ITRM990704A1 - SPINAL ANESTHESIA NEEDLE WITH VARIABLE SETUP POINT. - Google Patents

Description

Description of the invention entitled:

"NEEDLE FOR SPINAL ANESTHESIA WITH VARIABLE POINT"

DESCRIPTION

Technical sector

The present invention refers to a needle for subarachnoid anesthesia, also called spinal anesthesia.

State of the art

Subarachnoid anesthesia consists in the injection of a local anesthetic into the subarachnoid space, that is, into the CSF. The drug comes into direct contact with the spinal cord and acts rapidly, providing complete and intense anesthesia of the affected metamers.

The advantages of this type of anesthesia are represented by the ease of execution, the immediacy of the effect and the favorable cost / benefit ratio.

However, the most common secondary effect is postpinal headache resulting from liquorrhea through the needle hole in the dura. The larger the hole is and has frayed edges, the more intense and longer the liquorrhea and the related headache it causes will be.

To reduce this secondary effect, so-called "atraumatic" needles with a pencil point have been devised. These needles are not sharp, are less tearing, and produce a smaller diameter hole.

Unfortunately, a disadvantage of atraumatic needles lies in the fact that the position of the hole, placed longitudinally on the edge of the needle body, near the tip, considerably affects both the resistance of the needle and the distribution of the anesthetic.

In fact, any collisions of the tip against the vertebra find the weak and critical point precisely in the position of the hole (of longitudinal shape) along the body of the needle.

Furthermore, the elongated shape of the hole itself can cause the hole to be located, at the time of injection, partly in the subarachnoid space and partly in the epidural space. In this position a quantity of anesthetic is inadvertently and unnecessarily poured into the epidural space, making the subarachnoid anesthesia insufficient or even causing it to fail.

Particular types of needles that have the tip hole arranged laterally on the needle body itself and therefore parallel to the longitudinal axis, are the Whitacre needle and the Sprotte needle.

The resistance of these needles, with a conical or pointed tip, is insufficient at the tip, as has already been said above. This means that the forces parallel to the needle body, which constitute the reaction forces of the tissues to the advancement of the needle itself, can easily generate a vector capable of arching the needle at the critical point (hole). A needle bent at the point, like a hook, could damage the dura, both in and out. In fact, this eventuality can occur when the needle collides with bone structures, or with the supraspinous, interspinous or yellow ligaments, which are particularly robust or even calcific.

Another type of needle is also known, the classic and traditional Quincke needle, whose tip hole is arranged at 45 °. This needle also has the drawback that its resistance to collisions is very low at the tip.

Its sharp tip tears and traumatizes the dura, facilitating post-spinal headache.

The purpose of the present invention is to produce a needle for spinal anesthesia that is at the same time atraumatic, much more resistant at the tip than conventional needles of the same caliber, and such as to ensure the safe injection of all the anesthetic that it is intended to inject into the liquor.

In other words, the needle will need to be safe, (avoids post-spinal headache), resistant, and reliable to ensure successful anesthesia.

Description of the invention

The object of the invention is achieved by means of a needle for spinal anesthesia, defined as a needle "with a tip of variable position", consisting of an external tubular body or external needle, having an axial hole and a non-cutting truncated cone tip, and by a mandrel with a substantially conical tip, introduced into the axial hole until it completely protrudes by means of its conical tip, from the truncated tip of the external needle.

The needle made up of these two parts is pushed into the body tissues until it passes the dura. The axial position of the outer needle hole ensures that, after pulling out the stylet, the outer needle hole is fully seated in the liquor. The gauge of the needle can also be reduced compared to conventional needles, since during the advancement of the needle, since the mandrel is inside the outer needle, there are no holes, and the resistance at the tip will be greater. This type of needle therefore behaves as a solid body practically without discontinuity or cavity during the advancement in the tissues, and from this results its greater resistance and versatility.

The advantages and characteristics of this type of needle with a variable geometry tip will emerge from the following description of a preferred embodiment thereof.

Brief description of the drawings

The present invention will now be described for illustrative and non-limiting purposes only, with reference to the attached Figures, in which:

Fig. 1 is a longitudinal sectional view of only the external component, or external needle, of the needle for spinal anesthesia with variable position tip according to the present invention;

Fig. 2 is a side view of only the internal component, or mandrel, of the needle for spinal anesthesia with variable tip according to the present invention;

Fig. 3 is a side view of the needle for spinal anesthesia according to the present invention, ready for use, ie in the condition in which the mandrel shown in Fig. 2 is fully inserted into the component or external needle shown in Fig. 1;

Fig. 4 is a sectional view of the detail relating to the tip of the spinal anesthesia needle shown in Fig. 3.

Preferred form of execution

In Figs. from 1 to 4 the same reference numbers always indicate the same components.

The needle for spinal anesthesia according to the present invention is constituted, unlike the conventional needles used for the same function, by a tubular body 1, which we will call external needle, and by a mandrel 9, which is inserted into the axial hole 4 of the body tubular 1.

The gauge, that is the external diameter of the external needle 1, can assume, for example, the values normally used for the Quincke, Sprotte, etc. needle. and in general for conventional type needles. The diameter of the axial hole 4 must allow easy sliding of the mandrel 9 inside it. The external needle 1 has a distal end 2 (see Fig. 1) which, in the absence of the internal mandrel 9, does not constitute a real tip, but forms a truncated cone portion 12, as can be seen from the detail of Fig. 4 (for the moment should not be considered the spindle 9 shown in Fig. 4).

