Min invasive CABG: Single-lung vent
Last updated: 06/03/2016
Minimally invasive direct coronary artery bypass (MIDCAB) originally describes left internal mammary artery (LIMA) takedown and anastomosis to the left anterior descending artery (LAD) via anterior thoracotomy, as performed either off-pump on on-pump with femoral cardiopulmonary bypass (CPB) cannulation. Other minimally invasive approaches include thoracoscopic and robotic techniques. Minimally invasive coronary artery surgery performed off-pump (i.e., beating heart) requires lung deflation on the side of the surgical incision for exposure and visualization. Lung isolation for these surgeries can be performed with either a double-lumen tube or bronchial blocker via a single lumen tube.
One lung ventilation can greatly increase the exposure of the heart if the surgeon utilizes a left anterior mini-thoracotomy approach. This can be accomplished using either a double lumen tube or a bronchial blocker. In general, adjusting the ventilator to reduce motion using smaller, more frequent tidal volumes can be beneficial as well. Compared with the typical thoracic surgery with one-lung ventilation, minimally invasive coronary artery surgery requires thoracic insufflation with carbon dioxide. Insufflation pressures are kept low (10-15 mmHg). Hemodynamic consequences include increased central venous pressure (CVP), increased pulmonary artery pressure (PAP), decreased cardiac output, and regional wall motion abnormalities. Management includes IV fluids and vasoactive medications (e.g., norepinephrine, vasopressin, dobutamine, epinephrine, milrinone, dopamine). Increased CO2 absorption from the thoracic insufflation can cause increased PaCO2 and ETCO2 levels.
Initiation of femoral-femoral CPB should be considered if complications such as hemodynamic instability, hemodynamic collapse (e.g., CO2 embolization), or uncontrolled surgical bleeding occur.
While complications from cardiopulmonary bypass and a full median sternotomy can be avoided, the ability to perform multiple grafts can be technically challenging and require multiple incisions. Studies to date have shown similar outcomes with respect to morbidity and mortality between minimally invasive and traditional open approach; however, the minimally invasive approach has been associated with fewer transfusions, shorter ICU stays, shorter hospital stay and reduced hospital cost.
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