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MindMap Gallery Chapter 4 Neural Anesthesia

Chapter 4 Neural Anesthesia

Chapter 4 of Anesthesiology: Intraspinal anesthesia, local anesthetic solution is injected into the subarachnoid space or epidural space in the spinal canal to temporarily block spinal nerve root conduction.

Edited at 2024-01-18 18:14:34

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Chapter 4 Neural Anesthesia

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Outline

general anesthesia
- 27
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Anesthesia method
- 11
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Anesthesiology
- 16
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Pre-anesthetic medication
- 10
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clinical anesthesiology
- 10
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Chapter 5 General Anesthesia
- 10
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Anesthesiology knowledge map
- 6
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Anesthesia Anatomy - Chest
- 5
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Chapter 3 Local Anesthesia
- 39
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airway management
- 12
- 1
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Chapter 4 Neural Anesthesia

definition

Inject local anesthetic solution into the subarachnoid space or epidural space in the spinal canal to temporarily block spinal nerve root conduction.

Anatomy

spine and spinal canal

7 cervical vertebrae C, 12 thoracic vertebrae T, 5 lumbar vertebrae L, 4 coccygeal vertebrae S

The spinal canal starts from the foramen magnum and ends at the sacral hiatus.

The adult spine shows four curves, the cervical and lumbar curves are forward, and the thoracic and sacral curves are backward.

When lying on your back, C3 and L3 are the highest, and T5 and S4 are the lowest.

ligament

supraspinal ligament, interspinous ligament and ligamentum flavum

The puncture needle passes through the skin, subcutaneous tissue, supraspinal ligament, interspinous ligament, and ligamentum flavum → epidural space (epidural anesthesia) → dura mater → subdural space → arachnoid membrane → subarachnoid space (spinal anesthesia) )

The ligamentum flavum has a dense structure

Spinal cord, meninges and cavities

The lower edge of the spinal cord is located at the lower edge of L1 or the upper edge of L2

For pediatric and adult lumbar puncture, choose L3-4

spinal nerve

There are 31 pairs of spinal nerves

Neck 8, chest 12, waist 5, sacrum 5, tail 1

cerebrospinal fluid

Cerebrospinal fluid dilutes and diffuses local anesthetics during spinal anesthesia

Anesthesia level (sensory nerve block range)

Mechanism and Physiology

drug action site

The main site of action is the spinal nerve root

subarachnoid block

Acts directly on the surface of the spinal cord and spinal nerve roots

epidural block

Enter the root subarachnoid space through arachnoid villi

Local anesthetic leaks into the intervertebral foramina to block spinal nerves

Enter the subarachnoid space through the dura mater and arachnoid membrane

blocking sequence

Autonomic nerves → sensory nerves → motor nerves → proprioceptive nerves

Motor nerve block: thick, late block, muscle relaxation

Sensory nerve block: medium, during block, pain disappears

Sympathetic nerve block: fine, early block, vagal hyperactivity

Classification

Subarachnoid block (spinal anesthesia, spinal anesthesia)

concept

Inject local anesthetic into the subarachnoid space to block the conduction function of part of the spinal nerves and cause anesthesia in the corresponding areas.

Classification

Specific gravity of cerebrospinal fluid (1.003 to 1.009)

press block plane

Equal specific gravity liquid

Heavy specific gravity liquid

Preparation by adding an appropriate amount of glucose (5%~10% glucose solution) to the local anesthetic solution can make the specific gravity of the solution reach more than 1.020

Light specific gravity liquid

Local anesthetic solution diluted with water for injection

Specific gravity of liquid medicine

High spinal anesthesia: sensory block level exceeds T4

Low spinal anesthesia: sensory block below the T10 level

Saddle anesthesia: The block range is limited to the perineum and buttocks.

