Noninvasive hemodynamic monitoring in the emergency department

Emergency department patients are frequently undifferentiated, need accurate risk assessment and stratification, and are time-critical in their need for diagnosis and resuscitation. Valid, noninvasive hemodynamic monitoring modalities are essential to differentiate high from low risk patients, and to perform goal-directed management. This review analyses recent literature, which describes innovation in the range of noninvasive monitoring tools and places them in the emergency medicine context. A range of noninvasive measures of hemodynamic status are both commonly used, or are in the research and development phase. Pulse oximetry waveforms, electrocardiogram-based heart rate variability, Doppler and B-mode ultrasound, echocardiography, transthoracic bioimpedance, pressure pulse waveform analysis and near-infrared spectroscopy all have potential value in diagnosis and monitoring of hemodynamics, particularly used to explore autonomic nervous system control of cardiovascular function and by extension the early phases of compensation for illness and injury. Noninvasive techniques coupled with advances in data visualization and pattern recognition bring the potential for revolution to emergency department hemodynamic monitoring. Noninvasive measures of hemodynamic status and function are increasingly being used, although much still remains in the research domain. Noninvasive measures may not only offer similar variables to traditional vital signs, but add a new dimension of hemodynamic descriptors.