4b: Anesthetics and Muscle Relaxants

Question 1

uses for local anesthesia

Answer 1

when surgery area is small, defined area; when patient needs to remain conscious during surgery

Question 2

requirements for general anesthetics

Answer 2

• rapid onset of anesthesia (LOC and sensation)
• skeletal muscle relaxation
• inhibition of sensory and autonomic reflexes
• easy adjustment of anesthetic dosage during surgery
• minimal toxic side effects
• rapid, uneventful recovery when stopped
• amnesia

Question 3

stages of general anesthesia

Answer 3

1: analgesia (begin to lose sensation)
2: excitement or delirium (unconscious but restless)
3: surgical anesthesia (regular, deep respiration)
4: medullary paralysis (bad, respiratory control centers are inhibited, need resp. & cardiac support immediately)

Question 4

balanced anesthesia

Answer 4

combination of IV and inhaled anesthesia throughout surgery to keep the patient at stage 3

Question 5

what is the only gas that is an inhaled general anesthetic (short-term, e.g. dental work)?

Answer 5

nitrous oxide

Question 6

classes of intravenous anesthetics

Answer 6

barbiturates, benzos, opioids, ketamine, propofol

Question 7

pharmacokinetics of anesthetics

Answer 7

• widely distributed (lipid soluble)
• may become stored in adipose tissue (causing confusion, disorientation during recovery)
• elimination occurs through lungs, transformation in liver, or both

Question 8

mechanism of anesthetics

Answer 8

inhibit neuronal activity throughout the CNS, increasing inhibitory neurotransmitters and decreasing excitatory transmitters

Question 9

adjuvants – preoperative meds

Answer 9

given as sedation 1-2 hours before general anesthetic, helps to relax patient, given in form of barbiturates, benzos, or opioids

Question 10

adjuvants – neuromuscular blockers

Answer 10

used with general anesthesia to ensure paralysis of skeletal muscles during surgery; allows a smaller dose of anesthesia (mechanism = blocking postsynaptic ACh receptor at NMJ)

Question 11

side effects of adjuvants (NM blockers)

Answer 11

tachycardia, increased histamine and plasma potassium, residual muscle pain and weakness

Question 12

rehab implications of general anesthetics

Answer 12

• pt may still be confused/delirious or weak
• early mobilization & breathing exercises to avoid accumulation of bronchial secretions
• potential long term effects on memory, attention, cognition

Question 13

examples of local anesthetics

Answer 13

(-caine): lidocaine, procaine, benzocaine, (original: cocaine)

Question 14

pharmacokinetics of local anesthetics

Answer 14

• should remain at site and NOT travel systemically
• eliminated by enzymes in the plasma
• excreted by metabolites

Question 15

uses for topical local anesthetics

Answer 15

wound cleaning, circumcision, cataract surgery

Question 16

uses for transdermal local anesthetics

Answer 16

local MSK pain such as OA, LBP, fractures, neuropathic pain; often used with ionto or phonophoresis

Question 17

uses for peripheral nerve blocks

Answer 17

dental procedures, surgeries of foot and hand, pain management after ortho surgeries (with diagnostic US to place needle); may be injected near brachial or lumbar plexuses to get larger portion of UE/LE (major PNB)

Question 18

uses for central nerve blockades

Answer 18

when analgesia is needed for large regions (childbirth, chronic pain relief)

Question 19

where is central nerve blockade normally administered and why?

Answer 19

at L3/4 or L4/5 to avoid end of spinal cord (at L2)

Question 20

differences between epidural and spinal nerve blockades

Answer 20

epidural: injected into epidural space (between vertebral column & dura mater) and easier to find

spinal: injected within subarachnoid space (between arachnoid and pia mater) and more rapid effects

Question 21

uses for sympathetic blockade

Answer 21

complex regional pain syndrome; reduces excessive sympathetic outflow to an extremity rather than providing complete analgesia

Question 22

mechanism of local anesthetics

Answer 22

inhibit the opening of sodium channels on nerve membranes to block action potentials (smaller diameter fibers are most sensitive and affected first) (type C pain affected first, then temp, touch, proprioception)

Question 23

local anesthetic systemic toxicity (LAST)

Answer 23

when local anesthetics are absorbed into circulation causing toxic effects: confusion, agitation, seizures, decreased HR and force of contractions (occurs when injected into wrong spot or dose is excessive)

Question 24

early symptoms of LAST

Answer 24

ringing in ears, agitation, restlessness, decreased sensation around tongue or mouth

Question 25

rehab implications of local anesthetics

Answer 25

• do not disturb transdermal patch during exercise
• do not apply heat over transdermal patches
• pt may not feel overstretched tissues
• LEs could buckle with ambulation
• may schedule treatment around injections

Question 26

What is the oldest medication for treating muscle spasms?

Answer 26

Diazepam (Valium)

Question 27

Diazepam (Valium)

Answer 27

• oldest med for treating muscle spasms
• strong sedative / anti anxiety drug
• inhibits GABA on alpha MN in spinal cord
• SE = sedation, tolerance, reduced psychomotor abilities, withdrawal causing seizures
• ideal for short term spasms but not long term use

Question 28

centrally acting antispasm drugs

Answer 28

• reduce spasms and enhance muscle relaxation
• increase sedation in CNS (mechanism not well defined further)
• serious side effects (drowsiness, nausea, vertigo, ataxia) and potential for abuse

Question 29

Baclofen

Answer 29

• used to treat spasticity
• administered orally or via pump internally
• few side effects

Question 30

What is the only muscle relaxant that acts directly on skeletal muscle to treat severe spasticity, and what is the major risk?

Answer 30

Dantrolene Sodium, which may cause fatal hepatitis

Question 31

Botulinum Toxicity

Answer 31

• type A = Botox, type B = Myobloc
• injected into dystonic muscle, relaxes after a few days
• can reduce spasticity from CP, TBI, CVA, SCI
• can inject into bladder to treat incontinence
• also treat chronic pain, migraines, neuropathic pain

Question 32

adverse effects of botulinum toxin

Answer 32

• does not cure spasticity
• doses have to be low and limited
• severe effects (possible death) if improperly injected into systemic system
• possible allergic reaction

Question 33

rehab implications for muscle relaxants

Answer 33

• complemented by thermal, manual, and electrotherapeutic techniques for acute spasm
• aggressive PT with goal of discontinuing muscle relaxants ASAP
• address strength, postural control, etc. to help combat spasticity
• patients may rely on spasticity for ADLs/function