PiccA patient’s PICC line becomes obstructed and presents to your ED for care. She is using it for chronic antibiotics for osteomyelitis. You are unable to aspirate and flush it with saline using a 10 cc syringe.


Trick of the Trade: Unblock the Obstructed IV line

Flush the line with a smaller (3 cc) syringe

Do you remember Pascal’s Principle from your high school physics class? I vaguely recall it, but never thought it’d be of clinical importance. Thanks to Dr. Matt Silver (San Diego Kaiser Permanente Medical Center) for this tip, which also applies to flushing any clotted peripheral line.

Use a saline filled 3 cc syringe to flush the line. Generally, it takes very little force on the plunger. No need for a heparin flush. No need for diluted thrombolytic.

Pascal’s principle explains the physics behind it.  You’d think that a larger syringe would transmit greater force. Not true… a small-volume syringe exerts greater pressure per force applied to the plunger than a larger syringe.  If it doesn’t work after positional maneuvers and a 3cc flush, the line is likely unusable.


Michelle Lin, MD
ALiEM Founder and CEO
Professor and Digital Innovation Lab Director
Department of Emergency Medicine
University of California, San Francisco
Michelle Lin, MD


Professor of Emerg Med at UCSF-Zuckerberg SF General. ALiEM Founder @aliemteam #PostitPearls at https://t.co/50EapJORCa Bio: https://t.co/7v7cgJqNEn
Michelle Lin, MD