2025 Intro to Clinical Anesthesia Exam 3 Flashcards
Lectures 7-8: Neuraxial
Neuraxial Anesthesia
Some studies show that neuraxial anesthesia reduces postoperative morbidity, and to a lesser extent decreases in intraoperative mortality.
It decreases the amount of intra-op narcotics needed
Leads to decrease in the incidence of atelectasis, hypoventilation, and aspiration pneumonia.
Increases tissue blood flow, improving oxygenation to those tissues
Suppresses the neuroendocrine stress response to surgery.
Gives the provider another option when dealing with a pt. that might not do well under a heavy General anesthesia.
Plays a HUGE role in Obstetric anesthesia.
VERTEBRAL COLUMN ANATOMY
SPINAL CORD ANANTOMY
KNOW THE LAYERS
Spinal Cord Anatomy
MECHANISM OF ACTION
Spinal into CSF - why it is quicker
Epidural bathing the nerves in the epidural space - why takes longer
Autonomic vs Somatic Nervous System
Involuntary - make them vasodilate
SOMATIC BLOCKADE
Neuraxial Blocks =
work so well because they interrupt the afferent (sensory receptors to the CNS) transmission of painful stimuli
They also block efferent (from CNS to muscles) impulses responsible for muscle tone.
DIFFERENTIAL BLOCKADE= sympathetic blockade (temp sensitivity) about two segments or more, cephalad than the sensory block(pain light touch) which in turn is several segments more cephalad than the motor block
This occurs because the concentration of the LA decreases the farther away from the site of injection it goes.
AUTONOMIC BLOCKADE
The interruption of efferent autonomic transmissions that neuraxial blockade causes, leads to many different manifestations throughout the body:
Cardiovascular
Pulmonary
GI
Urinary Tract
Metabolic and Endocrine
Cardiovascular changes Neuraxial
MOST COMMON
Hypotension- upwards of 40% of spinal anesthetics as result of decreased SVR, peripheral blood pooling with decreased venous return to heart or both.
Factors such as pt. positioning and a pregnant pts uterus weighing on the vena cava can make this hypotension even worse.
Decreases the effective circulating blood volume, often leading to Decreased CO
Higher level of block = ↑ chance of hypotension
Risks for hypotension include hypovolemia, Age >50 yrs., emergency surgery, obesity, chronic alcohol consumption, and chronic hypertension.
A high sympathetic block leads to more vasodilation because it blocks the bodies compensatory vasoconstriction pathways.
Bradycardia- occurs in 10-15% spinal anesthetics.
Either direct (blockade of cardiac accelerators T1-T4)
Or indirect- decreased output of myocardial pacemaker cells from ↓ venous return
Those at higher risk of bradycardia
Baseline HR <60 bpm, ASA 1, age <50. current beta blocker therapy
Healthier the patient, more at risk for bradycardia
Neuraxial blocks CAN NOT block the vagus nerve!!
Unopposed vagal tone may explain the sudden bradycardia, complete heart block, or cardiac arrest that is rarely seen with spinal anesthesia more than epidural anesthesia.
How do we prevent/treat hTN (hypotension) Neuraxial
If the pt is previously hypovolemic, then volume loading has been shown to work well.
LUD ( left uterine displacement) helps prevent decreased venous return
Quick temporary fix can be to lower the pts head or even put them in head down position.
Excessive symptomatic bradycardia should be treated with Atropine
hTN should be treated with Vasopressors
Pulmonary Neuraxial
Respiratory Mechanics- NA block to mid thoracic level has minimal respiratory effects.
High spinal- May paralyze accessory muscles impairing cough and active exhalation. Worse for those with pulmonary secretions and/of obstructive pulmonary disease.
C3,4,5- stay alive- Innervation of the diaphragm. If you knock this out prepare for intubation.
Change angle of bed to counteract rising spinal. Individual anatomy plays a roll in this
Have patient squeeze hand- C6 thumb, C7 middle finger… C5 pinky numb, need to adjust angle of bed????
GI and Urinary Tract Neuraxial
The sympathectomy that allows Vagal dominance leads to a small contracted gut with active peristalsis.
Can lead to better operating conditions during intestinal surgery.
