Emergency Medical Services
Background: Screening for sepsis in the filed can be challenging as laboratory data such as serum lactate or procalcitonin are not readily available. The systemic inflammatory response syndrome (SIRS) criteria are inaccurate at predicting clinical outcomes in sepsis. Shock index (SI), defined as heart rate / systolic blood pressure, has previously been shown to identify high risk septic patients. The modified shock index (MSI) is also calculable in the field. Our objective was to compare the ability of SI, and MSI criteria to predict the primary outcome of hyperlactatemia (serum lactate ≥ 2.0 mmol/L) as a surrogate for disease severity, hospital admission for sepsis, death from sepsis
Methods: This was a prospective observational study conducted as part of our county EMS system’s quality and research program. Our IRB approved prehospital research registry uses a comprehensive database and record-keeping system that prospectively identifies and collects relevant data for all potential sepsis cases. Patients with Abnormal vitals and a positive shock index (HR/sBP > 0.7) or modified shock index [MSI] (HR/mean arterial pressure 1.3) are called in as sepsis alerts. Data on whether or not patients actually ended up having sepsis (defined as a serum lactate of 2 or greater at hospital admission) were collected from the receiving hospitals at our monthly QI meetings.
Results: A total of 468 patients over the 10-month period were transported to five main receiving hospitals, and qualified as “sepsis alerts” based on our prehospital sepsis alert criteria. Of these 250, or 53% were correctly identified as having sepsis, based on hospital laboratory criteria as defined above. 96% of our sepsis alerts were admitted for sepsis workups. There were a total of 40 deaths or 16% of our sepsis alerts died of sepsis in the hospital. The serum lactate was elevated in 246 patients or 53% of our cohort, which corresponded to those acutely identified as having sepsis.
Conclusion: The shock index and modified shock index, which can be easily calculated in the field using standard vitals signs can be a useful surrogate marker for early sepsis recognition, and correlate to serum lactate values.