Mod3: Spinal Anesthesia Part 2 Flashcards
Spinal Anesthesia: Assessment of Block
The skin area innervated by a given spinal nerve and its corresponding cord segment is also know as:
Dermatome
Corresponds to a portion of the spinal cord that gives rise to all nerve rootlets of a single spinal nerve
Required Block Levels
What’s the Dermatomal block Level for Upper Abd/C-Section procedures?
T4 = nipple line
[Dermatomal block Level]
“Upper Abd/C-Section procedures”
Required Block Levels
What’s the Dermatomal block Level for GYN/Urological procedures?
T6: Xiphoid level
“GYN/Urological procedures”
XX
Required Block Levels
What’s the Dermatomal block Level for Hip Surgery?
T10 = Umbilicus
“Hip Surgery”
Required Block Levels
What’s the Dermatomal block Level for Upper Leg procedures?
L1 = Upper Anterior Thigh
“Upper Leg procedures”
Required Block Levels
What’s the Dermatomal block Level for Foot & Ankle procedures?
L2 = Mid Anterior Thigh
“Foot & Ankle procedures”
Required Block Levels
What’s the Dermatomal block Level for Perineal procedures?
L1-L2 or
S2 w/saddle block
“Perineal procedures”
Sacral nerves are larger and harder to block
Spinal Anesthesia: Assessment of block
How do we assess that our blocks are working?
Assess progress of block level q 2-3 minutes initially
Asseess until desired level is attained
Fast onset, usually
Takes ~10 min
Spinal Anesthesia: Assessment of block
Once block established, reassess block level every
30-45 minutes
Spinal Anesthesia - Physiology of local anesthetic neural blockade
Local anesthetics block conduction of:
Electrical impulses along nerves
Spinal Anesthesia - Physiology of local anesthetic neural blockade
Local anesthetics block conduction of Impulses along nerves. However, exact location of action is:
Unknown
Spinal Anesthesia: Neurophysiological effects - Differential Blockade
Different nerve fibers serving different functions display varying sensitivity to LA blockade. What’s the order of sensitivity? in other words, what the first thing to be blocked? what’s the last thing to be blocked?
ANS>Pain>Temperature>Touch>Motor
“A PTT M”
Spinal Anesthesia: Neurophysiological effects - Differential Blockade
The mechanism of action of differential blockade is:
Not clearly known!!!
Spinal Anesthesia: Neurophysiological effects - Differential Blockade
Which factors affect the mechanism of action of LA?
Nerve fiber diameter is one factor but not the only
Decrease in LA concentration in CSF as function of distance from injection site
Spinal Anesthesia: Neurophysiological effects
Differential Blockade manifests as a spatial separation in sensations blocked. How does Sympathetic block extend in reference to sensory block?
2 dermatomes higher than sensory block
Spinal Anesthesia: Neurophysiological effects
Differential Blockade manifests as a spatial separation in sensations blocked. Where is Sensory block localized in reference to Motor block?
2 dermatomes higher than Motor block
Spinal Anesthesia: Neurophysiological effects
Patients & surgeons can appreciate the differential blockade and can find it worrisome. This could be evidenced by which statement from a pt?
“Don’t let him start. I can still move my foot!!!”
The pt fail to recognize the difference between sensory and motor
Spinal Anesthesia: Assessment of block
Which three methods are used to assess differing blockade?
Autonomic nervous system response
Sensory response
Motor response
Spinal Anesthesia: Assessment of block
Autonomic nervous system blockade manifest as:
Skin flushing
Warm skin
Vasodilation
Spinal Anesthesia: Assessment of block
Which object/instruments could be used to assess Sensory nerves blockade?
Broken tongue blade
works well to determine sensory block level
Alcohol swab to detect temp response
Spinal Anesthesia: Assessment of block
Methods to assess differing blockade: How do you assess Motor nerves?
Ask patient to move lower extremities to assess motor block level
Spinal Anesthesia: Cardiovascular Physiology
Blockade of SNS efferent fibers to vascular smooth muscle could cause:
Hypotension (40% ± incidence)
Hypotension is the most common side effect encountered
Bradycardia (10-15%)
2nd and 3rd degree heart block
Spinal Anesthesia: Cardiovascular Physiology
Hypotension caused by Blockade of SNS efferent fibers to vascular smooth muscle is the result of:
Arterial dilation (decreased SVR)
Venous dilation (decreased preload=decreased CO)
Spinal Anesthesia: Cardiovascular Physiology
Which block factor determines Extent of Hypotension caused by blockade of SNS efferent fibers to vascular smooth muscle?
Level of block
Spinal Anesthesia: Cardiovascular Physiology
Which factors may amplify Effect of Hypotension caused by Blockade of SNS efferent fibers to vascular smooth muscle?