The decrease in narcotics needed also helps the return of GI function after surgery.
Renal function is pretty much unchanged with normal SBP’s
Neuraxial Anesthesia at the lumbar and sacral levels causes loss of Autonomic bladder control which can lead to Urinary retention.
Metabolic and Endocrine Neuraxial
The trauma from surgery produces a Systemic Neuroendocrine Stress Response.
This response causes things like; Intra-op HTN, tachycardia, hyperglycemia, suppressed immune responses and altered renal function.
NA can PARTIALLY suppress this response in major invasive abdominal and thoracic surgeries
NA can TOTALLY BLOCK this response during lower extremity surgery
Indications for Neuraxial Anesthesia
Neuraxial blocks can be used alone or in conjunction with General anesthesia and Peripheral nerve blocks.
Someone with decreased pulmonary function may be a good candidate for NA, as long as the level required for the surgery isn’t high enough to bring into effect the pulmonary issues that can come with NA.
Contraindications for Neuraxial Anesthesia
Major contraindications
Lack of Consent
Coagulation abnormalities
Severe hypovolemia
Elevated intercranial pressure (especially with intercranial masses)
At risk for cerebral herniation with spinal anesthesia
Infection at the site
Relative contraindications
Severe Aortic or mitral stenosis
Severe Left ventricular outflow obstruction (Hypertrophic obstructive cardiomyopathy)
Performing Neuraxial Anesthesia: Selling It
During you Pre-op interview you should investigate into possible contraindications for NA
You need to thoroughly explain the process of placing and Neuraxial block and what the pt can expect to experience after the block is placed.
The ability to minimize anxiety and explain the block/ answer questions with confidence is big.
Performing Neuraxial Anesthesia: Surface anatomy/landmarks
Your best friend is the palpable spinous process ( even better if they are visible) they will define the midline of the spine.
First palpable Cervical spinous process is C2. (C7 is most prominent)
Spinous process of T7 is usually at the same level as the inferior angle of the scapulae.
If you draw a line between the highest points of the iliac crest that would cross the body of L4 or the space of L4-5.
Positioning is Vital
Performing Neuraxial Anesthesia Patient Positioning: Sitting
Performing Neuraxial Anesthesia Patient Positioning: Laying on Side (lateral decubitus)
Baricity tells you whether it rises, sinks or sits where it is
Performing Neuraxial Anesthesia: Prep
GO TIME!!!!
Strict Aseptic Technique for Spinal and Epidural Anesthesia
Wear Cap and Mask
Remove Jewelry
Wash Hands prior to procedure
Consider bouffant hat for patient
Clean patient’s back with chlorhexidine/alcohol mini-prep stick
Apply sterile gloves
Sterile drape on patient’s lumbar spine
Performing Neuraxial Anesthesia: Midline Approach
Midline Approach
Most commonly used approach
Palpate space between two spinous processes
Topicalize with lidocaine in midline, in lower 3rd of interspace.
Infiltrate subq tissues and interspinous ligament
Introduce introducer at slight cephalad angle until form tissue is felt.
Insert spinal needle through introducer
Needle passes through ligamentum flavum, then epidural space, and then dura/arachnoid.
*Changes in resistance felt at each layer. Pop usually felt at dura
Depth of dura is 5-6 cm in normal body habitus
If CSF does not appear, may rotate pencil tip needle, advance, redirect.
Once CSF appears you gently attach your LA syringe and aspirate CSF into your LA this mixture will create a swirl called barbitage.
You then slowly inject the LA and remove everything, take off plastic drape and lay the pt. down.
https://youtu.be/SZ2TClYz4zI
Troubleshooting Midline Approach:
If bone is contacted at shallower depth
Likely hitting more cephalad process, redirect caudally
Bone contacted deeper
Likely hitting caudad spinous process, redirect cephalad
Bone in contacted at same depth
Likely contacting lamina, ie off midline.
Patient can usually perceive needle off to one side
Performing Neuraxial Anesthesia: Paramedian Approach
Troubleshooting the paramedian approach:
If bone is contacted at a shallow depth it is most likely the medial part of the lower lamina so the needle must be redirected cephalad and a little more lateral
If you contact bone at a deeper level, that’s usually the lateral part of the lower lamina so you only need to redirect cephalad
Different spinal needles
PDPH - post dural puncture headache
22g - do not need introducer
NEEDLE We Use
Notch is always up
What affects the level of a spinal block?
