WO2001035841A1

WO2001035841A1 - Needle for spinal anaesthesia, having a point with variable configuration

Info

Publication number: WO2001035841A1
Application number: PCT/IT2000/000457
Authority: WO
Inventors: Aniello De Nicola
Original assignee: Svas Biosana S.R.L.
Priority date: 1999-11-17
Filing date: 2000-11-10
Publication date: 2001-05-25
Also published as: ITRM990704A1; AU1884701A; IT1307277B1; ITRM990704A0

Abstract

A needle for spinal anaesthesia, comprising two parts (1, 9), that is, an internal pointed mandrel (9), and an external needle (1) having a non cutting point, used for the injection of the anaesthetic. The internal mandrel (9) renders the needle more robust and forms part of the needle point (1, 9).

Description

Description Needle for spinal anaesthesia, having a point with variable configuration

Technical Field

The present invention relates to a needle used for subarachnoid anaesthesia, also called spinal anaesthesia.

Background Art

The subarachnoid anaesthesia consists in injecting a local anaesthetic in the subarachnoid space, that is, in the liquor. The drug comes into intimate contact with the spinal nerves and acts rapidly, thereby giving rise to a complete and intense anaesthesia of the corresponding body metameres. The advantages of this kind of anaesthesia are due to the simplicity of execution, the immediateness of its onset, and to the favourable ratio between the costs and the number of benefits thereby obtained.

However, the post-spinal headache represents the most common side effect following the liquorrea (loss of liquor) occurring through the hole realised in the dura mater. The wider the hole, and the more "frayed" are its boundaries, the greater and longer will be the liquorrea and the thereby induced headache.

Needles having a pencil-like point, - so-called non traumatic needles - , have been devised to reduce said secondary effect. These needles are less sharp and tearing (lacerating) , and give rise to a hole having a smaller diameter. A disadvantage of the non traumatic needles resides however in the fact that the needle hole position, which is longitudinally located on the periphery of the needle body, in proximity of the point, noticeably influences both the needle resistance and the distribution of the anaesthetic. In fact, the position of the elongated hole on the needle body, is a critical and "weak" feature of the needle, in the eventuality of needle point collisions with the vertebra. Moreover, the elongated form of the hole may sometimes lead to a situation according to which, at the time the injection is performed, part of the hole is located in the subarachnoid space, and the remaining part in the epidural region. In this position, part of the anaesthetic is uselessly and inadvertently injected in the epidural region, thereby leading to an insufficient subarachnoid anaesthesia or even making it unsuccessful.

Particular kinds of needles, known as Whitacre or Sprotte needles, have a laterally positioned hole of their points, located on the body of the needle, and therefore parallely to the longitudinal axis thereof. The resistance of these needles having a conical or ogival point, is insufficient in the region of their point, as has been said above. This means that the forces which act parallely to the needle body, and which are the reaction forces caused by the body tissues to the advancement of the needle, may easily generate a vector which is capable of bending the needle at the region of its critical point (that is, the hole). A needle which is bent at its point, like a fish-hook, could damage the dura mater, both during its advancement or retraction. This may in fact occur when the needle collides with a bony structure, or with the supraspinous or interspinous ligament, or the ligamentum flavum, which are particularly robust or even "stony". Another kind of needle, the classical and traditional Quincke needle, which has a 45° inclination ofits point hole, is also well-known. Even this needle has the disadvantage that its resistance to collisions is very low at its point. In fact, its sharp point tears (lacerates) and causes traumas to the dura mater, facilitating the occurrence of post-spinal headache. The goal of the present invention is to realise a needle for spinal anaesthesia which at the same time is non traumatic, has a much higher resistance of the point in comparison with prior art needles - for an equal gauge - , and is such as to ensure the injection of the whole amount of anaesthetic which must be injected in the liquor. In other words, the needle must be safe (avoiding the occurrence of post-spinal headache), resistant, and reliable in order to ensure that the anaesthesia will not fail.

