General Anesthetics, Local Anesthetics & Muscle Relaxants Flashcards
General Anesthesia
Used for more extensive surgeries/procedures
Reversible state of unconsciousness
Local Anesthesia
Small, defined surgery
Patient remains conscious
Anesthetic agents must be able to…
- Have a rapid onset
- Cause skeletal muscle relaxation
- Inhibit sensory/autonomic reflexes
- Easily adjustable
- Minimal toxic side effects
- Rapid, uneventful recovery
- Amnesia
General Anesthesia - Stage I
Analgesia
Patient begins to lose sensation but is still conscious
General Anesthesia - Stage II
Excitement or Delirium
Patient is unconscious and amnesiac, may also be agitated and restless
General Anesthesia - Stage III
Surgical Anesthesia
Level is desirable for surgery
Onset of regular, deep respirations
General Anesthesia - Stage IV
Medullary Paralysis
Cessation of spontaneous respiration due to inhibition of respiratory control systems
Cardiovascular collapse + altered BP regulation
AVOID this stage at all costs due to risk of death
Order of Administration - General Anesthesia
Initially given through IV until patient achieves stage III, then inhaled anesthesia to maintain appropriate level
“Balanced anesthesia”
What is the only inhaled general anesthetic?
Nitrous Oxide - Short term procedures (dental work)
Classes of Intravenous Anesthetics (5)
- Barbiturates
- Benzodiazepines
- Opioid Analgesics
- Ketamine
- Propofol (Diprivan)
What happens with the administration of Ketamine Anesthesia?
Dissociative anesthesia causing patient to become detached from surrounding environment - appears awake, but is actually sedated and will not recall events
Likely to experience hallucinations, strange dreams, or delusions
What is the drug of choice for general anesthesia?
Propofol (Diprivan) - Rapid recovery, good for short term invasive procedures
Mechanism of Action - Anesthetics
Inhibit neuronal activity throughout CNS, decrease activity of neurons in RAS (sedation, hypnosis, amnesia), inhibit neuronal function in SC (immobility/inhibit pain response), and bind to receptors in CNS to enhance inhibition
What are anesthetic adjuvants?
Drugs administered with general anesthesia to enhance effects
What are the 2 types of adjuvants?
- Preoperative medications
- Neuromuscular blockers
Preoperative Adjuvant
Given 1-2 hours before general anesthesia to relax patient and reduce anxiety
Includes barbiturates, benzos, and opioids
Neuromuscular Blocker Adjuvant
Ensure skeletal muscle paralysis when used with general anesthetics by blocking post-synaptic ACh receptors. Allows a smaller dose of general
Adjuvant side effects include:
Tachycardia, increased histamine release, increased plasma potassium levels, residual muscle pain/weakness, immunological reactions (anaphylaxis)
Rehab Implications for Neuromuscular Blockers
Residual paralysis can persist after surgery and depress skeletal muscle contractions for several hours
Long term detrimental effects on memory, attention & cognition (older adults)
Perform early mobilization & breathing exercises for those experiencing bronchial secretions
Mechanism of Action - Local Anesthetics
Produce a loss of sensation to specific body parts by inhibiting the opening of sodium channels & blocking afferent nerve transmission (APs) along peripheral nerve.
Used for minor surgeries, painless
(+) Rapid recovery, little residual effects, no post-op lethargy
(-) Length of time require to establish anesthetic effect
Examples of Local Anesthetics
Ending in “-caine”
Lidocaine, Procaine, Benzocaine
How do you prevent washout for local anesthetics?
Administer it with a vasoconstrictor
When does toxicity result from local anesthetics?
When drug reaches systemic circulation
Administration of Local Anesthetics
Topically, transdermally, peripheral nerve block, central nerve block, sympathetic blockade & IV regional blockade
What are topical anesthetics used for?
Wound cleaning, circumcision, cataracts surgery
What are transdermal anesthetics used for?
Localized musculoskeletal pain - OA, LBP, fractures, neuropathic pain
What are peripheral nerve blocks used for?
