End-tidal CO2-arterial CO2 differences: a useful intraoperative mortality marker in trauma surgery

The gradient of end-tidal CO2 to arterial CO2 (Pa-ET)CO2 has been identified as a predictor of mortality in patients undergoing emergency trauma surgery. In an effort to further elucidate this phenomena, we accumulated additional data on trauma patients undergoing emergency surgery.

Five-hundred and one patients undergoing emergent trauma surgery at an Urban Level I Trauma Center were used as a database. Data were obtained both prospectively and retrospectively. End-tidal and CO2 measurements were serially obtained during surgery. Data were arbitrarily placed in three categories: initial OR, post-resuscitation, and final OR. (Post-resuscitation was identified after bleeding controlled and vital signs normalizing). Correlation of the end-tidal CO2 with the PACO2 difference were correlated with various factors including survival.

Overall mortality was 29%. Mean ISS was 22 +/- 9.8. Mean emergency department systolic blood pressure was 81 mm Hg. Sixty-three people died in the operating room, 54 died within 24 hours post-op, and 30 patients died greater than 24 hours post-op. The average (Pa-ET)CO2 difference was <10 mm Hg in all survivors at all measurement times. The average (Pa-ET)CO2 was >10 mm Hg in non-survivors in patients that died at all time intervals.

(Pa-ET)CO2 can be used as a predictor of mortality and may be useful as an intraoperative tool for assessing the physiologic conditions of the patient. This predictor of mortality was valid even in patients that died greater than 24 hours after surgery. This information is almost always already available and may be used to further guide the decisions regarding patient care, particularly in decisions regarding damage control surgery.