Age > 50
Concurrent GA
Obesity
Hypovolemia
Spinal Anesthesia: Cardiovascular Physiology
Effect of Hypotension caused by Blockade of SNS efferent fibers to vascular smooth muscle may be worse in patients on which drugs?
ACE inhibitors
Spinal Anesthesia: Cardiovascular Physiology
Bradycardia caused by Blockade of SNS efferent fibers to vascular smooth muscle is the result of:
Blockade of sympathetic cardioaccelerator fibers originating from T1-T4
Bradycardia starts to be seen with T6 sensory level blocks
Spinal Anesthesia: Cardiovascular Physiology
Bradycardia caused by Blockade of SNS efferent fibers to vascular smooth muscle is the result of Blockade of sympathetic cardioaccelerator fibers originating from T1-T4. Why is it noted with T6 sensory level blocks?
Sympathetic block level is 2 dermatomes higher than sensory level block
Spinal Anesthesia: Cardiovascular Physiology
How does Bradycardia caused by Blockade of SNS efferent fibers to vascular smooth muscle manifest?
Diminished venous return and associated decreased stretch of intracardiac stretch receptors
Severe bradycardia/asystole reported
Spinal Anesthesia: Cardiovascular Physiology
What are risk factors for Bradycardia caused by Blockade of SNS efferent fibers to vascular smooth muscle?
Age < 50
Any ASA
Use of beta blockers
Spinal Anesthesia: Cardiovascular Physiology
What’s the treatment for Bradycardia caused by Blockade of SNS efferent fibers to vascular smooth muscle?
Epinephrine
Spinal Anesthesia: Cardiovascular Physiology
What’s the major risk factor for 2nd and 3rd degree heart block caused by Blockade of SNS efferent fibers to vascular smooth muscle?
Preexisting 1st degree heart block
Spinal Anesthesia: Treating CV hemodynamic changes
When is it recommended to initiate treatment for CV hemodynamic changes?
BP is decreased more than 25-30% baseline
SBP<90 in normotensive pt
HR falls below 50-60 beats/min
Pt becomes symptomatic
Spinal Anesthesia: Treating CV hemodynamic changes
Which vasopressors are used to treat CV hemodynamic changes from spinal blockade?
Ephedrine
Phenylephrine
Spinal Anesthesia: Treating CV hemodynamic changes
What’s the dose and and what are the effects of Ephedrine when used to treat CV hemodynamic changes from spinal blockade?
5-10mg Ephedrine (IV)
Alpha and beta adrenergic activity (inc HR)
Increases CO (venous return) and SVR
Spinal Anesthesia: Treating CV hemodynamic changes
Dose and effects of Phenylephrine when used to treat CV hemodynamic changes from spinal blockade?
50-100 mcg Phenylephrine (IV)
Primary alpha-agonist activity
Increases SVR (may decrease CO)
Spinal Anesthesia: Treating CV hemodynamic changes
Fluid Administration when used to treat CV hemodynamic changes from spinal blockade. Prehydration with:
Crystalloid solution
500-1000 mL
Spinal Anesthesia: Treating CV hemodynamic changes
When treating CV hemodynamic changes from spinal blockade, why must we be cautious placing in head up position to decrease cephalad spread?
Exaggerates decreased BP by decreasing venous return
Spinal Anesthesia: Treating CV hemodynamic changes
NYSORA Recommendations in the treatment of CV hemodynamic changes from spinal blockade
NYSORA Recommendations
Spinal Anesthesia
Complications:
Postdural puncture headache (PDPH)
Backache
Total spinal
Neurologic Injury
Transient neurologic syndrome (TNS)
Spinal hematoma
Spinal Anesthesia: Complications
Causes of Postdural puncture headache (PDPH):
Loss of CSF through meningeal needle hole (?)
“Saggy Brain”
Spinal Anesthesia: Complications
Characteristics of Postdural puncture headache (PDPH):
Bilateral in the frontal-occipital region
Worsens with upright position
Improves in supine position
Photophobia
Tinnitus
N/V
Spinal Anesthesia: Complications
Incidence of Postdural puncture headache (PDPH):
Increased in young patients, women, and parturient
Decreases with increasing age
Decreases with use of smaller diameter (larger gauge) spinal needle with noncutting tips
Remaining supine does not decrease incidence
Spinal Anesthesia: Complications
How should the cutting needles be inserted to decrease incidence of Postdural puncture headache (PDPH)?
With bevel aligned parallel to long axis of dural fibers
Spinal Anesthesia: Complications
Treatment of Postdural puncture headache (PDPH):
Usually resolves over 48hr without invasive therapy
Bedrest/fluids/analgesics/caffeine
Epidural blood patch
Spinal Anesthesia: Complications
When is backache a common complication?
