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by Linda B. Mongero, C.C.P.
Columbia Presbyterian Hospital, New York, New York, USA |
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Perfusion Management of the Patient Undergoing Robotic Cardiac Surgery
The perfusion circuit configured for robotic surgery is quite simple with the aid of augmented return by either kinetic-assisted or vacuum-assisted venous return. The chest is completely closed, thereby requiring the venous and arterial cannulae to be inserted via femoral artery and veins. Because the aortic cross clamp is placed with a Chitwood clamp through a small incision in the chest wall for Mitral Valve procedures, the superior venous return (SVC) must be redirected to the pump with separate venous cannulation of the jugular vein. And, for closure of the ASD procedure, the SVC is cannulated to ensure drainage while the SVC is snared.
Using transesophageal echocardiography, the jugular vein is cannulated and positioned percutaneously with a Biomedical (Minneapolis, Minnesota, USA) #15Fr. or #17Fr. arterial cannula. This cannula is shorter and better suited for neck cannulation even though it is an arterial cannula. Heparin (5000 units) is flushed through the cannula, and a heparin drip is run through the side port on the cannula to prevent thrombus formation. The femoral vein is cannulated under direct vision using a modified Seldinger technique. The venous cannulae (#19-21 Fr.) have one end-hole and twelve side-holes, and are constructed of polyurethane with wire reinforcement, which resists collapse under high negative pressures. The 3/8" I. D. venous tubing (3/16" wall) is attached to the venous centrifugal pump that is operated with the outlet in the upward position to facilitate the removal of air from the venous line. Output from the venous pump enters a 1900 ml collapsible venous reservoir bag, which then empties into the inlet of the arterial centrifugal pump. The arterial limb of the circuit also consists of 3/8" tubing and is connected to the outlet of the arterial centrifugal pump. The arterial pump is operated in the normal downward position to protect against air embolism. Output from this pump is directed to an adult membrane oxygenator and then to an arterial filter before being returned to the patient. Connected to the top of the reservoir bag is 1/4" tubing passed through a roller pump, through which air can be easily aspirated from the system. As this is a closed circuit in series with the patient, there should be no air entrainment into the venous line. Remember that an open stopcock on the negative side of the pump connected to the patient may entrain air to the circuit.
Use of the Estech, (Danville, California, USA) remote access perfusion cannula (RAP) is ideal for the ASD procedure under closed chest technique. Both right and left radial arteries should be used to measure arterial pressure. Continuous comparison of the right and left radial artery tracings will ensure subtle changes which will indicate movement of the cannula or balloon which could obstruct the inflow of the innominate artery, the first branch of the aorta arch.
The perfusionist should set up a pressure transducer and monitoring line for the cardioplegia delivery pressure. The same monitoring line will also be used to measure the negative pressure when left ventricular venting is performed. Typical cardioplegia delivery pressures range from 150-400 mmHg. When the lumen is not being used for cardioplega delivery or venting, the pressure reading will represent the aortic root pressure. Delivery flow rate of cardioplegia should also be monitored. The maximum recommended flow is 350 ml/min. Arterial flow and line pressure should be monitored as usual (expect higher arterial line pressures than usual due to the length of the cannula). Arterial line pressures of ~ 300-350 mmHg are normal and are not damaging to the blood, as the outflow velocity is very low due to the multiple blood outflow ports of the cannula. Close collaboration between the surgeon and the perfusionist is very important.
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