Intravenous cannulas are frequently used in the treatment of medical and surgical patients. They provide direct access to the venous system of a patient thereby allowing the user to perform a number of procedures including: the taking of blood; the administration of intravenous medications; and the administration of crystalloid or colloid solutions.

Intravenous cannulas in general use each comprise a sterile plastic intubation tube of varying gauge connected to a plastic base comprising an injection port, two wings'for adhesive attachment of the cannula to a patient and a rear opening for connection of apparatus for taking blood, giving medication or sealing the rear opening. Extending through the base and plastic intubation tube is a lumen for accepting a trocar. Commonly, a short resilient rubber tube, having a lumen, is situated in the lumen of the base of the cannula, aligned with the injection port. The rubber tube seals the injection port from the lumen of the cannula.

The intubation tube gauge used is chosen according to the clinical context. A small gauge is adequate for the administration of antibiotics whereas a large gauge is required for emergency fluid resuscitation. Standard syringes and tubing (known as intravenous giving sets) can be used in combination with all intravenous cannulas, irrespective of the gauge of the intubation tube as they are

attached to the rear opening which is of constant standard size.

A typical intravenous cannula is disclosed in GB1026119 and intravenous cannulas of this type are marketed, for example, under the trademarks Venflon0 or Biovalve@.

All members of a medical team (nursing staff included) have routine training in intravenous cannulation. Acutely ill patients commonly have an intravenous cannula inserted by a paramedic prior to arrival at hospital. Most acute medical and surgical patients will have an intravenous cannula inserted when they are admitted to hospital. The rationale for their insertion is that blood can be taken through the cannula for analysis and then if necessary the same cannula can be used for injection and/or infusion of treatments without the need for additional trauma to the patient.

Once inserted, an intravenous cannula ideally remains fixed to the patient for as long as the patient requires the administration of intravenous therapy or blood taking.

However, an intravenous cannula has only a finite life span since the plastic tubing causes a local inflammatory reaction in the host vein. The intravenous cannula is also a source of infection since it constitutes a foreign body breaching the protective layer of the skin. Local skin infections are a recognised complication of long term placement of intravenous cannulas. Some institutions therefore date stamp the intravenous cannula and remove them after a specified time of use. Consequently, each patient requiring intravenous therapy is likely to have numerous intravenous cannulas inserted during their in-patient stay.

When inserting a standard intravenous cannula into a vein, the trocar must be positioned in the lumen of the cannula such that the trocar tip passes out of the end of the intubation tube. The trocar tip is used to puncture the various tissues. After insertion of the intubation tube into vein, the trocar is removed and discarded. Intravenous giving sets, phlebotomy equipment or a sealing cap are then attached to the rear opening of the cannula. Once the trocar is removed, blood can flow along the lumen.

The person inserting the intravenous cannula must undertake two simultaneous tasks: 1. removal and disposal of the trocar ; and 2. prevention of blood spillage from the rear opening of the intravenous cannula.

The division of attention between the two tasks leads to unsafe practice. Frequently, those inserting intravenous cannulas find themselves spilling blood and yet being unable to dispose safely of the trocar at the time of the cannulation. Such practice puts the health care practitioner at risk of a needle stick injury. As the number of patients carrying Human Immunodeficiency and hepatitis viruses continues to rise, it is crucial to prevent blood spillage and to facilitate the safe disposal of sharp objects.

One way to reduce the blood flow along the lumen and thereby limit the risk of blood spillage is to apply finger pressure to the vein adjacent to the end of the intubation tube of the intravenous cannula before equipment is attached to the rear opening. Despite this, there is frequently back flow of

blood along the intravenous cannula lumen and out of the rear opening, resulting in spillage of blood. In addition, pressure on the cannula in the vein inadvertently traumatises the vein at the point of compression and may accelerate the process of local vein inflammation (thrombophlebitis) resulting in a shorter lifetime for the intravenous cannula.

