Reg 2 Flashcards
Local anesthetics
Drugs used to produce reversible conduction blockade of impulses along central and peripheral nerve pathways
Regional anesthesia
insensibility of a part induced by interrupting the sensory nerve conductivity of that region of the body
The result of a conduction blockade of specific peripheral nerves or nerve groups
Esters:
Are less stable (shorter shelf life)
Metabolized in the plasma by pseudocholinesterases
More prone to cause allergic reactions
Amides
More stable
Metabolized by liver
Rare allergies
SPINAL
Small volume
Direct-Sheath
Rapid onset
Total neural block-both sensory and motor
Epidural/PNB
Large volume
Outside-Sheath
Slow onset
Block varies with dose
PERIPHERAL vs. CENTRAL
advantages
Segmental block Slow onset = time to Rx side effects Flexibility in density Flexibility in duration Less side effects
PERIPHERAL vs. CENTRAL
disadvantages
More technical & more failure
More time consuming
Greater LA volume- [>toxicity risk]
Faulty block
Definition spinal
It is the reversible chemical blockade of neuronal transmission produced by injection of a LA into the CSF contained in the subarachnoid space
goal of spinal
Render patient insensitive to surgical stimuli while producing minimal physiologic alteration
Types neuraxial anesthesia
Spinal
Epidural
Caudal: similar to epidural. But in sacrum. Kids only
neuraxial uses
Alternative to general anesthesia
Can be used in conjunction with GA
Post-operative analgesia: may use lower opioid use with and decreases incidence of atelectasis, hypoventilation, and aspiration pneumonia
Management of acute or chronic pain
advantages and system improvements with neuraxial
- Sympathectomy-mediated increases in tissue blood flow
- Improved oxygenation from decreased splinting
- Enhanced peristalsis
- Suppression of the neuroendocrine stress response
advantages spinal anesthesia
- Simple
- Predictable
- Fully conscious patient
- Analgesia into the post-op period
- Ideal for lower abdomen, pelvis/ perineum, and lower extremities
- Reduces risk of DVT
- Use small dose of LA, less toxicity
Disadvantages spinal anesthesia
-Sympathetic blockade 100% of the time =Hypotension -Intense motor blockade =May last for hours post-op -Surgeons complain “It takes too long
Absolute Contraindications
-Patient refusal
-Severe psychiatric disease:
May not cooperate
-Infection at the site
-Septicemia or bacteremia
Absolute Contraindications: cardiovascular
Cardiovascular disease:
-Severe aortic/mitral stenosis and septal hypertrophy
Absolute Contraindications: Fluid status
Severe hypovolemia:
- Can be corrected before the spinal
- Pt in shock
Absolute Contraindications CNS
CNS disease:
- MS or nerve injury
- Herpetic infections
- Increased ICP- brain herniation
Absolute Contraindications: allergies
Allergy to LA:
- Ester LA
- Reaction to the preservatives
Absolute Contraindications: blood
Blood clotting anomalies:
-Anticoagulant therapy
ASRA guidelines
relative Contraindications
-HIV: Associated with neurological manifestations -Surgery of unknown duration -Untreated chronic HTN: *Unstable BP after spinal *Greater drop in BP than normal pt -Procedures above the abdomen -Obesity
relative Contraindications
- Deformities of the spinal column
- Chronic HA or backache
- Bloody tap
- Multiple attempts
relative contraindication : blood clotting
- Minor abnormalities in blood clotting:
- ASA therapy
- Small dose of heparin
- Check coags before spinal insertion and document
- Risk for spinal hematoma
- Platelet count
pros and cons for Sick Elderly Patient
-PROs
*Possibility of less post-operative delirium
-CONs
*Hypotension, bradycardia
Rebound HTN, tachycardia = Fluid & pressors
pros for OB pt
Decreased M&M
Less effects on mother and fetus
Informed Consent
- Make sure you document you have discussed the advantages and disadvantages with the patient and alternative techniques
- Make sure pt knows that spinals sometimes do not work
- May need to convert to a GA
- Make sure patients understands and accepts risk
- Document the informed consent
Vertebral Column
- 7 cervical, 12 thoracic, 5 lumbar, 5 sacral (fused) vertebra
- Differ in shape and size according to level
- The vertebral bodies are connected by the intervertebral disks
Spinal column forms a …
DOUBLE C
Ligamentous elements provide …
structural support.
Along with muscles help maintain shape
Ventrally –
- Motor
- Vertebral bodies and intervertebral disks are connected + supported by anterior and posterior longitudinal ligaments
Dorsally –
- Sensory
- LF, ISL, SSL provide additional stability
spinal canal layers
- ligamentum flavum
- epidural space (potential)
- dura mater
- subdural space (potential)
- arachnoid mater
- subarachnoid space
- pia mater
- meninges-cover the spinal cord
- spinal cord
spinal cord Extends from
- foramen magnum to L1 in adults
- L3 in children
Anterior & posterior nerve roots at each spinal level join one another and …
exit the intervertebral foramina forming spinal nerves from C1 to S5
Where does the SC end?
