Intraoperative end-tidal carbon dioxide values and derived calculations correlated with outcome: Prognosis and capnography

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Abstract

Objective

To determine how much information concerning resuscitation and outcome is provided by the end-tidal CO2 and derived variables obtained during surgery.

Design

Retrospective chart review.

Setting

Emergency hospital operating room.

Patients

One hundred critically ill or injured patients requiring major surgery and having a mortality rate of 41%.

Interventions

Standard intraoperative monitoring, including continuous capnography, plus arterial blood gas analyses every 1 to 1.5 hrs during surgery.

Measurements and Main Results

There was only a fair correlation between the PaCO2 and end-tidal CO2 (r2 equals .14). The mortality rates in these patients were highest in those patients who had the lowest end-tidal CO2 values, the highest arterial to end-tidal CO2 differences, and the highest estimated alveolar deadspace fraction. A persistent end-tidal CO2 of less than equals 28 torr (less than equals 3.8 kPa) was associated with a mortality rate of 55% (vs. 17% in those patients with a higher end-tidal CO2). The mortality rate was also increased in patients with a persistent arterial to end-tidal CO2 difference of more than equals 8 torr (more than equals 1.1 kPa) (58% vs. 23%).

Conclusions

End-tidal CO2 and derived values should be monitored closely in critically ill or injured patients. Efforts should be made--by increasing cardiac output and core temperature and by adjusting ventilation as needed--to maintain the end-tidal CO2 at more than equals 29 torr (more than equals 3.9 kPa) and the arterial to end-tidal CO2 difference at less than equals 7 torr (less than equals 1.0 kPa).

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