ultrasound guided peripheral ivPlacing a peripheral IV under ultrasound guidance is often much more challenging than it outwardly appears, especially for novice users. One of the more difficult aspects is in making sure that the target vessel is perfectly in the middle of the screen and then guessing where that corresponds to the middle of the ultrasound probe.

Trick of the Trade:

Use the M-mode line to optimize needle-vein alignment

M-mode and ultrasound


Some ultrasound machines have a special line that can be superimposed down the middle of screen, though this is often buried in complex settings and is generally directed towards biopsies and other needle-guided procedures. For example, on Zonare machines this is called the “Biopsy Guide”.

For a simpler solution, one can use the M-mode line on many machines. M-mode displays one line over time and is especially useful for certain applications in emergency medicine like assessing for a pneumothorax or measuring fetal heart rates.

However, most machines require the user to press the M-mode button twice to engage it. Generally, the first press puts the M-mode line on the screen and then the user can move the line if needed or press the button again to start classic M-mode.

Instead, I press the button once to bring up the M-mode line directly in the middle of screen when placing peripheral IVs. I know that this line corresponds to the middle of the ultrasound probe and then I line up my IV catheter with the mark on the probe—knowing that it will proceed along the path of the vertical M-mode line.

Jeff Wiswell, MD

Jeff Wiswell, MD

Attending physician
Department of Emergency Medicine
Mayo Clinic Health System