- Tamponade
- Emboli - heart: infarction, brain: stroke, gut: ischaemia
