REGIONAL ANESTHESIA Flashcards
Membrane
• 90% of lipids
• 10% protein
Negative resting potential
-70 to -90 mV
Classification of
Regional Anesthesia:
I. _____ – skin or mucous membrane
II. _____ – incision site / tissue to be cut (e.g. sebaceous cyst)
III. _____ – around tissue to be cut (e.g. breast mass)
IV. _____ (Bier Block)
V. _____ BLOCK – along nerve or course of nerves
A. Peripheral Nerve Blocks
B. Central Blocks
I. TOPICAL – skin or mucous membrane
II. INFILTRATION – incision site / tissue to be cut (e.g. sebaceous cyst)
III. FIELD BLOCK – around tissue to be cut (e.g. breast mass)
IV. INTRAVENOUS REGIONAL (Bier Block)
V. CONDUCTION BLOCK – along nerve or course of nerves
A. Peripheral Nerve Blocks
B. Central Blocks
CONDUCTION BLOCK types
A. Peripheral Nerve Blocks
B. Central Blocks
Incision site like sebaceous cyst anesthesia used
Infiltration
around tissue to be cut like breast mass anesthesia used
Field block
INTRAVENOUS REGIONAL ANESTHESIA aka.
Bier Block
Branches of trigeminal nerve
(ophthalmic, maxillary, mandibular)
CERVICAL PLEXUS BLOCK
• Anterior rami of _____ spinal nerve roots
C1-C4
BRACHIAL PLEXUS BLOCK
• Anterior rami of ____ spinal nerve roots
C4-T2
Major Peripheral Branches a. Axiliary N – __
b. Musculocutaneous – __
c. Radial – __
d. Median – __
e. Ulnar – __
Major Peripheral Branches
a. Axiliary N – shoulder abduction
b. Musculocutaneous – elbow flexion
c. Radial – elbow, wrist, and finger extensions
d. Median – wrist and finger flexion
e. Ulnar – wrist and finger flexion
operations of upper extremity anesthesia used
BRACHIAL PLEXUS BLOCK
__ provides alternatives to general anesthesia
Neuraxial anesthesia
__ pass freely in and out
__ barred outside
Channels guarded by “gates”
• K+ pass freely in and out
• Na+ barred outside
Nerve stimulation
o Gates open
o Na+ rushing in
o Shifting of polarity
o Depolarization
INTERCOSTAL NERVE BLOCK
• Anterior rami of __ eleven spinal nerves • At inferior surface of ribs
1st
COMPLICATIONS OF INTERCOSTAL NERVE BLOCK
Pneumothorax
ANKLE BLOCK
• Blocks five nerves supplying foot
1-5
a. Deep peroneal
b. Superficial peroneal
c. Saphenous
d. Posterior tibial
e. Sural
ANKLE BLOCK
• Precaution
• Avoid __ to reduce risk of ischemia
epinephrine
PUDENDAL NERVE BLOCK
• sacral plexus __-__
(S2 – S3 – S4)
Fan-shaped injection at the base blocks dorsal and ventral branches
DORSAL PENILE BLOCK
Local anesthetic deposited at sub arachnoid space
SPINAL ANESTHESIA
Drugs Used in Spinal Anesthesia
• Tetracaine
• Lidocaine
• Bupivacaine
T L B
Factors Determining Level of Anesthesia (in spinal anesthesia)
• volume of solution
• concentration
• barbotage
• speed of injection
• patient position
• specific gravity of solution
• site of injection
• height of patient
• increasedintra-abdominalpressure
Position in spinal anesthesia
Lateral decubitus – knees flexed to chest chin put down on chest (nose-to-knee)
