WO2021053487A1

WO2021053487A1 - Canula for medical use, in particular for insertion into arteries

Info

Publication number: WO2021053487A1
Application number: PCT/IB2020/058512
Authority: WO
Inventors: Andrea UGOLINI (percentage share: 55%); Gabriele Maria IACONA (percentage share: 25%)
Original assignee: Agt S.R.L. (Percentage Share: 20%)
Priority date: 2019-09-17
Filing date: 2020-09-14
Publication date: 2021-03-25
Also published as: IT201900016466A1

Abstract

The present invention relates to a cannula for medical use, in particular for the insertion into arteries. According to the invention, the cannula for medical use, in particular for the insertion into arteries (10) comprises an insertion duct (1) for inserting in the artery, inside which flows a body fluid, in particular blood, said duct (1) having a first distal hole (3), an elbow (2) and, in proximity of said elbow (2), a second hole (4), said cannula being characterized in that it comprises, inside said main duct (1), a second duct (5), arranged substantially in correspondence with said elbow (2), provided with a front opening (11), substantially coaxial to the main duct (1), said body fluid stream being partially deviated, before said distal hole (3), through said front opening (11), so that a part of it flows into said second duct (5), in the opposite direction to that of the stream along said first duct (1), exiting through said second hole (4).

Description

CANNULA FOR MEDICAL USE, IN PARTICULAR FOR INSERTION INTO ARTERIES

The subject matter of the invention is a new cannula for insertion into the arterial circulation during extracorporeal circulation and ECMO (ExtraCorporeal Membrane Oxigenation).

To carry out surgical procedures on the heart or large vessels, a total or partial by-pass of the cardio- respiratory system is required, which is carried out using a mechanical extracorporeal circulation system.

In severe pathological states of the heart and/or lung, it is sometimes necessary in emergency to use a mechanical cardio-respiratory support system equipped with an oxygenating membrane called ECMO in an emergency or urgency.

Both systems require the drainage of venous blood from the patient to the machine by inserting one or more cannulae into the central or peripheral venous circulation and the re-infusion of oxygenated and temperature-controlled arterial blood into the central or peripheral arterial circulation.

When the doctor opts for the insertion of an arterial cannula in the femoral artery, he has the possibility to choose between multiple cannulas by adopting different insertion techniques. The arterial blood infused into the patient is retrograde directed to the heart and through the arteries originating from the aorta to all organs. Conventional cannulas guarantee an effective transport of the blood in the arterial circulation, but its distribution is subject to numerous variables determining the genesis of pressure gradients in several points of the circulation itself downstream of the cannula. The lower limb carrying the arterial cannula receives flow released from the end of the cannula. This flow perfuses the femoral artery in the space between the wall of the femoral artery and the external part of the cannula. For reasons that will be mentioned later in this document, limb perfusion is not always effective in cases of prolonged cardio- circulatory assistance, ischemic phenomena are frequently generated in the limb subject to cannulation.

The origin of the lower limb ischemia appears to be multifactorial: external diameter of the cannula equal to or greater than the internal diameter of the femoral artery, incorrect angle of insertion of the cannula into the artery, presence of atherosclerotic plaques in the arteries of the lower limb, diameter excessively small of the arteries, presence of thrombi in the distal arterial circulation in the presence of low circulatory flow, states of hypercoagulability, loss of laminar and slightly pulsatile distal flow, vasoconstriction, accidental dislocation of the cannula, arterial and venous cannulae on the same limb. Inadequate blood flow to the lower limb is the pathophysiological element common to all the aforementioned variables. If prolonged over time, ischemia produces permanent damages to the limb or permanent loss of the same.

Surgical techniques exist aiming to prevent or delay the genesis of ischemic phenomena affecting the lower limb.

A technical solution consists in the insertion of a small distal perfusion cannula into the femoral artery (percutaneously or surgically) downstream of the insertion point of the systemic perfusion cannula. The distal perfusion cannula is fed by deviation from the systemic perfusion cannula. It is a difficult technique to implement especially when the diameter of the femoral artery is small, it requires accurate, slow positioning and a certain dexterity if a percutaneous approach is used. Unfortunately, the distal perfusion cannula is subject to thromboembolic occlusion, precisely due to its reduced diameter and small movements of the cannula can significantly alter the flow generated through it.

