Instrument For The Withdrawal Of Body Fluids

Abstract

An improved syringe for the withdrawal of body fluids, especially adapted for transport and storage as well as for the centrifugation of the fluid samples, preferably blood samples, comprises a tube having a hermetically end, the closure of which, being a stopper or cap, is entirely or partly made of resilient material, through which a needle, preferably of stainless steel, extends, which ends in or is tightly pressured against a piston mounted in the tube. Said piston is preferably provided with a concave at the side where the needle ends. Thus a hermetically sealed compartment is obtained through which the needle extends. Said Compartment is suitable for aseptic storage of auxiliaries such as anticoagulants and/or antiseptics.

Description

BACKGROUND OF THE INVENTION

An instrument which is frequently applied for drawing body fluids more particularly blood, is a hypodermic syringe. When this syringe is not used for injection purposes, but for taking samples of a body fluid, this fluid after the puncture has to be transferred into a container in order to transport said fluid or to perform clinical-chemical determinations in it. The drawbacks of such a method are obvious as these operations take much time and the chance of mistakes is increased. Moreover, after the use the syringe has to be cleaned and, if necessary or desired, sterilized again and provided with fresh anticoagulants and/or antiseptics.

Of the hypodermic syringes which have been developed so far for the withdrawal of body fluids no variants are known which are also suitable for the storage, the transport and the centrifugation of these fluids.

Since there is at present a strong tendency towards greater efficiency and, connected therewith, greater uniformity of apparatuses to be used in clinical-chemical determinations, the need is felt of a fluid drawing instrument which is also equipped for the transport, the storage and the centrifugation of the fluid.

A partial, but by no means ideal solution of the above-mentioned problems was found in the use of an apparatus comprising the following two essential parts:

1. a vacuum ampoule fitted at one side with a cap or stopper of resilient material;

2. a holder with a needle pointed at both ends in which the vacuum ampoule can be placed.

By means of such an apparatus blood can be taken by inserting the needle into a blood vessel and then exerting pressure on the ampoule so that the needle will pierce the resilient cap of the ampoule. However, such a device is rather expensive, due to the fact that special vacuum ampoules are required. Another great objection is that the movement which has to be made to withdraw the fluid (exerting such a pressure on the vacuum ampoule that the needle will pierce the cap of the ampoule) is essentially contrary to the movement made when an ordinary hypodermic syringe is used. Moreover, so much pressure should be exerted that there is a danger of the needle piercing the vein, which can give rise to hematomae and other injuries. Besides the ampoule cannot be filled up completely there will always remain a certain space above the blood containing air or another gas, in consequence of which undesired changes may occur during the transport of the blood.

SUMMARY OF THE INVENTION

An instrument has now been found adapted to be employed for the withdrawal of body fluids. This instrument is also suitable for the transport and the storage of these fluids, as well as for the centrifugation and other preparatory operations prior to the performance of clinical-chemical determinations, to which instrument no such drawbacks as those mentioned above are attached. It can be constructed at such a low cost that after a single use the instrument can be discarded.

The instrument according to the invention is characterized by a tube having one hermetically closed end, the closure of which is entirely or partly made of resilient material, through which material a needle extends which ends in a piston mounted in the tube, which piston is fitted with a device which enables said piston to be moved.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The instrument according to the invention is illustrated in FIG. I in the sheet of drawings, representing one of the possible embodiments of the invention.

The process of taking body-fluids with such a device is very simple. The needle is inserted into the body in the conventional manner, after which the fluid is withdrawn by moving the piston backwards. After the puncture the detachable parts of the instrument, including the needle, are removed, after which the body of the instrument, a handy tube, containing a hermetically sealed quantity of fluid, remains. If a specimen of blood has been taken which is to be transported over long distances, for instance, by airmail, the air has to be removed from the tube, because, due to excessive shaking during the transport, hemolysis may be caused. For this purpose the needle is not immediately entirely removed from the tube, but only in part, so that the end of the needle just remains in communication with a concave which should preferably be made in the closure. By moving the piston towards the needle while keeping the tube in a vertical position, the air first collects in the concave, after which it is removed through the needle. Then the needle can be entirely drawn from the closure.

Now, the tube containing the fluid (FIG. III) can be stored or transported and, if desired, centrifuged to separate any solid substance from the fluid.

The parts of the instrument according to the invention are illustrated further with reference to FIG. I in the sheet of drawings.

The tube (1), e.g., of cylindrical shape, should preferably be made of transparent material. Tubes made of synthetic material, such for example as polystyrene, acrylstyrene, polypropylene and polymethylpentene or other polyolefins, are very suitable for this purpose. The dimensions and the content of the tube depend, of course, on the purpose for which the instrument according to the invention is used, but it is a prerequisite that the tube should be adapted to be used in the common laboratory centrifuges. For the performance of most clinical-chemical determinations in the blood of adults a blood sample of 10 ml. is sufficient.

At one end the tube is hermetically closed, for example with a cap or a stopper partly or entirely made of resilient material, for example, rubber. There should preferably be a concave (3) in the closure communicating with the interior of the tube, which permits any air present in the tube to be removed easily, as described above. The needle (4) which should be made of durable material, preferably stainless steel, extends through the resilient part of the closure either centrically or eccentrically according to the location of the concave. Moreover, the needle should preferably be fitted with a guard (5) preventing the needle from penetrating further into the tube.

