I'm an other....
If you are interested in fine tuning your skills in IV stuff when you become ALS , one of the best things you can do to get familiar with it, is play with the stuff. Get yourself a catheter and safely play with it, notice all the anatomy of it, study the differences from a 14 gauge to a 22 or 24 gauge. Each size will give you a slightly different approach on the technique you use.
( terminology -
Stylus= the metal needle that actually does the penetration and adds rigidity
Sheath or Catheter= The plastic based part that goes over the stylus, which can be made of many materials from polyurethane to teflon
Flash chamber= Where you see the blood when you are in the vein.
Bevel= The tip of the Stylus, which has the cutting edge to penetrate the skin. Used in terms such as... bevel up or bevel down. The sharp end.
Bevel indicator= Many catheters have a marking or indicator on or near the flash chamber indicating whether you are bevel up or down while you are in the skin )
Hub= The portion of the sheath closest to you, and what you hook the rest of your IV stuff to.
Now, hopefully knowing the terminology will help with the mental picture... If you compare a 22 guage ( small cath ) to a 14 gauge ( big cath ), there are differences in the bevel, and the distance from the end of the sheath to the end of the bevel. This determines my decision how far I may advance the catheter once I get a "flash" ( visible blood in the flash chamber, indicating you are in the vein ), and how much I need to advance.
If you play with some old IV tubing, you can almost visualize what would be going on within a vein. Notice that you may get blood flash, but only the bevel in the vein.... causing a sheath hang if you chose to thread at this point. Advance the whole assembly a little further, and you get the sheath within the vein wall. Advance the whole assembly too far, and the tip of the bevel can poke thru the opposite side of the vein, causing a hang up. Most folks chalk it up to "Valves". ( thats another theory ).
Reducing your catheter assembly angle will help prevent poking thru the other side of the vein.
When I stick, I choose to use a low angle, and stick fast thru the skin at a predeterimined length based on what I see and feel in the vein. Once I get a flash, I thread in. I do not advance anymore, unless I am using big catheters, just because the rate of "hang ups" by the sheath go up due to sheath to tip of bevel difference. I also do not retract the stylus until the hub is fully seated against the skin. The stylus gives you rigidity while advancing the sheath. If you take that away, as you advance the sheath, your chances of buckling the sheath have gone way up.
Some shallow veins, I have done sticks with the bevel down, helps prevent double wall punctures. I also increase my venipuncture angle as well with this. This takes some practice.
I also use BP cuffs for my tourniquet. I have better pressure control, plus I can grab a BP quickly and get right to stickin. I inflate to the pts systolic, this gives me the best back pressure. Geriatrics, I use less pressure ( until the vein feels spongy... not rock hard. ( side note.... you gotta check your equipment, if you have a leaky cuff, it will slow you down. I always know where my leaky cuff is..... in the back up unit. ).
So many techniques.... so many variations. These are the ones that have granted me great success. When you clinb that ALS ladder, I hope you are as passionate and learn what is best for you. Take all these ideas on this post and play away. You will find your niche.
As far as bending the catheter for a better angle, I have only done that with vacutainer systems, or just by pulling blood via syringe... and that is to make up for any angle issues the larger syringes create. I would be leary of how you do something like that with a catheter, especially the technique you use to make your bend, if contaminate the sheath ( phlebitis, although the stats are low for in field folks ), but more importantly... causing a nick or burr in the sheath. Not to mention, that cancels out any reason to re-insert the stylus. ( I know what the books say, but many of near impossible lines were saved by rotating the stylus for a bevel down position to re-insert the stylus to re-seat the sheath. The bevel rides down the sheath - vs - bevel up where it punctures the sheath. Try it with some training caths. Place a slight bend in the sheath, re-introduce the stylus both bevel up - then bevel down. Pretty neat trick when that 1 in 1000 comes around and it works ).
We tried to create a plastic embolism in the lab, it never happened. Even when we went beyond extreme sheath shredding. Those sheaths are tough. Try that too... give one a rip, not easy. And we have not been able to find any documented cases of such with todays caths ( 80's on up ). What we did end up doing was shearing the vein wall more, creating a bigger hematoma.
----excerpt from my soon to be book... "... And why do I care how it works?"