Cardiopulmonary Bypass

CPB strategy

  1. Heparin
  2. Expose the heart. Check BP/Aorta. 
  3. Aortic cannulation; check cannula for pressure/flow
  4. Atrial cannulation; venous clamp off; on bypass. Lungs off
  5. Inspect the heart. Place aortic/retrograde cardioplegia. Reduce pump flow/cross-clamp aorta. Return to normal flow/check line pressure. Begin cardioplegia. Set patient temperature. 
  1. Release aortic cross-clamp after warm cardioplegia. Be certain six conditions reviewed before weaning CPB. Lungs deflating/inflating. Good contractility. Stable heart rhythm. No bleeding in inaccessible areas. Temperature at desired level. No retained air. 
  2. Wean off bypass. Venous line clamped/remove when stable. Remove aortic vent. Protamine. Follow RAP, PAP and BP. Be alert for haemodynamic reaction. Remove aortic cannula. 

CPB Problems

Patient arrest when CPB machine not ready

  • Start CPR – continue to open chest vs external CPR
  • Call for help – surgeon, anaesthetist, another perfusionist
  • CO2 flushing of circuit
  • Use prepared circuit with CO2 flushing
  • Fully primed circuit (closed)

High line pressure + falling levels

Stop pump and treat cause:

  • Dissection – another cannulation site, cool and fix dissection
  • Arch vessel cannulation or obstructing head vessel lumen
    • Long cannula – check carotid pulse – unequal?
    • Ipsilateral flushing/sweating
    • unequal pupils
    • unequal nirs – stop perfusion and reposition cannula
  • Mural placement – check back flow
  • Line obstructed – kink/clamped/pressed on/
  • Abutting wall
  • Clotted circuit

Low volume

Strategy for finding cause:  Buy time to find cause by:

  • Giving volume
  • Increasing height of table 
  • Add vacuum to venous return

Find and resolve the problem by checking systematically: Surgeon starts with the line starting from his end, perfusionist starts with the line at his end. 

Surgeon: 

  • Is there enough blood volume to go into the line? 
    • Check for bleeding in the pleura, pericardium, spilling out – suck it out
    • Check for vasodilator use – counter with vasoconstrictor
    • Check for dissection – cool and repair dissection
  • Is the line in the right position?
    • Check for obstruction of the line tip in the IVC against the hepatic flow – withdraw cannula and see if pressures are ok. 
    • Check for obstruction of the venous cannula in the RA – adjust the cannula position
    • Check for obstruction of the venous cannula outside the RA – check for kinks/clamps/obstruction/stepping on line
  • Is the line of sufficient size?
    • Check if venous line is too small –  change line?

Perfusionist:

Check for obstruction: Air, Leaks, Clamps, Obstructions, line too small

Overflowing reservoir

  • Volume overloaded 
    • Anticipate and sequester
    • RAP
    • Store volume by sequestration
    • Vasodilator
    • Diuretic
    • CUF – continuous ultrafiltration 
  • If line pressure ok
    • Increase flow
    • Vasodilator
    • Raise table
    • Head up
    • Heart distension

AIR EMBOLISM

  • Stop the pump
  • Cool the patient
  • Head down

Embolism outside the patient –

  • clamp lines,
  • reverse flows 
  • clear the air in the arterial circuit upto the aortic cannula.

Embolism inside the patient

  • Reduce the harmful effects of embolism: Cool the patient, delay warming, keep hypothermic, keep cool after op, hyperbaric oxygen
  • Reduce chances of embolism going to vital organs:  High flow, high pressure, high MAP, low CVP, keep head neutral
  • Reduce chances of further complications of embolism: Delay protamine to prevent clots

Low O2

Oxygenator

Increase FiO2

Oxygenator failure – if at the beginning or end, come off bypass. 

If in the middle, cool the patient, off CPB, change the oxygenator. 

Changing the oxygenator

Clogged circuit – change everything

Not clogged – change only the membrane oxygenator

HEAT EXCHANGE LEAK

Like TURP syndrome

Volume increasing, haemolysis,haemoglobinuria, hyponatraemia, hypokaelamia, bacteraemia, 

Antibiotics

NO OXYGEN

Spare cylinder

Cool/circ arrest

Run on air – open 1/4 line via pump head

Ventilate if on partial bypass

Connect 1/4 tubing to gas inlet, put the tubing around the pump to act as sucker into oxygenator

HIGH CO2

Increase sweep gas flow

Hypermetabolism – fever, malignant hyperthermia

Oxygenator failure

1. Stop the Pump

2. Clamp the arterial and venous lines (to isolate the patient from the circuit)

a. Remove any air in the arterial circuit up to the aortic cannula

3. Deep Trendelenburg position

4. Make a stab wound or exit wound in the aorta

5. Bilateral carotid compression

6. Temporary retrograde perfusion

a. Remove the aortic cannula and purge arterial circuit of air

b. Place aortic cannula in SVC

References:

http://tele.med.ru/book/cardiac_anesthesia/text/he/he019.htm#he019p119