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发表于 2011-1-21 12:59:25
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本帖最后由 stroller 于 2011-1-21 13:04 编辑
Part 1 - IV Technique: A Tutorial on the Basics
IV's
What is an IV? First off, "IV" is the common term for "intravenous." Let's confine the discussion to peripheral (small veins in arms and legs), not central lines. Basically it's a plastic straw sleeved over a needle. The needle pierces the skin and vein, and the "straw" is slid off into the vein, then taped into place, and the needle removed. IV's come in different widths (represented by standardized color coding) and lengths. There are different indications for different sizes.
First question for CM: What size IV did you place in MJ's left leg?
IV's are usually placed in hand and arm veins that are easy to see and feel. Leg or foot veins are reserved for occasions of special need, when arm and hand veins are inaccessible. Inaccessible could mean that the veins are not suitable for IV cannulation due to repeated punctures and scarring; inaccessible can also mean that limbs are not suitable due to infection, surgical procedure, positioning of the patient for care, etc. Speculation can also include that punctures and bruising are easier to conceal on a patient's legs than arms, once the patient is dressed and going about his daily routine. The point is, without a report from Murray, we don't know exactly why Murray placed an IV in the patient's leg (likely the left saphenous vein, according to testimony and anatomy, which is a nice big vein in most people). However, we do know that this is fairly unusual in a healthy patient who is ambulatory, and presumably may need to be up walking or to the bathroom while undergoing this "therapy."
In terms of the diameter of intravenous cannulae, bigger size equals more flow. If you remember back to basic physics, doubling the diameter of a tube does not double the flow; it actually increases the potential volume of flow by 16 times. This is useful to know when it is necessary to infuse large amounts of volume rapidly, such as when a patient is bleeding excessively, or when aggressive IV hydration is planned. Larger IV's (20g and larger-- the smaller the number the bigger the IV) can be kept several days by capping and flushing several times a day, and protecting the equipment beneath a bandage. Generally, large IV's are placed for hydration (which do not last long; they clot off or infiltrate, slipping out of the vein). Smaller IV's, such as 22g, are placed for intermittent injection, such as a patient who needs IV antibiotics for several days or weeks, or frequent pain meds. (A smaller IV usually lasts more days in adults)
CM: Why exactly did you place an IV in MJ's leg on the last day of his life? How long was that IV in place? You spoke with a LEO and stated you had given this patient IV propofol and other intravenous medications nightly for the past 8 weeks. Did you start a new IV each night? Did you ever attempt to "keep" any IV beyond one therapeutic episode? If so, how did you do that? If not, why not? After several weeks of nightly use, did it occur to you that a nightly IV would be needed for the meds you planned to give MJ?
IV Tubing
For purposes of this discussion, we will confine the descriptions to very simple sets of IV tubing. There has not been any reports that any electronic infusion devices were found at the scene, or reported to have been used by CM. CM has admitted to placing an IV for "hydration". So we will assume he was using simple IV tubing. Like this:
Simple IV tubing
We also know from paramedic testimony at the scene that CM's tubing was simple and "old fashioned", as it was not a needle-less system, and the paramedic's equipment was not compatible with CM's rubber capped medication ports (Y-sites). Paramedics had to change out CM's tubing for their own, in order to be able to administer drugs during resuscitation attempts. This older style of IV tubing requires a needle to pierce the rubber Y-sites to inject meds into a running IV, or to "piggyback" in another IV line. There are many brands of tubing, but nearly all of them have a Y-site about 5 inches from where the end of the tubing connects to the IV cannula in the patient, and at least one Y-site halfway down the tubing, for injecting meds.
Y-site Example
Piggyback lines are typically hooked into the Y-site closest to the patient. With this old style tubing, one would slip a needle attached to the second IV line directly into the rubber stopper, and tape it in place. These systems have fallen out of favor in the past 10-15 years as nearly all hospitals and home health agencies have had to change to needleless systems to meet patient safety requirements. I've been a nurse since the mid 1980's so I have had lots of experience using these "old" systems in the past.
Piggyback Example
This type of tubing flows by simple gravity into an IV, and many things can speed up or slow down the flow, such as the size of the IV, or the position of the limb. There are 2 general types of tubing: maxi drip, and mini drip. Maxi drip is 10 to 15 drops per cc, and is typically used on adults. Mini drip tubing is 60 drops per cc, and is typically used on infants and children, as well as adult drips that require more precise regulation. Rate of infusion is achieved by adjusting the roller clamp (in blue, above) counting how many drops per minute are seen in the drip chambers, and multiplying by 60 to determine hourly rate. In the old days, a strip of tape was placed on the bag and "time taped" so all caregivers would know how much should have infused at a certain point in time.
