In this issue of A & A Case Reports, Fierro et al.1 describe what appears to be embolized peripheral thrombus to the right atrium from a leg vein during cardiopulmonary bypass (CPB) in an elderly female undergoing aortic valve replacement and coronary artery bypass graft (CABG), detected by intraoperative transesophageal echocardiography (TEE). This case highlights the potential value of routine use of TEE including prebypass examination during cardiac surgery, as well as the need for the cardiac anesthesiologist to appreciate the value of TEE during CPB.
This is an area not well described except in isolated case reports. The recently updated ASE/SCA Guidelines for Performing a Comprehensive Transesophageal Echocar diographic Examination2 treats the period during CPB as somewhat of a “black box,” categorizing it as the period between which comprehensive anatomic examination is performed to assess the efficacy of surgical intervention relative to the prebypass baseline. In many practices, the TEE image is frozen as soon as CPB commences. This is an appropriate maneuver when the probe is not being used, given concerns regarding possible thermal injury to the esophagus, but should not stop the clinician from performing the functions I describe below. The experienced cardiac anesthesiologist should appreciate the value that TEE adds to assessing the proper conduct of CPB on many fronts including: (a) verifying the position and outcome of insertion of aortic and venous cannulae (particularly of value in excluding aortic dissection from the arterial cannula or placement of the venous cannulae into a hepatic vein instead of the inferior vena cava); (b) verifying the position of specialized cannulae such as the retrograde coronary sinus catheter (usually inserted before instituting CPB, except during mitral valve surgery when it is usually placed during CPB) and the left ventricular vent (always placed during CPB to prevent systemic air embolism); (c) recognizing ventricular distention due to problems with anterograde administration of cardioplegia (usually from varying degrees of aortic insufficiency that may not always appear significant before placement of the aortic clamp but can worsen because of distortion of the anatomy of the aortic valve by the clamp); (d) assessment of air in the right or left heart and its adequate removal after removal of the aortic cross-clamp, and as noted in this specific case report; and (e) the presence of thrombus or other solid material in a heart chamber or in a cannula.
The increasing use of real-time 3D imaging is facilitating this general process, particularly regarding cannula visualization. For those not yet so fortunate, there are numerous reviews and cases showing what they can expect when their current equipment is upgraded.3,4
In my experience imaging during CPB can be considerably more difficult than before or after, given that the size of various chambers is usually diminished. However, the simple recognition of a normal chamber size (denoting distention) is easy to detect, as occurred in this case.
Over the years, I have become increasingly interactive with the surgeons regarding the diagnostic role of TEE, and while most of what is done confirms proper surgical technique, the rare unexpected event in which the surgeon and perfusionist are stymied but where TEE shows precisely what is wrong usually “seals the deal” for membership on the surgical team. All cardiac anesthesiologists should push themselves to excel in on-bypass imaging, despite the lack of formal guidelines. Although there are clear cost issues related to whether TEE should be used in all CABG, valve, or thoracic aortic cases, I suspect that the growing recognition of the value of routine TEE to assess the conduct of CPB will eventually result in upgrading guideline recommendations to all on-pump CABG cases (as already occurs in many hospitals around the world in the absence of contraindications to its use).
A final related note on this case is the changing epidemiology of perioperative venous thromboembolism resulting (in my opinion) from the widespread use of intraoperative TEE. In my training, it was generally considered that intraoperative pulmonary embolism would be very low on the differential diagnosis of acute hemodynamic instability. Although Mangano5 back in 1980 presented a case report of purported intraoperative pulmonary embolism in a patient undergoing aortic aneurysm resection, diagnosed solely based on hemodynamic changes (consistent with acute right heart failure) from a pulmonary artery catheter (long before the first use of intraoperative TEE), there now are many case reports of intraoperative thromboembolism either noted while a TEE probe was already in place or imaged once a probe had been inserted.6–11 However, with regard to diagnosis of actual pulmonary thromboembolism, only right-sided large saddle emboli are ever likely to be imaged with TEE. Detection of thromboembolism by capture into the venous cannula appears to be a unique way to make this diagnosis, as these authors so well describe.
Martin J. London, MD
Department of Anesthesia and Perioperative Care
VA Medical Center and University of California, San Francisco
San Francisco, California
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