End-tidal carbon dioxide (ETCO₂) monitoring could aid resuscitation of trauma patients presenting with hypovolemic shock undergoing emergency surgery, a retrospective study suggests. ETCO₂ of less than 20 mm Hg was a 95% predictor of intraoperative cardiac arrest or death.

“Our results suggest that end-tidal carbon dioxide is a valuable short-term prognostic indicator in trauma patients underdoing emergency surgery,” said Danielle K. Bodzin, MD, an anesthesiologist at University of Miami/Jackson Memorial Medical Center. “We suggest that continuous end-tidal carbon dioxide monitoring early on in the resuscitation bay and during transport prior to entering the operating room [OR] could be a very useful practical marker of successful resuscitation, and may help us determine which trauma patients might benefit from early, aggressive resuscitation.”

ETCO₂ is a surrogate measure of cardiac output that can reflect sudden change. Dr. Bodzin said it can help gauge the adequacy of resuscitation during nontraumatic cardiac arrest.

Highly Predictive

Dr. Bodzin and her colleagues retrospectively queried the Anesthesia Information Management System at the Ryder Trauma Center in Miami. The researchers used an algorithm to identify patients (between years 2005 and 2015) who underwent emergency surgery after trauma with a maximum or average ETCO₂sustained for at least five minutes below or equal to 30 mm Hg. Neurologic cases were excluded.

Over the 10 years evaluated, researchers found 413 patients who met the inclusion criteria. Of these, 133 patients met the primary outcome of death or cardiac arrest. Two receiver operating characteristic curves were plotted for maximum and average less than or equal to 30 mm Hg within the predefined time frame.

“Both of our classifiers were over 8,” said Dr. Bodzin, “which suggests that end-tidal carbon dioxide is a valuable short-term prognostic indicator in trauma patients undergoing emergency surgery.”

The researchers, who presented their findings at the 2015 annual meeting of the American Society of Anesthesiologists (abstract 5007), concluded that ETCO₂ of less than or equal to 20 mm Hg was highly predictive of mortality.

“As the number of end-tidal carbon dioxide gets lower,” Dr. Bodzin said, “it’s even more predictive of intraoperative cardiac arrest or death.” For example, ETCO₂sustained below 15 mm Hg for five minutes is a 98.9% specific predictor of cardiac arrest or death. An ETCO₂ sustained less than 10 mm Hg for five minutes is a 99.6% predictor of mortality.

Dr. Bodzin noted that these findings were limited by the retrospective nature of the study. In addition, continuous ETCO₂ monitoring had not yet been implemented in the hospital’s resuscitation bay when the data were collected. “There was a time after we intubated and before we got to the OR that we were not monitoring. End-tidal carbon dioxide monitoring isn’t routinely employed during transport, and it’s not routinely employed as part of Advanced Trauma Life Support guidelines in the trauma bay.

“Future efforts should focus on the comparison of end-tidal carbon dioxide values to validated trauma prognostic scales and the mathematical modeling of temporal end-tidal carbon dioxide response to ongoing resuscitation,” Dr. Bodzin said.

Adam B. King, MD, assistant professor of critical care medicine at Vanderbilt University in Nashville, Tenn., and moderator of the session, observed that emergent transportation of patients is unfavorable for precise measurements.

“There’s usually a nonanesthesia provider transporting the patient, and you’re resuscitating with the Ambu bag, so it’s difficult to control,” said Dr. King. “On top of that, you’re adrenaline-rushed and moving quickly, so you have no idea what the tidal volume is or how fast you’re giving it.

“It’s an interesting concept,” Dr. King concluded, “but I think the researchers have to work on stabilizing the intraoperative tidal volumes in order to make the results more meaningful.”