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| Guest Commentary |
By Rafael Cabrales, MD
Section Head, Cardiothoracic Anesthesiology
Cleveland Clinic Florida, Weston, Florida, USA |
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Combination of minimally invasive coronary bypass and percutaneous coronary intervention in patients with multivessel disease: a Cardiothoracic Anesthesiologist’s Perspective
The advent of off pump coronary revascularization (OPCAB) in the 1990’s introduced new challenges in anesthetic management of the patient with coronary artery disease as we moved away from techniques performed with cardiopulmonary bypass (CPB). Surgical techniques have made significant progress and are progressively becoming less invasive while interventional cardiologists are become more invasive in their approach. The rapid progression of minimally invasive off pump revascularization techniques such as endoscopic, atraumatic coronary bypass (endo-ACAB) and robotically assisted procedures continue to challenge our management in these patients. Hybrid revascularization has unique patient management concerns and the Anesthesiologist plays a vital role in the success of a hybrid revascularization program.
First of all, intraoperative management of the patient undergoing hybrid revascularization requires all of the skills necessary for off-pump revascularization. Invasive hemodynamic monitoring as well as proactive hemodynamic management is essential to this procedure and these techniques are complicated by the need for single lung ventilation during dissection of the internal mammary artery. Single lung ventilation can be accomplished by the use of either double-lumen endotracheal tubes or the use of any of the commercially available bronchial blockers. The use of high insufflation pressures during thoracoscopy can accentuate hemodynamic changes in hypovolemic patients and can cause transitory myocardial regional wall motion changes in patients monitored with transesophageal echocardiography. The possibility of having to convert from a minimally invasive procedure to a sternotomy either due to technical difficulties or hemodynamic instability makes the use of bronchial blockers useful for this procedure as lung ventilation can be resumed through a single lumen tube rapidly and there is no need to change a double lumen tube at the end of the procedure for postoperative ventilation. The use of minimally invasive surgical procedures makes these patients good candidates for fast-track or ultra-fast track weaning and extubation protocols.
Transesophageal echocardiography plays a vital role in hybrid revascularization. Assessment of myocardial regional wall motion changes pre and postoperatively is reassuring and the presence of a new regional wall motion change after revascularization may be the earliest sign of inadequate revascularization or the presence of ischemia in a non-revascularized area. The use of novel echocardiographic techniques such as contrast echocardiography may also become useful in assessing revascularization intraoperatively.
Intaoperative myocardial protection during temporary occlusion of coronary arteries while grafting as well as protection of the non-revascularized areas is a challenge for the anesthesiologist. In canine models the administration of magnesium prior to temporary occlusion has been found to reduce infarct size histologically. Inhaled anesthetic agents also have ischemic preconditioning properties which may be helpful in myocardial protection strategies. Sodium channel blockers may be the next step in myocardial protection. Administration of sodium channel blockers prior to occlusion may provide myocardial protection during periods of occlusion by decreasing the influx of sodium into the myocite during ischemia. This temporary effect may provide a window of protection in which to accomplish adequate revascularization and minimizing myocardial ischemia during periods of vascular occlusion. While these techniques show promise it is too early to tell if they actually have an impact on patient outcomes.
At the conclusion of the procedure, the challenge is to continue managing the patient’s hemodynamic parameters appropriately as the presence of one or more non-revascularized areas may put the patient at risk for perioperative myocardial ischemia. Medical management with attendant control of heart rate and blood pressure are crucial. Pain management strategies are an important part of patient management during minimally invasive procedures and hybrid revascularization. The use of neuraxial opiods as well as intercostal nerve blockade have all been described successfully as pain management strategies. These techniques are useful in fast-track extubation protocols but can have beneficial hemodynamic effects as inadequate pain control can lead to unwanted hypertension and tachycardia in a patient that is still not fully revascularized.
Robotically assisted surgery can be accomplished at remote locations with the use of satellite linkup. This pushes our boundary of monitoring patients out of the operating room and opens up the door for telemedicine. Remote monitoring of patients under anesthesia has been described and accomplished successfully and in the near future an experienced cardiac anesthesiologist may be able to monitor and treat patients remotely with the assistance of the local anesthesia team.
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