1. Field of the Invention
The present invention relates to a hub device for use in transferring liquids therethrough in opposite directions, and more particularly, concerns a filtered hub device for aspirating and injecting liquids, such as liquid medications.
2. Description of the Prior Art
In the procedure of transferring a liquid from one source to another, especially when the purity, cleanliness or sterility of the liquid must be preserved, care must be taken to prevent contamination of the liquid during the transfer stages. In particular, many medical liquids are stored in containers or bottles holding a large quantity of the medical liquid. Small amounts of the liquid are withdrawn, for example, into a syringe by aspirating the liquid through a hollow cannula or the like attached to the syringe. To assure that clean or filtered liquid is withdrawn from the larger container, a cannula with a filter may be attached to the syringe during the aspirating process. Such a filter-type cannula is described in U.S. Pat. No. 4,127,131. Before the liquid collected into the syringe is ejected, such as by injecting the liquid into a patient or another container for perhaps additional testing, the filter cannula is generally removed and another similar filter cannula is required. Thus, two such filtered cannulae are often required in this type of liquid transfer procedure: one for aspirating, and another one for injecting the liquid. This, of course, assures filtration of the liquid in both directions, but also requires not only two separate filter cannulae, but also the extra procedural steps of removal and replacement of the cannula. On the other hand, if no filtration is necessary during the aspirating step, the standard aspirating syringe could be used without a filter-type cannula attached thereto. Then, the user would only have to attach the filter cannula before the injection step to assure that filtration of the liquid occurs during this step. In this case, however, the user must remember to place the cannula onto the syringe between the steps of aspiration and injection of the liquid which is being transferred. Should the user forget this intermediate step, then no filtration of the liquid will occur during the entire transfer operation. Therefore, it is desirable to provide an attachment device, particularly suitable for, but not limited to, syringes, which is attachable prior to aspiration of the liquid from the first source and which remains attached to provide a filtration mechanism when the liquid is injected from the syringe to the transferred location. It is to this end which the present invention is directed.