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Module 25 Section 3 |
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Module 25
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Fluorescein Angiography, Part 1 |
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Section 3: |
The Injection | ||||
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Setting up and administering the injection |
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Setting up and administering the injection Some states allow photographers to inject if under the supervision of an MD. Some states only allow the photographer to be a phlebotomist (get the vein) if properly trained. Other states do not allow the photographer to do any of this unless he/she is a registered nurse. As the photographer, I would encourage you to do as much of the injection procedure as you are legally allowed to do. The more control you have over the entire procedure, the better your pictures will be. You will also be more efficient if you don't have to go fetch someone to inject every time you perform an FA. However, no matter what your situation, never inject fluorescein without an MD within easy reach. I prefer to have the patient in position for photography when the needle is inserted into the vein. This way the arm does not have to be moved once the needle is inserted, eliminating the chance that the connection with the vein will be lost with movement of the arm.
Apply the tourniquet just above your targeted injection site. If you are having problems finding a vein, check the tightness of the tourniquet. Tourniquets sometimes slip loose while you are looking for a vein. Use an antecubital (in front of the elbow) vein if at all possible. Some like the convenience of a vein in the back of the hand, but use these veins only if an antecubital vein cannot be used. You want a firm, medium sized vein that is as close to the heart as is practical. The quality of your images will improve dramatically (higher contrast) if you get a fast injection into a good sized, firm, antecubital vein.
Wipe the area of the vein with an alcohol swab before inserting the needle. Wiping with alcohol while you look for a vein may help you see the veins better, especially the ones on the hand. Notice in the photo that the nurse is not wearing gloves; this makes it easier to find a vein. In our state, glove are optional during a phlebotomy procedure. Finding a vein where a vein is not obviously present is a skill that takes practice. Your sense of touch is more important to you than what you do or do not see when searching for a vein. The vein will feel like a mushy, springy rope under the skin. Once you find a vein, immobilize it by pressing on it with the index finger of your free hand. Insert the needle, bevel side up, into the vein just above where your finger is applying the pressure. Insert the needle into the vein like you insert your arm into the sleeve of your shirt. This requires that you go in at a 'flat" angle. You want to follow the path of the tunnel without poking the needle through the wall of the vein.
If you have been successful, you will see blood traveling up the tubing that comes from the needle. Tape the wings of the butterfly to the skin once you see that blood is coming from the vein. If the cap is still on the end of the tubing, then the blood will go about an inch up the tubing and stop. Leaving the cap on allows you plenty of time to hook up the syringe. You will want to leave the cap off of the tubing (before inserting the needle) if the vein is fragile or if the vein is in the hand. This will relieve some of the venous pressure and help prevent the vein from "blowing" (swelling due to bleeding at the injection site). When the cap has been taken off of the tubing, the blood should continue to travel though the tubing to the end, and out. You want the blood to reach the end of the tubing before you attach the dye syringe to the end of the tubing. This will eliminate any air in the tubing. You don't want to inject any air into the vein. You can remove the tourniquet as soon as you have a blood return, or you can wait until the blood is near to the end of the tubing. Be sure the tourniquet has been removed when the injection begins.
Once the syringe has been attached, draw gently back on the plunger. Blood should easily travel into the syringe and mix with the dye. If it does not, or if the flow is very difficult, then you have a poor connection with the vein. Reposition the needle within the vein to try to re-establish the blood flow. If this does not work, you should consider taking the needle out and starting over again with another vein. If you are using a small volume of dye (e.g. 2ml of 25%), draw 2 to 3ml of blood into the syringe to mix with the dye. This will insure that most of the dye goes into the vein, because some will be left in the butterfly tubing. You could also use another syringe of normal saline to inject following the injection of the dye; this flushes the dye from the tubing. Injecting into a poor needle-vein connection will cause extravasation of the dye. This means that the dye will go under the skin or into muscle tissue instead of into the vein. This situation becomes very obvious to the patient immediately after the injection because it is very painful. A normal injection of dye into a vein causes no pain or discomfort. Treat the area of extravasation with an ice pack immediately, followed by warm compresses when the patient gets home. The area will be discolored (orange) for several days. An oral NSAID such as ibuprofen (400 to 600 mg) will ease the discomfort. If you think that at least half of the dye made it into the vein before the extravasation, encourage the patient to tough it out and try to get some photos. If using a digital camera, you will know if some of he dye made it through because you will have some useful photos showing dye circulation. Most patients appreciate not having to make a return visit. The patient may be agreeable to trying to find another vein even if all the dye had extravasated. The extent of extravasation can be limited if you place your finger on the skin above the vein at the sight of the needle insertion. This allows you to feel for a "ballooning" vein while the dye is being injected. Any swelling under your finger would warn you to stop the injection immediately. With a good injection, you will feel the "whoosh" of the dye being squirted through the vein. Leave the needle in the arm until the early and mid phase angiogram as been completed, then remove it, apply a bandaid, and have the patient apply finger pressure to the site while you wait for the late photos. Avoiding an arterial injection Most of the time, it's pretty hard to accidentally find an artery instead of a vein when doing venapuncture. Arteries ordinarily lie much deeper in the tissue and veins are closer to the surface. If you feel a strong pulse in the vessel, it may be an artery. If you puncture the vessel with the needle and the force of the blood return pushes the plunger, then you definitely have an artery. Stop the injection procedure and find a vein. If you do accidentally inject into an artery, you can still proceed with the angiogram. The patient will complain of a hot flush as the dye perfuses into the tissue below the injection site. The patient's arm and hand will turn a bright yellow-orange, which will eventually (hours) dissipate. Of course, some folks have great veins for venapuncture and others don't. What do you do if you can't get the needle into a vein with a good blood return? We have the patient come back another day and have her drink at least four 8oz. glasses of water (more is better) beginning 2 hours before the appointment time. We have used this procedure many times, and I don't recall the last time that it did not work. Oral administration of fluorescein If a venous injection cannot be made, it is possible to get photos from oral administration of fluorescein, but the results are roughly equivalent to only taking very late photos of a venous injection. Mix a vial of fluorescein with about 6 fluid oz. of a soft drink and have the patient drink the mixture within a period of a few minutes. Use a high flash setting and take a photo every 5 minutes starting 15 minutes after ingestion and continuing until 40 minutes after ingestion.
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| This subject is continued in Part 2, Module 26, but each Module has a Post-Test. | |||||
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