Unit 1 Pharmacology Guiding Questions Flashcards
what is general anesthesia?
a reversible state of unconsciousness
An ideal anesthetic agent must be able to produce each of the following conditions:
-rapid onset of anesthesia
-skeletal muscle relaxation
-inhibition of sensory and autonomic reflexes
-easy adjustment of the anesthetic dosage during procedure
-a minimum of toxic side effects
-rapid, uneventful recovery after administration is terminated
-amnesia
Two primary routes of administration of anesthetic agents:
IV or inhaled
advantage of IV anesthetics
rapid onset, allowing patient to pass through first two stages of anesthesia very quickly
disadvantage of IV anesthetics
there is a relative lack of control over the level of anesthesia if too much is injected
what is balanced anesthesia?
when a combination of IV and inhaled agents are used to provide optimal anesthetic effects with minimal side effects
primary form of inhaled anesthetics
halogenated volatile liquids (enflurane, halothane, insoflurane)
uniform distribution of general anesthetics is largely due to
their high degree of lipid solubility
why does it take a while for anesthetics to leave a patients system?
it may become temporarily stores in adipose tissues
why does it take a while for anesthetics to leave a patients system?
it may become temporarily stores in adipose tissues
elimination of anesthetics occurs primarily through
excretion from the lungs, biotransformation in the liver, or a combination of both.
adjuvant drugs used to balance the effects of general anesthetic include
preoperative medications and neuromuscular blockers
when are preoperative sedatives given to patients
1-2 hours before the administration of general anesthesia
how are sedatives normally administered
orally or by intramuscular injection
some commonly used preoperative sedatives include
barbiturates, opioids, and benzodiazepines
what goals to antihistamines achieve?
produce sedation and reduce vomiting during and after surgery
how do neuromuscular blockers work?
they block the postsynaptic acetylcholine receptor located at the skeletal neuromuscular junction
possible side effects if neuromuscular blockers include
cardiovascular problems, increased histamine release, increased plasma potassium levels, residual muscle pain and weakness, and immunological reactions
local anesthetics can be applied directly to
the surface of skin, mucous membranes, cornea, and other regions to produce analgesia
local anesthetics can be applied topically to
reduce pain prior to minor surgical procedures
preliminary studies suggest that topical anesthesia can be used to improve
motor function in patients with skeletal muscle hypertonicity resulting from a CVA or head trauma
how can transdermal administration of local anesthetics be enhanced?
by the use of electrical current or ultrasound
what percentage of lidocaine is used in transdermal patches to treat localized pain in musculoskeletal conditions and neuropathic pain?
5%
With this method, the drug is injected directly into the selected tissue, allowing it to diffuse to sensory nerve endings within that tissue.
infiltration anesthesia
the anesthetic is injected close to the nerve trunk so that transmission along the peripheral nerve is interrupted
peripheral nerve block
polonged administration of local anesthetics within skeletal muscle can produce
localized muscle pain and necrosis
injection of the drug into the epidural space (the space between the bony vertebral column and the dura mater)
epidural nerve blockade
what is a caudal block?
injecting the local anesthetic into the lumbar epidural space via the sacral hiatus
injection within the subarachnoid space (the space between the arachnoid membrane and the pia mater)
spinal nerve blockade
where are epidural and spinal blocks usually administered?
L3-4 or L4-5 vertebral interspace
the anesthetic is injected into a peripheral vein
located in a selected arm or leg
IV regional anesthesia
why is a tourniquet applied during IV regional anesthesia?
to localize the drug temporarily within the extremity and to prevent the anesthetic from reaching the systemic circulation where it would cause toxic side effects on the heart and CNS
the ability of a local anesthetic dose to block specific nerve fiber groups depending on the size (diameter) of the fibers
differential nerve block
what is local anesthetic systemic toxicity
when the anesthetics are absorbed into the general circulation and exert toxic effects on other organs and tissues
local anesthetics most important systemic effects involve
the CNS and cardiovascular system
what happens if local anesthetics reach the systemic circulation?
they can inadvertently disrupt the excitability of the CNS and cardiac tissue
symptoms such as ___ can occur if sufficient amounts of anesthetics reach the brain
somnolence, confusion, agitation, excitation, and seizures
The primary cardiovascular effects associated with local anesthetics include
decreased cardiac excitation, heart rate, and force of contraction
Early symptoms of CNS toxicity typically include
ringing/buzzing in the ears (tinnitus), agitation, restlessness, and decreased sensation in the tongue, around the mouth, or other areas of the skin
what indicates cardiotoxicity?
Changes in heart rate (bradycardia), electrocardiogram (ECG) abnormalities, or clinical signs of cardiac depression (fatigue, dizziness)
characterized primarily by an exaggerated muscle stretch reflex. occurs in many patients following injury to the CNS
spasticity
typically arise from an orthopedic injury to a musculoskeletal structure or peripheral nerve root. often a continuous tonic contraction of specific muscles
spasms
how does diazepam work?
by increasing the central inhibitory effects of gamma-aminobutyric acid. it binds to receptors located at GABAergic synapses and increases the GABA-induced inhibition at that synapse
use of Diazepam
used to treat spasms associated with musculoskeletal injuries. also to control muscle spasms associated with tetanus toxin
primary side effect of diazepam
produces sedation and general reduction in psychomotor ability
can also produce tolerance and physical dependence, and sudden withdrawal after prolonged use can cause seizures, anxiety, agitation, tachycardia, and even death.
what do centrally acting antispasm drugs do?
they may decrease polysynaptic reflex activity in the spinal cord
how are centrally acting antispasm drugs used?
as adjuncts to rest and physical therapy for short term relief of muscle spasms associated with acute, painful musculoskeletal injuries. given with NSAIDS
primary side effects of centrally acting antispasm drugs
drowsiness and dizziness
additional: nausea, light-headedness, vertigo, ataxia, and headache
how does baclofen work?
Preferential binding to GABAB receptors enables baclofen to act as a GABA agonist, inhibiting transmission within the spinal cord at specific synapses.
How is baclofen used?
administered orally to treat spasticity associated with lesions of the spinal cord, including traumatic injuries resulting in paraplegia or quadriplegia and spinal cord demyelination resulting in MS
most common side effect of baclofen?
drowsiness
others: fatigue, nausea, dizziness, muscle weakness, and headache
how does gabapentin work?
by inhibiting calcium entry into presynaptic nerve terminals that release glutamate and other excitatory neurotransmitters
what is gabapentin used for?
decreasing the spasticity associated with spinal cord injury and multiple sclerosis
also helpful in treating various types of neuropathic pain
primary side effects of gabapentin?
sedation, fatigue, dizziness, and ataxia
what is botulinum toxin used for (clinically)?
control localized muscle dystonias, including conditions such as spasmodic torticollis, blepharospasm, laryngeal dystonia, strabismus, and several other types of focal dystonias
