Regional Anesthesia Basic Overview (pt 1) Flashcards
What is the definition of Regional Anesthesia?
Selective anesthesia and analgesia achieved by exposing selected nerves to LA.
What is a Field Block?
Uses local infiltration, but specifically identifying a nerve root/bundle
Describe the advantages/disadvantages of Topical Regional Anesthesia
Advantages:
-Easy
-Low skill
-Low risk
-Great for mucus membranes
Disadvantages:
-Short duration 1-4 hours
-Slow onset over skin (needs soak time)
-Doesn’t work well or at all on inflamed/infected tissues
Describe the uses for Topical Regional Anesthesia
-IV placement
-Eye procedures
-ENT procedures
-Awake fiberoptic intubation
-Dental pain
-Surgical wound closure
-Acute/chronic pain mgmt
What is EMLA cream?
A Eutectic mixture of local anesthetics.
-Mixture of 2.5% Lido and 2.5% Prilocaine
What is a concern with Benzocaine spray?
Methemoglobinemia
What is local infiltration?
The injection of LA directly into a tissue.
-Used for traumatic wound closure, surgical wound closure, and pre-emptive analgesia (Trocar sites, joint injection)
What are the advantages and disadvantages of Local Infiltration?
Advantages:
-Fast and easy
-Low skill
-Lower risk
Disadvantages:
-Short duration 1-6 hrs
-Doesn’t work well or at all on inflamed/infected tissues
-Requires provider to place injections systematically to ensure good coverage (patchy coverage is common)
What is a Field Block?
Infiltration of LA around an area that you wish to anesthetize.
-Know the path in which the nerves innervate that area.
What are some uses of Field Blocks?
-Carotid endarterectomy (Superficial Cervical Plexus)
-I&D of wounds
-Intercostobrachial and medial brachial cutaneous nerves
-Dentistry
-Plastic surgery (Breast reduction/augmentation)
What are the advantages/disadvantages of Field Blocks?
Advantages:
-Easy to perform
-Low risk procedure
-Multiple LA options
-Can be used to supplement patchy peripheral or NA blocks
Disadvantages:
-Inconsistent coverage
-Only covers superficial structures
-Relatively short DOA
What is a Bier Block?
The injection of LA into the venous system of an exsanguinated extremity to produce surgical anesthesia for short periods.
-Exsanguinate an entire limb via a tourniquet
-Fill venous system of that extremity using an IV with a large volume (50 mL) of a dilute local solution (LIDOCAINE ONLY).
-Gives you full anesthesia of the arm
-Very short procedures (ex: Carpal tunnel)
-If surgeon takes a long time, can’t really use it. In about 30 minutes, will see tourniquet pain issues.
What are the uses of a Bier Block?
-Best suited for short soft tissue upper extremity procedures
-Can be used for lower extremity.
What are the advantages of a Bier Block?
-Relatively easy to perform
-Provides surgical anesthesia quickly
What are the disadvantages of a Bier Block?
-Tourniquet pain limits useful duration
-Tourniquet must be inflated for at least 20 minutes
-Will start to see Tourniquet pain after about 30 minutes
-Must be able to obtain IV access on operative limb
-Pt habitus must be suitable for proper tourniquet fit
-Failed tourniquets risk large volume LA immediately entering central circulation
-Acute LA Toxicity
Where should the IV be placed for a Bier Block?
Preferably, in the hand of the operative arm.
Describe the procedure of placing a Bier Block.
1) Establish IV access
2) Apply DOUBLE pneumatic tourniquet to upper arm (pad arm with cotton)
3) Exsanguinate arm (raise arm up, apply Esmarch bandage in a spiral from hand to proximal cuff of tourniquet)
4) Inflate distal cuff first to 50-100 mmHg above SBP (usually 200-250 mmHg for an arm)
5) Inflate proximal cuff
6) Deflate distal cuff (allows local to seep underneath distal cuff)
7) Inject LA (ONLY LIDO ALWAYS)
-Want venous distention, LA all over extremity.
8) Remove IV
What local anesthetic do you use for a Bier Block?
