The use of bedside ultrasonography has become an integral tool for evaluating and managing the critically ill patient. Improved image quality and increased portability of ultrasound machines have augmented the utility of physician-performed bedside ultrasonography in the emergency department and the intensive care unit. Not only is ultrasound useful diagnostically, but it can also shine a light into the darkness of invasive procedures traditionally performed with a landmark or “blind” technique. While initially the ultrasound-guided procedure may take more time as the practitioner's skills are developing, the ultimate benefits of fewer complications, less time to completion, and fewer attempts to complete the procedure make this technique worthwhile to master.1,2
Increased utilization of bedside sonography in the critical care arena has generated a large amount of research in the field. This has led to a paradigm shift in the way that procedures are performed at the bedside. Emblematic of this shift is the document released in 2001 by the Agency for Research and Health Care Quality, Making Health Care Safer: A Critical Analysis of Patient Safety Practices, which states that the body of evidence supports the use of ultrasound guidance for placement of central venous catheters.3
The performance of multiple critical care procedures may be improved with the addition of sonographic guidance. This chapter provides information about how ultrasound can be used to guide the following invasive procedures: central venous access, arterial line placement, pericardiocentesis, thoracentesis, paracentesis, lumbar puncture, endotracheal tube placement confirmation, and thoracostomy tube placement confirmation.
There are multiple transducers to choose from when performing a sonographic study. Selecting the correct probe can make the difference between a good image that is helpful and an image that is of poor quality and misleading. As a general rule, the higher the frequency, the better the resolution. The tradeoff is that high-frequency sound waves cannot penetrate deep into the tissues of the body. A high-frequency linear transducer is used to image superficial structures and is ideal for sonographic guidance when obtaining vascular access, performing lumbar puncture, and confirming placement of a thoracostomy or endotracheal tube. The curvilinear probe (2.5–5 MHz) is most often used for evaluating deep structures in the abdomen and pelvis. Because of its lower frequency, it results in good sound-wave penetration, but with a relative loss of resolution. The phased array probe (1–4 MHz) is ideal for intercostal imaging since it has a small footprint, a narrow superficial field of view, and a wider deep field of view (Figure 45-1).
The three most commonly used probes. On the left is the high-frequency linear probe. In the center is a low-frequency curvilinear probe and to the right is a phased array probe.
When performing an ultrasound-guided procedure, the ultrasound machine should be positioned in such a way as to ...