After general anesthesia, but
More common after spinal (11%)
Spinal Anesthesia: Complications
Causes of Backache after spinal anesthesia?
Needle trauma
Local anesthetic irritation
Ligament strain secondary to muscle relaxation
Spinal Anesthesia: Complications
The complication from spinal anesthesia that manifest as “Blockade of entire spinal cord and occasionally brain stem” is also known as:
Total spinal
Spinal Anesthesia: Complications
Which pt’s populations are more susceptible to “Total spinal”, and why?
Obese & Parturients
Relative decreased CSF volume a/w Obesity & Pregnancy
LA spreads more
Spinal Anesthesia: Complications
When does “Total spinal” occur?
Immediately or
up to 60 mins after injection
Spinal Anesthesia: Complications
Symptoms of “Total spinal”:
Profound hypotension and bradycardia
Apnea/respiratory arrest (phrenic nerve paralysis)
Spinal Anesthesia: Complications
Treatment of “Total spinal”:
Protect the airway
Vasopressors
Anticholinergics
Fluids
Oxygen with controlled ventilation
Spinal Anesthesia: Complications
T/F
If managed appropriately, “Total spinal” will resolve without sequelae
True
Spinal Anesthesia: Complications
Incidence of Neurologic Injury:
Rare (0.03-0.1% incidence) but
Widely feared!!!
Spinal Anesthesia: Complications
Causes of Neurologic Injury:
Direct needle trauma to spinal cord or nerves
Spinal cord ischemia
Introduction of bacteria or neurotoxic chemicals (prep solution) into SAS
Toxic LA buildup “Cauda Equina Syndrome”
Spinal Anesthesia: Complications
The condition that occurs when the bundle of nerves below the end of the spinal cord called cauda equina is damaged is known as:
Cauda Equina Syndrome
Signs and symptoms include low back pain, pain that radiates down the leg, numbness around the anus, and loss of bowel or bladder control
Spinal Anesthesia: Complications
T/F
“Cauda Equina Syndrome” is the Result of subarachnoid injection through microbore, high resistant catheters
True
Catheters produce little turbulence and the undiluted solution pools around cauda equina nerve roots
Spinal Anesthesia: Complications
The painful condition of the buttocks and thighs with possible radiation to the lower extermities, beginning as soon as a few hours after spinal anesthesia and lasting as long as ten days is also known as:
Transient Neurologic Syndrome (TNS)
Pain in buttocks or leg (posterior thigh usually)
Pain can be mild to severe
Spinal Anesthesia: Complications
What differentiates Transient neurologic syndrome (TNS) from “Cauda equina syndrome”?
TNS is exclusively a pain syndrome
There is no bowel or bladder dysfunction
Neurologic, MRI , and Electrophysiologic examinations are normal
Spinal Anesthesia: Complications
All local anesthetics are implicated in Transient neurologic syndrome (TNS), except:
Chloroprocaine
Risk > with lidocaine
Spinal Anesthesia: Complications
Which condition increase the risk of Transient neurologic syndrome (TNS)?
Lithotomy position
Obesity
Spinal Anesthesia: Complications
Pain from Transient neurologic syndrome (TNS) resolves in:
72hrs
Spinal Anesthesia: Complications
What’s the incidence of “Spinal hematoma”?
Rare (<1 in 150,000)
Spinal Anesthesia: Complications
How does “Spinal hematoma” manifest?
Lower extremity numbness
Lower extremity weakness
Spinal Anesthesia: Complications
Why is early detection “Spinal hematoma” critical?
Delay >8hrs in decompressing spinal cord
Could lead to decreases chance of neurologic recovery
Spinal Anesthesia: Anticoagulated Patients
Which anticoagulants present a very low risk in spinal anesthesia?
ASA
NSAIDS
SQ heparin
Spinal Anesthesia: Anticoagulated Patients
After low dose low-molecular-weight heparin (LMWH) administration, delay spinal anesthesia for:
12 hrs
Spinal Anesthesia: Anticoagulated Patients
After high dose low-molecular-weight heparin (LMWH) administration, delay spinal anesthesia for:
24hrs
Spinal Anesthesia: Anticoagulated Patients
If taking twice daily, Post-op delay LWMH for:
24 hrs
Spinal Anesthesia: Anticoagulated Patients
If taking once daily, Post-op delay LWMH for:
6-8 hrs
Spinal Anesthesia: Anticoagulated Patients
After the last dose of Ticlopidine (Ticlid), avoid spinal anesthesia for how long?
14 days
Ticlopidine (Ticlid) is a blood thinner
Spinal Anesthesia: Anticoagulated Patients
After the last dose of clopidogrel (Plavix), avoid spinal anesthesia for how long?
7 days
Spinal Anesthesia: Anticoagulated Patients
For reference, consult:
American Society of Regional Anesthesia (ASRA)