NO LA OTHER THAN LIDOCAINE USED.
30-50 mL of 0.5% Lidocaine.
-3 mg/kg max dose
-Never ever use bupivicaine or anything other than Lido for a Bier Block
What should you do if tourniquet pain starts during a Bier Block?
Can inflate distal cuff and then deflate proximal.
-Never deflate cuff less than 20 minutes from injection
How do you deflate the tourniquets at the end of a Bier Block?
If you’re worried about toxicity:
-Deflate cuff for 10 seconds
-Reinflate for 1 minute
-Allows initial bolus of lidocaine that entered systemic circulation to dissipate and get soaked up before the rest is let out (Gradual LA Washout)
What are the advantages of Peripheral Nerve Blocks?
-Specific control of what is being blocked
-And possibly more important, what is not blocked. Requires working knowledge of fine anatomic detail
-Can avoid systemic side effects of neuraxial techniques
-Continuous Perineural catheters can be used
What are the disadvantages of Peripheral Nerve Blocks?
-Anatomical variability and technical difficulty can lead to failure (Especially in landmark techniques)
-Inadvertent blockade of nerves due to proximity (ex: Phrenic nerve block)
What are the advantages of Neuraxial Anesthesia?
-Provide coverage to large sections of the body
-Catheter placement allows for analgesic control
What are the disadvantages of Neuraxial Anesthesia?
-Can be technically difficult
-Sympathectomy
-Contraindicated for many comorbidities and pt specific factors (Coagulopathy/anticoagulation, Uncooperative pt, Stenotic heart valve lesions, etc.)
What things do you need to consider when forming an anesthetic plan?
-Surgical procedure (intensity, positioning, length)
-Patient (consent, comorbidities, any c/i like coagulopathy, Aortic Stenosis, etc.)
-Anesthetist (skill, comfort level)
-Surgeon (surgical skill, comfort with blocks)
-Facility resources
-Pre-op and PACU Staff
What characteristics do you need to consider when selecting a LA?
-Onset
-Duration
-Depth of blockade desired
-Additives
Which two local anesthetics have a fast onset, short duration, and create a dense block?
-Lidocaine
-Mepivicaine
Which two local anesthetics have a slower onset and longer duration?
-Bupivicaine (dense block)
-Ropivicaine (less profound block)
Why is epinephrine added to LAs?
-Intravascular marker
-Decreases uptake, prolonging duration?
Which other additive is added to LAs in order to decrease uptake, prolonging duration?
Phenylephrine
What is the purpose of adding Dexamethasone and Clonidine to LA?
To prolong the duration
What is the purpose of adding Sodium Bicarb to a LA?
To speed up the onset
What puts you at increased risk for infection with RA?
-Continuous > single shot
-Femoral or Axillary site used
-Recent trauma
-Recent ICU admission
-Compromised immunity (Diabetes)
-Catheter in place for >48 hours
-Absence of ABX use
How can you lower the risk of infection with RA?
-Avoid puncture of infected tissue
-Ensure good aseptic technique: Good skin prep (Betadine – vs – Chlorhexadine), Sterile technique, Catheter dressed well (Biopatch, chlorhexadine dressing)
-Judicious Pt selection
-Reduce trauma r/t block placement
What increases the risk of hematoma?
-Prolonged needling
-Larger needle size
-Trans-arterial technique
-Pt with coagulopathy (Rx and patho): Current Neuraxial Anticoagulation guidelines apply to RA. Caveat – Common and well accepted to judiciously practice outside of guideline. Different blocks carry different risks
How can you decrease the risk of hematoma?
-Consciously avoid vascular structures, both deep and superficial structures.
-Veins collapse easily with minimal pressure from needle or US
-May be piercing vein and not see it, or get bloody aspiration
-Hold pressure after inadvertent vascular puncture. >5 minutes if arterial
Why are hematomas bad?
Increase pressure on the nerve, leading to injury.
What incidental blockade can occur with ISB/SCB/Superficial Cervical Blocks?
1) Phrenic Nerve Blocks (occurs almost 100% of the time with ISB).
