End-tidal carbon dioxide monitoring in conjunction with blood gas analysis can be predictive of clinical outcome in a patient undergoing emergency surgery for trauma. The presence of acidosis or hypercarbia is associated with a worse prognosis,
Parameters:
(1) End-tidal carbon dioxide (ETCO2)
(2) End-tidal CO2 and arterial CO2 difference
(3) arterial pH
ETCO2 and arterial CO2 difference in mm Hg =
= (arterial pCO2) - (ETCO2)
A low ETCO2 is associated with poor outcome.
(1) Dudaryk et al report an ETCO2 <= 20 mm Hg at 5 minutes after starting mechanical ventilation in the operating is associated with increased mortality.
(2) Domsky et al report a persistent ETCO2 <= 28 mm Hg is associated with increased mortality.
An increase in the ETCO2 and arterial CO2 difference is associated with mortality:
(1) Campion et al reported an ETCO2 and arterial pCO2 difference > 10 mm Hg is associated with increased mortality.
(2) Tyburski et al (2003) reported a similar cut-off.
(3) Tyburski et al (2002) reported better survival if the difference was <= 9 mm Hg.
The difference between ETCO2 and pCO2 is maximal when the ETCO2 is low and when there is hypercarbia with acidosis.
An arterial pH less than 7.30 is associated with a ETCO2 and arterial pCO2 difference > 10 mm Hg.
