Regional Anesthesia Test 1 Flashcards
What is the definition of a drugs pKA?
It is the ph level of the drug?
What is the significance of a drugs pKA in relation to absorption?
The closer the drugs pKa is to the bodies pH, the quicker onset it will have, the only exception is Chloroprocaine due to its concentration
Which regional anesthetic has the quickest onset of action and why?
Chloroprocaine; its concentration
In local anesthesia agents, lipid solubility directly correlates with what?
Potency
In local anesthesia agents, protein binding directly correlates to what?
Duration
What three other factors also impact local anesthesia duration of action?
- lipid solubility
- Vasoconstrictors
- tissue blood flow
In local anesthesia agents, speed of onset directly correlates to what?
pKa
In local anesthesia agents, onset of action indirectly correlates to what?
ionization
How does blood flow affect the absorption of local anesthetics?
Tissue sites with greater blood flow exhibit increased absorption of local anesthetics
What is the pneumonic for tissue sites from most vascular to least? Most blood flow to the least?
In Time I Can Please Everyone But Sally & Shelby
List the tissues sites in order from most vascular to least as related to absorption of local anesthetic agents and onset of action.
- IV
- Tracheal
- Intercostal
- Caudal
- Paracervical
- Epidural
- Brachial Plexus
- Subarachnoid, Sciatic, Femoral
- Subcutaneous
If the plasma concentration of local anesthesia becomes significantly elevated what can happen?
it can lead to toxicity of the CV and the CN systems
What is the most common cause of Local Anesthetic Systemic Toxicity(LAST)?
the inadvertent intravascular injection and administration of an excessive dose of local anesthetic.
What substance sequester any lipid binding drug in cases of LAST?
Lipids
What are clinical signs of increased plasma concentrations of local anesthetics @ 5 mcg/ml?
Lightheadedness, tinnitus, circumoral and tongue numbness
What are clinical signs of increased plasma concentrations of local anesthetics @ 10 mcg/ml?
Muscular twitching and visual disturbances
What are clinical signs of increased plasma concentrations of local anesthetics @ 15 mcg/ml?
convulsions and unconsciousness
What are clinical signs of increased plasma concentrations of local anesthetics @ 20 mcg/ml?
unconsciousness and coma
What are clinical signs of increased plasma concentrations of local anesthetics @ 25 mcg/ml?
Respiratory arrest and CVS depression
What drug should you pretreat with 5-10 minutes before administering local anesthetics? And why?
Pretreat with benzodiazepine such as versed, versed elevates the seizure threshold in case they become toxic
What patient habitus is particularly at risk for LAST?
patients with poor muscle mass as there is not protein to bind too
How long does it take from of the time of injection can LAST occur?
5 - 25 minutes
What should you do frequently while injecting the local anesthetics?
aspirate frequently
What is the 4 most important treatments of LAST?
- airway management
- seizure suppression
- CPR
- 20% Lipid emulsion injection
At what dose should lipid emulsion be given for LAST?
1.5 ml/kg initial bolus, followed by 0.25 ml/kg/min for 30 - 60 minutes
Bolus could be repeated 1 -2 times for persistent systole
Infusion rate could be increased if the BP declines
What is meant by Lidocaine(2345678)?
234 g/mol Molecular Weight
56 % Protein bound
7.8 pKa
Is it ionized or unionized local anesthetic that renders the nerve insensate?
unionized
On what structure in the nerve does neuromuscular blockade occur
Axon
What is the name of the node in which the nerve blockade jumps from and how many nodes to achieve blockade??
Node of Ranvier; 2-3 nerves to achieve blockade
From what vertebrae does the Cervical Plexus originate from?
C1, C2, C3, C4, C5
From what vertebrae does the Phrenic Nerve originate from?
C3, C4, C5 with major contribution from C4
From what vertebrae does the Brachial Plexus originate from?
C5, C6, C7, C8, T1
What are four complications of a Cervical Plexus Block?
- Phrenic nerve block(hiccups)
- Horner’s syndrome(ptosis~eye drooping, miosis~eye constriction, anhydrosis~inability to sweat, enophthalmosis, scleral hyperemia, facial flushing, nasal congestion)
- Hoarseness
- Accidental intrathecal or epidural injection
* upper extremities blocks should never be done in adults while they are anesthetized*
What is the pneumonic to identify the blocks of the Brachial Plexus?
Real Trojans Drink Cold Beer
Roots,Trunks,Divisions,Cords,terminal Branches
To do an Interscalene Block what nerves do you want to block?
Distal roots and proximal trunks
To do a Supraclavicular Block what nerves do you want to block?
Distal trunks and proximal divisions
To do a Infraclavicular Block what nerves do you want to block?
Among the cords
To do an Axillary Block what nerves do you want to block?
the Terminal Branches
What is the acceptable amperage to inject LA at?
0.2 - 0.5 with muscle stimulation
What are the 6 acceptable twitches for a successful blockade of the Brachial Plexus
- pectorals major
- deltoid
- biceps
- triceps
- forearm
- hand
What are 3 advantages to Interscalene blockade?