-Diaphragm paralysis, reduced ventilation
-CXR shows hemidiaphragm ipsilateral side of block. Doesn’t effect most healthy people
2) Recurrent Laryngeal Nerve
-Vocal cord paralysis
3) Sympathetic Cervical Ganglion (Horner’s Syndrome)
What incidental blockade can occur with a Paravertebral Block?
Costal or Epidural spread
What are the symptoms of intra-arterial injection of LA?
Most arteries flow to the periphery.
-Allows local some time to be absorbed by tissue
However, Vertebral and Carotid: direct flow to brain
-Even LA volumes 1-3ml cause almost immediate seizure, neurological LA toxicity S/Sx
What are the symptoms of intra-venous injection of LA?
Most veins all flow directly to the heart
-Local Anesthetic Systemic Toxicity (LAST)
-Neuro s/sx may be delayed or absent
-CV instability is often first sign
-Compression of vessels during US/needling may hide IV puncture (no aspiration of blood)
How do you prevent LAST?
-Continuous monitoring (ECG, BP, SpO2) for at least 30 minutes after high dose blocks
-Notify patient of symptoms to watch for (metal taste, ears ringing, circumoral numbness, anxiety)
-Frequent aspiration every 3-5 mL
-Slow injection of LA
-Avoid traumatic needling
-Judicious dosing of LA
-Epi marker in high volume blocks to detect increases in HR
-Have a plan (ASRA checklist or NYSORA flowchart)
-Have 20% Lipid Emulsion in area where blocks are performed.
What conditions do you decrease the dose of LA?
-Advanced age
-Poor cardiac function
-Pre-existing conduction abnormalities
-Dec plasma proteins
> ____% increase in HR may indicate intravascular injection (according to powerpoint)
> 10%
Never use Epi in blocks in what areas?
-Fingers
-Toes
-Penis
-Nose
-Ears
What are the CNS symptoms of LAST?
-Metal taste
-Tinnitus
-Double vision
-Dizziness
-Circumoral numbness
-Excitation (Agitation, confusion, twitching, seizure) or Depression (drowsy, obtunded, coma, apnea)
-Patient may be sedated from Benzo administration to report CNS symptoms
-Benzo may prevent seizure
What are the cardiovascular signs of LAST?
May be the first/only signs.
-Excitation followed by depression
-Inc BP and inc HR
-Ventricular ectopy, multiform VT, VF (Hallmarks of cardiac toxicity of LA)
-Progressive BP decline, bradycardia leading to asystole (hallmark of severe LA toxicity)
What is the treatment of LAST?
-Get help
-Lipid Emulsion
-ASRA checklist/NYSORA flowchart
-Alert cardiopulmonary bypass team
-Airway mgmt with ETT/vent
-Abolish seizure (Versed, avoid prop if CV unstable)
-Manage arrhythmias via ACLS (Epi, Amiodarine (300/150), Magnesium (1-2g)
What drugs do you AVOID during tx of LAST?
-CCBs
-BBs
-Lidocaine
-Phenytoin
-Vasopressin (controversial)
What is the dosage for administering 20% Lipid Emulsion therapy for tx of LAST?
-Bolus 1.5 mL/kg (lean body weight). Usually ~100 mL
-Infusion at 0.25 mL/kg/min (~18 mL/min)
-Repeat bolus q 5 min if persistent CV collapse
-Infusion doubled to 0.5 mL/kg if hypotension continues
-Continue infusion for at least 10 minutes after CV stable
What is the upper limit for 20% Lipid Emulsion administration?
10 mL/kg over first 30 minutes.
Which blocks have increased risk for Pneumothorax?
-Highest risk is Supraclavicular 0.5-6%
-Lower incidence occurs with ISB, ICV, and Suprascapular
-Also can occur with thoracic blocks like Paravertebral, PEC blocks, and intercostal blocks
What are the S/Sx of Pneumothorax?
-Decreased breath sounds
-Decreased HR and BP
-Decreased O2 sat -> cyanosis
-Increased HR, RR, JVD
-SOB w/retractions and nasal flaring
-Pain in chest/epigastric area that worsens with cough or deep breath (sudden onset, sharp)
-Tracheal shift away from PTX (late sign)
-Progressively expanding chest wall
How do you perform US assessment of a PTX?
