Measuring cardiac index with a focused cardiac ultrasound examination in the ED

Noninvasive technology may assist the emergency department (ED) physician in determining the hemodynamic status in critically ill patients. The objective of our study was to show that ED physicians can accurately measure cardiac index (CI) by performing a bedside focused cardiac ultrasound examination.

A convenience sample of adult subjects were prospectively enrolled. Cardiac index, left ventricular outflow tract (LVOT) diameter, velocity time integral (VTI), stroke volume index, and heart rate were obtained by trained ED physicians and a certified cardiac sonographer. The primary outcome was percent of optimal LVOT diameter and VTI measurements as verified by an expert cardiologist.

One hundred patients were enrolled, with obtainable CI measurements in 97 patients. Cardiac index, LVOT diameter, VTI, stroke volume index, and heart rate measurements by ED physician were 2.42 ± 0.70 L min(-1) m(-2), 2.07 ± 0.22 cm, 18.30 ± 3.71 cm, 32.34 ± 7.92 mL beat(-1) m(-2), and 75.32 ± 13.45 beats/min, respectively. Measurements of LVOT diameter by ED physicians and sonographer were optimal in 90.0% (95% confidence interval, 82.6%-94.5) and 91.3% (73.2%-97.6%) of patients, respectively. Optimal VTI measurements were obtained in 78.4% (69.2%-85.4%) and 78.3% (58.1%-90.3%) of patients, respectively. In 23 patients, the correlation (r) for CI between ED physician and sonographer was 0.82 (0.60-0.92), with bias and limits of agreement of -0.11 (-1.06 to 0.83) L min(-1) m(-2) and percent difference of 12.4% ± 10.1%.

Emergency department ED physicians can accurately measure CI using standard bedside ultrasound. A focused ultrasound cardiac examination to derive CI has potential use in the management of critical ill patients in the ED.