An alternative is the surgical insertion of a tubular prosthesis into the femoral artery and the connection of the systemic perfusion cannula to the prosthesis. In this way, it is possible to ensure adequate flow upstream and downstream of the femoral artery. It is an exclusively surgical procedure, therefore carried out in the operating room, which can give rise to bleeding and/or infections and not feasible in an urgent/emergency situation.

The use of a single cannula capable of ensuring a bidirectional flow, that is, upstream and downstream of the insertion point, however, remains the quickest solution in emergency situations at the patient's bed. It is possible to use a cannula with an extremely thin wall thickness and an external diameter smaller than the diameter of the artery (in other words a non-occluding cannula) to obtain an optimal systemic flow and at the same time a flow to the lower limb downstream of the point of insertion of the cannula. However, the amount of flow to the lower limb is not predictable and over time it can generate a severe impairment of the lower limb perfusion. Furthermore, a cannula that is too small compared to the diameter of the femoral artery generates an increase in pressure in the system with the risk of hemolysis and suboptimal systemic flow.

In a conventional cannula, lateral holes have been added just below the insertion point in the femoral artery through which the blood can flow towards the lower limbs (document W003/068303). This solution is not without problems such as occlusion of the holes or significant bleeding in case of incorrect positioning or accidental dislocation. To deal with these drawbacks, the design of the cannula around the holes has been modified by creating two tracks around a single large hole with the aim of keeping the femoral artery open and ensuring adequate distal flow ("A femoral artery cannula that allows distal blood flow "by Magovem, J. et al., The Journal of Thoracic and Cardiovascular surgery, September 2005). A clinical application is not yet known.

An innovative design describes a cannula with distal opening, elbow and lateral hole to ensure distal flow at the point of insertion into the artery (EP2694148). The elbow is preformed and has a growing protuberance to facilitate the positioning of the cannula inside the artery, facilitate its insertion and prevent accidental dislocation. The proposed solution would seem to solve the problem caused by compression downstream of the femoral artery caused by an incorrect angle of insertion of the cannula into the artery. There is clinical evidence of a distal flow generated by the cannula, as in other technical solutions, but the behavior of the blood flow generated downstream of the insertion point in the femoral artery and downstream of the lateral hole has not yet been described. Nor is it known whether adequate distal flow can be ensured for long-lasting circulatory media.

All the aforementioned solutions aim to achieve a bidirectional flow. Obtaining adequate systemic flow with cannulas inserted into even relatively small femoral artery is now a certainty, even if it is not possible to state the same with regard to the flow in the lower limb carrying the arterial and / or venous cannula.

In view of the above, the Applicant has realized a cannula for insertion into the artery capable of generating a predictable and modulable distal flow. The solution according to the present invention proposes a bidirectional cannula ensuring adequate blood flow in both directions thanks to the presence of a flow diverter near the elbow, and at the same time avoids creating spasms and compression.

The main object of the present invention is to provide a bidirectional arterial cannula solving the technical problem described above, obviating the drawbacks and overcoming the limitations of the known art, allowing to ensure adequate blood flow, both in the direction of insertion and in the opposite one.

Within this aim, an object of the present invention is to realize a bidirectional cannula that can be easily inserted in and removed from the artery.

Another object of the invention is to realize a bidirectional cannula that remains in the required position and does not involve high risks of complications (bleeding and/or occlusion).

A further object of the invention consists in realizing a bidirectional cannula that is able to give the widest guarantees of reliability and safety in use.

Another object of the invention consists in making a bidirectional cannula that is easy to make and economically competitive if compared to the known art.

The aforementioned object, as well as the aforementioned objects and others which will appear better later, are obtained by a cannula for medical use, in particular for insertion into arteries comprising a duct for insertion into the artery, inside which runs flows the body fluid, in particular blood, said duct having a first distal hole, an elbow and, close to the latter, a second hole, the cannula being characterized by the fact that it comprises, inside the main duct, a second duct, in correspondence of the elbow, provided with an anterior opening, coaxial to the main duct, and in which the current of body fluid is partially diverted, before the distal hole, through the anterior opening, so that a part of it flows into the second duct, in opposite direction to that of flowing along the first duct, exiting through the second hole.

In particular, according to the invention, the cannula for medical use comprises a flow diverter near the front opening of the second duct and inside the first duct.