In order to avoid these problems, a number of modified intravenous cannulas have been developed to either shield the trocar during its removal or to prevent the back flow of blood. Even though these safer intravenous cannulas are commercially available, the majority of intravenous cannulas used worldwide do not contain any safety features. The primary reason for this is economics as the new intravenous cannulas are considerably more expensive than the older design. Consequently, most health care practitioners perform intravenous cannulation using the older design with its inherent safety flaws.

Accordingly, in a first aspect of the present invention, there is provided a cannula system for performing a medical intubation comprising: a base; an intubation tube extending from the base; the cannula system including a lumen extending through the base and the intubation tube for accepting a trocar, wherein the base includes: an injection port for injecting a fluid into the lumen ; and a resilient sealing member for sealing the injection port from the lumen; and

wherein the system includes a ram for distorting the sealing member to prevent fluid loss from the lumen, on withdrawal of the trocar therefrom.

The ram is of a suitable size and shape that it can be used to distort the sealing member as the trocar is removed from the lumen, thereby preventing or decreasing blood loss from the lumen. The trocar can be disposed of safely.

If desired, the ram may be tethered to the cannula, for example by a plastics tether. It is preferred however that the ram is a disposable item, to ensure sterility. A plurality of disposable rams may therefore be supplied for use with a cannula.

The ram may preferably be in the form of a plug adapted for insertion into the injection port. A first (distal) end of the ram can be received in the inner part of the injection port, and applies pressure to the ram to distort the sealing member when pressure is applied to a second (proximal) end.

The first end of the ram may be tapered. The tapered shape of the ram preferably mirrors the internal profile of the lumen'thereby increasing the effectiveness of the seal when the ram is inserted. In a particularly preferred embodiment, the first end of the ram is hemispherical.

The base of the injection port, where the injection port meets the lumen, may have a smaller internal diameter than the rest of the injection port. Preferably the first end of the ram has a round cross-section of smaller diameter than the base of the injection port. More preferably, the diameter of the first end is up to 3 mm. The length of the

first end of the ram is preferably longer than the diameter of the lumen of the base at the injection port. Preferably, the first end of the ram has a length of from 1 to 10 mm.

The ram is preferably made of a plastics material. More preferably, the tube is made out of the same plastics material as the cannula, for example polypropylene.

The cannula can be one of entirely conventional form, and the ram is of a suitable shape and size to be used with the cannula.

In a second aspect of the invention there is provided a method of intravenous cannulation comprising the steps of: providing a trocar within the intubation tube of a cannula system described above; puncturing the venous tissue of a patient with the trocar and thereby inserting the intubation tube into a vein of the patient; withdrawing the trocar from the cannula ; and distorting the resilient sealing member with the ram during the step of withdrawing the trocar from the cannula, to prevent or decrease the loss of blood through the intubation tube during withdrawal of the trocar.

A preferred embodiment of the invention is now further described with reference to the drawings in which:- Figure 1 shows a side view of a cannula with a trocar in position.

Figure 2 shows a plan view of the intravenous cannula of Figure 1.

Figure 3 shows a side view of the intravenous cannula of Figure 1 without the trocar in position.

Figure 4 shows the ram for distorting the sealing member.

Figure 5a shows a side view of the intravenous cannula of Figure 3 with the ram in place.

Figure 5b show a rear view of the intravenous cannula of Figure 3 with the ram in place.

Figure 6a shows a side view of the intravenous cannula of Figure 3, with the ram distorting the sealing member.

Figure 6b shows a rear view of the intravenous cannula of Figure 3, with the ram compressing the rubber tube.

Referring to Figures 1 and 2, the cannula 1 has a base 5 made from a plastics material and an intubation tube 10 made from a flexible plastics material integral with the base 5 and attached to the base 5 at the proximal end of the intubation tube 10. A lumen 12 extends from a rear opening 14 of the base 5 through the base 5 and the intubation tube 10.

Integral with the underside of the base are two wings 15 which are used for attaching the cannula 1 to a part of a body using adhesive tape.

A hollow trocar 30 is adapted to pass through the lumen 12 to puncture the tissues of the patient and facilitate insertion of the cannula. The proximal end 35 of trocar 30 has a tubular handle portion 38. The handle portion 38 is sealed with a removable plastics end cap 40. The trocar 30 is of sufficient length that when the handle portion 38 abuts the rear opening 14, the distal end of the trocar 30 protrudes from the distal end 32 of the intubation tube 10.