Disclosure of Invention

The object of the invention is attained by means of a needle for spinal anaesthesia , which is defined as needle with a "variable point configuration", and which is formed by an external tubular body, or external needle, having an axial bore and a conical and non-cutting point, and by an internal mandrel with a substantially conical point, said mandrel being introduced inside the axial bore, until it completely protrudes with its conical point, beyond the frustoconical point of the external needle.

The needle, formed by said two parts, is pushed inside the body tissues until it passes through the dura mater. The axial position of the bore of the external needle, ensures that - after having withdrawn the mandrel - the bore of the external needle is located entirely inside the liquor. The gauge of the needle may also be less than that of conventional needles, since during the advancement of the needle the mandrel is inside the external needle, and no hole exists, and the resistance at the point will therefore be greater. That is, this kind of needle behaves like a solid body having substantially no discontinuity or recess, during its advancement in the tissues, and this is the reason ofits enhanced resistance and versatility.

The advantages and features of this kind of needle, having a point with a variable configuration, will result from the following description of a preferred embodiment thereof.

Brief Description of Drawings

The present invention will now be described only for illustrative and non-limitative purposes, with reference to the annexed figures, wherein: Fig. 1 is a longitudinal sectional view of the external component alone, also called external needle, making part of the needle for spinal anaesthesia with a variable point configuration according to the present invention;

Fig. 2 is a side view of the internal component alone, or mandrel, making part of the needle for spinal anaesthesia with a variable point configuration according to the present invention;

Fig. 3 is a side view of the needle for spinal anaesthesia according to the present invention, which is ready for use , that is, in the condition in which the mandrel shown in Fig. 2 is entirely introduced inside the external component or needle shown in Fig. 1;

Fig. 4 is a sectional view of the detail of the point of the needle for spinal anaesthesia shown in Fig. 3.

Best Mode of Carrying out the Invention

In Figs. 1-4 the same reference numbers always denote the same components.

The needle for spinal anaesthesia according to the present invention, is formed, unlike conventional needles used for the same purpose, by a tubular body 1, which will be called external needle, and by a mandrel 9, the latter being introduced inside the axial bore 4 of the tubular body 1.

The gauge, that is the external diameter of the external needle 1, may for instance correspond to the values normally used by the Quincke needle, the Sprotte needle , etc., and generally by conventional type needles.

The diameter of the axial bore 4 must ensure an easy sliding of the mandrel 9 inside the bore.

The external needle 1 has a distal end 2 (see Fig. 1) which , in absence of the (internal) mandrel 9, does not form a real point, but only a frustoconical portion 12 (frustum of a cone), as may be seen from the detail shown in Fig. 4 (ignore for the moment the mandrel 9 illustrated in Fig. 4). It may also be noted that the external needle 1 has a distal hole 3 forming a natural extension of the axial bore 4 in the longitudinal direction; in other words , the bore 3 is formed perpendicularly to the longitudinal axis of the external needle 1, and not laterally and longitudinally as in conventional needles having a pencil-like point, or with an inclination of 45° (Quincke). Moreover, the external needle 1, deprived of the mandrel 9, cannot sting or cause traumas, because ofits frustoconical shape.

When the mandrel 9 is introduced inside the axial bore 4 of the external needle 1, up to the end-of-stroke position, that is the position in which the conical point 8 entirely projects from the hole 3 (see Fig. 4), the grip portion of the mandrel 9, which is formed by the two portions 10 and 11, is restrained inside the cylindrical bore 7 and inside the conical bore 6 of the proximal end 5 of the external needle 1.

Therefore, it will be obvious that the needle for spinal anaesthesia according to the present invention is capable of modifying its distal geometry (configuration) when the mandrel is inserted. In fact, the point 8 of the mandrel 9 acts as the real point of the needle, when it projects out of the distal hole 3 of the external needle 1, as shown in Fig. 4.

