Sepsis alerts in EMS and the results of pre-hospital ETCO2

Field sepsis alerts have the ability to expedite initial ED sepsis treatment. Our hypothesis is that in patients that meet EMS sepsis alert criteria there is a strong relationship between prehospital end-tidal carbon dioxide (ETCO2) readings and the outcome of diagnosed infection.

In 2014, our EMS service initiated a protocol requiring hospitals to receive notification of a "sepsis alert" on all suspected sepsis patients. The EMS service transports 70,000 patients/year to a number of urban centers. All patients transported to our major urban teaching hospital by our EMS service in one year in which a sepsis alert was announced were included in this study. The primary outcome variable was diagnosed infection and secondary outcomes were hospital admission, ICU admission and mortality. Positive lactate was defined as >4.0 mmol/L. ROC curve analysis was used to define the best cutoff for ETCO2.

351 patients were announced as EMS sepsis alert patients and transported to our center over a one year period. Positive outcomes were as follows: diagnosed infection in 28% of patients, hospital admission in 63% and ICU admission in 11%. The correlation between lactate and ETCO2 was -0.45. A ROC curve analysis of ETCO2 vs. lactate >4 found that the best cutoff to predict a high lactate was an ETCO2 of 25 or less, which was considered a positive ETCO2 (AUC = 0.73). 27% of patients had a positive ETCO2 and 24% had a positive lactate. A positive ETCO2 predicted a positive lactate with 76% accuracy, 63% sensitivity and 80% specificity. 27% of those with a positive ETCO2 and 44% of those with a positive lactate had a diagnosed infection. 59% of those with a positive ETCO2 and 89% of those with a positive lactate had admission to the hospital. 15% of those with a positive ETCO2 and 18% of those with a positive lactate had admission to the ICU. Neither lactate nor ETCO2 were predictive of an increased risk for diagnosed infection, hospital admission or ICU admission in this patient population.

While ETCO2 predicted the initial ED lactate levels it did not predict diagnosed infection, admission to the hospital or ICU admission in our patient population but did predict mortality.