-Use a linear or phase array probe
-Air rises to the highest area. Place them supine and look at the anterior chest, mid-clav line between the 2nd-4th rib
-Looking for pleural sliding during respiration, acoustic artifacts seen when pleural layers are touching, and for lung edge (where lung stops touching chest d/t air pocket)
What is pleural sliding?
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
-Can see “shimmering effect” In 2D mode
-In M Mode, normal lungs are “Sea Shore” and PTX causes Stratosphere or Barcode pattern. PTX does not have motion because there’s no lung there.
What are B-Lines?
-Present in normal lung
-Artifact due to acoustic differences of air/water in lung tissue
-If absent = PTX
What are Comet tails?
-Present in normal lung
-Artifact due to US waves bouncing off interface of the pleural layers
-Move synchronously with respiration
-If absent = PTX
If even 1 of either B-lines or Comet tails is present, what does that mean?
There is NO Pneumothorax
What are A-Lines?
-Present in PTX
-Horizontal lines equally spaced, emanating from the pleural line
-Echo into a hollow chamber. No lung tissue there. Means PTX.
What is the Lung Point Assessment?
-The location on the chest where the lung stops touching the chest wall.
-Most specific sign for PTX
-Most difficult to find (even for experienced operators)
-By finding edges of air pocket on the chest, a calculation can be made to estimate Pneumo size
-Finds dividing line of PTX and normal lung
What is the treatment for PTX?
-Admission to the hospital
-Monitor closely
-Supportive therapy
-Chest Tube possible
-May resolve spontaneously over time
Most nerve deficits associated with RA are _____.
Transient
-Transient paresthesias are reported in up to 10%
-Can last days - weeks
-Permanent injuries are very rare (localized numbness -> paralysis)
What increases risk of Nerve Injury?
-Needle mvmt around partially anesthetized nerves (use of a blunt needle decreases risk)
-Increased risk with proximal blocks
-Pre-existing pathologies (DM, PVD, atherosclerosis)
What are the different mechanisms of nerve injury?
-Mechanical
-Stretch
-Pressure/Compression (hematoma, neural edema, intraneural or intrafascicular injection
-Chemical (LA, Epi. All LA are toxic, Ropivicaine is least)
-Vascular (prolonged disruption of blood flow to nerve. Lidocaine inhibits neural blood flow, seen even after Lido wash out).
What is Intraneural injection?
-Needle is inside nerve and injection of LA inside the nerve
-Pressure increases inside nerve, decreasing blood flow, creating injury
-Epineurium (outer layer) is very tough and fibrous, does not swell up)
What is intrafascicular injection?
Injection of LA into the bundles of nerves surrounded by tough, fibrous perineurium
-Where the axons are running
-Blunt needle is less likely to pierce!
-Not easily distended to compensate
-Higher injection pressure = increased fascicular pressure
-Perineurium and supporting connective tissues have blood vessels.
What is the difference between proximal vs distal regarding Intrafascicular Injection?
Injection risk increases with proximal and decreases with distal.
Proximal:
-Few large fascicles
-Inc fascicle density
-Tightly bound by sheath
-Easy to needle
Distal:
-Many small fascicles
-Low Fascicle:Epineural density
-No sheath
-Difficult for needle to enter fascicle.
Describe the vasculature associated with an Intrafascicular injection.
-Ischemia leads to injury
-Intrinsic: within epineurium
-Extrinsic plexus around nerve, anastomosis with inner
-Microvascular blood flow issues may be why some patients are at increased risk
-LA decreases blood flow, possibly contributing to injury
How do you manage post-op Neuropathy?
-Tell patient what S/Sx to report
-Assess reversible causes: cast too tight? compartment syndrome? Hematoma?
-Ask Surgeon - possible procedural contribution?
-Consult neuro asap, especially if motor is involved
-EP testing
Motor involvement is very bad sign. Resolution of sensory symptoms usually occurs within 4-6 weeks, and can take up to 1 year.