Dental procedures and foot/hand surgeries
Major vs Minor nerve blocks
What are central neural blockades used for?
Obstetric operations and chronic pain relief
Epidural vs Subarachnoid - Administered L3-4 or L4-5
What are sympathetic blockades used for?
Complex regional pain syndrome
What is a Differential Nerve Block?
Local anesthetics that blocks specific nerve fiber groups based on size/diameter. Small diameter fibers (Type C pain fibers) are the most sensitive and first affected by anesthesia
*Clinically significant that sensory pain fibers can be blocked without affecting motor fibers
Local Anesthetic Systemic Toxicity (LAST)
When local anesthetics are absorbed into the general circulation and cause toxic effects on organs/tissues. Can disrupt cardiac and CNS excitability
Early S/S of “LAST”
Ringing in ears, agitation, restlessness, decreased sensation in tongue/mouth/skin
Can be counteracted by lipid compounds that soak up the molecules to limit their effect
Rehab Implications for Local Anesthetics
Be aware of patients with transdermal patch - Do not disturb it during exercise. NO heat over patches.
Be cautious of central nerve blocks - LE may buckle
May be diminished sensation below level of anesthesia
What conditions are Skeletal Muscle Relaxants used for?
Spasticity & Muscle Spasms (Hyperexcitable muscle)
What is the goal of Skeletal Muscle Relaxants?
Normalize muscle excitability without decreasing muscle function. They do NOT prevent muscle contractions
Types of Antispasm Drugs
Diazepam & Centrally Acting Antispasm Drugs
Types of Antispasticity Drugs
Baclofen, Intrathecal Baclofen, Dantrolene Sodium, Diazepam & Tizanidine
Diazepam (Valium)
Antianxiety drug, Skeletal muscle relaxant
Increase inhibitory effects of GABA on AMN activity in SC
Centrally Acting Antispasm Drugs
Mechanism of action not well defined
Inhibit neurons in polysynaptic pathways to decrease AMN excitability and cause relaxation. Short term relief.
Baclofen
Derivative of GABA - Inhibitory effect on AMN activity causing relaxation of skeletal muscle.
Side effects: Transient drowsiness, fatigue, nausea, dizziness, weakness, headache, hyperthermia, hallucinations, and seizures
Intrathecal Baclofen
Administered directly into subarachnoid space in smaller doses for greater effect (reduced pain and improved function) on severe spasticity. Can be administered via implantable pump - common for SCI, MS, CP, CVA, and TBI patients
Dantrolene Sodium
Effects skeletal muscle cells directly - NOT used to treat spasms caused by musculoskeletal injury.
Side effects: Weakness, hepatotoxicity, fatal hepatitis, drowsiness, dizziness, nausea, and diarrhea
Gabapentin
Decrease spasticity associated with SCI & MS. Also used for seizure management and neuropathic pain.
Side effects: Sedation, fatigue, dizziness and ataxia
Tizanidine
Controls spasticity as a result of spinal lesions (SCI, MS) and cerebral lesions. Do NOT use them acutely (slow recovery). Milder side effects and less muscle weakness than baclofen and diazepam
Side effects: Sedation, dizziness, dry mouth
Botulinum Toxin
Control localized hyperexcitability and decrease muscle excitation by disrupting synaptic transmission at NMJ. Injection needs to be specific to a certain muscle; NOT systemically administered (paralysis with loss of respiratory function)
Used for dystonias, torticollis, and strabismus
Types of Botulinum Toxin
Type A: Botox
Type B: Myobloc
Reducing spasticity can improve facilitation of…
Volitional motor function - Improved gait and other functional activities
Rehab Implications for Skeletal Muscle Relaxants
Therapy should be AGGRESSIVE so that the patient can discontinue medication ASAP - Address strength, flexibility, posture, lifting techniques, body mechanics, etc to help decrease potential for recurrence
Be aware of patients that rely on their spasticity (LE extensor pattern)