Preferably, this flow diverter is structured like an umbrella. The opening diameter of the umbrella is less than the diameter of the main duct.

Furthermore, said flow diverter includes bevels on each point having angles, so as to minimize the turbulences that can cause thrombogenesis.

Furthermore, said flow diverter can be integral with the second duct.

Alternatively, said flow diverter is a separate piece with respect to the second duct, and can be supported by reinforcing means.

In addition, the cannula for medical use according to the invention comprises one or more flow modulators, located in proximity to said flow diverter so as to act directly on the blood flow diverted either in the first duct or in the second duct, or preferably in both, by reducing the intensity of turbulence.

Preferably said flow modulators are flow rectifiers.

Further characteristics and advantages will become clearer from the description of two preferred but not exclusive embodiments of a bidirectional cannula, illustrated by way of non-limiting indication with the aid of the attached drawings wherein: figure 1 is a side view of a bidirectional cannula according to the invention; figure 2 is a sectional side view of a first embodiment of a bidirectional cannula according to the invention; figure 3 is a rear view with respect to the direction of insertion of the bidirectional cannula according to the embodiment of Figure 2; figure 4 is a cut-away front perspective view of the bidirectional cannula according to the embodiment of Figure 2; figure 5 is a sectional side view of a second embodiment of a bidirectional cannula according to the invention; figure 6 is a rear view with respect to the direction of insertion of the bidirectional cannula according to the embodiment of Figure 5; figure 7 is a perspective front cut-away view of the bidirectional cannula according to the embodiment of Figure 5; figure 8 is a rear view with respect to the direction of insertion of the bidirectional cannula of a third embodiment of a bidirectional cannula according to the invention; and figure 9 is a perspective view from the rear side of the bidirectional cannula according to the embodiment of Figure 8.

Preliminarily, it should be noted that in the description the terms "forward or distal" and "posterior or proximal" refer to the direction of insertion of the cannula according to the invention by the healthcare professional.

With reference initially to Figure 1, a bidirectional cannula according to the invention is shown, indicated as a whole with the reference number 10, which comprises an insertion duct 1, able to be inserted into the artery (not shown), with an elbow 2, a first distal hole 3, and a second hole 4 near the elbow

2.

Coming now to also observe the attached figures 2- 4, in which a first embodiment of the cannula 10 according to the invention is illustrated, it can be observed that, inside said main duct 1, starting from the elbow 2, a second coaxial duct 5 is provided, which ends before said distal hole 3 in an anterior opening 11, in correspondence with which it provides a flow diverter 6.

As mentioned, the duct 1 is bent at the elbow 2, with an obtuse angle, near which said second hole 4 is provided.

As mentioned, a flow diverter 6 is provided on the distal end of second duct 5, whereby the blood flowing inside the cannula 10 according to the invention is divided into two streams or flows, respectively, the first, which continues straight towards the distal hole 3, and the second, which, thanks to the action of the flow diverter 6, flows in the opposite direction to that of arrival, to go out from the second hole 4, towards the lower limbs (not shown as well).

The extent of the deviation will depend on the ratio between the area of the maximum section of the flow diverter 6, the area of the internal section of the main duct 1, and will be a number between 0 and 1.

A ratio close to 1 increases the percentage of blood diverted to the excluded limb, conversely a ratio close to 0 provides that the cardiac direction is favored. If the ratio is 1, the diameter of the flow diverter 6 is the same as that of the duct 1, and all the flow is diverted.

Preferably, said flow diverter 6 is structured like an umbrella. The opening diameter of the umbrella being less than the diameter of the duct 1. The flow diverter 6 is preferably shaped in such a way as to add bevels on each point that has angles, so as to minimize the turbulences that can cause thrombogenesis .

In this embodiment, this flow diverter 6 is held in position by a plurality of fins 9 distancing it from the internal wall of the duct 1.

Alternatively, the flow diverter 6 is integral with the second duct 5.

A second embodiment is illustrated in Figures 5 to 7, wherein the reference numbers of the common or similar elements with respect to the first embodiment correspond to those of the preceding figures.

In said second embodiment, the bidirectional cannula 10 has flow modulators 7 and 8 inside. Said flow modulators 7, 8 are located in proximity to the flow diverter 6 so as to act directly on the deviated blood flow, both in the first duct 1 and in the second duct 5, or preferably in both, reducing the intensity of the turbulence.