The end of the needle which is in the tube should end in or tightly press against a piston (7). Preferably the needle reaches to the interior of the piston so that on injection it can no more move sidelong. Hence a needle which is pointed at both ends is the most suitable needle to employ in the instrument according to the invention. Thus a perfectly hermetically sealed compartment (6) is obtained, through which the needle extends either centrically or eccentrically.

In the piston there should preferably be a concave at the side where the needle ends, which offers advantages on examination of the sediment obtained after centrifuging, which has collected in the concave. Also, the piston is fitted with, or can be fitted with a device for moving it. For this purpose a piston rod is mostly used. With a view to centrifuging the fluid, the piston rod should be detachable annexed, in any case that part which sticks out of the tube after withdrawal of the fluid. To fulfill this requirement the piston rod can be provided with, for example, a breaking point. However, it is to be preferred to provide the piston with a device (8), for example a screw thread or a catch, to fasten a loose piston rod, but other devices, too, can be used in the instrument according to the invention to move the piston.

The other open end of the tube can be closed with a cap (9), which can be provided with an opening, if desired, through which quite easily a piston rod can be put. For special purposes said opening is closed by a film, for example, of rubber or plastic (10). Such a closure is required if microbiological determinations are to be performed in connection with which not only compartment (6), but the whole inner side of the tube should be sterile.

The part of the needle extending out of the tube can be protected with a cover, which serves a double purpose: it protects the needle and keeps it sterile. The material of which said cover is made should preferably be pervious to sterilizing gases such as ethylene-oxide.

The device according to the invention can be supplied perfectly sterile and is constructed in such a way that the sterility will be maintained for a virtually unlimited time.

To the instrument according to the invention, which is illustrated in FIG. I in the sheet of drawings and which is one of the possible embodiments of the invention, belongs a loose piston rod, which must be mounted on the piston before use. Such a piston rod (FIG. II) can be made of durable material, for example stainless steel. If the sterility should be extremely great on taking the fluid, the piston rod can be sterilized before it is fitted in the tube, for example, by flaming.

The fluid-withdrawal instrument according to the invention is destroyed or discarded after use; a piston rod of durable material can be used over and over again. However, the piston rod can also be made of synthetic material, in which case it is discarded together with the fluid-withdrawal instrument after one-time use. If sterility is required, such a loose piston rod of synthetic material can be manufactured in a sterilized package.

In practice most determinations have been performed in blood serum so far, that is to say, in the fluid that remains after clotting has taken place. The instrument according to the invention enables this serum to be prepared a short time after the puncture and free from hemolysis.

However, a number of determinations in blood are performed starting from whole blood or blood plasma, that is to say, starting from blood which has not been allowed to clot.

Examples of such determinations are: the determination of amino acids, amino-nitrogen, ascorbic acid, lactic acid and alcohol, and further, for example, the hematocrite value, the oxygen-binding capacity, the prothrombin time and the erythrocyte-sedimentation time.

Dependent on the determinations to be performed in blood, the following anticoagulants are often used: sequestering agents such as salts of ethylenediamine-tetraacetic acid, for example, potassium or sodium EDTA, heparin, for example, potassium, sodium or lithium salts, sodium fluoride, sodium citrate, potassium or sodium oxalate or potassium-ammonium oxalate.

Said coagulants, in a solid or in a liquid form, can be passed aseptically into the sterilized device according to the invention, and that into the compartment (6) between the piston and the closure. As the needle presses tightly against or reaches to the interior of the piston, said substances cannot penetrate into the needle so that they cannot constitute a danger to the patient or block up the needle. The instruments according to the invention filled with different coagulants should be clearly distinguishable from each other, for example, by a clear code and/or differences in color.

The following four types of blood withdrawal instruments are suitable for most clinical-chemical determinations:

1. blood-withdrawal instrument having an empty sterile space between stopper and piston;

2. blood-withdrawal instruments having a sequestering agent in the compartment in question, for example, tri-potassium EDTA;

3. blood-withdrawal instrument containing heparin in the form of the sodium salt;

4. blood-withdrawal instrument containing sodium citrate.

For determinations to be performed in body fluids other than blood, such as lumber fluid, interarticular fluid and pleural fluid, other auxiliaries such as antiseptics, can be present in the instrument according to the invention. It stands to reason that the nature of the determination to be performed plays a part in the choice of the auxiliary. Likewise the diameter and the length of the needle must be adapted to the field of application.

Claims

It is claimed:

1. An instrument for the withdrawal of body fluids comprising a tube having an open end and a hermetically closed opposite end, the interior of said tube being at substantially atmospheric pressure, a closure member at the closed end of the tube providing said hermetic seal which is at least partly made of resilient material through which material a hollow needle extends which terminates in and is sealed by a piston slidably mounted in the interior of said tube provide a hermetically sealed compartment between said closure member and said piston, said compartment being penetrated by said needle, said piston being provided with means for moving the piston away from the closed end of the tube.

2. The instrument of claim 1, in which said closure has a concave communicating with the interior of the tube.

3. The instrument of claim 1, in which said piston possesses a concave portion at the side where the needle terminates in the piston.

4. The instrument of claim 1, in which said piston is fitted with means for fastening a piston rod.

5. The instrument of claim 1, in which the open end of said tube is closed with a cap fitted in the middle with a film which can easily be penetrated by a piston rod.

6. The instrument of claim 1 which includes a piston rod attached to said piston.

7. The instrument of claim 1 in which said needle is provided with a guard to prevent further penetration into said tube.