Mod IV: Regional Anesthesia Part 4 Flashcards
Regional Anesthesia
Incidence of Pneumothorax
Very rare but
profound complication
Regional Anesthesia - Pneumothorax
Brachial plexus blocks with the Highest risk of Pneumothorax:
Supraclavicular block
0.5-6%
Regional Anesthesia - Pneumothorax
Brachial plexus blocks with the Lower incidence of Pneumothorax:
Interscalene block (ISB)
Infraclavicular block (ICB)
Suprascapular block
Regional Anesthesia - Pneumothorax
Thoracic blocks associated with a risk of Pneumothorax:
Paravertebral
Pectoral nerve (PECs) Blocks
Intercostal Blocks
Regional Anesthesia - Pneumothorax
Signs & Symptoms of Pneumothorax
Decreased
Breath sounds, HR, BP - O2 Sat => cyanosis
Increased
HR, RR, JVD - SOB – retractions, nasal flaring
Pain
Chest/Epigastric - May be worse with cough or deep breath
Onset is commonly sudden - sharp
Tracheal shift away from pneumothorax
Progressively expanding chest wall
Regional Anesthesia - Pneumothorax
Characteristics of pain a/w Pneumothorax:
Chest/Epigastric
May be worse with cough or deep breath
Onset is commonly sudden
Sharp!!!!
Regional Anesthesia - Pneumothorax
Tracheal shift - which way?
Away from pneumothorax!!!
Regional Anesthesia - Pneumothorax
Changes to chest wall a/w pneumothorax:
Progressively expanding
Regional Anesthesia - Pneumothorax
How is a Pneumothorax diagnosed:
Physical assessment
CT scan
Chest X-ray
Ultra sound
Regional Anesthesia - Pneumothorax - Diagnosis
Gold Standard for detecting Pneumo:
CT scan
Regional Anesthesia - Pneumothorax - Diagnosis
Chest X-ray sensitivity to detect Pneumo:
As low as 36-48% sensitivity to detect Pneumo
Not very sensitive to finding Pneumo
Small Surg. Center may not have the ability
Regional Anesthesia - Pneumothorax - Diagnosis
Ultra sound - Advantages:
Portable
May expedite diagnosis, treatment and resuscitation of unstable PT
Overall Dx sensitivity 58.9-100%, Specificity 94-100%
Regional Anesthesia - Pneumothorax - Diagnosis
What improves Dx reliability with Ultra sound?
Using multiple findings together
Pleural sliding AND Comet-tail artifact
Specificity 96.5%
Regional Anesthesia - Pneumothorax - Diagnosis
When is Ultrasound Negative predictive value 100%?
When both findings (Pleural sliding AND Comet-tail artifact) are present
100% probability pneumothorax is not present
Regional Anesthesia - Pneumothorax - Diagnosis
Which type of US machine is a big plus?
M-mode capable US machine
Regional Anesthesia - US assessment for Pneumothorax
US machine with Best images:
Linear transducer
Regional Anesthesia - US assessment for Pneumothorax
Why are US machines with Phase array preferred for detecting pneumo in Obese PTs, Large breasts?
Provides deeper images
with ↓ quality
Regional Anesthesia - US assessment for Pneumothorax
Assessment - Where to look?
Air rises to highest area
Supine - most common
Anterior chest midclav line b/t 2nd-4th rib
Probe orientated parasagittal
Midclavicular => Ant Axillary line
Examine multiple interspaces ↑and↓ the highest point
Regional Anesthesia - US assessment for Pneumothorax
Assessment - What are we looking for?
Pleural sliding during respiration
Acoustic artifacts seen when pleural layers are touching
Lung edge– where lung stops touching chest wall d/t air pocket
Regional Anesthesia - US assessment for Pneumothorax
US Assessment of Pleural Sliding - How?
