Keywords

1 Introductions

1.1 What Is Lumbar Subarachnoid Block?

Lumbar subarachnoid block alleviates pain below the umbilical region by anesthetizing the anterior and posterior roots of the spinal cord with the injection of topical anesthetics into the subarachnoid space from an intervertebral point below the third lumbar vertebra, which subsequently affects the anterior and posterior roots of the spinal cord. Strong alleviation of cancer pain may be obtained with lower doses of opioids (mostly morphine) compared to topical anesthetics. Before applying lumbar subarachnoid block in patients with cancer pain, a single test block is often used to confirm the effectiveness of the block treatment for the patient.

2 Indications

  • Surgery in the lower back or limbs and/or lower abdominal region.

  • Strong pain in the lower body.

  • As a test before administering opioids into the subarachnoid space to treat cancer pain.

3 Anatomy (Fig. 70.1)

As the medullary cone usually reaches to a height between the first and second lumbar vertebrae, the needle is inserted below this level to avoid spinal cord injury.

Fig. 70.1
figure 1

Above: Pencil -type needle. Below: Quincke-type needle

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The spine is naturally curved, forming an “S” shape with the cervical vertebrae inflecting forward, the thoracic vertebrae inflecting backward, and the lumbar vertebrae inflecting forward. When a patient assumes the dorsal position, the fourth cervical and third lumbar vertebrae generally become highest, while the fifth thoracic and third sacral vertebrae are lowest. The direction of the flow of the drug is dictated by whether the needle is inserted into the cranial or caudal side of the third lumbar vertebra [1].

4 Instruments and Drug Solutions

4.1 Equipment and Drugs Required for Lumbar Subarachnoid Block

Needle: :

22–29-G 75–90-mm nerve block needle (*1)

Injector: :

Glass syringe

Drugs: :

1% mepivacaine or lidocaine (for skin anesthetization)

0.25–0.5% high-density or isodense bupivacaine (for injection into the subarachnoid space) (*2)

Under X-ray: nonionic water-soluble contrast medium for myelography

Antiseptic kit: :

Cotton balls, chlorhexidine-containing ethanol, etc.

Equipment: :

For ultrasonic guidance: a convex or linear probe

For X-ray guidance: :

A C-arm X-ray unit

(*1) Needle selection: One potential complication of lumbar subarachnoid block is a headache after piercing the dura mater. As the occurrence of this complication depends on the needle gauge (thicker needles are more likely to cause headaches than thinner needles) and shape (Quincke needles are more likely to cause headaches than pencil-point needles [2]), the needle used for the operation must be selected taking these parameters into consideration.

(*2) Topical anesthetics used for injection: The specific weight of the cerebrospinal fluid (CSF) is 1.005–1.009, whereas that of high-density bupivacaine is 1.025–1.031 and that of isodense bupivacaine is 1.002–1.007. Accordingly, the distribution of the drug differs depending on which topical anesthetic is used . Generally, high-density drugs are more desirable when only one side of the patient, a wider area, or an area above the umbilical region is targeted. On the other hand, isodense drugs are better if the patient is unable to lie with their affected side pointing down.

5 Procedures and Techniques

5.1 Landmark Method

The landmark technique is generally performed in the lateral position. Have the patient bend his/her hip and knee joints, and subsequently bend forward their neck and back. The point of needle insertion is determined using a line connecting the right and left upper posterior iliac crests (called Tuffier’s line or Jacoby’s line) that generally runs through the fourth lumbar spinous process (50%), the fourth/fifth lumbar intervertebral region (25%), or the fifth lumbar spinous process (25%). If lumbar X-ray images obtained prior the operation are available, the level of Jacoby’s line should be confirmed.

Two approaches are used for the landmark technique: (1) the median approach, in which the needle is inserted between the two spinal processes that flank the target insertion point, and (2) the paramedian approach, in which the needle is inserted slightly off the median line. The latter approach is used in patients with deformed lumbar vertebrae or other factors causing the use of the median approach to be difficult.

Following the administration of subcutaneous infiltration anesthesia, insert the needle, and advance it carefully. After feeling some resistance when the needle tip reaches the yellow ligament, the resistance will disappear when the tip enters the epidural space, after which the arachnoid membrane can be felt as the needle pierces through it. In order to prevent trauma, however, it is recommended that the piston be removed frequently to check for leakage of cerebrospinal fluid (CSF).

Once CSF leakage is noted, turn the needle several times by 90-degree increments to confirm that the CSF is clear at all angles, then attach the syringe containing the drug, and inject the solution.

5.2 Ultrasound-Guided Method

This technique is performed with the patient in the lateral position. It is desirable to run a preliminary scan with the ultrasonic apparatus in order to generate a block map that will serve as a guide for locating the puncture point, direction, and depth required to insert the needle [3].

On a median sagittal tonogram (Fig. 70.2), move the probe cephalad from the caudal end along the sacral bone, fifth lumbar vertebra, and fourth lumbar vertebra so that the probe is positioned over the target intervertebral location. At this position, generate an image containing the supraspinous ligament, yellow ligament, and dura mater, which will be used to guide the location of the puncture point, direction, and depth for needle insertion.

Fig. 70.2
figure 2

Sagittal view

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With a transverse (short-axis) view in which the probe is turned 90 degrees from the sagittal view (Fig. 70.3), generate an image containing the dura mater and surrounding area. Adjust the axis of the probe so that the shading on the spinal processes disappears, the intervertebral joint appears symmetric on both sides of the processes, and the dura mater and epidural space appear as if they are connecting the bases of the processes. Subsequently insert the needle along the axis obtained above.

Fig. 70.3
figure 3

Horizontal view

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5.3 X-ray Fluoroscopy-Guided Method

For this technique, the patient lies in either the lateral or abdominal position. If the abdominal position is used, insert a pillow under the lumbar area in order to place the lower back and bed in parallel, making it easier to observe the intervertebral region. Adjust the axis of the X-ray tube so that the spinal processes run in the center and the end plates are aligned in a single line.

After confirming the space between the spinal processes, apply topical anesthetics to the target area, and advance the needle so that the needle is displayed as a single dot.

6 Complications

Headache after piercing the arachnoid membrane: In addition to the gauge and shape of the needle, age and gender influence the incidence of headache after this procedure, with headaches being more frequently observed among young and female patients, especially those who are pregnant.

Damage to the nerve: Care must be taken to choose an insertion point below the medullary cone and avoid causing any damage during catheter insertion.

Cauda equina syndrome: Very rarely, temporary abnormal sensations, mobility disturbances, and/or bladder or rectal dysfunction may be observed, most of which remit within approximately 2 months.

Respiratory depression: Respiratory depression may occur if the target area for anesthesia is positioned at a higher level, causing the anesthetic to spread to the phrenic nerve.