3.1 Catheter types: (A) multilumen, (B) large bore (e.g. dialysis, plasmapheresis), and (C) introducer.
Figure 3.2 Non‐occlusive thrombus in right internal jugular vein.
Figure 3.3 Depth scale set at 2.6 cm. Note that entry point to vessel is at 1 cm. The operator should be aware of these depths while performing the procedure.
Figure 3.4 Note the angle between the needle and ultrasound probe is 70–80°. This optimizes needle tip visualization and vein penetration. This angle is suggested for central venous access of the internal jugular, lateral subclavian (or axillary), and femoral veins.
Figure 3.5 Ultrasound of the guidewire. (A) Following cannulation of the vein the guidewire is passed through the introducer needle and the needle is removed. (B) The ultrasound is again placed at the insertion site to visualize the guidewire (C) and confirm that the guidewire is in the vein and not in the artery (D) before dilation of the vessel is performed.
Figure 3.6 Arterial line catheter types. (A) Longer catheter (12 cm) used for axillary or femoral arterial lines. (B) Shorter catheter (4.5 cm) used for radial arterial lines.
Figure 3.7 Arterial line catheter types. (A) Angiocatheter. (B) Assembly (needle, angiocath, and guidewire incorporated into a single unit). (C, D) Guidewire and introducer needle separately.
Figure 3.8 Introducer needle angles for arterial catheter insertion. (A) Axillary line cannulation with needle positioning shown at a steeper angle (70–80°). This steeper angle is used to improve visualization of the needle tip under ultrasound (not shown) in the larger axillary or femoral vessels. (B) Radial line cannulation with needle positioning shown at a more shallow angle (e.g. 45° or less) to avoid penetrating the posterior wall of this small artery.
Figure 3.9 Arterial line waveform with peak wave followed by dicrotic notch. An adequate waveform (e.g. not damped) should be confirmed before suturing the catheter in place.
Additional material for this chapter can be found online at:
www.wiley.com/go/mayer/mountsinai/criticalcare
This includes multiple choice questions and Videos 3.1, 3.2 and 3.3.
CHAPTER 4 Bedside Ultrasound
Daisi Choi1 and John M. Oropello2
1 Weill Cornell School of Medicine, New York, NY, USA
2 Icahn School of Medicine at Mount Sinai, New York, NY, USA
OVERALL BOTTOM LINE
Bedside US is a safe, non‐invasive diagnostic procedure that allows rapid evaluation of undifferentiated hypotension and identification of reversible causes of shock. It is also a useful tool for promptly excluding immediately life‐threatening emergencies.
The focused assessment using sonography for trauma (FAST) exam is the standard of care in the initial evaluation of trauma patients with hypotension or signs of shock. Until recently, there was no standardized sonographic approach for evaluating the critically ill medical patient.
In 2009, the American College of Chest Physicians produced a consensus statement describing competence in critical care US. The components of critical care US the intensivist should achieve competence in for routine ICU operations include the following:Critical care echocardiography.Pleural ultrasonography.Lung ultrasonography.Abdominal ultrasonography.Vascular ultrasonography: guidance of vascular access and diagnosis of venous thrombosis.
Indications
Initial evaluation of undifferentiated hypotension and shock.
Non‐invasive monitoring of hemodynamic status and following response to therapy.
Respiratory failure.
Cardiac arrest.
Vascular access.
Basic concepts
Ultrasound physics (Table 4.1)
Sound waves: series of mechanical pressure waves that require a medium to travel through.
US waves undergo attenuation, reflection, refraction, and scattering as they travel through tissue.
Acoustic impedance: resistance of tissue to passage of US waves.
Degree of reflection is determined by difference in acoustic impedance of two tissues at interface.
US image is formed from reflected echoes.
Table 4.1 Features of ultrasound physics.
| Body tissue | Acoustic impedance | Degree of reflection |
|---|---|---|
| Air | Very low | High |
|
|
