4.1 Central Neuraxial Blocks - Spinal Flashcards
(65 cards)
Absolute contraindications for spinal anaesthesia
Absolute contraindications for spinal anaesthesia
include
- patient refusal,
- raised intracranial hypertension,
- neurological disease of indeterminate origin,
- coagulopathy,
- severe hypovolaemia
- local infection.
Relative contraindications
Relative contraindications include
- systemic sepsis,
- surgery of indeterminate duration,
- arthritis,
- kyphoscoliosis
- previous lumbar surgery.
Spinal and MS patients
Central neuraxial block in patients with multiple sclerosis is
controversial. There is no clinical study which has shown that spinal
anesthesia worsens pre-existing neurological disease. Perioperative
surgical stress may exacerbate the condition, and hence a central
neuraxial block may be preferred
Spinal cord has three coverings
Dura mater
Arachnoid mater
Pia mater
Dura mater
border
(outermost) extends from foramen magnum to S2.
Arachnoid mater
Arachnoid mater (middle) extends to S2.
Pia mate
Pia mater (innermost) ends in the filum terminale
Supraspinous ligament
Supraspinous ligaments extend from
C7 to sacrum
connecting the tips of
the spinous processes.
Above C7, they are called the ligamentum nuchae.
How are the spinous processes connected
How are laminae connected
How are vertebral bodies held together
The spinous processes are
interconnected by the interspinous ligaments.
The laminae are connected by the ligamentum flavum.
The vertebral bodies are held together by the anterior and the posterior longitudinal ligaments.
Structures pierced while performing
a spinal anaesthetic via midline
Structures pierced while performing a spinal anaesthetic via midline approach are
1 skin
2 subcutaneous tissues
3 supraspinous ligaments,
4 interspinous ligaments
5 ligamentum flavum
6 dura mater
7 subdural space
8 arachnoid mater
and
9 subarachnoid space.
Structures pierced while performing
a spinal anaesthetic via paramedian approach
what is not pierced vs midline
However, via the paramedian approach
all the above structures are
encountered
except the
supraspinous
and
interspinous ligaments.
1 skin
2 subcutaneous tissues
3 ligamentum flavum
4 dura mater
5 subdural space
6 arachnoid mater
and
7 subarachnoid space.
Spinal nerves
How many
Do each have 2 components?
what are those componenets
1
Thirty-one pairs of spinal nerves
arise from the spinal cord with
anterior motor and posterior sensory roots.
How are the spinal nerves named
From vertebral body above or below
Does this differ anywhere
The spinal nerves are named
as per the intervertebral foramen
from which they exit.
In the cervical region,
they are named according to the
lower cervical vertebral body
(C3 emerges from intervertebral foramen
formed by C2 and C3),
but in the
thoracic and lumbar region
they are named
according to the
upper vertebral body
(L3 emerges from intervertebral
foramen formed by L3 and L4).
What happens dorsal nerve roots
The dorsal nerve roots
divide into two or three
bundles during their exit
and
redivide further before forming
dorsal root ganglia.
What happens ventral roots
Most ventral nerve roots exit
as a single bundle,
explaining the slower onset of
motor blockade because
of smaller surface area for
local anaesthetic action.
What factors affect spread in SA space
The factors affecting the spread of
local anaesthetic in subarachnoid
space include the following.
- Drug factors
- Patient factors
3 Technique
Concentration has no effect on the spread of local anaesthetic, as a new concentration is formed after mixing with the cerebrospinal fluid (CSF).
Drug factors
Drug factors: baricity, volume, specific gravity and dose of local anaesthetic.
Patient factors
Patient factors:
raised intra-abdominal pressure
(pregnancy, obesity, ascites),
spinal column anatomy,
patient position and
patient height.
Technique
Technique:
direction of the needle bevel and site of injection.
Effect of Epinephrine and phenyl
Epinephrine and phenylephrine
are both vasoconstrictors.
They prolong the duration of action
of local anaesthetic
by decreasing their systemic absorption.
Risk of Epinephrine
Because of its vasoconstrictive properties,
epinephrine may cause anterior spinal artery ischaemia.
Risk of phenyl
The risk of transient neurological symptoms (TNSs) has been shown to
increase with the use of phenylephrine.
Clonidine effect on SAB
Clonidine prolongs both sensory and motor blockade.
Effect of AChI on SAB
(how exert effect)
problems
Acetylcholinesterase inhibitors
like neostigmine
exert their effect by increasing
acetylcholine and nitric oxide.
However, their use is limited by side effects such as nausea, vomiting, agitation, bradycardia, restlessness and lower-limb weakness.