Unilateral block: The block effect is limited (or mainly limited) to one lower limb or called unilateral spinal anesthesia

Indications

Lower abdominal and pelvic surgery, anus and perineal surgery, lower limb surgery

Surgery within 2 to 3 hours

Contraindications

Spinal anesthesia should be absolutely contraindicated in patients with central nervous system diseases, serious systemic infections, hypertension and coronary artery disease, patients with shock, patients with spinal trauma or a history of severe low back pain, patients with significantly increased intra-abdominal pressure, uncooperative patients, patients with mental illness, For severe neurosis and children, spinal anesthesia, coagulation abnormalities, and anticoagulation treatment are generally not used.

effect

direct effect

spinal nerves, anterior and posterior roots and spinal cord

indirect effect

Physiological effects of autonomic nerve paralysis

breathe

Intercostal muscle paralysis: may cause hypoventilation

Phrenic nerves C3~C5 are blocked: when the block level reaches the neck, respiratory arrest may occur.

The level of spinal anesthesia is too high (T4-5), which may induce bronchospasm

cycle

Dilated blood vessels, low blood pressure, slowed heart rate

Digestion

Increased gastrointestinal motility, increased gastric juice secretion, reflux and retrograde peristalsis, and intestinal spasmodic pain ,feel sick and vomit

Urology

urinary retention

Clinical application

Commonly used local anesthetics

Bupivacaine, Ropivacaine

subarachnoid puncture

Position: lying on side, flexion, holding knees

Positioning: L 3～4 or less

When using a heavy specific gravity solution, the surgical side should face down.

When using a light specific gravity solution, place the surgical side up

Sellar area anesthesia is usually done in a sitting position

puncture site

L2-3 or L3-4 spinous process space

Determining method

Take the highest points of the iliac crests on both sides as a connecting line, and the intersection with the spine is the fourth lumbar vertebra.

L3~4 spinous process space

Abdominal surgery → Easy to choose L2~3; Lower limb and perineal and anal surgery → L3~4 or below

Adjustment of blocking plane

Acupuncture of the skin to measure pain, and hand testing for loss of skin touch (temperature sensation, reflexes, muscle tremors)

complication

intraoperative complications

Blood pressure drops, heart rate slows

Volume expansion and fluid replenishment before anesthesia

BP still does not rise → Vasopressor, ephedrine 5~10mg

Respiratory depression

Oxygen, mask-assisted breathing, if breathing stops, immediate endotracheal intubation, artificial respiration

feel sick and vomit

Correct low BP, inject haloperidine, glastron, and atropine intravenously, and suspend surgical stimulation.

Postoperative complications

Headache after spinal anesthesia (the most common complication of spinal anesthesia), urinary retention, purulent meningitis

Neurological complications after spinal anesthesia

cranial nerve palsy

Dizziness, strabismus, diplopia

adhesive arachnoiditis

Sensory impairment, sensory loss, paralysis, meningeal chronic proliferative reaction

cauda equina syndrome

Sensory and motor functions of lower limbs do not recover for a long time after spinal anesthesia

N system - recovery from sacral N involvement, fecal incontinence, and urethral sphincter paralysis is unusually slow

Epidural block (epidural anesthesia)

concept

Inject local anesthetic into the epidural space to block the roots of the spinal nerves and cause temporary paralysis in the areas they control.

Classification

High epidural block C5~T6

Thyroid, upper limb or chest wall surgery

Median epidural block T6~Tl2

abdominal surgery

Low epidural block (space between spinous processes in waist)

Lower limb and pelvic surgery

Sacral canal block (sacral hiatus)

Anal and perineal surgery

epidural space puncture

Position: side lying, sitting

Choice of puncture point

The spinal nerves that innervate the center of the surgical area correspond to the spinous process spaces.

Determination of epidural space

Sudden disappearance of resistance and negative pressure phenomenon

Dosing method

Test dose: 3～5 ml

Additional dose: the dose required to meet the surgical requirements

Maintenance amount: add 1/2 or 1/3 of the initial amount

complication

Dural perforation, local anesthetic toxicity, difficulty or breakage of catheter extraction, nerve damage

Epidural hematoma: the first cause of epidural complications with paraplegia

Applicable certificate for sacral canal block

Anal and perineal surgery, abdominal surgery in children

Combined subarachnoid and epidural block (combined spinal and epidural anesthesia)

1. Use an epidural needle to guide spinal anesthesia needle puncture, which is more likely to be successful.

2. Compared with simple epidural, it has quick onset and precise effect.

3. Epidural catheter can prolong the action time.

4. The dosage of spinal anesthesia is small, and epidural block can improve the block plane.