Ultrasound Basics (lecture 1) Flashcards
Needle is placed in line with and parallel to the transducer.Both the needle shaft and tip are visualized.
IN Plane
3 things necessary to perform safe peripheral block:
- U/S
- Nerve Stimulation
- Injection Pressure Monitoring
Needle is placed perpendicular to the transducer.
Needle shaft and tip are visualized as a hyperechoic dot on ultrasound.
Out-of-Plane
3 types of regional anesthesia
- Neuraxial
- Peripheral Nerve Block
- Intravenous regional Anesthesia (IVRA)
one example of IVRA
Bier’s Block
3 types of neuraxial anesthesia
- spinal
- Epidural
- Caudal
Types of Peripheral nerve blocks:
- Upper Limb (Cervical Plexus, Brachial Plexus)
- Trunk
- Lower Limb (Lumbar Plexus, Sacral Plexus)
List upper limb blocks:
- Cervical Plexus
- Interscalene
- Supraclavicular
- Infrclavicular
- Axillary
- Peripheral Nerves
- Bier Block
Types of Trunk blocks
- Paravertebral /ESP/MTP
- Pecs
- Serratus Anterior
- Rectus Sheath
- TAP/QL
- Ilioinguinal/Iliohypergastric
Types of Lower Limb blocks
- Fascia Iliaca
- Femoral
- Adductor Canal
- Sciatic (Sub-Gluteal)
- Popliteal Sciatic (Tibial/Common Peroneal)
- IPACK (Interspace between the Popliteal Artery & the Capsule of the posterior Knee)
- Ankle (5 individual nerves)
Ultrasound imaging uses the transmission and reflection of high-frequency ____, ____ waves (“ultrasonic sound” waves) in tissues
longitudinal
mechanical
Steps of U/S image formation
- The electricity is sent to the probe.
- The crystals converts electricity into sound waves
- The sound waves propagate through tissue
- The returning waves hit the crystals which amplify the wave.
- This then gives you a 2D image
Example of strong reflection
Bone (white dot)
Example of weaker reflections
Solid organs (gray dot)
Example of no reflection
Full bladder/blood (black dot)
characterised by a signal void behind structures that strongly absorb or reflect ultrasonic waves
Acoustic Shadowing
Acoustic Shadowing
Acoustic Shadowing
Enhancement
an area of increased brightness underneath fluid resulting from the lack of impedance when sound waves pass through fluid and increased echoes from underlying structures
IOW, the U/S thinks that it needs to amplify the signal because its first encounter is fluid filled (which elicits no reflections), so everything beyond the fluid will be brighter.
Enhancement
Color Doppler mode is intended to add color-coded qualitative information about ____ and ____.
- Velocity
- Direction of Fluid Motion
Mnemonic for color doppler
BART
Blue Away Red Towards (the probe)
What option can you select/utilize on the U/S after turning it on to expedite your on-screen view?
choose a preset anatomical selection
(will present a standardized initial image)
High frequency =
GOOD resolution/BAD Penetration
Low Frequency =
BAD resolution/GOOD penetration
Overall Gain adjusts:
brightness uniformly to all depths
Time Gain Compensation (TGC) adjusts:
brightness/amplification of echos at different depths
What was adjusted here:
GAIN
What was adjusted here:
depth
When applied the ____ narrows the effective beam width and in this region lateral resolution is optimised
focus
Outside of the focus region the effective beam width is ____ and lateral resolution is reduced
wider
What was adjusted hers:
Focus
Set the system to the ____ frequency relevant to the depth of your scan
highest
Mnemonic for remebering U/S settings
Fun Dogs Go Fetch
Frequency, Depth, Gain, Focus
Phenomenon: Ultrasound waves are mostly reflected by air, we need to place a layer of gel or liquid between the face of the transducer and the area we wish to scan to form an airtight seal
Acoustic Coupling
Mnemonic: probe maneuvers
PART
Pressure, Alignment, Rotation, Tilt
Apply the optimum with the transducer so as not to distort the anatomy (veins)
pressure
Sliding movement of the probe across the skin to track structures
Alignment
Twisting movement, moving from short axis to long axis views
Rotation
Rocking the probe to optimize the angle of reflection
Tilt
PART photo
LA reversibly ____ of excitable membranes
decrease the rate of depolarisation and repolarisation
LA agents act through ____ channels on neuronal cell membranes and ____ action potentials.
sodium
block conduction
LA agents ultimately stop the transmission of signals from nerves to the ____.
