CP33 Centrifugal Ventricular Assist
1. Centrifugal pump console
2. Sterile disposable pump head (2)
3. Electromagnetic flow probe
4. Sterile custom tubing pack (heparin bonded)
5. Tubing clamps
6. 1L double-spiked bag balanced electrolyte solution
Preparation of the left ventricular assist device by the perfusionist is begun by inserting the 3/8″ x 3/32″ wall tubing with spike into the bag of solution. Debubble the circuit up to and including the Bio-Medicus pump head by gently applying positive pressure to the bag of solution while venting through the other spike. Once the pump head is filled with solution, a clamp is placed on the tubing distal to the outflow of the pump head. Hang the solution on an IV pole and engage pump head to console. When the pump is turned on, spike the solution bag with the other 3/8″ x 3/32″ tubing, completing the recirculation loop. Continue recirculating the circuit until all air is removed. The system is now ready to be passed into the sterile field, divided, and connected to appropriate cannulae.
1. Left atrial cannula (typically venous-appropriate size for patient) (see cannula chart)
2. Aortic cannula previously placed for cardiopulmonary bypass Purse string sutures are placed in the left atrium, and the cannula is tied securely to avoid air entrainment into the assist circuit. The left atrial cannula is connected to the inflow of the bio-pump, carefully avoiding air bubbles. The outflow from the bio-pump is then connected to the aortic cannula previously used for cardiopulmonary bypass, and air again is evacuated.
1. Right atrial cannula
2. Pulmonary artery cannula (similar to type used for aortic cannulation) Cannulae are brought out through the superior or inferior aspect of the incision. The skin is approximated, whereas the sternum is not. The perfusion lines are secured to the drapes.
INITIATION OF VENTRICULAR ASSIST
After weaning from cardiopulmonary bypass, and once the decision has been made to support the patient on ventricular assist, flow is initiated and increased incrementally. The total systemic blood flow (native ventricular output +ventricular assist pump flow) should be maintained at 2.2 L/min/m2. If the left ventricular assist pump cannot maintain 2.2 L/min/m2 with good cannula placement and adequate volume, then right heart failure is significant and right heart assist may also be required.
The patient weaned from cardiopulmonary bypass should have heparin neutralized with the appropriate dose of protamine. The first 24h of ventricular assist will require no heparin therapy ; after the initial 24h, a heparin drip should be started to maintain an activated clotting time of 180-200s. The ventricular assist device unit is never decreased below 500 cc/min, regardless of the level of anticoagulation.
DISCONTINUATION FROM VAD
After 24 h, if the patient’s clinical picture is stable, the left assist pump flow rate is decreased to a level that causes the left atrial pressure to rise to 20-25 mmHg. Cardiac output calculations should be assessed to determine the function of the ventricle. When the surgeon has decided that the native ventricle can support the required cardiac output, the assist device may be removed. Removal of the device should be in the cardiac surgery intensive care unit or the operating room.