4b: Anesthetics and Muscle Relaxants Flashcards
uses for local anesthesia
when surgery area is small, defined area; when patient needs to remain conscious during surgery
requirements for general anesthetics
- 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
stages of general anesthesia
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)
balanced anesthesia
combination of IV and inhaled anesthesia throughout surgery to keep the patient at stage 3
what is the only gas that is an inhaled general anesthetic (short-term, e.g. dental work)?
nitrous oxide
classes of intravenous anesthetics
barbiturates, benzos, opioids, ketamine, propofol
pharmacokinetics of anesthetics
- widely distributed (lipid soluble)
- may become stored in adipose tissue (causing confusion, disorientation during recovery)
- elimination occurs through lungs, transformation in liver, or both
mechanism of anesthetics
inhibit neuronal activity throughout the CNS, increasing inhibitory neurotransmitters and decreasing excitatory transmitters
adjuvants – preoperative meds
given as sedation 1-2 hours before general anesthetic, helps to relax patient, given in form of barbiturates, benzos, or opioids
adjuvants – neuromuscular blockers
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)
side effects of adjuvants (NM blockers)
tachycardia, increased histamine and plasma potassium, residual muscle pain and weakness
rehab implications of general anesthetics
- 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
examples of local anesthetics
(-caine): lidocaine, procaine, benzocaine, (original: cocaine)
pharmacokinetics of local anesthetics
- should remain at site and NOT travel systemically
- eliminated by enzymes in the plasma
- excreted by metabolites
uses for topical local anesthetics
wound cleaning, circumcision, cataract surgery
uses for transdermal local anesthetics
local MSK pain such as OA, LBP, fractures, neuropathic pain; often used with ionto or phonophoresis
uses for peripheral nerve blocks
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)
uses for central nerve blockades
when analgesia is needed for large regions (childbirth, chronic pain relief)
where is central nerve blockade normally administered and why?
at L3/4 or L4/5 to avoid end of spinal cord (at L2)
differences between epidural and spinal nerve blockades
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
uses for sympathetic blockade
complex regional pain syndrome; reduces excessive sympathetic outflow to an extremity rather than providing complete analgesia
mechanism of local anesthetics
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)
local anesthetic systemic toxicity (LAST)
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)
early symptoms of LAST
ringing in ears, agitation, restlessness, decreased sensation around tongue or mouth
