Neuroaxial Anesthesia
By: Shari Leacock
Definition
 Temporary loss of sensation due to administration of a local
anesthetic drug directly into the central nervous system
 The anesthetic drug is placed around the nerves of the CNS to
prevent pain sensation and muscle relaxation to facilitate surgical
procedures
 These techniques can also be used for analgesic purposes
 Often administered with opioid analgesics to improve block and provide
post operative pain relief
 Examples include morphine, fentanyl, diamorphine.
 Clonidine prolongs duration of action of analgesia however it is associated
with hypotension.
Anatomy
Indications
 Lower abdominal surgeries – Cesarian section
Bowel surgery
Hernia repair
 Surgeries of the lower limbs – orthopedic,
vascular surgery
 Surgeries in the perineum – hemorrhoid repair
Contraindications
Absolute
Relative
 Patient refusal
 Hypovolemia
 Lack of cooperation
 Coagulation disturbances
 Difficulty with patient positioning
 Stenotic valvular disease
 Increased intracranial pressure
 Bacteremia
 Infection at site of needle insertion
 Anatomical abnormalities of the
spine
Advantages
 Avoiding airway management concerns that accompany general
anesthesia
 Ability to monitor patient mental status as patient is awake
 Anesthetic action generally lasts longer than the procedure and offers pain
relief
Risks and Complications
 Hypotension
 Nausea
 Bradycardia
 Post dural puncture Headache – associated with larger gauge and type of
needle used
 Cauda equina injury
 Spinal hematoma
 Epidural abscess
 Cardiac arrest – rare
Spinal
Epidural
 Sub arachnoid space -Into the
CSF
 Epidural space
 Loss of motor and sensory
function at and below the level
of injection
 Loss of function only at the level of
the spinal nerve
 Must be given only below the
level of L3 to avoid damage to
spinal cord
 May be given at cervical,
thoracic or lumbar sites
 Requires lower dose of
anesthetic
 Requires larger volume for same
anesthetic effect
 Faster onset of analgesia
 Slower onset of analgesia
Drugs
 Both amide and ester anesthetics can be used
 Bupivacaine is the most common for Neuroaxial anesthesia
Baricity
 Ratio of densities/specific gravity of two solutions – LA vs CSF
 CSF density is 1.0003 +/- 0.0003
 Hyperbaric solutions – higher density than that of CSF and tend to sink and
flow in the direction of gravity.
 Add 5-8% dextrose
 Isobaric – same density as CSF
 Hypobaric – Lower density than CSF and these rise in relation to
gravitational pull
 Add distilled water
 POSTURE is used to control spread
Bupivicaine (Marcaine)
 Amide local anesthetic
 Hyperbaric solution usually 0.75% is used
 Prepared alone or with epinephrine
 Onset of action: 1-17 minutes (route and dose dependent)
 Duration of action: 2-9 hours (route and dose dependent)
 Half life: 8.1 hours in neonates and 2,7n hours in adults
 Metabolism: Hepatic
 Excretion: renal (6% unchanged)
Bupivacaine ctd
 Side effects: restlessness, anxiety, drowsiness, tinnitus, hypotension,
arrhythmias,
 Adverse effects: seizures, cardio-toxicity and cardiac arrest
 Contraindications: persons with hypersensitivity reactions to amide group of
anesthetics, obstetrical paracervical blocks and Regional anesthesia (biers
block)
Technique - Equipment
 Sterile drapes
 Cleaning solution: Clorhexidine (preferred) or betadine
 Needles including – Apply local to skin, introducer, spinal needle)
 Syringes
 Local anesthetic for skin and soft tissues
Types of Needles
Tuohy Needle
Procedure
 Sterile PPE is donned and patient is positioned accordingly either sitting up
or lateral decubitus position
 Area is cleaned and draped.
 ASIS is used as a land mark as it coincides with L3-L4 interspace
 Palpate spinous processes in the midline
 Needle is inserted and the correct space is confirmed
Confirmation of correct needle
insertion
Spinal
 Return of CSF through spinal
needle
 Use of litmus paper – should turn
blue
 Test for glucose using glucometer
Epidural
 Loss of resistance to air or saline
 ALWAYS aspirate to rule out CSF
or blood
References

Press, C. D., MD. (2015, November 30). Subarachnoid Spinal Block: Overview, Periprocedural Care, Technique.
Retrieved July 22, 2018, from https://emedicine.medscape.com/article/2000841-overview?pa=mjq
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rbjc8DNLE5/iq6fCdb243nPhN45bRyFifRUcxgL5uirmrJC0so7wvS3wxSmSU=

Spinal anaesthesia. (2018, July 10). Retrieved from https://en.wikipedia.org/wiki/Spinal_anaesthesia

(n.d.). Retrieved from https://www.uptodate.com/contents/overview-of-neuraxial-anesthesia#H200678350