An injection port 18 for introducing medication into the lumen 12. The injection port 18 has a channel connected to the lumen 12 of the base 5 at the opening 20 of the injection port, the diameter of the opening 20 is less than the diameter of the channel of the injection port 18. The injection port 18 has a removable plastics cover 25. A resilient hollow rubber tube 27 is positioned in the lumen 12 of the base 5. The rubber tube covers the opening 20 and seals the injection port 18 from the lumen 12. Fluid can be injected into the injection port 18 using a syringe (not shown). Fluid pressure forces the fluid through opening 20, distorting the rubber tube 27, breaking the seal, and thereby allowing fluid to enter the lumen 12.

Referring to Figure 4, the ram 42 has a circular cylindrical body 45 having a first end portion 47 with a smaller radius than the body, and having a hemispherical end, and a second end portion 50 with a larger radius than the body. The first end portion 47 is sufficiently narrow to pass through opening 20 and is sufficiently long to compress rubber tube 27 such that the opposite internal surfaces of the rubber tube 27 can touch together.

In use, the removable cover 25 of the injection port 18 is removed. The trocar 30 is positioned in the lumen 12. The end 32 of the trocar 30 is inserted through the skin and the wall of an appropriate vein so that the distal end of the trocar 30 lies within the lumen of the vein. The cannula 1 is then advanced an additional distance so that the distal end of the intubation tube 10 is wholly within the walls of

the vein. The intubation tube 10 is then advanced within'the lumen of the vein, whilst the trocar 30 is held stationary.

The ram 42 is inserted into the injection port 18 such that the first end portion 47 is positioned over the opening 20.

The trocar is slowly removed from the intubation tube 10 and the base 5. At the same time, pressure is applied to the second end portion 50 of the ram 42. As pointed end 32 of the trocar is pulled past the injection port 18, the pressure applied to the ram 42 moves the ram 42 relative to the injection port 18. The. first end portion 47 of the ram 42 enters the lumen 12 of the base. As the first end portion 47 enters the lumen 12, it compresses the rubber tube 27.

The ram 42 is pressed far enough that the internal surfaces of the rubber tube 27 touch together, closing the lumen 12.

The rubber tube 27 is sufficiently long that the compression of the rubber tube 27 by the ram 42 does not break the seal at the ends of the rubber tube, meaning that the injection port is still sealed from the lumen. Blood flowing from the vein is therefore prevented from passing along the lumen 12 by the rubber tube 27. The trocar 30 can be removed fully from the base 5 and placed in a suitable receptacle such as a clinical sharps bin, without risk of blood flowing out of the rear opening 14 of the base 5. Pressure is continuously applied to the second end portion 50 of the ram 42 to prevent blood flow along lumen 12. Phlebotomy equipment, an intravenous giving set, a syringe or a sealing cap (not shown) is attached to the rear opening 14 of the base 5.

When the equipment is attached, pressure on the second end portion 50 of the ram 42 is released and blood is allowed to flow along the lumen 12. When phlebotomy equipment is applied, once sufficient blood has been collected, pressure

is reapplied to the second end portion 50 of the ram 42 to close the lumen again. The phlebotomy equipment can then be removed and either a giving set, a syringe or a sealing cap can be applied to the rear opening 14 of the base 5. If no further changes are required at the rear opening 14, the tool 42 is removed from the cannula 1 and disposed of.

The tip of the first end 47 of the ram 42 is shaped to mirror the internal profile of the lumen opposite the opening 20, which ensures that the rubber tube 27 forms an effective seal.

A new ram 42 is required whenever a change of apparatus attached to the rear opening 14 of the base 5 takes place.

There are typically three to four changes made per day to the equipment attached to the rear opening of an intravenous cannula.

Whilst the invention has been described with reference to the illustrated preferred embodiment, it is to be appreciated that many modifications and variations are possible within the scope of the invention.