Arterial to end-tidal CO2 laparoscopic gradient reversal during pheochromocytoma resection

We report the development of severe intraoperative hypercarbia and a pronounced arterial to end-tidal gradient reversal during laparoscopic pheochromocytoma resection. Although complex physiologic mechanisms may be responsible for this finding, anatomic alterations such as a direct communication between a capnoperitoneum and/or capnothorax and the airways resulting from prior pathology and the type of procedure should also be considered.

During anesthesia for laparoscopic pheochromocytoma removal we noticed an abrupt, extensive increase of the end-tidal CO(2) accompanied by a change of the capnographic CO(2) tracing and reversal of the normal arterial-to-end-tidal gradient. These changes consistently disappeared by intermittent deflation of the abdomen and at the end of surgery. A chest x-ray revealed a right-sided loculated pneumothorax with pleural thickening. Peritoneo-thoracic CO(2) tracking and pleural scaring with pulmonary adhesions resulting in a unidirectional communication between the pleural space and airways may best explain the chest x-ray and clinical findings.

Severe intraoperative hypercarbia and arterial to end-tidal CO(2) gradient reversal represents an intraoperative challenge. The possibility of a direct communication between the pleural space and the bronchial tree should be considered when other etiologies have been excluded. Simple maneuvers such as abdominal de- and re-inflation and analysis of the end-tidal capnographic tracing might aid in the differential diagnosis and management.