Micro perfusion device

Details Micro perfusion device Micro perfusion device

2002-08-22

2004-03-16

Kennedy, Sharon (Department: 3762)

Surgery

Means for introducing or removing material from body for...

Material introduced into and removed from body through...

C604S164020, C604S164040, C604S165020

Reexamination Certificate

active

06706009

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATION(S)
This is a continuation application of International Patent Application PCT/CH01/00095, filed on Feb. 13, 2001, which claims priority to German Patent Application No. DE 100 08 825 A1, filed on Feb. 25, 2000, both of which are incorporated by reference herein.
BACKGROUND OF THE INVENTION
The invention relates to a micro perfusion device for obtaining at least one constituent of a body fluid by means of a subcutaneously positioned perfusion catheter.
FIG. 7D
shows a micro perfusion device as described in “Open-Flow Microperfusion . . . ”, Z. Trajanoski et al., Diabetes Care, Volume 20, Number 7, July 1997, pages 1114 ff. The device comprises a casing
1
which may be fixed to the skin. A flexible, permeable perfusion catheter
5
a
projects from the casing
1
, said catheter being subcutaneously positioned in a tissue
3
. A supply catheter
7
a
for a rinsing liquid—referred to as perfusate in the following protrudes into the perfusion catheter
5
a.
The perfusion catheter
5
a
and the supply catheter
7
a
form a double-lumen catheter in the tissue
3
, comprising an inner lumen within the supply catheter
7
a
and a surrounding outer lumen between the supply catheter
7
a
and the perfusion catheter
5
a.
In the casing
1
, the outer lumen feeds into a discharge channel
8
to which a discharge catheter is connected. In order to obtain body fluid from the tissue
3
, the perfusate is guided through the supply catheter
7
a
up close to a front distal end of the perfusion catheter
5
a.
Once the perfusate has emerged at the front distal of the supply catheter
7
a,
it flows back along the supply catheter
7
a
in the outer lumen. A rinsing liquid is used as the perfusate which penetrates the constituent whose concentration in the body fluid is to be ascertained. Furthermore, body fluid is sucked into the outer lumen through the perforated perfusion catheter
5
a
by the rinsing effect. The mixture of perfusate and body fluid is discharged through the discharge channel
8
to a measuring means. The fluid is conveyed through the device by means of a pump.
The placement procedure prior to the use of the perfusate can be seen from
FIGS. 7A
to
7
D. An injection needle
4
a
is used to position the device. Before it is positioned, the perfusion catheter
5
a
tightly surrounds the injection needle
4
a.
Once the skin has been pierced and the injection needle
4
a
positioned in the tissue
3
(FIG.
7
A), the injection needle
4
a
is retracted again (FIG.
7
B), and the perfusion catheter Sa remains in the tissue in the position shown. The supply catheter
7
a
is then inserted through the casing
1
into the perfusion catheter
5
a
(FIG.
7
C). It is inserted in the perfusion catheter
5
a
until it takes up most of the length of the perfusion catheter
5
a
(FIG.
7
D). The front end of the supply catheter
7
a
is, however, some distance short of the front end of the perfusion catheter
5
a.
Micro perfusion devices of the type described require piercing the skin, retracting the injection needle and subsequently providing a perfusate supply.
BRIEF SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a micro perfusion device which can be easily positioned and operated.
The present invention, in one embodiment, is a micro perfusion device for obtaining at least one constituent of a body fluid using a subcutaneously positioned perfusion catheter comprising a casing, a supply for a perfusate, a hollow injection needle, the perfusion catheter and a discharge channel formed in the casing for discharging the perfusate together with the at least one constituent. The injection needle comprises a front needle opening, distal when subcutaneously positioned, and a rear needle opening. The front needle opening can be formed by a front-facing opening in the conventional way, for example by needle grinding. It can also be formed by a lateral opening in a surface of the injection needle. In one embodiment, the rear needle opening is formed on the rear facing side of the injection needle. It can be formed by a slit or a bore or by laterally cutting the surface area of the injection needle. The injection needle is accommodated by the casing, and may be slid from a front sliding position to a rear sliding position. In its front sliding position, it protrudes through the perfusion catheter. In its rear position, it protrudes into the perfusion catheter, however the perfusion catheter protrudes beyond its front needle opening in the rear position. The injection needle can be a steel needle. Alternatively, other needles can be used as long as they have a sharp tip to cleanly penetrate the skin, are sufficiently rigid for positioning, and are histocompatible.
The injection needle in one aspect of the invention serves to position the perfusion catheter in a tissue whose body fluid and/or from its body fluid the at least one constituent is to be obtained. Alternatively, the injection needle not only fulfills the function of positioning the perfusion catheter, but also fulfills the further function of introducing the perfusate into the perfusion catheter. To this end, a fluid connection from the perfusate supply into the injection needle is formed by the rear needle opening, at least in the rear sliding position of the injection needle. When the device is implanted, i.e. subcutaneously positioned, the perfusate is thus introduced through the perfusate supply, the rear needle opening, the hollow injection needle and finally through its front needle opening into the surrounding perfusion catheter and then rinses the perfusion catheter. Since the injection needle assumes the double function of positioning and introducing the perfusate, the step of subsequently inserting a perfusate supply into the perfusion catheter can be omitted.
According to one embodiment of the present invention, the micro perfusion device can be formed by simply developing catheter heads such as those for infusing insulin within the framework of diabetotherapy. A particularly suitable catheter head is described in DE 198 21 723.4 by the Applicant. The catheter head described therein already comprises an injection needle accommodated slidably in the catheter head casing, with a front and a rear needle opening. The rear needle opening is formed by a lateral opening through which, once an infusion catheter has been positioned, the insulin solution is supplied for the purpose of priming the catheter head. With respect to the injection needle of this catheter head, only a fluid-proof connection is required in the area of the rear needle opening for supplying the perfusate. Furthermore, a discharge channel having a fluid-proof connection to the infusion catheter or perfusion catheter, respectively, has to be formed in the catheter head. As a perfusion catheter, the infusion catheter can be perforated.
The micro perfusion device, in one embodiment, serves to measure or ascertain the glucose concentration in the body fluid in the vicinity of the implanted perfusion catheter. In this case, the at least one constituent of the body fluid is glucose. The body fluid together with the perfusate can be obtained quite simply by the rinsing process. By using an appropriate perfusate or rinsing fluid, a particular constituent can also be selectively obtained by means of the micro perfusion device in accordance with the invention, in addition to the body fluid rinsed with it.
Perfusion, according to one aspect of the present invention, is achieved by suctioning the discharge channel by means of a pump. The perfusate can also be pressed into the injection needle. Alternatively, it can be conveyed by a combination of pressure and suction.
In one embodiment, the fluid connection between the perfusate supply and the injection needle only exists in the rear sliding position of the injection needle. In this case, the perfusate supply is a supply channel formed in the casing. In the rear sliding position, the injection needle opens into this supply channel via its rear needle openi

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