Normal pH of local anesthetics:
5.5 - 6.0
Doesn’t work well w/ infected tissue (more acidic)
Can add bicarb to buffer
How do most local anesthetics work?
Block Na channels and impair propagation of AP
Thinner myelinated nerve fibers are more easily BLK
Advantages of epi in locals
Vasoconstrictor
Increased duration of action
Decreased bleeding and volume needed to anesthesia
Disadvantages of epi in locals
Increased myocardial activity
Tachycardia
HTN
Dysrhythmias
Avoid pts w/ known CV dz, HTN, DM, thyroidtoxicosis
Describe the ideal anesthetic
Short latency Superior penetration Non-addictive Completely reversible Low toxicity Stable and water soluble Non-irritating Inexpensive
MC adverse effects of local anesthetic
Urticaria
Erythema
Edema
Dermatitis
Toxicity from locals - prodromal sxs
Cicrumoral numbness
Tinnitus
Lightheaded / dizzy
Tingling Metallic taste in mouth
Toxicity from locals - CV problems
HTN then HOTN
Tachy or brady
V-fib - CV collapse
Toxicity from locals - severe CNS:
Tonic-clonic activity
ALOC -> unconsciousness
What do you do prior to injecting to avoid intravascular injection?
Aspirate first
Bupivicaine not recommended for:
Kids under 12yrs
Method for injecting local
Large coverage with one puncture (longer, small gauge needle
Bent 45 degrees, hub the needle, inject as you withdraw
Sequence of clinical anesthesia
Vasodilation - loss of symp tone
Loss of
- Pain/temp sensation
- Pressure sensation
- Motor fx
Peripheral nerve blocks - common sites?
Digit blocks - (Common w/ rib blocks as well)
Plantar aspect of foot
Palmar aspect of hand
Max dose Bupivicaine?
2mg/kg up to 100mg
Where is epidural anesthesia injected?
Into the epidural space, NOT the CSF
Describe epidurals
Skin taped Cath - Req continuous inf of LRG anesthetic volume
Acute complications of nerve blocks
HOTN (neurogenic shock) - txt w/ IVF/pressors (v-con)
High spinal - brady-c, HOTN, arm tingling, and respiratory distress (txt-ventilate)(diaphragm C3-C5)
Cauda equina - bladder/bowel dysfx, m/s alts in legs
Dermatomes - Clavicles, nipples, umbilicus
Diaphragm innervation
Diaphragm inervation C3-C5
Clavicles - C5
Nipples - T4
Umbilicus - T10
Conscious sedation provides
Analgesia and anxiolysis
Minimally depressed LOC
Usual combo for conscious sedation?
Benzo + narcotic
OR
Propofol + narcotic
Intubation in conscious sedation?
Nope - patient maintains their own airway
Nice perks of conscious sedation?
Still follows commands (verbal stimuli)
Doesn’t remember any of it later (antegrade amnesia)
Examples of procedures in which conscious sedation is used
Bronchoscopy EGD/colonoscopy Thoracostomy Closed reduction of fx’s Procedures in kids
What does propofol provide (and not provide)?
It’s a sedative-hypnotic
So… anxiolysis, muscle relaxant, anticonvulsant
BUT
NO DIRECT ANALGESIC EFFECT
Patient safety during conscious sedation
Req crash cart
- Follow SOP’s
- NPO prior
- ASA class I and II patients
- Dedicated staff
Crash cart:
O2 Airway adjuncts ACLS drugs Defibrillator Suction Narcan - (narc rev) Flumazenil - (Benzo rev)
PACU
Home w/ chaperone once goals are met: (ADMIT if not)
- stable - out of bed for 30mins/amulatory/vitals
- A/O x3
- pain / nausea controlled
- voids
Goals of general anesthesia
Pain control
Amnesia
Muscle relaxation
General anesthesia - airway/breathing mangement
Intubate/ventilate Laryngoscope or Glidescope
Concerns about eyes w/ general anesthesia
Protect eyes (lubricate and tape close)
Complications of general anesthesia
Hypoxemia
CV events
Aspiration
Nerve injury
TXT of MC adverse effects of local anesthetic
Txt - O2, Epinephrine, fluids, antihistamine, steroids
Lidocaine dosing w/out EPI?
4mg/kg up to 300mg
Lidocaine dosing WITH Epi
7mg/kg up to 300mg
1% Lidocaine conc?
10mg/mL
2% Lidocaine conc?
20mg/mL
Lidocaine onset?
2-5m
Lidocaine duration?
0.5-2hrs
Management of CNS toxicity
Hypercarbia - Hyperventilate
Seizures - Benzo
Management of CV toxicity
HOTN - IVF
Arrythmias - Wide = Shock and Narrow = Rx
Management of Malignant hyperthermia toxicity
TXT - Cool rapidly, Bicarb, Dantroline
Malignant hyperthermia pathophys
Hypermetabolism > Fever, Tetany, Hyperkalemia
Malignant hyperthermia etiology?
Rare inherited condition (MC) from colatile agents and succinylcholine
How to prevent toxicity
Administer locals in combinations of SML volumes of different agents (Do not max out one thing)
Bupivicaine onset?
5-10m
Bupivicaine duration?
2-4hrs
Purpose of local anesthetic?
Minor surgery/laceration repair
What to ensure prior to PNB?
Eval neurovascular status prior to injection
What procedures is a spinal (subarachnoid) block generally for?
GYN
GU
Low ABD
LE
Where is a spinal (subarachnoid) block injected?
Into the sub-arachnoid space (the CSF)
Describe spinal (subarachnoid) block Rx attributes?
Anesthetic and Narcotic +/- Epi
What does a spinal (subarachnoid) block do to the nervous system?
Blocks - Sympathetic, Sensory, and Motor fx (everything)
Epidurals block?
Blocks sensory but not necessarily motor function
Rib fracture preferred anesthesia?
Epidurals
Late complications of CNB
MC - urinary retention
Spinal HA 2/2 CSF leaking out of the dura - ICP decreases with postural changes
Epidural hematoma - compresses spinal cord - suspect if pt is anticoagulated
MC late complication of a CNB?
Urinary retention -
Monitor UOP post-op (cath w/ foley even w/ BPH)
Late CNB complication of Spinal HA TXT
txt with IV fluids, caffeine, blood patch (autotransfuse blood into epidural space)
Late CNB complication of Epidural hematoma primary concern? And 2nd line anesthesia?
Anticoagulanted patient = anesthesia will likely be avoided in these patients (Endotracheal anesthesia)
How does a epidural hematoma usually present?
Compressed spinal cord causes Loss of neuro fx below infusion site (bladder/legs)
Narcotics reversal
Narcan
Benzo reversal
Flumazenil
General anesthesia prevention
Protect eyes (lube/tape) Pressure points (pad) PVT hypothermia Do not hyperextend joints
Mitigating aspiration complications during general surgery
NPO prior
Antacids
Cricoid pressure during intubation (Sellick maneuver)
Sellick maneuver is?
A way of reducing aspiration by putting pressure onto the cricoid during intubation.