PNB Complications Flashcards
Higher incidence of neurologic injuries involve which blocks
Brachial plexus blocks
_______________ while doing a block is associated with high incidence of post op neurologic injury
Elicitation of paresthesia
What is more common with PNB
Transient neurologic dysfunction
Typically resolves with time
Most symptoms of PNB injury resolve when
Within 2-4 weeks
Surgeries associated with most complications r/t PNB
Rotator Cuff Repair
Carpal Tunnel Release
Patient characteristics associated with PNB injury
Preexisting neurologic disease**
DM **
Smoker
BMI extreme
Male
Elderly
Perioperative characteristics associated with PNB injury
Pain with injection***
Prolonged tourniquet time***
Positioning ***
Parenthesis with needle placement
Sedated during block
Hypothermia
Prolonged hospitalization
Barriers to PNI recognition
Sedation
Post op pain/analgesia
Regional anesthesia (failure to report, failure to peruse)
Patient periop naivety/uncertainty
Dressings,drains, casting ***
Types of neurologic injury
Mild
Recovery 2-3 weeks
Neuropraxia
Most common
Cause of neuropraxia
S/S
Hit nerve with needle- mild inflammation
No deficit in sensory or motor
Tingling or paresthesias
Types of neurologic injury
Severe
Regeneration 1mm/day
Recovery 6-12months
Axonotmesis
Causes of axonotmesis
Injury to nerve directly but not transected
Types of neurologic injury
Degeneration
Neuroma formation
Permanent and irreversible
Neurotmesis
Causes of neurotmesis
S/S
Complete disruption in axoplasmic flow
Sensory or motor in either direction disrupted
Aka Wallerian degeneration
Sunderland classification of nerve injury and prognosis
1 2 3 4 5
1- neuropraxia good
2- axonotmesis. Fair
3,4,5- neurotmesis poor
4 causes of neural injury
Mechanical
Ischemic
Chemical
Co-existing neurologic disease and comorbidities (obese, smoker, elderly)
4 types of mechanical nerve injury
Needle contact
Intrafasicular injection
Compression
Stretch
Needle angle to reduce intraneural injury
Tangential and long axis approach
Does intraneural injection always cause neurologic dysfunction
No
Chemical nerve injury MOA
- all LA are neurotoxic
- duration of nerve exposure to LA increases risk
- pre-existing neural blood flow increases risk if low
- adjuvants may have neurotoxic potential
MOA for LA being causative agents for neurotoxic injury
Increase in cystolic Ca
Depletes ATP, mitochondrial injury, membrane dysfunction, cell death
Which nerves more susceptible to neurotoxicity injury
Small diameter
Transmitting pain and temperature
LA
Vasodilator to vasoconstrictor
Lidocaine(dilate)
Bupivacaine
Mepivacaine
Ropivacaine (constrict)
All LA except______ have shown to reduce neural blood flow
Tetracaine
Lidocaine 2% reduces neural blood flow by ______ when epi added
20-80%
Doses of bupivacaine >0.5% have mild _______ action
Vasodilator
Should always use __________ drugs for PNB
Preservative free drugs
3 non LA drugs that have been shown to be neurotoxic at high doses
Ketamine
Midazolam
Dexamethasone (dose dependent)
_____________ has been shown to be neuroprotective and may prolong block duration
Dexmedetomidine
Which route of dexamethasone administration prolongs block more IV or PNB additive
Added to PNB
Buprenorphine addition findings
Prolong by 8 hours
SIGNIFICANTLY INCREASES RISK OF PONV
When doing PNB on diabetic pt you should
Reduce concentration and volume of LA in PNB
Eliminate adjuncts (especially epi)
Pt undergoing chemo changes in PNB
Limit concentration, volume, and adjuncts
Tips for performing PNB
Eval for pre-existing neurologic disease/disorder pre-op
Use lowest concentration and volume possible
