Carbon dioxide embolism during salvage transanal total mesorectal excision in “frozen pelvis”: Two case reports

Figure 1 Perioperative hemodynamic and capnographic trends that demonstrate the biphasic signature of carbon dioxide embolism. A: Case 1: The graph depicts the sequence of events surrounding the transient hemodynamic collapse. Phase 1 (“gas lock”) was characterized by the precipitous drop in end-tidal carbon dioxide (ETCO₂, orange solid line) coincident with the significant decline in mean arterial pressure (blue dashed line) and heart rate (pink dash-dot line). Phase 2 (“rebound hypercapnia”) was manifested during resuscitation as a paradoxical surge in ETCO₂ (> 50 mmHg) due to the washout of dissolved carbon dioxide; B: Case 2: The graph illustrates the event that progressed to cardiac arrest, and the subsequent cardiopulmonary resuscitation (CPR). The values shown represent the last recorded measurements immediately prior to CPR initiation. A similar biphasic pattern was observed: An initial drop in ETCO₂ during the gas lock phase, followed by the rebound hypercapnia upon return of spontaneous circulation. CPR: Cardiopulmonary resuscitation; CO₂: Carbon dioxide.