Respiration causes visceral and parietal pleura to slide over each other
US can see this sliding motion
Air between pleural layers disrupts US beam
No pleural sliding = Air present = Pneumothorax
Regional Anesthesia - US assessment for Pneumothorax
US Assessment of Pleural Sliding - 2D mode
Dynamic measure of movement
Hyper-echoic pleural layers slide back and forth
“Shimmering effect” can be seen along pleural line
No Shimmer = Pneumothorax
Regional Anesthesia - US assessment for Pneumothorax
US Assessment of Pleural Sliding - M-mode
Views motion over time, static measurement
Easier to appreciate small movements
Normal Lungs – Sea Shore pattern
Water waves – Static Soft tissue above pleura
Shoreline – hyper-echoic Pleural line
Sand – sliding lung motion à granular sand appearance
Pneumothorax – Stratosphere or Barcode pattern
No motion seen à same appearance above/below pleural line
Regional Anesthesia - US assessment for Pneumothorax
Acoustic Reverberation:
A-Lines, B-Lines, and Comet-tails
Regional Anesthesia - US assessment for Pneumothorax
Acoustic Reverberation present in normal lung:
B-Lines and Comet-tails
Regional Anesthesia - US assessment for Pneumothorax
Assessment of Acoustic Reverberation - B-Lines artifact due to:
Acoustic differences of air/water in lung tissue
Regional Anesthesia - US assessment for Pneumothorax
Assessment of Acoustic Reverberation - Comet-tails artifact due to:
US waves bouncing off interface of the pleural layers
Move synchronously with respiration
Regional Anesthesia - US assessment for Pneumothorax
Assessment of Acoustic Reverberation - IF B-Lines and Comet-tails Absent =
Pneumothorax
Regional Anesthesia - US assessment for Pneumothorax
Assessment of Acoustic Reverberation - IF even 1 B-Lines and Comet-tails present =
NO Pneumo
Regional Anesthesia - US assessment for Pneumothorax
Assessment of Acoustic Reverberation - A-Lines
Present in Pneumothorax
Horizontal lines equally spaced emanating from pleural line
A-Lines = Pneumothorax
Regional Anesthesia - Pneumothorax - Diagnosis
Shows location on chest where lung stops touching chest wall
Lung Point Assessment
Most Specific sign for Pneumo
Most difficult to find
Difficult even for experienced operators
Regional Anesthesia - Pneumothorax - Diagnosis
How to estimate Pneumo size?
By finding edges of air pocket on the chest
A calculation can be made to estimate Pneumo size
Regional Anesthesia - Pneumothorax
Treatment:
Admission to the hospital
Monitor closely
Supportive therapy
Chest Tube possible
May resolve spontaneously over time
Complications of Peripheral Nerve Blocks
Nerve injury:
Infrequent Complication
Transient Deficits most common
Transient paresthesia reported in up to 10%
s/s last days - weeks
s/s rarely last weeks - months
Complications of Peripheral Nerve Blocks
Permanent injuries:
Very rare – 1.5/10,000
Can range from localized numbness => paralysis
Regional Anesthesia
Risk Factors Associated with Injury:
Technique
Anatomic
Pre-existing pathology
Procedural
Regional Anesthesia
Technical Risk Factors Associated with Injury:
Paresthesia, NS, US
Blunt needle ↓ risk
Needle movement around partially anesthetized nerves
Injection pressure/pain
LA selection and dosing
Skill of CRNA
Regional Anesthesia
Anatomic Risk Factors Associated with Injury:
Block performed
↑ risk proximal
↓ risk distally
Regional Anesthesia
Pre-existing pathologic Risk Factors Associated with Injury:
Diabetes
PVD
Atherosclerosis
Regional Anesthesia
Procedural Risk Factors Associated with nerve Injury:
Surgical risks – surgeon skill
Position, tourniquet, length,
Dressing, cast
Regional Anesthesia
T/F: Frequently see multiple factors present with nerve injury.
