Category: vascular access

Does a 48 mm single-lumen angiocath in a central vein assume the infection risk of a central line or a peripheral line? Stated differently, does the infection risk of a central line stem from the line itself, the vein, or some other factor? Many of us who trained without ultrasound are very adept at cannulating the subclavian vein by landmarks. To be able to place a simple angiocath into a central vein in non-sterile fashion would be very convenient in difficult access patients. I can’t advocate for this unproven maneuver at large, but it may have a role in patients who need vascular access expediently but don’t need a central line, perhaps as a bridge to a conventional peripheral line or a formal central line.

Journal of Emergency Medicine 37:4 p419

Excerpted from MSSM M&M teaching points:

* Accidental arterial cannulation is usually benign but should be detected before dilation to avoid significant vessel injury. When performing an ultrasound-guided central line, the point where the needle tip enters the vein must be in the visualized ultrasound field. This may be accomplished by entering the skin with the needle a short distance away from the probe, rather than immediately adjacent to the probe, which will lead to the tip entering the vein out of the vertical plane visualized on the screen. Alternatively, the tip of the needle can be tracked into the vein by sliding the probe along the skin as the needle tip approaches the vein, keeping the tip in the visualized ultrasound field.

* If venous placement is not certain, verification may be performed using a number of techniques.
**A quick blood gas may be helpful if the PaO2/SaO2 values are conclusive; unfortunately blood gas results may lie in between definitively arterial and venous values.
** Transducing the pressure waveform is effective but takes time to set up.
** A brief and definitive technique uses a quick pressure column setup as follows:

1. Insert the guidewire, remove the needle.
2. Slide the conventional angiocath that comes in all central line kits over the wire, remove the wire.
3. Attach an extension set to the angiocath. An extension set comes in the introducer kit for this purpose. For triple lumen kits, ask the nurse to give you an extension set, or use the circular plastic sheath that stores the guidewire as extension tubing.
4. Keeping the tubing parallel to the floor, allow 20-30 cm of blood to fill the tube.
5. Hold the tube straight up to the ceiling. If the angiocath is in a vein, the column of blood will fall back down to the level of the CVP. If the angiocath is in an artery, the column of blood will continue to rise.
6. If the angiocath is in the vein, thread the guidewire, pull out the angiocath and continue Seldinger technique as usual. If the angiocath is in the artery, either remove the angiocath and hold pressure or call vascular surgery for advice.

** To estimate how low a bag of saline needs to be so that it does not overcome arterial blood pressure, use the formula SBP/2 = height in inches. For example, if the patient has an SBP of 70 mmHg, this corresponds to a height of 35 inches. If the fluid bag is hanging more than 35 inches above a patient with an SBP of 70, it will flow into an artery, fooling the unsuspecting observer into thinking the catheter is in a vein. Therefore, to verify venous placement by attaching a bag of saline, the bag of saline must be lower in inches than half of the patient’s systolic blood pressure.

Demonstrations and discussions of full sterile technique, quick pressure column technique, and a number of other central line-related topics can be found on Haru Okuda and Scott Weingart’s central line project page:

http://ehced.org/howtos/centrallineproject/central-lines.htm

Agree with previous rave reviews in terms of ease of use, success
rates, reliability.

I would add, as far as pain is concerned, that I have used this device
in quite a few awake infants and young children. We see a tertiary
population, often with underlying disease making PIV access difficult;
I have personally watched the pain response in these patients to PIV
attempts, and have found it much LESS painful to insert an EZ IO in
awake patients. We have done this without local infiltration with
lidocaine. One key is NOT to start and stop the drill as it goes
through the skin – I have seen residents do this and it twists the
skin which hurts. As long as the trigger is held until the needle is
in the bone, patients cry much less than they do with PIV placement.

The caveat, however, is that infusion through the IO definitely
appears painful. We now routinely instill 1cc of 1% lidocaine through
the IO, then wait 2 minutes before pushing fluids (this isn’t
necessary, of course, in an emergent resuscitation of an unconscious
patient). Another technique is to put 2-3 cc of 1% lidocaine in the
bag of IVF that you are infusing which seems to decrease infusion pain
well.

Garth Meckler, MD, MSHS
Fellowship Director and Assistant Section Chief
Pediatric Emergency Medicine
Oregon Health & Science University