- appropriate for shoulder surgery
- risk of pneumothorax is small
- landmarks are easy to find in obese patients
What are 4 disadvantages to Interscalene blockade?
- paresthesias are usually elicited
- ulnar nerve is frequently spared(C8-T1)
- NOT appropriate for patients with significant pulmonary compromise
- Phrenic nerve blockade typically ensues, however only 10% are symptomatic
What are 4 complications of a Interscalene blockade?
- unintentional epidural or spinal anesthesia
- puncture of the vertebral artery
- Phrenic nerve block(hemidiaphragmatic paralysis, unilateral)
- LAST
What is the position and technique for an Interscalene block?
- patient in supine position with HOB slightly elevated and head turned to away from the side being blocked
- sternocleidomastoid muscle is palpated
- roll fingers off posteriorly
- intersection at C6
What are the 4 drugs used for a ISB and what is the dosages associated with them?
Lidocaine 20-30 mls
Mepivacaine 20-30 mls
Bupivacaine 20-30 mls
Ropivacaine 20-30 mls
What are 3 advantages of Supraclavicular Blocks?
- Brachial plexus is most compact here(3 trunks)
- Arm can be in any position
- Most homogenous block of brachial plexus-get the most coverage(Ulnar nerve is not spared)
What are 3 disadvantages of Supraclavicular Blocks?
- Difficult to perform and to teach
- considerable experience is required
- Pneumothorax is a major risk
What are 4 complications of a Supraclavicular Block?
- puncture of the subclavian artery
- pneumothorax
- phrenic nerve block(Hemidiaphragmatic Paralysis)(Unilateral)
- LAST
What are the 4 drugs and dosages used for SCB?
- lidocaine 30 mls
- bupivacaine 30 mls
- ropivacaine 30 mls
- mepivacaine 30 mls
What are 4 advantages of Infraclavicular Blocks?
- Nerves frequently missed with the axillary approach are blocked
- The musculocutaneous nerve IS usually blocked
- Unlike the axillary approach, does not require positioning of the arm
- Phrenic nerve blockade IS NOT a possibility
What are 3 disadvantages of Infraclavicular Blocks?
- No pulse to assist in blocking bundle
- If injection is too far proximal to the clavicle, the musculocutaneous and axillary nerves will be missed
- Needle insertion too medial can result in a pneumothorax
What are the 4 drugs and dosages used for ICB?
- lidocaine 30 mls
- bupivacaine 30 mls
- ropivacaine 30 mls
- mepivacaine 30 mls
What 3 nerves are involved with an Axillary block?
- median nerve
- ulnar nerve
- radial nerve
My Uncle Rapped
What are 3 advantages to an Axillary blockade?
- provides anesthesia for surgery on forearm and wrist
- fewer complications than for SCB
- probably the safest and most reliable for the patient
used for A-V fistulas
What are 3 disadvantages of an Axillary block?
- arm must be ABducted for block
- NOT for shoulder or upper arm surgery
- musculocutaneous nerve lies outside of per vascular sheath. Separate block is required.
What is the technique of an Axillary block?
- patient supine, head turned away from block
- arm abducted 90 degrees
- forearm flexed 90 degrees
- palpate brachial artery as far proximal
What are the 4 drugs and dosages used for AB?
Lidocaine 20-30 mls
Mepivacaine 20-30 mls
Bupivacaine 20-30 mls
Ropivacaine 20-30 mls
What nerve is not routinely blocked with ISB?
ulnar nerve
Which block is appropriate for shoulder surgery?
Interscalene Block
What volume of LA would you inject for an ISB?
20 - 30 mls
What nerve mediates extension of the wrist?
Radial nerve
Which nerve extends the elbow?
Radial nerve
If you get paresthesia, is it ok to inject?
No
These two nerves mediates flexion of the wrist.
median and ulnar nerve
If you obtain a twitch of deltoid at 0.15 mA, is it ok to inject?
No your too close
3 Characteristic movement of fingers, wrist and elbow in response to nerve stimulation of the Radial nerve.
- extension at elbow
- supination of forearm
- extension of wrist and fingers
4 Characteristic movement of fingers, wrist and elbow in response to nerve stimulation of the Median nerve.
- pronation of forearm
- flexion of the wrist
- opposition of middle, forefinger and thumb
- flexion of the lateral three fingers
3 Characteristic movement of fingers, wrist and elbow in response to nerve stimulation of the Ulnar nerve.
- flexion of the wrist
- adduction of all fingers
- flexion and opposition of medial two fingers toward thumb
Characteristic movement of fingers, wrist and elbow in response to nerve stimulation of the Musculocutaneous.
flexion of the elbow
If you get paraesthesia while advancing PNS with needle do you inject or not?
No you back out a bit
What are signs and symptoms of Horner’s Syndrome?
Horner’s syndrome(ptosis~eye drooping, miosis~eye constriction, anhydrosis~inability to sweat, enophthalmosis, scleral hyperemia, facial flushing, nasal congestion)
