New, smaller, wall-less cannulas designed for augmented venous drainage in MICS
Ludwig K. von Segesser1, Denis Berdajs2, Saad Abdel-Sayed1, Piergiorgio Tozzi1, Enrico Ferrari1.
1CHUV, Lausanne, Switzerland, 2Toronto General Hospital, Lausanne, ON, Canada.
OBJECTIVE: Inadequate venous drainage during minimally invasive cardiac surgery (MICS) becomes evident when the blood scavenged in the pulmonary circulation floods the surgical field. The present study was designed to assess the in vivo performance of new, smaller, virtually wall-less, venous cannulas designed for augmented venous drainage in comparison to traditional thin-wall cannulas.
METHODS: Remote cannulation was realized in 5 bovine experiments (74.0±2.4 kg) with percutaneous venous access, dilation up to 18F and insertion of either 19F thin wall, wire wound cannulas or, through the same access channel, new, smaller, virtually wall-less, braided cannulas designed for augmented venous drainage. A standard minimal extracorporeal pump set (MECC) with a centrifugal pump and a hollow fiber membrane oxygenator, but no in-line reservoir was used. 150 pairs of pump-flow and required pump inlet pressure values were recorded with high fidelity micro-tip pressure transducers and a flow meter calibrated by a volumetric tank and timer at increasing pump speed from 1500 RPM to 3500 RPM (500 RPM increments).
RESULTS: Pump flow accounted for 1.73±0.85 l/min for wall-less versus 1.17±0.452 l/min for thin wall at 1500 RPM, 3.91±0.86 versus 3.23±0.66 at 2500 RPM, 5.82±1.05 versus 4.96±0.81 at 3500 RPM. Pump inlet pressure accounted for 9.6±9.7 mmHg versus 4.2±18.8 mmHg for 1500 RPM, -42.4±26.7 versus -123±51.1 at 2500 RPM, and -126.7±55.3 versus 3.1±116.7 for 3500 RPM. The pump flow/pump inlet pressure relationship is shown in Fig.1.
CONCLUSIONS: At the well accepted pump inlet pressure of -80 mmHg, the new, smaller, virtually wall-less, braided cannulas provide unmatched venous drainage in vivo. Early clinical analyses have confirmed these findings.
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