Most Important factors affecting the dermatomal spread of you spinal LA
Baricity of Anesthetic Solution
Position of the patient
During injection and immediately after injection
Drug dosage
Site of injection
Other factors
Age, curvature of the spine, drug volume, intraabdominal pressure, needle direction, pt height, and Pregnancy.
Baricity
Can make something more dense by adding glucose = hyperbaric = to sink
to make things lighter = so they rise = can add sterile water or fentanyl
Baricity and Positioning
Head up position causes hyperbaric solution to settle caudad and hypobaric to ascend cephalad. The opposite goes for the head down/supine position.
If you’re doing a spinal for a broken hip in the Lat. Decubitus position you can use a hypobaric solution to affect the up hip (broken hip)
ISOBARIC solution tends to stay at the site of injection.
Hyperbaric solution tends to move to the most dependent part of the spine T4-T8 when in the supine position.
Baricity: What can you add????
Morphine- hydrophilic, dose 75-200 mcg, onset of analgesia 30-60 minutes duration 12-36 hours.
Side effects- Nausea, vomiting, pruritus. Potential for respiratory depression (post-op pulse ox, decreased IV/PO opioid admin)
Duramorph????
Fentanyl- Lipid soluble, dose 10-25 mcg. May decrease hypotension d/t spinal
Epi- 100-200 mcg increases duration of sensory and motor block up to 30 minutes
Dosages, uses, and duration of commonly used spinal anesthetics
M+M
Page 1581
Management after you rock the spinal!
Use your ears- listen for tachycardia secondary to vasodilation
I start a phenylephrine infusion around 0.2 mc/mg/min right after spinal is placed
Treat hypotension and Bradycardia aggressively
Patient will feel nauseous before BP cuff displays hypotension
Assess level of block with cold/pin prick
Low-dose propofol common for total joint patients in line with hemostasis
Epidural Anesthesia
Injection of local anesthetic into the epidural space
Goal of anesthetizing spinal nerve roots that transverse the space
Used for anesthesia of abdominal, thoracic, pelvic, and lower extremity procedures and post-op analgesia
Sensory level required for each surgery depends on dermatome level of skin incision AND level required for surgical manipulation.
Epidural Kit
With the tuohy needle you dont need an introducer
OMG we got Loss of resistance LOR
LOR meaning????
Remove LOR Syringe and count visible markings on needle to calculate depth.
Thread catheter until 20cm mark is at hub
Remove needle over catheter making sure not to pull catheter out as well.
Not mark on catheter at skin and withdraw to leave 4-6cm in the epidural space.
Attach catheter connector and hold below insertion site to spot check no CSF (intrathecal) or blood (intravascular).
Attach 3 cc Syringe and gently aspirate to confirm
Test dose with 3 cc 1.5% Lido with Epi 1:200,000
Clear Occlusive Dressing
Epidural Catheters
Troubleshooting your Epidural
False LOR- can occur with loose connection between LOR syringe and needle.
Can add 0.5ml air to saline in syringe and inject through needle
Air bubble will compress because of resistance if in soft tissue
Bubble will not compress if in epidural space
Pass spinal needle through epidural needle
If Dural puncture occurs, likely to be in epidural space
Difficulty threading catheter
Ask patient to take a breath while keeping gentle pressure, may open space at tip of Touhy
Reinsertion of epidural needle at steeper angle
Withdraw epidural needle and advance while applying downward pressure on hub
Inject 5 cc Saline through needle into epidural space to open it
Paresthesia during needle or catheter placement
Stop further advancement
If during needle placement, withdraw and reposition at angle away from paresthesia
Common during catheter placement
If it resolved continue threading catheter
Blood in Epidural Needle/Catheter
Remove needle and flush with saline
Clotted blood can prevent LOR and increase risk of Dural puncture
Local anesthetics and Adjuncts for Epidural Anesthesia
Bupivacaine the most properly
Epidural Complications
Risk of permanent injury 4.2 per 100,000 (0.004%)
Inadequate of Failed NA- defined as need to repeat NA, convert to general, or abort planned surgery
High or total spinal- May result from unintentional injection of med intended for epidural space into subdural or subarachnoid (spinal) space.