This is a maxi drip drip chamber.
This is a mini drip drip chamber.
Note the needle-like dropper inside. (Sorry- not a great pic.)
Another question for our doctor:
CM: What kind of tubing were you using? Where did you get it? How many sets of tubing did you purchase at one time?
It is a virtual certainty that CM was using maxi drip tubing.
Needles and syringes:
They come in many sizes. Most people order them by the box or case, so I would be highly surprised if CM had a wide variety of different sizes available. Educated speculation leads me to believe CM probably had 3cc syringes, and possibly 5cc or 10cc syringes. I think it's doubtful he had 20cc syringes, or 1cc syringes.
Propofol 20cc with Syringes
CM: What size needles and syringes did you have in use when providing care to MJ at his home? Where did you get them?
IV Bags:
1000cc plastic bags of Normal Saline (NS) were in evidence in the room, and on the pharmacy order by CM.
What is curious to me is on an initial pharmacy order reported, CM ordered only 9 1 liter bags. This is curious because a full case of liter bags is 12 bags. Why would a doctor order only a partial case from a pharmacy, and why would a pharmacy fill a partial case order without requiring the customer to purchase a full case? NS is cheap, so cost likely wasn't a factor. More on meds ordered will be addressed in Part 2.
1000cc Bag of Normal Saline
Glass and plastic medication vials:
These are stoppered with a rubber cap and a plastic flip off lid, for sterility. To access the medication, you must push some air into the sealed vial, in order to create positive pressure to withdraw a medication into a syringe. (Using sterile technique.) CM did not have needle-less systems in use, so he would have had to do this with an ordinary needle. Inject an equal quantity of air into the vial, flip it upside down, and withdraw medication into a syringe. If you don't do this, you can usually withdraw smaller amounts of medication, but beyond about 5cc, there is a vacuum built up in the vial that makes sucking out the med with a needle and syringe difficult.
The plunger of the syringe will have a tendency to be sucked back toward the vial. This is also true if someone attempts to drip medication from a sealed glass vial without properly "venting" the bottle to allow air inside. (This will be an important detail to remember as the 4 part series unfolds.) The "-pam" injectable drugs CM ordered (lorazepam and midazolam) come in 2cc single use vials-- ordering records indicate CM was not using multi-dose vials. It also does not appear CM was using pre-filled syringes from the pharmacy ordering information. Lidocaine comes in 10cc vials most commonly, but it is also available in larger vials. Propofol comes in 20cc vials, and 100cc vials. (It also comes in 50cc vials, but CM was not ordering this size.) I have not discussed glass "crack open" ampules because there is no evidence reported that these were in use.
To close this article, I'd like to take a minute to discuss rate control devices for IV's. Many people know about electronic IV and syringe "pumps" and have seen them on TV or in a hospital. There have been no reports of any of this type of equipment found at the scene, and no reports from CM that he used any kind of pump in the care of MJ. However, there are several "old fashioned" volume control devices that I'd like to discuss. These are very cheap and easy to use, if a provider knows about them and has access to purchasing them. The first is a simple pediatric buretrol.
This fits in between the IV bag and the regular tubing, and a provider allows a small amount of fluid or meds to fill the chamber. The bigger bag is then clamped off. This only permits what is in the buretrol to infuse, not the whole bag or bottle of meds. A buretrol costs about $20. A cheap IV pump about $300.
Buretol
Buretol & Bag
Another low tech option for rate control of IV medications is a "grenade" pump. This is a hard plastic shell with an interior balloon that is filled by syringe. It infuses at a preset rate, such as 2cc/ hr, or 10cc/ hr, until the balloon is empty. These are commonly used in joint surgeries for post op pain control, and I used a similar "grenade" pump for labor epidurals many years ago. They are cheap and low tech, but a layer of added safety for the patient. They can be easily pressed into use for IV medications, and when I was flying military air evac years ago, I used them occasionally in flight.
"Grenade" Pain Pump
So why did I bring up low tech infusion control devices? Precisely because CM did not have any in use that we know of during the care of MJ. This information will be important in part 4 of this article.
That's enough for today! Part 2: The Evidence: What we think we know, will be out soon!
~KZ |
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发表于 2011-1-21 12:50:48
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