L1Adults
where does dural sac end?
S2
Cervical level in relation to nerves
nerves arise above their perspective vertebrae hence 8 nerve roots
Thoracic level in relation to nerves
nerves exit below
Below L1 =
- lower spinal nerves form the cauda equina
- Usually avoid potential needle trauma because these nerves float in the dural sac below L1 and tend to be pushed away rather than pierced
Largest intervertebral space is …
Thickest is…
Largest intervertebral space is L4-5
Thickest is T1
Blood supply to spinal cord
- Single anterior spinal artery:
- Formed from vertebral artery at the base of the skull
- Course down the anterior surface of the cord
- Supplies the anterior 2/3 of the cord
Paired posterior spinal arteries
- Arise from the posterior inferior cerebellar arteries
- Course down along the dorsal surface of the SC medial to the dorsal nerve roots
- Supplies the posterior 1/3 of the cord
Additional blood flow to the arteries from the
intercoastal arteries
artery of adamkiewicz or arteria radicularis magna
- arising from the aorta
Typically unilateral and nearly always arises on the left side, providing the major blood supply to the anterior lower 2/3 rds of the spinal cord = injury here results in anterior spinal artery syndrome
Must be more careful with anterior
Principal site of action for neuraxial blockade is the …
nerve root
LA bathes the nerve roots in subarachnoid space or epidural space
Blockade of neural transmission (conduction) in the posterior nerve root fibers interrupts
somatic and visceral sensation
Blockade of anterior nerve root fibers prevents
efferent motor and autonomic outflow
Sensory blockade –
somatic + visceral
Smaller and myelinated fibers vs larger unmyelinated fibers
Smaller and myelinated fibers are generally more easily blocked than larger unmyelinated fibers
differential blockade
Because the concentration of LA decreases the further away from the injection site
Dermatome Sensory BlockadeRule of TWO (2)
Sympathetic blockade 2 segments higher than sensory blockade which is 2 segments higher than motor blockade
Classifications of nerve Fibers bloackade-
small myelinated get blocked 1st, then small to large fibers
sympathetic blockade
T8, temperature
Sensory blockade
T10, pin prick
Motor blockade
T12
T4 blockade
will get bradycardia
Cervical segments
C5- Anterolateral shoulder
C6- Thumb
C7- Middle finger
C8- Little finger
Thoracic segments
T1- Medial arm T3- 3rd, 4th interspace T4- Nipple line, 4th, 5th interspace T6- Xiphoid process T10- Navel T12- Pubis
Lumbar segments
L2- Medial thigh
L3- Medial knee
L4- Medial ankle
L5- Dorsum of foot
Sacral segments
S1- Lateral foot
S2- Posteromedial thigh
S3,4,5- Perianal area
Order of Nerve Fiber Blockade
- B fibers-Autonomic, sympathetic efferent
- C and A Delta Temperature, Touch
- A Gamma- muscle tone
- A Beta- small motor, pressure
- A Alpha- Large Motor, Proprioception
- This is the order for motor blockade
Due to small size autonomic fibers are
blocked quickly
Sympathectomy is accentuated in
the hypovolemic pt
earliest sign that spinal is working
Drop in BP is the earliest sign that the spinal is working
A rapid drop in BP may cause nausea and dizziness
Treat quickly
Temperature and Light Touch
- Innervated by the unmyelinated C and myelinated A-delta fibers
- Loss of these follows autonomic blockade
how to assess temp and light touch?
alcohol swab
Loss of temperature correlates with
sensory loss
Motor Impairment & Touch
Myelinated A-beta & A-gamma
Loss of motor & touch follows loss of
light touch and temperature discrimination
Differential block
Motor block is
2 dermatones below sensory block
Profound Motor Block
Myelinated A-alpha
Motor block and loss of propioception
Pt’s will feel legs are still in the air after being prepped
Assess block
S1-2-
S1-2- dorsiflex his feet
Assess block
L4-5- flex his toes
flex his toes
Assess block
L2-3-
raise his knees
Assess block
T6-T12-
lift shoulders off the bed
S2-5
- Saddle block
- No affect on the ANS
- Surgical anesthesia limited to perineum, perianal, & genitalia
T10 (umbilicus)
- Low spinal
- Blocks S1-5 & L1-5
- Produce vasodilation, lower BP
- Good for GYN, vaginal delivery, lower extremity surgery, TURP, & cysto
T4 (nipple)
- High spinal
- Used for upper abdominal surgery
- Can feel traction
- Can cause vasodilation and block cardioaccelator fibers