Evaluation of laboratory results and monitor parameters in patients with shock in the emergency department

OBJECTIVES: End-tidal CO2 is a new, non-invasive parameter that is easy and quick to measure. The objective of this study was to determine the clinical value of EtCO2 and its relations with monitor parameters and laboratory values, in evaluating patients with shock and predicting their mortalities; in patients treated for shock in the emergency department. METHODS: Prospective cross-sectional study was designed to include patients diagnosed as shock in Ege University Department of Emergency Medicine. Systolic and diastolic blood pressures, pulse rate, respiratory rate, body temperature, oxygen saturation and EtCO2 levels were recorded. EtCO2 levels were recorded by macrostream method in intubated patients and by sidestream method in patients with spontaneous respiration. Blood gas and laboratory values were recorded and on 2nd hour control vital signs, EtCO2 and lactate levels were measured. SOFA scores were calculated and recorded for each patient. First day mortality, internation or externation status were recorded. Following hospital internalization or externation, patients were tracked to measure 30 day mortality. RESULTS: 300 patients were included in the study. Mean age was 68±16. 46.3% were male and 53.7% were female. Mean EtCO2 value was 21.4±6.4 mmHg. Mortality in the first 24 hours was 16.7%, mortality in the first 30 days was 56.7%. In the patient group who died in the first 24 hours, mean EtCO2 was 17.2 (95% CI:18.4-20.5), while in the patient group who survived, mean EtCO2 was 22.3 (95% CI:23.4-25.2). The difference between these two groups, were considered to be statistically significant (p<0.001). When monitor parameters were compared with ROC analysis by means of predicting 1st day mortality, area under the curve was largest for EtCO2 (AUC:0.76; %95 GA:0.66-0.84; p<0.001). Area under the curve for 2nd hour control EtCO2 measurements was even larger (AUC:0.81; %95 CI:0.73-0.90; p<0.001). In the group of patients who died within 30 days, EtCO2 levels were statistically significant (p<0.001) and area under the curve in the ROC curve analysis was similar to that of 1st day mortality. Cut-off value for EtCO2 was determined as 21mmHg, using the ROC analysis and 50% percentile. For patients with EtCO2 levels≤ 21mmHg, sensitivity was 78%, specificity was 52.8% and negative predictive value was 92.3%. The relative risk of low EtCO2 levels in determining 1st day mortality were calculated as 3.42. A negative correlation was found between lactate and EtCO2 levels (p=0,026). EtCO2 was found to be correlated to bicarbonate (p<0,001) and base excess (p<0,001) but not correlated to pH (p=0,349). CONCLUSION: EtCO2 may be used to predict mortality in patients with shock. The fact that EtCO2 measurement is fast and non-invasive is crucial for shock patients who require early diagnosis and immediate treatment. The correlation of EtCO2 levels with lactate renders EtCO2 even more significant. Monitoring EtCO2 in patients with capnography may reveal better clinical results by means of predicting mortality. Keywords: Shock, End-tidal Carbondioxide, Mortality, Lactate, SOFA score