Regional anesthesia Flashcards
what is RA
it involves the injection of LA agents around nerves in the PNS or CNS causing Reversible abolition of pain and sensation in a part of the body without loss of consciousness
what are the types of RA (2)
- Neuraxial anesthesia (Spinal anesthesia and Epidural)
- Peripheral nerve blockades
when LA are injected into the subarachnoid space what do they inhibit
nerve impulse conduction in all nerves with which it comes in contact (motor, sensory, autonomic) via sodium channel blockade.
what is the MOA of LA
LA produce anesthesia by inhibiting excitation of nerve endings or by blocking conduction in peripheral nerves by binding to and inactivating sodium channels
which nerves are affected first after injection of LA (2)
- autonomic
- sensory
what happens when autonomic fibers are blocked (2)
- vasodilation
- hypotension
what are advantages of spinal anesthesia (7)
- Avoids hazards of GA
- Rapid action
- consciousness is preserved
- Alternative to GA for certain poor risk patients
- Lesser post op confusion
- Safe and cheaper alternative
- prolonged post op analgesia
where does the spinal cord end in adults
L1
where does the spinal cord end in children
L3
what is the most dependent part in supine position
T4-T8
in the cervical area what is the first palpable spinous process
C2
the spinous process of T7 is at what level
is at the level of inferior angle of Scapula
what is at S2-S4
perineum
in the cervical area what is the most prominent spinous process
C7
- bony knob at the back of the neck
what is at T4
nipples
what is the line joining the top of the iliac crests at L4/L5
tuffiers line
what layers do you penetrate when trying to reach the subarachnoid space (9)
- Skin
- Subcutaneous fat
- Supraspinous ligament
- Interspinous ligament
- Ligamentum flavum
- Dura matter
- Subdural space
- Arachnoid matter
- Subarachnoid space
what is at T6
xiphoid
what are absolute contraindications for spinal anesthesia (5)
- Inadequate drug/ equipment
- Severe hypovolemia
- Increased ICP
- Patient refusal
- Infection at puncture site
what do dermatomes help with
to know the level of your spinal anesthesia
what are indications for spinal anesthesia (2)
- Operations below lower half of body
- surgery on the lower limb, pelvis, genitals, and perineum, and most urological procedures, obstetric procedures e.g. cesarean section - Patients with systemic disease
what is at T10
umbilicus
what is found at T1-T4
cardiac accelerators fiber
- will result in bradycardia & decrease in contractility if affected
what is at t12, L1
inguinal ligament, crest of ilium
how do you manage the complication hypotension
(4)
- oxygen therapy
- vasoconstrictor drugs
- ārate of I.V
- treat bradycardia
what is found at T5-L1
vasomotor fibers
- which determine tone, result in vasodilation on blockade
how can you manage the complication high/total spinal (5)
- Asses patient using ABCD approach.
- give high flow oxygen.
- in cases of maternal collapse patient may require mechanical ventilation.
- Treat Hypotension and bradycardia (atropine) if present.
- Reverse Trendelenburg positioning often proves essential
what are relative contraindications for spinal anesthesia (5)
- Sepsis
- Coagulopathy
- Uncooperative patient
- Spinal deformity
- Preexisting neurological deficit
what causes the post dural puncture headache (2)
- Due to leak of CSF from dural defect leads to traction in supporting structure especially in dura and tentorium
- vasodilatation of cerebral blood vessels.
what are immediate complications of spinal anesthesia (6)
- Hypotension
- Bradycardia
- high and total spinal block
- urinary retention
- Epidural hematoma
- Bleeding
what are late complications of spinal anesthesia (3)
- Post dural puncture Headaches,
- infections
- urinary retention
why is a decreased dose required for spinal anesthesia in pregnancy (2)
- Mechanical factor-compression
- Compression of IVC causes shunting of blood to the venous plexus in the vertebral canal-decreased vertebral canal space and CSF volume - Hormonal factors- higher progesterone levels
- increases the sensitivity of neuronal membranes to LA
what is the difference between high and total spinal
- High spinal involves a spread of LA affecting spinal nerves above T4.
- Total spinal, there is an intracranial spread of LA resulting in loss of consciousness.
where is the postdural puncture headache usually located (2)
-. bifrontal
- occipital
when is a postdural puncture headache usually worse(3)
- upright position
- coughing
- straining
what does post-dural puncture headache cause (5)
- nausea
- photophobia
- tinnitus
- diplopia[6th nerve]
- cranial nerve palsy
what is treatment for post-dural puncture headaches (4)
- keeping patient supine
- adequate hydration
- NSAIDS
- epidural blood patch ( if headache not relieved with 12-24hr)
what factors may increase the incidence of post spinal puncture headaches (6)
- age
- younger > older - gender
- females > males - needle size
- larger > smaller - needle bevel
- less when the bevel is placed in the long axis of the neuraxis - often with pregnancy
- often with multiple punctures
what is the onset of post-spinal puncture headache
12-72 hrs following procedure
how do you perform the spinal anesthesia in lateral decubitus position (3)
- Needs to be Parallel to the Edge of the Bed
- Legs Flexed up to Abdomen
- Forehead Flexed down towards Knees
which positions can you place patient in for spinal anesthesia (2)
- sitting
- lateral decubitus
what are examples of opioids (4)
- fentanyl-12.5mcg
- sufentanyl-2.5-5mcg
- Diamorphine -0.3mg
- morphine- 0.1-0.2mg
what is baricity
Density of solution in relation to density of CSF
how do you perform the sitting spinal anesthesia (4)
- With Legs hanging over side of bed
- Put Feet up on a Stool (no wheels)
- Assistant MUST keep the patient from Swaying
- Curve her back like a āCā,
what factors affect block height (6)
- Baricity of anesthetic solution
- Position of the patient
- Drug Dosage (mg)
- Concentration times volume
- Addition of Opioids
- Site of Injection
what do hypobaric solutions do
rise against gravity
what do hyperbaric solutions do
tend to follow gravity
what do isobaric solutions do
tend to remain in the same height where they were injected
what adjuvants can be used (4)
- opioids
- epinephrine
- clonidine
- neostigmine
how do opioids help (4)
- improves analgesic by prolonging sensory block
- reduces local anesthetic requirements
- they enhance the effect of the LA, allowing for the use of lower doses of LA whilst still achieving effective pain control ( reduces risk of toxicity ) - reduces duration of motor blockade
- this is useful in cases where pain relief is desired without prolonged muscle paralysis, aiding in quicker recovery of movement post procedure - improves hemodynamic stability.
how does epinephrine work (2)
- Decreases blood flow
- prolongs block by decreasing the rate of LA reabsorption.
how does clonidine work
prolongs duration of sensory analgesia
how does neostigmine work
inhibits breakdown of acetylcholine
- can reverse non depolarizing neuromuscular blockade
what are types of PNB (2)
- upper PNB
- axillary
- interscalene - lower PNB
- sciatic
- popliteal
- lumbar plexus
what tool can help you when performing a PNB
ultrasound
what are complications of PNB (4)
- Intravascular injection
- Local anesthetic toxicity
- Nerve damage
- INFECTION
how should you prepare for a PNB (4)
- Consent
- infection control
- Equipment:
- drugs
- syringes
- needle
- USS machine
- nerve stimulator - Assistance
what are the LA drugs (2)
- esters
- procaine
- cocaine - amide
- Lignocaine 3mg/kg
7mg/kg with adrenaline
- Bupivacaine 2mg/kg
2mg/kg with adrenaline
- Ropivacaine 3mg/kg
3mg/kg with adrenaline
which LA drugs are commonly associated with allergic reactions
esters
