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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.
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Chapter 4 Neural Anesthesia
- bacteria
This is a mind map about bacteria, and its main contents include: overview, morphology, types, structure, reproduction, distribution, application, and expansion. The summary is comprehensive and meticulous, suitable as review materials.
- Plant asexual reproduction
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- Reproductive development of animals
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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.