A third embodiment is illustrated in Figures 8 and 9, wherein the reference numbers of the common or similar elements with respect to the first embodiment correspond to those of the previous figures.

In said third embodiment, the bidirectional cannula 10 provides two lateral channels 12, obtained externally on the cannula 10, just above the elbow 2 thereof, the realization of said channels 12 inevitably implying, in correspondence with them, a narrowing of the internal section of passage of the cannula. Their function is to allow correct alignment of the cannula 10 inside the artery.

The edges of the artery into which the cannula is inserted will occupy said channels 12, ensuring correct orientation, and creating resistance to the insertion or extraction movements of the cannula itself.

According to the invention, the bidirectional cannula is made of material suitable for surgical use.

The operation and advantages of the bidirectional cannula 10 according to the invention are clear and evident from what is described above.

Substantially, it was found that the bidirectional cannula 10 according to the invention allows to achieve the results and purposes defined in the introductory part of the description as it allows to ensure a blood flow both towards the upper part and towards the lower part of the body.

Another advantage of the bidirectional cannula 10 according to the invention consists in the fact that it is functional and efficient without the need to carry out a too invasive surgical operation and / or the use of additional surgical instruments.

A further advantage of the bidirectional cannula 10 according to the invention consists in the fact of being easily and quickly insertable and removable, without wasting time and without causing particular complications during the surgical operation in which it is used.

Another advantage of the bidirectional cannula 10 according to the invention consists in the fact of coping with arterial spasms.

Another advantage of the bidirectional cannula 10 according to the invention consists in the fact of coping with arterial spasms. A further advantage of the bidirectional cannula according to the invention consists in the fact that it does not cause compression of the artery downstream of the insertion.

Furthermore, an advantage of the bidirectional cannula according to the invention consists in the ease of being produced in a simple way, for example by 3D printing or injection molding.

The bidirectional cannula thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the inventive concept.

Furthermore, all the details can be replaced by other technically equivalent elements.

In practice, the materials employed, as far as they are compatible with the specific use, as well as the contingent shapes and dimensions, may be any according to requirements.

The present invention has been described, for illustrative but not limitative purposes, according to its preferred embodiments, but it is understood that variations and/or modifications can be made by an expert in the art, without thereby departing from the relative protective scope, as defined in the attached claims.

Claims

1. Cannula for medical use, in particular for insertion into arteries (10) comprising an insertion duct (1) for inserting in the artery, inside which flows a body fluid, in particular blood, said duct (1) having a first distal hole (3), an elbow (2) and, in proximity of said elbow (2), a second hole (4), said cannula being characterized in that it comprises, inside said main duct (1), a second duct (5), arranged substantially in correspondence with said elbow (2), provided with a front opening (11), substantially coaxial to the main duct (1), said body fluid stream being partially deviated, before said distal hole (3), through said front opening (11), so that a part of it flows into said second duct (5), in the opposite direction to that of the stream along said first duct (1), exiting through said second hole (4).

2. Cannula for medical use (10) according to claim 1, characterized in that it comprises, in proximity of said front opening (11) of said second duct (5) and inside said first duct (1), a flow deviator (6).

3. Cannula for medical use (10) according to claim 2, characterized in that said flow deviator (6) is integral to said second duct (5).

4. Cannula for medical use (10) according to claim 2, characterized in that said flow deviator (6) is a separate piece with respect to said second duct (5).

5. Cannula for medical use (10) according to one of claims 2 - 4, characterized in that said flow deviator (6) is supported by reinforcing means (9).

6. Cannula for medical use (10) according to one of claims 2 - 5, characterized in that said flow deviator (6) includes chamfers on each point presenting angles, so as to minimize turbulence.

7. Cannula for medical use (10) according to each one of the preceding claims, characterized in that it comprises one or more flow modulators (7,8). 8. Cannula for medical use (10) according to claims 6 or

7, characterized in that said one or more flow modulators (7,

8) are located in proximity of said flow deviator (6) so as to act directly on the diverted blood flow either in said first duct (1) or in said second duct (5), or preferably in both.

9. Cannula for medical use (10) according to claims 7 or

8, characterized in that said one or more flow modulators (7,8) are flow rectifiers.

10. Cannula for medical use (10) according to one or more of the preceding claims, characterized in that it comprises one or more lateral channels (12), obtained externally on the cannula, above said elbow (2).