Ultrasound Applications in Critical Care Medicine

The use of ultrasound has expanded enormously over the last two decades in critical care research and practice. Despite the fact that the method has several inherent limitations and is largely operator dependent, it enables clinicians for rapid, by-the-bed, and relatively inexpensive diagnostic evaluation of unstable patients. Point-of-care ultrasound applications such as lung ultrasound are gradually replacing traditional imaging modalities (i.e., chest X-rays), while the use of ultrasound for procedure guidance has been shown to reduce complications and thus to increase patients' safety [1–3]. In this issue, various papers illustrated the important role of ultrasound in the intensive care unit (ICU). K. Stefanidis et al. applied echogenic technology during ultrasound-guided cannulation of the internal jugular vein (IJV) and of the subclavian vein (SCV), respectively. Both case-control studies included intubated critical care patients and were performed under controlled ICU conditions. Ultrasound-guided cannulation of the IJV was attempted on the transverse axis and cannulation of the SCV on the longitudinal axis via an infraclavicular approach. In both studies, the use of echogenic technology significantly improved cannula visibility and decreased access time and technical complexity optimizing thus real-time ultrasound-guided central venous cannulation irrespective of the technique used. Current trends promote the optimization of two-dimensional ultrasound imaging by applying various technologies. Advances in ultrasound software can reduce artifacts and " noise " such as speckle arising from coherent wave interference or clutter arising from beamforming artifacts, reverberations , and other acoustic phenomena, while infusion of contrast agents during imaging facilitates interpretation of various pathologies [4, 5]. In that sense, the application of echogenic material could optimize procedural ultrasound applications. This may be of importance as ultrasound scanning is oftentimes performed under suboptimal conditions in the ICU, while the presence of mechanical ventilation, air and/or edema, may affect the clarity of images [6]. The clinical notion that IJV cannulation in patients at risk for intracranial hypertension could impair cerebral venous return was explored by D. Vailati et al. in a prospective study. They used two-dimensional and Doppler techniques to evaluate IJV cross-sectional diameter and flow patterns before and after ultrasound-guided cannulation in neurosur-gical patients placed in a supine or a head-up position at 30 degrees. No significant alterations in IJV flow rates following cannulation were recorded; however, the study was focused only on the venous system and no data about the arterial flow were presented. Future studies exploring changes in both vascular circuits are clearly …