Puncture Sites in spinal anesthesia
• Interspaces between L2-L3, L3-:4, L4-L5
• Line joining highest points of iliac crests
• crosses either body of L4 or interspace
• between L4-L5
DELAYED COMPLICATIONS – leak of CSF
Headache
Levels of Spinal Anesthesia – Dermatomes Involved
____ - sensory loss involves lowers lumbar and sacral segments.
Saddle Block
Levels of Spinal Anesthesia – Dermatomes Involved
__ – level of umbilicus (T10) lower thoracic lumbars and sacrals
Low Spinal
Levels of Spinal Anesthesia – Dermatomes Involved
__ – costal margin (T6) lower thoracic lumbars and sacrals
Mid-Spinal
Levels of Spinal Anesthesia – Dermatomes Involved
__ – nipple line (T4) thoracic segments (T4 – T12) lumbars and sacrals
High Spinal
Distance from skin to epidural space – __
4-5 cm
Position of epidural anesthesia
Position
• Cervical epidural – sitting (C7)
• Thoracic epidural (T7)
• Lumbar epidural
(L1-L2, L2-L3, L3-L4, L4-L5)
Method of Identifying Epidural Space
Principle: negative pressure in space
Drop of saline at hub of epidural needle is sucked in once it enters space
Hanging Drop
Central neuraxial block
Epidural anesthesia
LA injected into the epidural space in the sacral canal through sacral hiatus
CAUDAL ANESTHESIA
Caudal anesthesia blocks lumbosacral plexus ____ and
coccygeal plexus ___
lumbosacral plexus (T12, L1-5, S1-3) and
coccygeal plexus (S4-5, coccygeal nerves)
In caudal anesthesia __mL of lidocaine is used in the technique
15-20 mL
Reversible inhibition of sensory nerve impulse conduction
Local Anesthetics
• Prevent transmission of information to the CNS
• No loss of consciousness
Local Anesthetics
NON PHARMACOLOGIC FACTORS INFLUENCING ACTIVITY OF LOCAL ANESTHETICS
1-5
- Dosage
- Addition of vasoconstrictor
- Site of injection
- Additives
- Mixture of LA
In Spinal anesthesia, lack of _____ around spinal cord are responsible for the rapid onset
nerve sheath
Local anesthetic additive that increase pH near pKA more ionized faster entry faster onset
NaHCO3
Clinically Useful Local Anesthesia
AMINO-ESTERS
Ester link between aromatic and main portion of the molecule
AMINO-AMIDES
Amide linkages
Local Anesthetics Classification
Amides
Lidocaine, Bupivacaine,
Ropivacaine, Levobupivacaine
Local Anesthetics Classification
Esters
Procaine, Chloroprocaine, Cocaine, Tetracaine
Local Anesthetics Mechanism of Action
blocks voltage-sensitive Na+ ion channels in neuronal membrane
\/
prevent Na+ influx (Depolarization)
\/
prevent transmission of nerve impulses
Low anesthetic potency & short duration of action
procaine & chloroprocaine
Intermediate anesthetic potency & duration of action
lidocaine, mepivacaine &
prilocaine
High anesthetic potency and prolonged duration of action
tetracaine, bupivacaine : racemic and levobupivacaine, ropivacaine, ethidocaine
decreases max rate of depolarization w/o altering RMP
LIDOCAINE
local anesthetic used in regional anesthesia for over 3 decades
BUPIVACAINE
- good motor/sensory block
BUPIVACAINE
Mechanism: depresses the rapid phase of Depolarization (V max)
BUPIVACAINE
compounds made up of same atoms connected by the same sequence of bonds with different 3D structure
Stereoisomers
pairs of stereoisomers that, in their 3D projection, are related to each other as an object to its mirror image, and thus are not superimposable
Enantiomers
(+)
enantiomer that rotates polarized light to the right
Dextrorotation
(-) enantiomer that rotates
polarized light to the left
Levorotation
equal amounts of enantiomers in a chiral compound
RACEMIC MIXTURES
Comparative effect of racemic bupivacaine, levobupivacaine & ropivacaine on isolated rabbit heart.
D-Bupivacaine
Methemoglobinemia
PRILOCAINE
requires __mg Prilocaine to produce clinical level of Methemoglobenemia
600
requires 600mg Prilocaine to produce clinical level of Methemoglobenemia
Reversed with _____
Methylene blue
EXTRAVASCULAR INJECTION BLOOD CONCENTRATION
Depends on:
• Absorption
• Tissue Redistribution
• Metabolism
• Excretion
Factors Affecting Absorption
• Site of injection – more blood supply > absorption
• Choice of Drugs – characteristics of the drug may affect
absorption • Dosage
• Addition of Epinephrine – depends on the sensitivity of the vessels at the site of injection and local anesthesia itself
Central nerve blocks
A. Spinal anesthesia
B. Epidural anesthesia
C. Caudal anesthesia