The grip portion of the mandrel 9 forms a single piece comprising two portions 10 and 11, and preferably it is made of plastics. When the grip portion of the mandrel 9 is restrained in the proximal end 5, and the mandrel 9 is completely inserted in the external needle 1, the rear portion 11 of the grip portion of the mandrel 9 projects out of the proximal end 5 of the external needle 1, as shown in Fig. 3. Also the proximal end 5, that is the cone of the external needle 1, is preferably made of plastics. Obviously, the external needle 1 and the mandrel 9 will be made of a resistant metal, e.g. stainless steel. The needle for spinal anaesthesia according to the present invention, having a variable point configuration, will be used in the following way. The needle shown in Fig. 3 is positioned at the desired place and is pushed until it reaches the subarachnoid space. As shown in Fig. 3, during this operation the mandrel 9 is located inside the axial bore 4 of the external needle 1. After the needle has gone beyond the dura mater, that is after hearing the typical dural "click", the mandrel 9 is withdrawn (extracted), and the frustoconical "pseudopoint" formed by the frustoconical portion 12 of the external needle 1, is then surely entirely located in the liquor. Then, a syringe containing the anaesthetic is fixed onto the cone 5 of the external needle 1 and thereafter the injection may be performed.

Form the above described operation it can be easily understood that the complete disappearance of the hole during the advancement of the needle of the present invention, prevents "steps" or surface irregularities of the needle itself, from cutting the tissues traversed by it, and also from removing fragments of these tissues. In this way the possibility is ruled out, that these fragments proliferate in the liquor, after having been pushed inside the same. Moreover, this configuration, with a "closed" hole, makes impossible the obstruction of the hole by the blood, or by tissue fragments. During the advancement, the specific symmetrical configuration of the needle practically eliminates its lateral shift.

The tissues are gradually moved apart without being lacerated, that is without being torn, and the bore obtained inside the body tissue may be reduced in diameter with respect to that produced by conventional needles. Since critical breakage points do not exist (no holes exist when the mandrel is introduced), also the overall gauge of the needle may be reduced. Therefore, the needle will be particularly resistant at its point, with regard to flexion, also when gauges of 25 G and 27 G are employed. The following comparative table contains the results of laboratory tests performed on needles having a sharp point (Quincke), needles with a "pencil-like" point and a lateral hole (Sprotte, Whitacre), and on the needle of the present invention.

From the preceding Table it may be seen that the needle with variable point configuration according to the present invention has resisted in a much better way to forces acting on its point, and tending to cause its flexion. Although the present invention has been illustrated with reference to a particular embodiment, it is obvious that it is not limited to particular materials, to a specific shape of the grip portions or the restrained joint portions, 5, 10 and 11, or to a strictly conical shape of the portion 12 and of the point 8 of the mandrel. These latter parts could for instance also be slightly cumbered but still substantially conical.

Claims

1. A needle having a variable point configuration, characterised in that it comprises an external tubular body or external needle (1) , with a non cutting, substantially frustoconical point (2), and with an axial bore (4), and an internal mandrel (9) having a substantially conical point (8), said mandrel (9) being introduced inside said axial bore (4) and protruding completely by means of its substantially conical point (8), from the substantially frustoconical point (2) of said external needle (1); wherein, there are further provided means (5, 6, 7; 10,11) acting as restrained joints, in order to ensure mutual immobility between the external needle (1) and said mandrel (9), at the time the needle (1, 9) is introduced in the body tissues, and moreover, in order to realise a sealed connection between the external needle (1) and a syringe for injecting the anaesthetic, after removal of said mandrel (9).

2. A needle according to claim 1, wherein the surface of the substantially conical point (8) of said mandrel (9) and the surface of the substantially frustoconical point (2) of said external needle (1), do not have surface irregularities or steps, and are perfectly smooth.

3. A needle according to claims 1 and 2, wherein the surface of the substantially conical point (8) of said mandrel (9) smoothly and gradually extends towards the substantially frustocomcal surface (2) of the external needle (1), without giving rise to surface irregularities and steps, and substantially without causing gaps between the external needle (1) and the mandrel (9) at the distal end (3) of the axial bore (4).