It is also noted that the external needle 1 has a distal hole 3 which constitutes a natural extension in the longitudinal direction of the axial hole 4; in other words, the hole 3 is made perpendicular to the longitudinal axis of the external needle 1, and not laterally and longitudinally as in the case of conventional pencil-tipped needles, or at 45 ° (Quincke). Furthermore, the external needle 1, without stylet 9, cannot puncture and does not traumatize, thanks to its truncated cone shape.

When the mandrel 9 is inserted into the axial hole 4 of the external needle 1, up to the end of the stroke, that is to the point where the conical tip 8 protrudes entirely from the hole 3 (see Fig. 4), the gripping part of the mandrel 9 , consisting of the two portions 10 and 11, remains interlocked in the cylindrical hole 7 and in the conical hole 6 of the proximal end 5 of the external needle 1.

It is therefore evident that the spinal anesthesia needle according to the present invention is such as to modify its distal geometry when the stylet is introduced. In fact, it is the tip 8 of the mandrel 9 that acts as the tip of the needle itself, when it comes out of the distal hole 3 of the external needle 1, as shown in Fig. 4.

The gripping part of the mandrel 9 forms a single piece which comprises the two portions 10 and 11, and is preferably made of plastic material. When the gripping portion of the mandrel 9 is wedged into the proximal end 5 and the mandrel 9 is fully inserted into the outer needle 1, the rear portion 11 of the gripping portion of the mandrel 9 protrudes from the proximal end 5 of the outer needle 1, as shown in Fig. 3. Also the proximal end 5, ie the cone of the external needle 1 is preferably made of plastic material. Obviously, the external needle 1 and the mandrel 9 will be made of resistant metal, for example stainless steel.

The operation of the spinal anesthesia needle with variable position tip according to the present invention is as follows.

The needle of Fig. 3 is positioned in the desired point and is pushed until it reaches the subarachnoid space. As shown in Fig. 3, during this operation the mandrel 9 is inserted into the axial hole 4 of the external needle 1. When the needle has passed through the dura, after the characteristic dural click, the mandrel 9 is extracted and the "pseudo- tip "of truncated cone shape constituted by the truncated conical portion 12 of the external needle 1, is safely and completely located in the liquor. At this point a syringe containing the anesthetic is fixed to the cone 5 of the external needle 1 and it is possible to proceed with the injection. From the described operation it is easy to understand that the complete disappearance of the hole during the advancement of the needle of the present invention prevents "steps" or unevenness of the same from shearing the crossed tissues and picking up fragments. In this way the risk that they, pushed into the liquor, can proliferate is avoided. Furthermore, the closed hole arrangement makes it impossible to obstruct it by blood or tissue fragments.

During the forward movements, the particular symmetrical tip of the needle of the present invention gives it a drift which is practically zero.

The fabrics are gradually "spread" without tearing them, and the hole obtained in the fabric can be reduced in diameter compared to that caused by conventional needles. Since there are no critical breaking points (there are no holes when the mandrel is fitted), the gauge of the needle as a whole can also be reduced. So the needle will be particularly resistant to bending at the tip, even in the smaller 25 G and 27 G gauges.

The following comparison table reports the results of laboratory tests carried out on needles with sharp point (Quincke), on needles with "pencil" point and with lateral hole (Sprotte, Whitacre), and on the needle of the present invention.

It can be seen from the previous table that the needle with variable attitude tip of the present invention resisted better than all the others to the forces acting on the tip which tended to cause it to bend.

Although the present invention has been illustrated

referring to a particular embodiment thereof, it is clear that it is not limited to particular materials, or to a specific configuration of the gripping and interlocking parts 5, 10 and 11, or to a strictly conical shape of the portion 12 and of the tip 8 of the spindle. These latter parts could for example be slightly rounded, even though they are substantially conical.

Claims (3)

CLAIMS 1. Needle for spinal anesthesia characterized in that it comprises an external tubular body, or external needle (1), having a substantially frusto-conical tip (2) that is not sharp and an axial hole (4), and an internal mandrel (9) having a substantially conical tip (8), in which said mandrel (9) is introduced into the axial hole (4) until it protrudes completely by means of its substantially conical tip (8), from the substantially frusto-conical tip (2) of said external needle (1) ; reciprocal locking means (5, 6, 7; 10, 11) being also provided which ensure relative immobility between the external needle (1) and the mandrel (9) during insertion of the needle (1, 9) in the tissues, and which on the other hand allow the external needle (1) to be connected hermetically to an anesthetic injection syringe, after the mandrel (9) has been removed. 2. Needle according to claim 1, wherein the surface of the substantially conical tip (8) of the mandrel {9) and the surface of the substantially frusto-conical tip (2) of the external needle (1), do not have any unevenness or steps and are perfectly smooth. 3. Needle according to claims 1 and 2, in which the surface of the substantially conical tip (8) of the mandrel (9) ends in the substantially frusto-conical surface (2) of the external needle (1), in a regular manner, i.e. without forming any unevenness and substantially without creating gaps between the external needle (1) and the mandrel (9) at the distal end (3) of the axial hole (4).