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Anaesthesiology
Neuraxial Anesthesia
Built from Barash Clinical Anesthesia, 9th Edition
What’s inside
11 sections · 198 slides
Overview
- What neuraxial anesthesia means
- Scope of this topic
- Key messages of this topic
- Key safety messages
- Two routes compared
- Continuous subarachnoid anesthesia
- Where epidural block is used
- Indications and contraindications
Neuraxial Anesthesia and Outcome
- Randomized trials and meta-analysis of neuraxial versus general anesthesia
- Cochrane overview of neuraxial versus general anesthesia
- Large database comparisons
- Subgroups that may benefit
- Evidence pointing the other way
- Cancer surgery and immune effects
Anatomy
- Why anatomy is the whole technique
- Parts of a vertebra
- The vertebral column as a whole
- Sacrum, coccyx and surface landmarks
- Ligaments of the vertebral column and how they feel
- Ligamentum flavum structure
- Tissue layers on the way to the epidural space
- Boundaries, veins and pressure in the epidural space
- Contents and discontinuity of the epidural space
- The three spinal meninges
- Structure of the dura mater
- Extent of the dural sac
- The subdural space
- The arachnoid mater as the true drug barrier
- Arachnoid granulations at the nerve roots
- The pia mater
- Cerebrospinal fluid: composition, volume and turnover
- Where the spinal cord ends
- Spinal nerves and dermatomes
- Naming of spinal nerves, cauda equina and sympathetic outflow
- Nerve tissue as a fraction of dural sac volume
- Why puncture level changes what the needle can hit
- Layers from skin to cerebrospinal fluid
Ultrasound Anatomy of the Spine
- Role and evidence for spinal ultrasound
- Paramedian longitudinal scan of the lumbar spine
- Transverse scan of a lumbar interspace
- Marking the skin from the ultrasound image
- Which insertion point the cross gives you
Technique
- Equipment and monitoring before you start
- Suggested contents for an epidural cart
- Suggested contents for an epidural cart (continued)
- Choosing sitting or lateral position
- Sitting position for neuraxial block
- Table tilt to increase lumbar flexion
- Lateral position for neuraxial block
- Which side down in the lateral position
- Comfort and sedation during placement
- Aseptic technique
- Spinal and epidural needle tip designs
- Epidural needles
- Combined spinal epidural using standard needles
- Midline and paramedian approaches
- Reading bone contact, and the midline approach
- Troubleshooting contact with bone
- Performing the paramedian approach
- Walking a thoracic epidural needle off the lamina
- Sequence of a midline neuraxial approach
- Starting a subarachnoid block
- Confirming entry, and walking off the lamina
- Redirecting a spinal needle through an introducer
- Managing a paraesthesia during needle insertion
- Injecting the subarachnoid dose and needle orientation
- Placing a continuous subarachnoid catheter
- Two ways to find the epidural space
- Variables in the loss-of-resistance technique
- Air versus saline in the loss-of-resistance syringe
- What the evidence says about air versus saline
- Intermittent advance of the epidural needle
- Including an air bubble in a saline syringe
- The Bromage technique
- The Doughty technique
- Son-of-Doughty hand positions
- Catheter versus needle injection, and removing the needle
- Epidural catheter construction and threading depth
- Combined spinal epidural technique
- Stabilizing the needles during combined spinal epidural block
- Why no fluid appears in the spinal needle
- Recovering from a failed spinal pass during CSE
- Effect of epidural injection on an established spinal block
- The dural hole and later epidural drugs
- Choosing between spinal, epidural and combined technique
- Combined technique in obesity
- Using neuraxial anesthesia efficiently
Pharmacology
- Density, baricity and position
- Gravity and hyperbaric drug in the supine patient
- Lead-in to the spinal dose table
- Common surgical procedures that can be done with subarachnoid spinal anesthesia
- Common surgical procedures that can be done with subarachnoid spinal anesthesia (continued)
- Practical comments on the spinal procedures listed above
- Spread of isobaric solutions
- Consistency of hyperbaric versus plain solutions
- Patient variables and spinal block spread
- Effect of dose on the spinal block
- Vasoconstrictors as spinal adjuvants
- Alpha-2 agonists and opioids as spinal adjuvants
- Lumbar versus thoracic epidural block
- Recommendations for epidural anesthesia
- What determines the spread of epidural block
- Site of injection and the direction of spread
- Onset, duration and the sensory-motor pattern
- Lead-in to the epidural local anesthetic table
- Local anesthetics used for surgical epidural block
- Maintaining the block through a long operation
- Sodium bicarbonate as an epidural adjuvant
- Epinephrine and alpha-2 agonists epidurally
- Epidural opioids
Test Doses
- Why every epidural catheter must be tested
- Possible locations of an intended epidural catheter
- The intrathecal test dose
- Block height after intrathecal versus epidural lidocaine
- Lead-in to the unintended intrathecal injection table
- Complications of unintended intrathecal injection of 45 mg of lidocaine in parturients
- The intravenous test dose and its limits
- The subdural catheter
- Proving the catheter is in the epidural space
- Every dose is a test dose
Physiology
- Site of action of neuraxial local anesthetics
- Sedation and anesthetic sparing
- Differential nerve block and its three levels
- Levels of the three blocks
- The old explanation of spinal hypotension
- Cardiac output and vascular resistance after spinal anesthesia
- Mechanism of hypotension after spinal anesthesia
- Risk factors for hypotension
- Heart rate changes and cardiac arrest under spinal anesthesia
- Cardiovascular effects of epidural anesthesia
- Intravenous fluid for neuraxial hypotension
- How ephedrine and phenylephrine differ
- Choosing among the vasopressors
- The Bezold-Jarisch reflex
- Ondansetron and the Bezold-Jarisch reflex
- Respiratory effects
- Gastrointestinal effects
- Temperature homeostasis under neuraxial block
Complications
- Backache, and needle factors in post-dural puncture headache
- Why parallel bevel orientation may work
- Patient risk factors for post-dural puncture headache
- Diagnosis and differential of post-dural puncture headache
- Imaging findings and their limits
- Course, chronicity and mechanism
- Proposed mechanism of post-dural puncture headache
- Preventing post-dural puncture headache
- Symptomatic treatment and the blood patch volume
- Epidural blood patch: efficacy and recurrence
- Unsettled questions and reported harms of blood patch
- Hearing loss after spinal anesthesia
- High and total spinal block
- Managing an ascending or total block
- Position when the block is climbing too high
- Local anesthetic systemic toxicity
- Neurologic injury: how common
- Mechanisms of neurologic injury after neuraxial block
- How needles injure cord and nerve
- Level errors, conus injury and cervical epidural risk
- Mass lesions that compress the cord
- Epidural haematoma
- Epidural abscess, other masses, and how they present
- Timing of surgical decompression
- Approach to suspected perioperative nerve injury
- Spinal cord hypoperfusion and its risk factors
- Pre-existing spinal stenosis
- Chemical injury and maldistribution
- Transient neurologic symptoms
Summary
- Core takeaways: anatomy and technique
- Core takeaways: drugs and physiology
- Core takeaways: complications
References
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- Barash, Cullen, and Stoelting's Clinical Anesthesia, 9th Edition