Injecting Set-Up
Despite the renaissance in regional anesthesia, much of the equipment innovation has been in the adult realm. As such, I think there will need to be some more focus on meeting the needs of pediatric regional going forward. Namely, a variety of short, small calibre cutting needles will need to be more commercially available, as piercing the skin with the traditional blunt needles is not only nearly impossible without an additional skin nick, but also potentially dangerous. One has to apply so much pressure to get through the skin or fascia that when the tissue finally retracts it leaves the needle tip at the depth one compressed the tissue to, perhaps even deeper (see blunt needle video). For that reason, we typically use small-gauge cutting needles, typically 25g, as our "block" needle. It is surprisingly hyperechoic.
There a few downsides to using a small gauge cutting needle. First, it glides through tissue with little to no resistance, which is why it is imperative to visualize the needle tip at all times. This is especially important when doing, say a parasternal block in a 3kg infant where the local is deposited millimeters from a beating heart. Second, the small calibre needle is typically malleable and may bend during the procedure. Adjustments to the patient's position (from supine to a modified lateral) may give one a better angle of approach and spare tension between the needle and probe. Lastly, at least at our institution, the 25g cutting needles are short, which means for older kids or deeper blocks, getting the required distance may preclude use of these needles.
22g block needle (blunt)
25g needle (cutting)
We typically employ two different techniques: "training wheels" vs “freehand.” Which technique we use depends on comfort level and the clinical situation. It takes time to become agile enough to hold the probe in one hand and then advance and inject with the other. With residents, we typically start out using “training wheels.” To test that the needle tip is in the correct place, we microinject a small amount of solution (tiny taps on the syringe plunger flange). Typically, just that small tap is enough to create visible turbulence and confirm needle tip position. That way, we can ensure that the LA is injected in the correct location--nothing worse than wasting your injectate volume for a 2-3kg infant in the wrong place. One thing to bear in mind is the tubing one uses to connect to the needle—use the smallest volume tubing possible, as this is all dead space. Once the correct plane is identified, switching over from saline to LA requires flushing the proximal saline left in the tubing, injecting one's LA dose, and then flushing the remaining LA volume from the line before moving to the contralateral side. As the comfort level increases, we typically switch over to freehand to avoid this dead space issue, as well as removing the need for someone to inject for you.
“Training Wheels”
- 25g cutting needle
- Tubing with the least amount of "dead space"
- Stopcock
- Syringe with sterile saline
- Syringe with LA
"Freehand"
- 25g cutting needle
- Syringe with LA