ing a valveless trocar system that would create an invisible pressure barrier [20] so as to prevent smudging of the camera’s lens with repeated tro­car withdraws and reinsertions– a known prob­lem with trapdoor style trocars (Fig.33.4). The system also was designed to maintain stable pneumatics and to address the problem of smoke accumulation. Specically, by adapting a special­ized, no-valve trocar to triple lumen insufation tubing, (a) smoke evacuation, (b) pressure moni­toring, and (c) CO2 delivery could be separately managed. While these were considered important advantages for advanced robotic and laparo­scopic abdominal surgery [21, 22], it should be underscored that the AirSEAL® system was not designed for transanal surgery per se, nor was the system designed to rectify the problem of cyclic billowing with TAMIS. Instead, like TAMIS itself, the advantage of AirSEAL® iFS for trans­anal access in resolving the issue of pelvic breath­ing and smoke accumulation was realized completely by accident [23, 24].

Today, AirSEAL® iFS is the commonest insuf­ation system preferred by experts for use in con­junction with the TAMIS platform for both local excision and taTME to resolve the issue of cyclic billowing, which is otherwise considered to be one of the most signicant intraoperative limitations based on European Registry data [25]. However, AirSEAL® iFS may or not be available, and thus other substitutes can be considered, including a

access and insufation are present, and pressure settings should always be slightly less for abdom­inal insufation relative to taTME insufation. This is to maintain a positive down-to-up pres- sure gradient, otherwise the actualized work­space will collapse. This is true even if there is only one AirSEAL® iFS system in use, and a traditional laparoscopic insufator is being used to insufate the abdominal cavity. In such a set­ting, cyclic billowing can occur at the point of peritoneal entry. In general, the peritoneal entry, which is most commonly achieved along the anterior reection (as this is the shortest distance to the abdominal cavity) should be the last major step in the taTME dissection. After this step, even with correct pressure settings, a diminished oper­ative view can often be observed.

tissue is placed on stretch, and when a lead point has not been released. Such phenomena are not infrequently encountered during dissection with laparoscopic and robotic colorectal surgery. Thus, triangles from tethering of unreleased points are not unique to taTME, but tend to be quite pronounced with this operation in particu­lar. When the point of tethering (usually the ven­tral tip of the triangle) is not recognized and the dissection proceeds dorsal to this point, the fas­cia is violated, and it results in disruption of the fascia plane. Because the pneumatic force is uni­formly distributed at this point of violation, the appearance of a linear fascial disruption will take on the shape of a circle and has thus been termed the “halo sign” [28]. Triangles and halos are important signs in maintaining plane recog­nition during taTME.Due to the unique fascial layering patterns, entry into false planes is quite typical during the natural course of taTME dis­section. Especially along the posterior dissec­tion, it is critical that the triangle and halo phenomena are recognized and appropriately managed (Fig.33.7).

Paroxysmal and otherwise unexplained altera­tion in end-tidal CO2 (ET-CO2) should immedi­ately alert the taTME surgeon and anesthesiologist to the possibility of air embolization. This sudden change in ET-CO2 is usually the sentinel event detected, heralding the onset of cardiovascular compromise. In most instances, ET- CO2 decreases, but an increase in this parameter has also been observed during air embolization. Treatment of CO2 embolization requires rapid intervention and mandates that surgeon and anes­thetist work in concert to rectify the problem. These steps include the immediate cessation of CO2 gas delivery, ooding of the operative eld with saline, or gauze soaked in saline to prevent further gas entrainment, while controlling ongo­ing venous hemorrhage. Simultaneously, the anesthetist should perform Durant’s maneuver – that is, maintain moderate Trendelenburg (head lower than level of feet) while placing the patient in left lateral decubitus position (left-side rota­tion of the operating table); this is believed to decrease or at least limit gas from traveling through the right side of the heart into the pulmo­nary arterial tree where right ventricular outow can become obstructed due to an air lock. Furthermore, increasing positive end-expiratory pressure (PEEP) can decrease the pressure gradi­ent between the lacerated venous vessels and the central cardiovascular system, thereby limiting the potential of further gas entrainment [36, 37].

Investigation into understanding the process of gas embolization during taTME remains an area of active research. Alternative exogenous gases, unfortunately, are not currently feasible for use with taTME. For example, helium, although essentially inert with no pharmacologic effects and although noncombustible, is rela­tively insoluble in blood and more likely to result in embolization [38], leaving exogenous CO