Do Not Fear the Difficult IV

To the Editor

It was with great interest that we read the recent prospective observational study by Ueda and Hussey,¹ detailing an ultrasound-guided needle tip navigation technique for peripheral intravenous cannulation in obese patients without visible veins. Their efforts in addressing the important practical context of obtaining large-bore intravenous access in situations traditionally deemed difficult should be congratulated. We have been using a very similar technique and would like to share our insights.

We believe it is very important to confirm a freely movable needle tip within the vessel, as described in step 7 by Ueda and Hussey.¹ By moving the needle tip up, down, left, and right, and observing that it moves independently of the vessel, 2 potential pitfalls that can lead to a false lumen during catheter advancement can be negated. Though the needle tip may appear intraluminal, the very tip may still be lodged in the deeper wall of the vessel (“back-walled”), especially in small vessels. Also, the needle tip can indent the superficial surface of the vessel without entering the lumen and on imaging still appear intraluminal. Achieving a freely movable needle tip within the lumen may avoid these pitfalls.

Additionally, ensuring a freely movable tip may obviate the need to assess for a “flash of blood,” a fact that by itself does not guarantee intraluminal needle tip placement. This can be advantageous during an ultrasound-guided radial arterial line placement on the same arm as the location of a noninvasive blood pressure cuff, as there is no need to stop cuff inflation to watch for a “flash.” This allows the practitioner to, during periods of patient hemodynamic instability, simultaneously place an arterial line while continuing to monitor blood pressure using the noninvasive cuff.

Last, we utilize a similar technique described by Ueda and Hussey,¹ alternating between sliding the ultrasound transducer until the needle image disappears and advancing the needle until the image reappears, starting after skin puncture, not just after vessel puncture. We find that this facilitates needle tip guidance through soft tissue toward the vessel, which can be challenging in deep, small, and/or tortuous vessels. While the hyperechoic needle may be more difficult to visualize in soft tissue before vessel puncture (when compared to within a hypoechoic vessel), maintaining a tilt on the probe during transducer manipulation so that the ultrasound beam is closer to perpendicular relative to the needle (see Figure) can improve visualization.²

Figure.: Tilting the transducer so that the ultrasound beam is closer to perpendicular relative to the needle (position A) improves visualization of the needle versus transducer position B.

Again, we congratulate the authors on their efforts in studying this important perioperative topic. Their demonstration of a remarkably high degree of first-pass cannulation success, even among trainees using their technique, should indicate that “difficult IV sticks” should no longer be feared.

Henry Huang, MD
Department of Anesthesiology
Baylor College of Medicine
Houston, Texas
[email protected]

Bing H. Feng, MD
Department of Anesthesiology
Michael E. DeBakey Veterans Affairs Medical Center
Baylor College of Medicine
Houston, Texas