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Dear Colleagues,
We are doing PK-PD work in rats and try to use the same rats for
longitudinal studies. For that we need to maintain the iv. cannulas
(indwelled into the Jugular vein) for several weeks. However, we experience
constant technical problems due to plagues/ clotting/ blockade of the
cannula. To prevent this problem we use heparinized PVP solution. Another
problem is that after a while the rat managed to reach the cannula and to
pull it out of the vein. The cannula is exteriorated at the lower dorsal
part of the neck, and it is secured with 3 sutures at that attach the PE 50
cannula to the vein, the muscle and the skin. Does any of you have
experience with prolonging the "life" of the cannula.
Thanks in advance for your suggestions.
Amnon Hoffman, Ph.D.
Dept. of Pharmaceutics
School of Pharmacy
The Hebrew University of Jerusalem,
POB 12065
Jerusalem 91120
Israel
Fax: 972-2-6436 246
Email: ahoffman.-at-.cc.huji.ac.il
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Dear Dr. Hoffman,
Usually, increased frequency of cannula care increases the long-term
cannula patency. We use heparinized(20-50 U/ml)sterile isotonic saline
to flush the cannula everyday. A blunt needle (23G1) and 1 ml syringe
are used to flash the cannula. The instilled solution is withdrawn. The
aspirated fluid/blood should be discarded as it may contain small
thrombi. The cannula is flushed with saline to clear it of blood, and
refilled with fresh heparin solution. The cannula should be flushed
with a volume of solution slightly larger than the volume of the
cannula. Forceful injection of saline (0.2 ml) may break up a
obstruction with the risk of a trapped emboli in the vasculature of the
lung. Of course the cannula has to be inside the vein to get blood.
Heparinized PVP solution offered no better advantage to us than
heparinized saline.
We usually exteriorize the jugular vein cannula by subcutaneous
tunneling from the vascular incision site to the back of the neck
(midway and dorsal to the ears). The cannula is clipped with the skin
to secure the position. The exterior length of the cannula is about 2
inches and plugged with a blunt quilting pin (0.5 inch)!
Some useful information can be found in the following article:
Cocchetto et al. J Pharm Sci 72(5):465-492, 1983. Good luck.
M. Delwar Hussain, Ph.D.
School of Pharmacy
University of Wyoming
Laramie, WY 82071-3375
Tel: 307 766 6129
Fax: 307 766 2953
E-mail: delwar.-a-.uwyo.edu
Internet: http://w3.uwyo.edu/~delwar
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Here are some suggestions for jugular vein catheters in rats:
1) be sure to flush the cannulas at least once (preferably twice) daily
with heparinized saline (first thing in the morning and just before leaving
for the day)
2) exteriorize the catheter further down the back so the rats can't reach
behind their heads
3) increase the conc. of heparin in the catheter
4) redesign your catheter (to avoid as many tubing joints as possible)
5) I have used a single piece of silastic tubing (about 6" long) with a
large bead of silicone placed on the tubing about 1" from the end. The
catheter is pushed in up to the silicone bead which is then sutured in place
subcutaneously. The tip that enters the heart is beveled slightly. The
catheter is exteriorized around the back of the neck and plugged with part
of a blunt needle that has been blocked with silicone. I have never had one
of these catheters pulled out and I have had good results keeping them open.
6) also, sometimes what can appear to be a blocked cannula can often be a
constriction related to the animal's position. Sometimes moving the animal a
little bit or gently manipulating the area transversed by the catheter can
eliminate the constriction.
Hope this helps. Feel free to write to me direct if you would like more
details.
Paul Damian
**********************************************************************
Paul Damian PhD, MPH phone (916) 752-7507
Program Coordinator, Western Region fax (916) 752-0903
Food Animal Residue Avoidance Databank farad.aaa.ucdavis.edu (FARAD)
Dept. of Environmental Toxicology pdamian.-at-.ucdavis.edu (personal)
University of California
Davis, CA 95616
**********************************************************************
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Dear Dr. Hoffman,
I have used an indvelling plastic catheter on rats up to a couple of weeks.
To keep the rats from chewing on them we made a saddle like construction in
leather. It has a connection at the back for a steel-coil, in which the
catheter can run. This steel-coil can be connected to the top of the cage,
thus enabeling a constant access to venous blood. When not doing
experiments the plastic catheter can be keept under the saddle. If the rats
are keept with the saddles pre-op. there are no problems post-op.
Magnus Hultin, Ph.D.
Dept of Medical Biochemistry and Biophysics
Ume=E5 University, Ume=E5, Sweden
At 13:23 1997-05-05 -0500, you wrote:
>PharmPK - Discussions about Pharmacokinetics
> Pharmacodynamics and related topics
>
>Dear Colleagues,
>We are doing PK-PD work in rats and try to use the same rats for
>longitudinal studies. For that we need to maintain the iv. cannulas
>(indwelled into the Jugular vein) for several weeks. However, we experience
>constant technical problems due to plagues/ clotting/ blockade of the
>cannula. To prevent this problem we use heparinized PVP solution. Another
>problem is that after a while the rat managed to reach the cannula and to
>pull it out of the vein. The cannula is exteriorated at the lower dorsal
>part of the neck, and it is secured with 3 sutures at that attach the PE 50
>cannula to the vein, the muscle and the skin. Does any of you have
>experience with prolonging the "life" of the cannula.
>
>Thanks in advance for your suggestions.
>
>Amnon Hoffman, Ph.D.
>Dept. of Pharmaceutics
>School of Pharmacy
>The Hebrew University of Jerusalem,
>POB 12065
>Jerusalem 91120
>Israel
>Fax: 972-2-6436 246
>Email: ahoffman.aaa.cc.huji.ac.il
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Hi Amnon,
I haven't read all of the responses yet so I don't know if you've heard
this response yet. I perform dozens of vascular surgeries, and usually
what we use to keep the catheter patent is heparanized saline at
(100U/ml. It is neccessary to flush the catheters every day in order to
maintain it patency over time. I also use a tether spring system to
protect the catheter. if you are not familiar with this system, it is a
stainless steel spring that is placed over the catheter and is stitched
to the animal's back. Because it is made of steel the animal cannot get
to the catheter. It is also designed to be able to accomodate a spring
if neccessary. I have recently investigated a company called Access
Technologies based in Virgina that have developed silastic catheters
with a rounded end. They claim that the rounded end damage the vessels
less upon insertion and therefore can maintain patency for a greater
length of time. I have purchased some and I will be trying them out
next week. If you are interested you can write me back and i can tell
how well they work. I hope that this information will be of some help
to you.
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