Sunday, July 22, 2007

Preceptor -- learning to teach heel stick blood draws

I occasionally help orient a new staff member or precept a student. I really enjoy this, because it makes me think. They always have questions. The one that makes me really think about how I'm performing a technical skill is "Why does this work for you and it doesn't for me?" -- could be blood draws, could be getting a preemie to eat. Could be something more technical.

When I get asked that question, I realize that I failed to properly explain the skill. I have to think through every single step of an action which has become so ingrained that I barely know how I'm doing it any more. Only by watching someone do what they think I've told them and what they think I've demonstrated do I learn the subtleties of finger placement so I can explain a little better the next time.

One thing that is exceptionally easy to do, but hard to teach is heel stick blood draws. Everyone does this a little differently, so in addition to demonstrating my technique, I encourage the student or orientee to observe other nurses and adapt the various differences in technique until something clicks.

There are some basics, though.

Prepping the skin is simple - clean with antiseptic (alcohol for most heel sticks), allow to air dry. I watched a new resident prep skin for a blood culture once. He went through the routine and then BLEW on the site. No. I didn't let him draw the blood until he'd re-cleaned the area.

We use an automatic safety lancet designed for heel sticks. Placement is important -- on the side of the heel, not in the center. Choice of inner or outer side depends on the baby's position and whether the nurse is right or left handed. It also may depend on just how badly damaged the skin already is.

Those things are easy to teach. Much harder is teaching just how hard to squeeze a given baby to get the blood you need without damaging the baby's skin or leaving a bruise. Most people are too gentle at first and have to be encouraged to squeeze just a little harder. With the smaller preemies, it's important to keep your fingers from slipping so that you don't tear the skin. With all of them, technique has to be adjusted to the gestational age and the baby's general condition.

It's important to get a free-flowing specimen for CBC's (blood counts) and electrolytes. If the blood isn't flowing freely, the CBC might clot and give false readings (or be rejected by the lab) and with electrolytes, the serum potassium can be falsely elevated if the blood cells are hemolyzed. Warming the heel prior to sticking helps. So does wiping off a drop of blood after every 2-3 that you collect. It's also important that the blood flows into the microtainer instead of being scooped off the skin. Scooping picks up micro clots which lead to bigger clots or which contain hemolyzed cells.

The objection I hear most often to wiping those drops is that the new nurse or student doesn't want to "waste" blood. It wastes more blood if the specimen is rejected due to a clot or gross hemolysis.

The microtainers we use have lines to let you know when you've collected enough blood. Some tests require that the container be filled to the top line, some just to the bottom one. For CBC's, it's important to fill to a level between the 2 lines so that there is enough blood for the test, but not too much for the EDTA that keeps the blood from clotting before it gets to the lab. Inverting the tube a few times (after capping it) helps to mix the blood with the EDTA so it doesn't clot. It also gives you the opportunity to examine the specimen for clots before sending it to the lab. If you can see a clot, toss the specimen and try again. There's no sense wasting the lab's time by sending an obviously clotted CBC.

Once you've collected the specimen you have to get the baby to stop bleeding. That can be as simple as placing a bandaid or gauze and tape on the area - or applying pressure for a couple of minutes. If the baby has a low platelet count or other bleeding issues, it can be much more difficult. Since a preemie has about 100 ml/kg total circulating volume, you want to avoid any unnecessary blood loss. The tiniest preemies have skin that is too fragile for bandaids or tape, so I generally apply pressure until the bleeding has stopped.


CLS said...

You also need to invert the tube to mix the anticoagulent with the whole sample. This is especially important with ETDA specimens.

Judy said...

Not something I'd forget to do -- but obviously it's easy to forget to mention it. Just one more example of how challenging it can be to teach something I do without thinking much about it.