Mod IV: Regional Anesthesia Part 4 Flashcards by Olivier Mba

_{Regional Anesthesia}

Incidence of Pneumothorax

Very rare but

profound complication

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_{Regional Anesthesia - Pneumothorax}

Brachial plexus blocks with the Highest risk of Pneumothorax:

Supraclavicular block

0.5-6%

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_{Regional Anesthesia - Pneumothorax}

Brachial plexus blocks with the Lower incidence of Pneumothorax:

Interscalene block (ISB)

Infraclavicular block (ICB)

Suprascapular block

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_{Regional Anesthesia - Pneumothorax}

Thoracic blocks associated with a risk of Pneumothorax:

Paravertebral

Pectoral nerve (PECs) Blocks

Intercostal Blocks

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_{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

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_{Regional Anesthesia - Pneumothorax}

Characteristics of pain a/w Pneumothorax:

Chest/Epigastric

May be worse with cough or deep breath

Onset is commonly sudden

Sharp!!!!

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_{Regional Anesthesia - Pneumothorax}

Tracheal shift - which way?

Away from pneumothorax!!!

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_{Regional Anesthesia - Pneumothorax}

Changes to chest wall a/w pneumothorax:

Progressively expanding

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_{Regional Anesthesia - Pneumothorax}

How is a Pneumothorax diagnosed:

Physical assessment

CT scan

Chest X-ray

Ultra sound

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_{Regional Anesthesia - Pneumothorax - Diagnosis}

Gold Standard for detecting Pneumo:

CT scan

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_{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

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_{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%

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_{Regional Anesthesia - Pneumothorax - Diagnosis}

What improves Dx reliability with Ultra sound?

Using multiple findings together

Pleural sliding AND Comet-tail artifact

Specificity 96.5%

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_{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

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_{Regional Anesthesia - Pneumothorax - Diagnosis}

Which type of US machine is a big plus?

M-mode capable US machine

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_{Regional Anesthesia - US assessment for Pneumothorax}

US machine with Best images:

Linear transducer

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_{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

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_{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

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_{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

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_{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

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_{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

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_{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

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_{Regional Anesthesia - US assessment for Pneumothorax}

Acoustic Reverberation:

A-Lines, B-Lines, and Comet-tails

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_{Regional Anesthesia - US assessment for Pneumothorax}

Acoustic Reverberation present in normal lung:

B-Lines and Comet-tails

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_{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:

**Moto**r involvement **bad sign**