Spinal needle

Details Spinal needle Spinal needle

2001-01-25

2003-05-06

Scherbel, David A. (Department: 3754)

Surgery

Means for introducing or removing material from body for...

Treating material introduced into or removed from body...

C604S161000, C604S164010, C604S164070, C604S168010, C604S170020, C606S167000, C606S186000

Reexamination Certificate

active

06558353

ABSTRACT:

BACKGROUND
1. Field of the Invention
This invention relates to innovative needles for facilitating lumbar puncture procedures generally and, more particularly, to a novel, atraumatic needle apparatus and method for reducing loss of cerebral spinal fluid (CSF) during such procedures.
2. Background
Spinal anesthesia is one of the most frequently employed methods of regional anesthesia. This regional anesthesia is accomplished by the temporary interruption of nerve transmission using a local anesthetic injected into the readily identifiable subarachnoid space. The ensuing anesthesia is predictable, occurs rapidly, and is associated with profound muscle relaxation. The patient may be wide awake, or if preferred, the anesthetic may be supplemented with varying amounts of sedative-tranquilizers. Spinal anesthesia is particularly useful for surgery involving the lower extremities, pelvis, perineum, and lower abdomen.
The spinal column, which surrounds the spinal cord, is formed by a series of vertebrae separated by cartilaginous intervertebral disks and united by a series of ligaments. The body of each vertebra bears the weight of the patient and forms the base of the neural arch. The arch, which surrounds the spinal cord, is made up of a pedicle and lamina on each side. Between the laminae of each vertebra there is a posterior opening in the vertebral canal. It is through this opening that a spinal needle is passed when performing a subarachnoid block.
In adults the spinal cord varies in length from 40 to 45 cm. and ends at various levels of the vertebral column depending on the age of the patient. In the newborn, the spinal cord extends to the third lumbar vertebra, but in the adult it usually ends at the lower border of the first lumbar vertebra because the spinal cord does not grow as much as the vertebral column. Thirty-one pairs of symmetrically arranged spinal nerves are each attached to the spinal cord by an anterior and posterior root. Because the spinal cord is shorter than the vertebral column, the spinal cord segments in adults do not lie opposite their corresponding vertebrae. The spinal nerve roots must travel obliquely in a caudad direction to reach their respective intervertebral foramina. The roots of the lumbar, sacral, and coccygeal nerves comprise the cauda equina and are necessarily the largest and longest in order to reach their intervertebral foramen. The greater size of these nerve roots provides a larger surface area to be exposed to the action of local anesthetics, thus allowing more rapid onset of anesthesia.
The spinal cord is covered by three membranes or meninges. The dura mater (the outermost membrane) is the downward continuation of the meningeal layer of the cranial dura mater. The middle of the three coverings, the arachnoid is a thin membrane closely adherent to the dura mater. The dura and the arachnoid are in such close contact that usually it is not possible to puncture the dura without also piercing the arachnoid. Nevertheless, on rare occasions, the tip of the conventional epidural or spinal needle may accidentally enter the subdural space. Local anesthetic inadvertently injected into the subdural space will diffuse poorly and result in inadequate contact with the nerve roots. Poor or absent anesthesia may ensue. Should subdural placement occur during an attempted epidural anesthetic, the improper position of the needle may not be recognized and the injection of an epidural dose of local anesthetic may result in a much higher block than anticipated.
The innermost membrane, the pia mater, is a thin, delicate, highly vascular membrane closely adherent to the spinal cord. The space surrounding the pia is filled with cerebrospinal fluid and is enclosed externally by the arachnoid. In addition to spinal fluid, this space contains the spinal nerve roots and the main blood vessels of the central nervous system. In the cervical and thoracic regions, the space is only about 3 mm deep, but below the lower border of the first lumbar vertebra, where the spinal cord usually ends, the space has a diameter of about 14 to 15 mm.
A typical spinal anesthetic delivery device comprises three components. A sharp, hollow introducer component a few centimeters in length that is used to puncture the skin, a more blunt hollow needle component several centimeters in length that is slideably disposed within the hollow introducer to allow the caregiver to delicately pierce the dura membrane, and a stylet component that is slideably disposed within the needle to selectively occlude the needle and control the flow of fluid therein. The introducer and needle components both have hubs on their proximate ends. The hubs act as handles or grips to facilitate manipulation of the introducer and needle.
Delivering spinal anesthesia may be accomplished using a lumbar puncture procedure. The lumbar puncture generally involves the following steps:
(1) Placing the patient receiving the procedure in the lateral decubitus position on the edge of the bed with the patient's back exposed to the caregiver carrying out the procedure;
(2) Placing the patient in a fetal like position with the head supported so that the head and spine are parallel to the bed and the knees are to the chest;
(3) Marking the posterior iliac crest and palpate the L4 spinous process;
(4) Anesthetizing the patient's skin in preparation for inserting an introducer and spinal needle;
(5) Inserting the introducer at the marked puncture point;
(6) Advancing the needle slowly through the introducer until the dura membrane is breached. A distinct “pop” may be heard when the membrane is pierced. The needle should be inserted approximately two centimeters into the skin.
(7) After the dura membrane is pierced, withdrawing the stylet disposed within the needle as the needle is advanced to verify the presence of CSF flowing back out of the needle;
(8) Injecting the anesthetic through the needle to induce the anesthetic block;
(9) Withdrawing the needle and introducer without replacing the stylet; and
(10) Dressing the puncture site with a bandage.
A spinal needle 9 cm long is usually adequate for lumbar puncture, but longer ones (10-15 cm) are available for the occasional obese patient or difficult paramedian approach. The removable, close-fitting stylet helps stiffen the needle and prevents coring of the tissue. Commonly, two sizes of spinal needles are used, 22-27 gauge. The larger diameter 22 gauge needle is easier to direct and renders the characteristic feel of the various ligaments penetrated easier to appreciate. However, the incidence of postspinal headache is increased with the larger needle, particularly if the larger needle is also equipped with a standard point which is a cutting bevel.
A postdural puncture headache is the most common postoperative complication of spinal anesthesia. The incidence increases with the larger spinal needles and those with a cutting bevel at the tip but decreases with increasing patient age. Postdural puncture headache also occurs more commonly in women than in men, and more often in pregnant women than in nonpregnant women. The headache is positional in that it comes on in the upright position and is relieved or at least improved in the recumbent position.
The causative mechanism of the postdural puncture headache is believed to be associated with the continuing leakage of cerebrospinal fluid (CSF) through the dural opening left by the spinal needle. The leakage of CSF causes a decrease in CSF pressure which, in turn, produces compensatory cerebral vasodilation. Bringing the patient into the erect position also results in traction on the pain-sensitive, dilated blood vessels. Accordingly, conservative therapy for the postdural puncture headache consists of bed rest and analgesics.
Various preventive measures for the postdural puncture headache have been advocated. The common practice of keeping the patient supine for 4 to 24 hours after lumbar puncture has been shown to be ineffective. For a standard point needle having a cutting bevel at its tip, insertion of the needle with

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