Signs and symptoms- rapid ascending sympathetic, sensory, and motor block with associated bradycardia, hypotension, dyspnea, dysphagia, dysphonia
May progress to unconsciousness and respiratory depression
Secondary to respiratory muscle paralysis and brainstem hypoperfusion
OB questionable epidural -> pull catheter and place spinal with decreased dose before C-Section.
Failed spinal and time -> place epidural, otherwise convert to GA
Subdural injection- potential space between dura and arachnoid mater. May cause patchy block, may result in more extensive cranial anesthesia ie apnea, unconsciousness
Nerve Injury- Rare and lower in OB patients as you are approaching below conus medullaris (usually L1)
Paresthesias are common- indicate needle has touched nerve tissue. Halt advancement, if persistent withdraw needle
Back Pain- local tenderness may be present for days after procedure, no difference in back pain 6 mo. out from delivery
Post-dural puncture headache- positional headache worse when sitting upright. May have nausea, vomiting, dizziness, tinnitus, photophobia, hearing loss.
Conservative treatment- IV fluids caffeine and cosnyntropin IV
Debilitating PDPH- consider epidural blood patch 20-30cc
Urinary retention- Blocks sensation of full bladder ->placement of urinary catheter for longer procedures/voiding before +/- bladder scan.
Transient neurologic symptoms- pain or dysesthesia (prickling burning etc) in buttock/lower extremity after uncomplicated spinal anesthesia.
Most common with lidocaine and mepivacaine
Local anesthetic systemic toxicity- (LAST) much less likely with spinal vs epidural anesthesia. Usually result of accidental intravascular injection.
Minor- Perioral numbness, tinnitus, twitching
Major- seizures, coma, severe hypotension, arrythmias, asystole
Spinal-epidural hematoma (SEH)- Hemorrhage into neuraxis exceptionally rare usually in patients with coagulopathy
Can require emergency decompressing laminectomy to preserve function
Infection- meningitis more common after spinal, epidural abscess more common after epidural anesthesia
What exactly are peripheral nerve blocks????
Mostly used for limbs
Single = 14-20hrs sometimes
Interdwelling = can go for several days
Benefits?? Very similar to Neuraxial anesthesia
Likes to tell pts, start taking pain meds once the block starts to wear off
Will do General, but decrease how deep and narcotics
Peripheral nerve block contraindications
If pre-existing deficit hard to tell if worn off
Potential complications
What to look for if you suspect Local anesthetic systemic toxicity
Need to know toxic dose of each local anesthetic with and without epi
Tinnitus = is like a “train running by your ear”
Management of local anesthetic systemic toxicity
Management of local anesthetic systemic toxicity
How does Lipid emulsion work??
Review of Local Anesthetics durations
Preparing for the block
Why do we use Ultrasound?
Improves success rate of the block
Decreases placement time
Reduces volume of LA required for successful block
Decreased chance of vascular puncture and local anesthetic systemic toxicity (LAST)
Reduced incidence of pneumothorax and phrenic nerve block
Less chance of nerve injury
Common Upper extremity blocks
Visual of Common Upper
Find a clearer Picture!!!
Range of Blocks Upper
Find a clearer picture!!!
Complications of Interscalene blocks
Horner syndrome
Supraclavicular complications
What one leads to potential for phrenic nerve knock out???
Lower Extremity blocks
Adductor preferred for knee surgeries so they can get up and moving quickly
Trunk/abdominal blocks
Can be used after surgery to help with pain post surgery
Do not want patient moving, why done intraoperatively
Trunk/abdominal blocks: Quadratus Lumborum
Erector Spinae Blocks/Paravertebral block (PVB)
Erector spinae plane (ESP):
Block is aninterfacial plane blockwhere a local anesthetic is injected in a plane preferably below the erector spinae muscle. It is supposed to work at the origin of spinal nerves
Paravertebral block (PVB):
Is a technique where a local anesthetic is deposited into a space found on both sides of the spine, called the paravertebral space.
Operating room… but also can be done in pre-op area
Paravertebral block (PVB)