CNS
LA agents (amides & esters) are best classified based on ____.
DOA
Short DOA (30-90 min) LA:
- 2-3% chloroprocaine
- 1% Prilocaine
Medium DOA (4-6 hours) LA:
- 2% Lidocaine
- 1.5% Mepivicaine
Long DOA (>8 hours, usually 12-18) LA:
- 0.5%, 0.25% Bupivicaine
- 0.2%, 0.5%, 0.75% Ropivicaine
Epinephrine effect on LA:
- ↓ absorption
- ↑ DOA
Sodium Bicarb effect on LA:
- ↑pH = ↑ uptake & ↑ onset
Clonidine & Opiates effects on LA:
- modifies quality of block
- ↑ DOA of analgesia 2/2 pain pathway modualtion
Dexamethasone (Decadron) effect on LA:
↑ DOA
Dexmedetomidine (Precedex) effect on LA:
↑ DOA
Local Anesthetic Agent Table Summary
Exparel is liposomal ____.
bupivicaine
concentration of Exparel
13.3 mg/cc
133mg/10cc vial
How much additional Bupivicaine HCl can be added to a 10cc vial of Exparel?
0.25%: ≤ 30cc
0.5%: ≤ 15cc
75 mg additional
6 Complications of Regional Anesthesia
- Vasovagal Syncope
- Methemoglobinemia
- LAST
- Spinal/Epidural Hematoma
- Post-Dural Puncture Headache
- Cauda Equina Syndrome
Vasovagal Syncope treatment
- Trendelenburg
- Anticholinergic
- Compressions (if HR low)
- Oxygen
- Reassure Pt
- Stand back and put bed rails up!
TACO
Main LA agent that causes Methemoglobinemia?
Prilocaine
What happens in MetHgb?
Methemoglobin (MetHb) is altered state of hemoglobin (Hb) in which the ferrous (Fe2+) irons of heme are oxidized to the ferric (Fe3+) state. The ferric hemes of MetHb are UNABLE to bind oxygen causing the oxygen dissociation curve to shift left, making it more difficult to release O2 (increasing affinity for O2).
MetHgb signs >10%
Central cyanosis (4-8 hours after prilocaine adm)
MetHgb sign <20%
- asymptomitic (OR)
- headache
- fatigue
- dyspnea
- lethargy (cerebral ischemia)
MetHgb signs >20%
- respiratory depression
- ALC
- shock
- seizures
- death
MetHgb >40%
life threatening
A life-threatening adverse reaction resulting from local anesthetic reaching significant systemic circulating levels.
Local Anesthetic Systemic Toxicity (LAST)
(LAST) is rare and almost always occurs within ____ of injection of the local anesthetic.
minutes
LAST signs:
- what first: CNS or CVS syptoms?
CNS usually
LAST CNS S&S
Circumoral numbness
Tinnitus
Restlessness
Tonic clonic seizures
Decreased consciousness
Apnea
LAST CVS S&S
Hypertension/Hypotension
Tachycardia/Bradycardia
Conduction defects (Prolonged PR, Prolonged QRS)
Ventricular dysrhythmias
Cardiac arrest
LAST Tx:
- Stop injecting LA
- Get Help/Lipid Emulsion if necessary
- Airway management (100% O2/AVOID hyperventilation)
- Control Seizures: Benzos, AVOID Propofol in hemodynamically compromised
- Tx HoTN & Bradycardia
Lipid Emulsion Tx >70kg pt:
- BOLUS 100cc Lipid Emulsion 20%
- Lipid Emulsion INF: 200cc over 20 min
slide: INF: 200-250cc over 15-20
Lipid Emulsion Tx <70kg pt:
- BOLUS 1.5cc/kg Lipid Emulsion 20%
- Lipid Emulsion INF: 0.25 cc/kg/min (IBW)
Lipid Emulsion MAX dose
12 cc/kg
Pt remains unstable after Lipid Emulsion Bolus & INF:
Re-BOLUS 1-2x same dose + DOUBLE INF *(do not exceed MAX 12 cc/kg)
*total volume can approach 1L in prolonged resuscitation (>30 min)
If cardiovascular event occurs, monitoring should be continued for how long?
at least 4-6 hours
If CNS event occurs, monitoring should be continued for how long?
at least 2 hours
LAST checklist chart photo
Intralipid (lipid emulsion) table photo
Intralipid (lipid emulsion) 20% photo
NSU Local Anesthetic Dosages