• Cardiothoracic
• Cardiopulmonary bypass
• Key components:
  Venous cannulae from SVC or IVC or RA drain blood into a reservoir
  Passed through an oxygenator (usually membrane or bubble)
  Passed through a heat exchanger then a filter
  Returned to patient distal to clamp in ascending aorta via a blood pump
  
• Blood pumps are roller or centrifugal and flow against resistance. They avoid stasis or turbulence to avoid embolism or haemolysis. They deliver a flow of 2.4L/min/m sq to correspond to the normal CI but is non-pulsatile
• Procedures needing CPB:
  CABG, valve replacement, large septal defects, heart and lung transplants and some aneurysms
• Steps taken
  1. Anticoagulate with 3mg or 300 IU/kg
  2. Ensure ACT is 4x normal at >400
  3. Pump priming will reduce haematocrit
  4. SBP needs to be reduced to <100mmHg to reduce risk of dissection
  5. Cardioplegia delivered by a pressurised bubble free circuit
• Complications
• Circuit related
• Cannula obstruction
  Failure of oxygenator
  Inadequate anticoagulation
  Aortic dissection
  Air embolism
  Haemorrhage
• Perfusion related
• Hypothermia
  Fluid overload
  Myocardial stunning
  Coagulopathy (especially if pump time >2hrs)
  SIRS
  Electrolyte disturbances
  Cerebrovascular events (1-5%)
• Cardioplegia solution
• Crystalloid (Ringer's lactate, dextrose and saline/dextrose have all been used) or blood based
• 20 mmol/L of potassium added
• Procaine added as stabilising agent and Mg added
• Stored at 4 degrees C to cool the heart to 10-12 degrees.
• Injected into coronary sinus or coronary arteries every 20 mins or when electrical activity returns. Core body temperature is between 28-32 degrees C.
• Post op care
• 'Fast track'
  Extubated in 8hrs
  Warmed
  Usually require fluids as warmed
  Haemodynamic stability
  Watch for hypokalaemia due to filtration of the pump prime
  Pain relief from high epidural
• Look out for bleeding due to plt haemodilution. Keep blood loss < 200ml/hr
  Re-sternotomy has a high in-patient mortality
• Coming off bypass
• Return temperature to 37 degrees
• Keep K 4-5
• Haematocrit >24%
• Sinus rate 70-100
• May need DC Cardioversion or internal defib or pacing wire if SR does not return
• The venous pump is gradually restricted to allow blood to flow into the RA
• As blood flows to the lungs and electric activity returns, ventilation with oxygen and volatile is recommended
• Once ventricles are contracting well, the circulating volume is returned to the heart
• Protamine 1mg per 100 IU is administered when surgically indicated. At this point the perfusionist must turn off the suction
• Take bloods for ACT, haematology, biochemistry, coagulation and ABGs