DR I Noeth Department Anaesthesiology Steve Biko Academic
Hospital REGIONAL ANAESTESIA
Slide 2
KEYPOINTS: Spinal, epidural and caudal blocks are known as the
neuraxial blocks Principal site of action of neuraxial blocks is
the spinal nerve roots Sensory, motor and to some degree
sympathetic block is achieved with neuraxial techniques Level is
below L1/2 in adults and L3 in children Nb definite contra-
indications to neuraxial techniques
Slide 3
ANATOMY
Slide 4
Anatomy Spine is composed of vertebral bones and cartilaginous
intervertebral discs 7cervical, 12 thoracic, 5 lumbar vertebrae The
5 sacral vertebrae is fused and there is small rudimentary
coccygeal vertebra Vertebral structure: body anteriorly, connected
via 2 pedicles to transverse processes that in turn is connected
posteriorly to the spinous process via 2 lamina. Each vertebral has
4 small synovial joints connecting it to the vertebra above and
below it allowing movement of the spinal column
Slide 5
ANATOMY
Slide 6
Lamina of S5 and S4 normally doesnt fuse, leaving small caudal
opening to the spinal canal called the sacral meatus Each vertebral
body is separated by an intervertebral disc Spinal column has
double-C shape: convex anteriorly in the cervical and lumbar areas
Ligament provide (together with muscles) structural support and
help maintain unique shape. Vertebral body and discs are connected
and supported by ant and post longitudinal ligaments and dorsally
the ligamentum flavum, interspinous and supraspinous ligaments
provide additional stability
Slide 7
ANATOMY
Slide 8
Slide 9
Spinal canal contains spinal cord, its coverings (meninges)
fatty tissue and an venous plexus Meninges: 3 layers: pia mater
closely adhered to spinal cord arachnoid losely adherent to thicker
and denser dural mater CSF containe between arachnoid and pia mater
Spinal subdural space potential space between dura and arachnoid
Epidural space between dura mater and ligamentum flavum
Slide 10
ANATOMY Spinal cord extends from the foramem magnum to L1 in
adults and L3 in children Ant and post nerve roots join each other
forming spinal nerves exiting through intervertebral foramina on
each level From L1 down lower spinal nerves travel some distance
before exiting through intervertebral foramina, forming the cauda
equina Safe level for neuraxial techniques below L1 in adult and L3
in children to avoid direct cord damage
Slide 11
ANATOMY
Slide 12
Mechanism of action Principle site of action of neuraxial
techniques is nerve root Blocking post nerve roots interrupts
somatic and visceral sensation Blocking anterior nerve root prevent
motor and autonomic outflow Differential blockade: sympathetic
blockade 2 levels above sensory block which in turn is 2 levels
above motor block
Slide 13
AUTONOMIC BLOCK Sympathetic plexus from T1 to L1 Blocking
anything from T5 downwards result in decreased vasomotor tone,
pooling of blood in lower limbs and decrease in blood pressure...
Normally with compensatory tachycardia Blocking T1-T4 blocks
cardiac accelaratory fibres leading to bradycardia and decreased
cardiac contractility Deleterious CVS effects must be countered by
volume loading pt with 10-20ml/kg IVI fluid and early
administration of vasopressors Bradycardia should be treated with
atropine
Slide 14
AUTONOMIC BLOCK GIT- Sympathetic block leads to vagal
predominance leading to small contracted gut with active
peristalsis. Hepatic bloodflow reduction mirrors drop in BP Urinary
Tract lumbar and sacral level blocks block both sympathetic and
parasympathetic bladder control leading to urinary retention till
block wears off Neuraxial techniques partially or totally block the
neuro- endocrine stress response induced by surgery
Slide 15
CONTRAINDICATIONS TO NEURAXIAL TECHNIQUES Absolute: Infection
at site of injection Patient refusal Coagulopathy or bleeding
diathesis Severe mitral or aortic stenosis Severe hypovolemia
Increased intracranial pressure
CONTRAINDICATIONS contd CONTROVERSIAL Prior back surgery at
site of injection Inability to communicate with patient Complicated
surgery major bloodloss expected
Slide 18
Patients with coagulopathy Excepted preoperative values INR -
< 1,5 ( 80 000 Bleeding time - 12 ( > 15 in experienced
hands)
Slide 19
Strategies for discontinuation of anticoagulation in peri-op
period Minimum delay pre-op or prior to placement or removal of
epidural catheter Mimimum delay post op or after removal of
neuraxial catheters UFH4h1h LMWH prophylaxis12h4h LMWH
treatment24h6-8h Aspirin0h Warfarin3-5daysImmediately But
controversial Fondaparinux36 hours but epidural catheter not
recommended Epidural not recommended Dosing not recommended
Complications contd: Cauda equina syndrome Associated with use
of continuous spinal catheters and 5% lignocaine Bowel and bladder
dysfunction together with evidence of multiple nerve root injury
Neurotoxicity following repeat intrathecal injection is higher with
lignocaine > tetracaine > bupivacaine > ropivacaine
Slide 55
Other regional techniques A nerve can be block anywhere along
its course Regional techniques avoid some of the complications
associated with neuraxial techniques Contra- indications: -
Uncooperative patient - Bleeding diathesis - Infection - Peripheral
neuropathy
Slide 56
Regional techniques
Slide 57
Slide 58
Normally done with nerve stimulator to identify correct nerves
to be blocked
Slide 59
Regional techniques: Biers block Intravenous regional technique
Normally of the forearm Short procedures (45-60min) Jelco/ IV
access established on dorsum of hand Double pneumatic tourniquet is
placed on upper arm The extremity is elevated and exsanguinated by
tightly wrapped Eschmark bandages Upper tourniquet is inflated 0.5%
lignocaine injected 25ml for forearm, 50ml for whole arm
Slide 60
Biers Block Anaesthesia normally established in 5-10min Pt
often complain of tourniquet pain after 20-30min When this occurs
the lower tourniquet is inflated and the proximal one
deflated.