True
Regional Anesthesia
Mechanisms of Nerve Injury:
Mechanical
Stretch
Pressure/compression
Chemical
Vascular
Intraneural injection
Regional Anesthesia - Mechanisms of Nerve Injury
Causes of Pressure/compression Nerve Injury:
Hematoma
Neural edema
Intraneural or intrafascicular injection
Regional Anesthesia - Mechanisms of Nerve Injury
Chemical causes of nerve Injury:
LA, EPI, Chemo
All LA drugs are neurotoxic to some degree
Histological changes present after injection
Usually no clinical significance
Ropivicaine less toxic
Regional Anesthesia - Mechanisms of Nerve Injury
Least neurotoxic LA:
Ropivicaine
Regional Anesthesia - Mechanisms of Nerve Injury
Vascular causes of nerve Injury:
Prolonged disruption of blood flow to nerve
Lidocaine inhibits Neural blood flow
This effect is Dose dependent
↓ BF shown even after Lido wash out
Regional Anesthesia - Mechanisms of Nerve Injury
Which was historically thought to be primary mechanism of nerve injury?
Intraneural injection
Regional Anesthesia - Mechanisms of Nerve Injury
Intraneural injection - US techniques introduced - What was the thinking?
Thinking was US would prevent intraneural injection
Post surgical neuropathies would then plummet right?
Neural injury rates have not changed after introduction of US
Regional Anesthesia - Mechanisms of Nerve Injury
Studies done using Stimulator to place needle for block. US monitoring of injection was then performed. What were the findings?
Turns out we have been routinely injecting nerves for years
Intra-Neural – vs – Intra-Fascicular
Regional Anesthesia - Nerve Anatomy
Protective connective tissue - Outer covering, inner supportive tissue of nerve aslo known as:
Epineurium
Regional Anesthesia - Nerve Anatomy
Injury to the Epineurium from Injection of LA is far less likely - Depends on:
Freedom to swell
Regional Anesthesia - Nerve Anatomy
Bundles of nerves surrounded by tough fibrous Perineurium
Fascicles
Blunt needle less likely to pierce
Not easily distended to compensate
Higher injection pressure
↑ Fascicular pressure
Regional Anesthesia - Nerve Anatomy
Why do risks of nerve injury increase proximally?
Fewer large Fascicles
↑ Fascicle density
Tightly bound by sheath
Easy to needle
Regional Anesthesia - Nerve Anatomy
Why do risks of nerve injury decrease distally?
Many small fascicles
Lower Fascicle:Epinural density, without sheath
Needle has trouble entering fascicle
Regional Anesthesia - Nerve Anatomy
Vasculature ischemia could lead to nerve Injury. Where is intrinsic nerve vasculature located?
Within the epineurium
Regional Anesthesia - Nerve Anatomy
Vasculature ischemia could lead to nerve Injury. Where is Extrinsic plexus nerve vasculature located?
Around nerve, anastomosis with inner
Regional Anesthesia - Nerve Anatomy
Why may some PTs be at ↑ risk for vasculature-ischemia related nerve Injury?
Microvascular Bloof Flow issues
LA has been shown to ↓ BF
Possible mechanism for injury
Regional Anesthesia - Post-op Neuropathy
Management of Post-op Neuropathy requires communication with:
Pt
Surgeon
Neurology
Regional Anesthesia - Post-op Neuropathy
Management of Post-op Neuropathy - Communication with Pt involves:
Reporting of S/s
Ensure them your on it!!
Don’t blow them off
Regional Anesthesia - Post-op Neuropathy
Reversible cause of Post-op Neuropathy:
Cast
Compartment syndrome
Hematoma
Regional Anesthesia - Post-op Neuropathy
Management of Post-op Neuropathy - Communication with Surgeon involves:
Possible procedural component
Regional Anesthesia - Post-op Neuropathy
Management of Post-op Neuropathy - Communication with Neurology involves:
Earlier involvement
Invole neurology immediately if Motor deficit
Electrophysiological testing
Follow up until symptoms resolve or stabilize
Regional Anesthesia - Post-op Neuropathy
Resolution of sensory symptoms:
95% in 4-6 weeks
99% within a year
Regional Anesthesia - Post-op Neuropathy
Resolution of Motor symptoms:
Motor involvement bad sign
